Description

BACKUP JIG FOR SURFACE MOUNTED DEVICE PRINT CIRCUIT BOARD AND THE DRIVE METHOD

Technical Field

[1] The present invention relates to a backup jig for a printed circuit board and, more particularly, to a backup jig for a surface mounted device of a printed circuit board with various merits in that a number of actuating pins may be separately actuated, a computer may be remotely controlled and monitored and production costs may be reduced, wherein at least one actuating pin is driven by a solenoid and a magnet or micro-motor as well as a lift device so as to support at least one surface mounted device of the printed circuit board and, in addition, a method for driving the same. Background Art

[2] A printed circuit board (PCB) is well known as a common electronic circuit board (a plate made of phenol or epoxy resin on which an electric wiring, a semiconductor and/ or a passive part, etc. are integrated) installed in electronic equipment such as consumer electronics necessarily required in modern life and is becoming increasingly advanced. A cellular phone and an MP3 player may be representative thereof. As is apparent from development of advanced electronic articles, various products with multiple functions are newly proposed in order to satisfy consumer needs and novel products are continually being released. Such technological progress tends to develop high density circuits and facilitate miniaturization thereof.

[3] The printed circuit board (PCB) described above may have a surface mounted device

(SMD) mounted thereon. Such an SMD generally means all kinds of electronic parts mounted on a surface of the PCB. Using a surface mount technique (SMT), different devices may be mounted on either side/both sides of the PCB and an increased number of devices may be mounted on the same, thus attaining high density mounting of the devices on the PCB.

[4] A conventional SMD is typically a lead type part, that is, comprises a fine wire such as an iron wire at a joint site. Such a lead type SMD is placed in a PCB hole and is fixed thereto by melting lead at the rear of the PCB hole, fabricating a PCB product. Such an SMD has a limitation of being mounted only on one side of the PCB.

[5] As for surface mounting of an increased number of parts on a PCB with a limited dimension owing to miniaturization of electronic parts, a great deal of studies and efforts have been conducted to develop SMTs. More particularly, a process for fixation of electronic parts has been changed from use of holes to a surface mounting mode, that is, SMT. Using an SMT, different parts may be mounted on either side/both sides

of a PCB and, in addition, the number of parts to be mounted on the PCB may increase so as to enable fabrication of a high density electronic circuit having SMDs.

[6] In order to mount SMDs on both sides of a PCB, a backup jig is required to support the PCB. A following description will be given of use of such backup jig, conventional backup jigs and problems thereof.

[7] In general, a dual in-line package (DIP) is one of packages for fixing IC chips, wherein two lines of electrode pins are aligned in parallel in a longitudinal direction and these pins are fitted in holes of a PCB and are soldered to a copper pattern for electric connection.

[8] As to an electronic circuit automation line in the form of DIP, only one side of the

PCB is used so that the electronic circuit may be produced while being transported along a guide rail without critical problems. Especially, since a screen printer using a metal mask is not demanded, electronic products may be manufactured without difficulty. However, as the conventional PCB has been changed into an SMD type PCB (hereinafter referred to as "SMD PCB") and a thickness of the PCB is decreasing, some significant problems have occurred.

[9] An SMD PCB is used at both sides thereof, such that an electronic part is mounted on one side while processing the other side (that is the rear side of the PCB). Compared to the top side of the PCB, the PCB has various parts pre-mounted on the rear side thereof and forms of the parts, that is, sizes and/or heights of the pre-mounted parts are different from one another. Therefore, it is very difficult to maintain a horizontal level during assembly process of the PCB. More particularly, a screen printer apparatus is applied with a certain level of force in a process for application of a solder paste (containing lead) to a PCB, causing bending of the PCB if the PCB has a small thickness. As a result, the lead moiety is not uniformly coated over the PCB, and therefore, may cause difficulty in PCB assembly and an increase in defect rate.

[10] Accordingly, in order to maintain a horizontal level of a PCB and support the same by a certain force, a multi-pin type backup jig using a vacuum bar, a fixable backup jig, a fixable backup pin jig, a cushion type backup pin jig, an air solenoid type valve, and the like has been proposed.

[11] As for the vacuum bar, several vacuum bars are used to grip and fasten a PCB upon arrival thereof at a working position through a guide rail in a production line, so as to fix an SMD PCB. However, such a vacuum bar has a relatively large size and, since a tube length to an air circuit is increased in proportion to an amount fastened by the bar, the overall equipment becomes complex and enlarged and an additional compressor is required to operate the equipment.

[12] A fixable backup jig often refers to a mold backup jig and is a device fabricated by

NC milling to form a mold while remaining a space except a position of a part pre-

mounted on a front side of an SMD PCB using aluminum or a plastic material, wherein a PCB arriving at a working position through a guide rail of a production line is supported from below and pulled by vacuum pressure so as to fix the SMD PCB. Such a fixable backup jig requires separate molds corresponding to types of the SMD PCB, causing additional expenses. Also, as the produced PCB is changed, the production line for the same should be altered. Additionally, a space for storage and management thereof are demanded owing to increased types of the molds and an alternative vacuum compressor to correct bending of the PCB is required.

[13] A fixable backup pin jig is a jig fabricated by arranging multiple pins with different heights in response to position, size and/or height of each part mounted on a front side of a pre- worked SMD PCB, on a flat panel so as to balance a PCB placed thereon. This backup pin jig is fabricated by simple equipment. However, it is necessary to rearrange the pins when a design of the PCB is altered and it is difficult to correctly adjust the height of the pins corresponding to each part mounted on the front side of the pre- worked SMD PCB.

[14] A cushion type backup pin jig generally has the same form as the fixable backup pin jig, however, multiple pins of the backup pin jig have substantially the same height and are made of a spongy material such as foamed urethane which exhibits cushioning properties when light pressing by a finger. With such a cushion type backup pin jig, when an SMD PCB having parts mounted on an under surface thereof arrives at a working position, a plate equipped with a jig moves up and down and a sponge is pressed to a height of the mounted part so as to horizontally support the PCB. Although such a cushion type backup pin jig has a simple form, a supporting force thereof is very weak and cannot be applied to a screen printer. In addition, this cushion type backup pin jig exhibits reduced durability insufficient to use for a long period of time.

[15] As for a multi-pin backup jig using an air solenoid valve, each pin is not fixed but is varied by the air solenoid valve actuated by springs and a controller fixed to a jig. That is, positions of pins are firstly adjusted by springs to match a height of each part mounted on a PCB and, after the positions of the pins are initially adjusted, the air solenoid valve is actuated according to signals of the controller to supply air to the pins. The set pins are fixed into position by air force so that the PCB may be horizontally supported. As for the multi-pin backup jig using an air solenoid valve described above, each pin is equipped with a spring to maintain an initial position corresponding to a height of each part mounted on a PCB. Such a conventional jig responds to a thickness and/or bending of the PCB by only the spring force, therefore, dully reacts to variation in initial values of the PCB. In addition, in the case where a production process is conducted after maintaining the heights of the parts mounted on

the PCB by the springs, blowing air into an air cylinder allows the PCB to be maintained in a horizontal state. Accordingly, since alternative compressor and pneumatic circuit are demanded to support the PCB and an air control box should be additionally installed, the above multi-pin backup jig encounters problems of requiring a great space for installation and more complicated configuration thereof. Moreover, after a process for manufacturing the PCB is terminated, the air solenoid valve is closed by a control signal generated from the control box and returns to its original condition by the spring force when air is vented from the cylinder. In the case where the spring force is weak or not uniform, the returning of the air solenoid valve is often difficult and malfunction thereof may sometimes be caused owing to aged springs. A conventional multi-pin backup jig using such an air solenoid valve cannot control separate pins and may only be either open or closed according to a signal of the control box. Consequently, individual control of respective pins in the multi-pin backup jig is impossible.

Disclosure of Invention Technical Problem

[16] Therefore, the present invention has been made to solve the above problems and other technical difficulties that have yet to be resolved and an object of the present invention is to provide a backup jig for an SMD PCB in which actuating pins of a backup jig appropriately support at least one SMD of a PCB without a primary supporting device such as a spring.

[17] A further object of the present invention is to provide a backup jig for an SMD PCB capable of stably supporting a PCB even when any external factor such as vibration occurs in an automatic apparatus inicluding a jig.

[18] A further object of the present invention is to provide a backup jig for an SMD PCB, requring no additional device such as a compressor, a pneumatic circuit, a control box, etc. except the backup jig.

[19] A further object of the present invention is to provide a backup jig for an SMD PCB, reading the stored value to continuously work in an optimum state without a requirement of resetting each value whenever the production of PCBs is conducted.

[20] A further object of the present invention is to provide a backup jig for an SMD PCB capable of monitoring a present condition of the backup jig as well as at least one actuating pin.

[21] Another object of the present invention is to provide a multi-pin type backup jig for an SMD PCB, not requring replacement of a jig in any PCB production line.

[22] And yet another object of the present invention is to provide a backup jig for an SMD

PCB having an actuation pin operating device, wherein the device is fabricated with an

electric and/or electronic element in place of a conventional mechanical element with deteriorated functions and reduced lifespan due to wear properties thereof. Technical Solution

[23] In order to accomplish the above objects, the backup jig for an SMD PCB according to the present invention may be a backup jig capable of supporting one side of a PCB mounted with at least one SMD so as to horizontally support the PCB and includes: a bottom cover placed in a plate to be elevated to the PCB; a control circuit board wherein a microcomputer is connected to a power supply and a computer and has a self-stored program running to control the overall backup jig, a driver circuit is driven by a pulse- width modulation (PWM) output, a circuit receives a signal from a current sensor and inputs the received signal into the microcomputer through an A/D conversion circuit, a sensor driver circuit receives an external actuating signal, and a telecommunication driver circuit is used for configuration and remote control of the microcomputer; a plurality of solenoids aligned on the top of the control circuit board and controlled by the same in order to support the SMD of the PCB which in turn horizontally supports the PCB; and a top cover connected to the solenoids to support the same.

[24] As for the backup jig for an SMD PCB of the present invention described above, each of the solenoids has a construction of: a bobbin located between the control circuit board and the cover; a coil wound around the bobbin;, a magnet built in the bobbin to move up and down inside the bobbin when current is applied to the coil; and an actuating pin fixed to the magnet at a bottom end while supporting at least one SMD of the PCB at a top end thereof.

[25] As for the backup jig for an SMD PCB of the present invention described above, each of the solenoids has a construction of: a bobbin located between the control circuit board and the cover; a coil wound around the bobbin; a magnet built in the bobbin to move up and down inside the bobbin when current is applied to the coil; and an actuating pin fixed to the magnet at a bottom end while supporting at least one SMD of the PCB at a top end thereof.

[26] In order to accomplish the above objects, the backup jig for an SMD PCB according to the present invention may be a backup jig capable of supporting one side of a PCB mounted with at least one SMD so as to horinotally support the PCB and includes: a bottom cover placed in a plate to be elevated to the PCB; a control circuit board wherein a microcomputer is connected to a power supply and a computer and has a self-stored program running to control the overall backup jig, a driver circuit is driven by a PWM output, a circuit receives a signal from a current sensor and inputs the received signal into the microcomputer through an A/D conversion circuit, a sensor

driver circuit receives an external actuating signal, and a telecommunication driver circuit is used for configuration and remote control of the microcomputer; a plurality of micro-motors aligned on the top of the control circuit board and controlled by the same; a plurality of lift devices fixed to the micro-motors to move up and down by driving the micro-motors in order to support the SMD of the PCB which in turn horizontally supports the PCB; and a top cover connected to the lift devices to support the same.

[27] As for the backup jig for an SMD PCB of the present invention described above, each of the lift devices has a construction of: a male screw part provided at the top end of a motor axis of each micro-motor; a female screw part formed around an inner circumference of the micro-motor such that the female screw part is gear coupled with the male screw part on the motor axis; and an actuating pin elevating by the male screw part in order to support the SMD of the PCB.

[28] In addition, as for the above backup jig for an SMD PCB of the present invention, the actuating pin has an elastic part to prevent damage of at least one SMD of the PCB when the top end of the pin supports the SMD.

[29] In order to accomplish the above objects of the present invention, there is provided a method for driving a backup jig for an SMD PCB including: a step of inputting some set values such as an initial value of the SMD PCB, a delay time value taken until a plurality of actuating pins of the backup jig are put into place to match at least one SMD and a production value as an electric current value transmitted from a control circuit board to a solenoid coil, into a microcomputer fixed to the control circuit board and storing the values therein; a step of generating an initial value PWM by applying a PWM output to match the set value to the solenoid coil so as to elevate the actuating pins to a maximum height, after the set value input step; a first comparison step of a current A/D value of the solenoid coil by feedback-receiving two different sets of information for the initial value of the PCB and for a current operation value of the solenoid coil actuated by the PWM output, as A/D inputs, and comparing both sets of information, after the initial value PWM generation step; a step of retaining the initial value setting according to a program command of the microcomputer, after the first comparison step of the current A/D value of the solenoid coil; a step of inputting a first sensor signal by receiving a signal from a sensor, when the PCB is transported to the top of the backup jig which in turn elevates a plate and a bottom cover placed therein, and determining whether the plate and the placed bottom cover move up or down; a step of delaying the production value setting by delaying a time taken until each actuating pin is put into place to match a height of the SMD to the initial set delay time value, when the PWM output applied to the solenoid coil is converted into the production value after the first sensor signal input step; a step of generating a

production value PWM by converting the PWM output into the initial set production value, if the actuating pin of the backup jig was put into place and the pre-determined delay time has passed, and applying the converted production value to the solenoid coil so that a force of the actuating pin is automatically controlled to adequately conduct production of the PCB; a second comparison step of a current A/D value of the solenoid coil by feedback-receiving two different sets of information for the production value of the PCB and for a current operation value of the solenoid coil actuated by the PWM output, as A/D inputs, and comparing both sets of the information, after the production value PWM generation step; a step of retaining the production value setting according to a program command of the microcomputer, after the second comparison step of the current A/D value of the solenoid coil; a step of inputting a second sensor signal by sensing a condition that the plate and the placed bottom cover move down through the sensor, when the production of the PCB is terminated after the retaining step of the production value setting, and transmitting the sensed result to the microcomputer so that the jig returns to the initial condition according to a pre-determined program.

[30] In order to accomplish the above objects of the present invention, there is further provided a method for driving a backup jig for an SMD PCB including: a step of inputting some set values such as an initial value of the SMD PCB, a delay time value taken until a plurality of actuating pins of the backup jig are put into place to match at least one SMD and a production value as an electric current value transmitted from a control circuit board to a micro-motor, into a microcomputer fixed to the control circuit board and storing the values therein; a step of retaining an initial condition of the micro-motor by operating a program of the microcomputer, after the set value input step; a step of inputting a first sensor signal by receiving a signal from a sensor, when the PCB is transported to the top of the backup jig which in turn elevates a plate and a bottom cover placed therein, and determining whether the plate and the placed bottom cover move up or down, after the initial condition retaining step for the micro-motor; a step of generating a clockwise (CW) PWM by applying a desired PWM output to match the set value from the microcomputer fixed to the control circuit board, after inputting the set value of the PCB, in order to drive the micro-motor in a clockwise direction so that the actuating pin elevates up to a contact face of the SMD; a first comparison step of a current A/D value of the micro-motor by comparing an A/D conversion value feed back from each actuating pin elevated by the PWM output of the microcomputer with another A/D value when the actuating pin arrives at a face of the PCB and retaining the current A/D value with reference to a difference between both the A/D values, after the CW PWM generation step; a step of stopping the CW PWM generation by stopping the PWM output to fix the height of the actuating pin, when the

multiple actuating pins are elevated to different heights so as to support the SMD which in turn horizontally support the PCB, after the first comparison step of the current A/D value of the micro-motor; a step of inputting a second sensor signal by sensing a condition that the plate and the placed bottom cover move down through the sensor when the production of the PCB is terminated, and transmitting the sensed result to the microcomputer so that the actuating pins of the jig return to the initial condition thereof according to a pre-determined program, after the CW PWM generation stopping step; a step of generating a counter clockwise (CCW) PWM by transmitting a PWM output for reverse revolution of the micro-motor from the microcomputer to the micro-motor so that the actuating pins of the micro-motor return to a minimum height of the backup jig, after the second sensor signal input step; a second comparison step of the current A/D value of the micro-motor by sensing a variation in A/D conversion values, one of which is feed back from each actuating pin returned by the PWM output of the microcomputer and the other being the A/D conversion value when the actuating pin reaches the minimum height, and comparing both the A/D values, after the CCW PWM generation step; and a step of stopping the CCW PWM generation by stopping the PWM output to the actuating pin returned according to a program command of the microcomputer, after the second comparison step of the current A/D value of the micro-motor.

Advantageous Effects

[31] As is apparent from the above description, a backup jig according to the present invention includes at least one actuating pin for favorably supporting SMDs of a PCB, wherein a computer, a control circuit board having an initial value, a delay time and/or a production value input therein, and solenoids and/or micro-motors controlled by the same are used without an initial supporting device such as a spring. According to the present invention, the PCB may be stably supported by solenoids and/or micro-motors driven by applying optimum current regardless of any external factor occurring in an automatic apparatus including a jig. Moreover, additional devices such as a compressor for supporting the PCB, a pneumatic circuit, a control box for the same, and so forth are not required except the backup jig, so that a space for installation thereof may be considerably reduced. In addition, it is not required to reset each value whenever the production of PCBs is conducted, instead, reading the stored value may continuously work in an optimum state. Finally, using a telecommunication cable between the microcomputer of the backup jig and the computer may monitor conditions of the current backup jig as well as each actuating pin.

[32] These objects and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the ac-

companyign drawings.

Brief Description of the Drawings

[33] FIG. 1 is a schematic perspective view illustrating a backup jig for an SMD PCB according to the present invention;

[34] FIG. 2 is a schematic side exploded view illustrating a solenoid;

[35] FIG. 3 is a schematic plan view illustrating bobbins of solenoids aligned and put into place on a control circuit board;

[36] FIG. 4 is a schematic diagram of FIG. 1;

[37] FIG. 5 is a flow chart illustrating a backup jig for an SMD PCB according to the present invention;

[38] FIG. 6 is a partial cross-sectional view illustrating another embodiment of the backup jig for an SMD PCB according to the present invention;

[39] FIGS. 7 and 8 are a schematic exploded view and a schematic side exploded view, respectively, illustrating both a micro-motor and a lift device;

[40] FIG. 9 is a schematic diagram of FIG. 6; and

[41] FIG. 10 is a flow chart of FIG. 6.

Best Mode for Carrying Out the Invention

[42] Particular characteristics and advantages of the present invention will be more apparent in the following description with reference to the accompanying drawings.

[43] FIG. 1 is a schematic perspective view illustrating a backup jig for an SMD PCB according to the present invention; FIG. 2 is a schematic side exploded view illustrating a solenoid; and FIG. 3 is a schematic plan view illustrating bobbins of solenoids aligned and put into place on a control circuit board. Additionally, FIG. 4 is a schematic diagram of FIG. 1; and FIG. 5 is a flow chart illustrating a backup jig for an SMD PCB according to the present invention.

[44] Such a backup jig for an SMD PCB of the present invention supports one side of a

PCB mounted with at least one SMD so as to horizontally support the PCB. This backup jig generally includes a bottom cover 1 placed in a plate, a control circuit board 2, a solenoid 10 and a top cover 3.

[45] The bottom cover 1 placed in the plate is elevated to the PCB transported along a guide rail. The bottom cover 1 may be installed to be elevated by a hydraulic cylinder or in a gear mode or a chain mode.

[46] The control circuit board 2 includes: a microcomputer 5 (MCU) connected to a power supply and a computer 8 and has a program stored therein to control the overall backup jig; a driver circuit receiving a PWM output to drive the solenoid 10 described below; a circuit receiving a signal from a current sensor 7 and inputting the received signal into the microcomputer 5 through an A/D conversion circuit; a sensor driver

circuit receiving an external actuating signal; and a telecommuncation driver circuit used for configuration and remove control of the microcomputer 5.

[47] A plurality of solenoids 10 are aligned on a top side of the control circuit board 2 and are controlled by the same. The solenoids support a plurality of SMDs in the PCB so as to horizontally support the PCB. Each solenoid 10 includes a bobbin 11 between the control circuit board 2 and the top cover 3 described below, a coil 12 wound around the bobbin 11, a magnet 13 built in the bobbin 11, which is elevated along an inner side of the bobbin 11 by applying electric current to the coil, and an actuating pin fixed to the magnet at a bottom end while supporting the SMD of the PCB at a top end thereof. Herein, the actuating pin 14 has an elastic part 15 to prevent the SMD from being damaged when the top end of the pin supports the SMD of the PCB.

[48] The top cover 3 is connected to the solenoids 10 to support these parts and has at least one through hole 4 to guide elevation of the actuating pin 14.

[49] Referring to FIG. 5 which is a flow chart to illustrate a process for driving a backup jig for an SMD PCB of the present invention, the following description will be given of operating the backup jig.

[50] First of all, the backup jig operating process includes a set value input stage SlO wherein an initial value of the SMD PCB, a delay time value taken until a plurality of actuating pins 14 of the backup jig are put into place to match at least one SMD, and a production value as an electric current value transmitted from the control circuit board 2 to the coil 12 of the solenoid 10 are input to the microcomputer 5 fixed to the control circuit board 2 and stored. In this set value input stage SlO, a production operator may adjust a set value in response to different features based on types of the SMD PCB via a telecommunication cable, so that the set value may be properly controlled to satisfy optimum production conditions. In this regard, a thickness, a bending degree and/or features of SMDs should be considered.

[51] After the initial value, the delay time value and the production value are input in the set value input stage SlO, the production operator may store the set value adjusted via the telecommunication cable in a memory built in the microcomputer 5 fixed to the control circuit board 2 (S20).

[52] After the set value input stage SlO, a PWM output matching the set value is applied to the coil 12 of the solenoid 10 so as to elevate the actuating pin 14 to a maximum height, which is an initial value PWM generation stage S30. In this stage, the production operator may operate a program based on the set values. The microcomputer 5 may apply a desired PWM output corresponding to the set initial value to the solenoid coil 12, so as to elevate each of the actuating pins 14 of the backup jig to the maximum height thereof.

[53] After the initial value PWM generation stage S30, a first comparison stage of a

current A/D value of the solenoid coil S40 is conducted, wherein different information for the initial value of the PCB and for a current operation value of the solenoid coil 12 actuated by the PWM output are feed back as A/D inputs and are compared to each other. In this stage, the microcomputer 5 receives the A/D inputs in feedback mode, that is, the above information for the initial value of the PCB and for the current operation value of the solenoid coil 12 actuated by the PWM output, among the set values adjusted by the production operator, and retains the current A/D value while comparing the feed back results to each other.

[54] After the first comparison stage of the current A/D value of the solenoid coil S40, a stage of retaining the initial value setting S50 is conducted to continuously retain the initial value according to a program command of the microcomputer 5.

[55] After the retaining stage S50 of the initial value setting, a stage of inputting a first sensor signal S60 is conducted, wherein a signal is received from a sensor 6 when the PCB is transported to the top of the backup jig which in turn elevates a plate and a bottom cover 1 placed therein, so as to determine whether the plate and the placed bottom cover 1 move up or down. In this stage, when the SMD PCB arrives via a guide rail for production of SMD PCBs, the plate equipped with the backup jig and the bottom cover 1 placed therein are elevated. The microcomputer 5 receives the signal from the sensor 6 pre-mounted at an arrival position of the plate and determines whether the plate and the placed bottom cover move up and down.

[56] After the first sensor signal input stage S60, a stage of delaying the production value setting S70 is conducted, wherein a time taken until each actuating pin 14 is put into place to match a height of the SMD is delayed by the initial set delay time value, when the PWM output applied to the coil 12 of the solenoid 10 is converted into the production value. In this stage, the microcomputer 5 senses the signal for elevating the plate and converts the PWM output applied to the solenoid coil 12 into the production value according to a corresponding program. The production operator may delay the time taken until each actuating pin 14 is put into place corresponding to features of the arrived SMD PCB, by the initial set value.

[57] After the stage of delaying the production value setting S70, a stage of generating a production value PWM S 80 is conducted, wherein the PWM output is converted into the initial set production value and the converted production value is applied to the coil 12 of the solenoid 10 so that a force of the actuating pin 14 is automatically controlled to adequately conduct production of the PCB.

[58] After the production value PWM generation stage S80, a second comparison step of a current A/D value of the solenoid coil S90 is conducted, wherein two different sets of information for the production value of the PCB and for a current operation value of the coil 12 of the solenoid 10 actuated by the PWM output are feed back as A/D inputs,

and these A/D inputs are compared to each other. In this stage, the microcomputer 5 receives the A/D inputs in feedback mode, that is, the above information for the production value set by the production operator and for the current operation value of the solenoid coil 12 actuated by the PWM output and automatically retains the current A/D value while continuously comparing the received results to each other.

[59] After the second comparison stage of the current A/D value of the solenoid coil S90, a stage of retaining the production value setting SlOO is conducted, wherein the production value state is continuously retained according to a program command of the microcomputer 5.

[60] After the retaining stage of the production value setting S 100, a stage of inputting a second sensor signal Sl 10 is conducted, wherein, when the plate and the placed bottom cover 1 move down after the production of the PCB is terminated, the sensor detects the above condition and transmits the sensed result to the microcomputer 5 so that the jig returns to the initial condition according to a pre-determined program.

[61] After the second sensor signal input stage Sl 10, a series of stages including generation of an initial value PWM, comparison of the current A/D value of the solenoid coil, as well as the initial value set retaining process are conducted in order to return the jig to the initial condition and stand-by until the SMD PCB arrives at a working position through the guide rail for production of SMD PCBs.

[62] So long as a power supply for the backup jig of the present invention is not turned off, the microcomputer 5 may continuously repeat production processes according to a pre-determined program command, in response to set values input by the production operator. Turning-off the power supply may stop the program operation of the microcomputer 5. If the power supply is again turned on, the most recent working state values are stored and the production operator may alter the set values and operate the backup jig, or otherwise, may read the stored values for the previous work and continue the same work.

[63] The backup jig for an SMD PCB described above has various advantages.

[64] For example, an operator may input and set desired initial values corresponding to environments for production of PCBs using a computer 8 so as to match different heights of SMDs mounted on one side of the PCB and such initial set values may be easily varied and input whenever parts mounted on the PCB are changed, thus simply rearranging the production of PCBs. Therefore, even without an alternative initial support device such as a spring, the backup jig according to the present invention including a computer, a control circuit board 2 having an initial value, a delay time value and a production value input therein, as well as at least one solenoid 10 controlled by the same, may appropriately support SMDs mounted on the PCB by a plurality of actuating pins 14 provided in the backup jig.

[65] In addition, in order to support the PCB in the optimum condition after setting an initial condition, a variation in force applied to at least one SMD over a certain period of time may be stored in a microcomputer, and therefore, optimum current may be applied to at least one solenoid 10 so as to support the PCB in consideration of external factors such as vibration of equipment. Accordingly, even though the external factor such as vibration of equipment occurs in an automatic apparatus including a jig, current is optimally applied to the solenoid 10 to be actuated and stably support a PCB, resulting in a considerable decrease in failure rate of PCBs.

[66] Since a backup jig of the present invention is self-driven by a microcomputer 5 built in the backup jig and a solenoid 10 fixed to a control circuit board 2 in the backup jig, no additional control box, other than the backup jig, is required. In other words, when the solenoid 10 controlled by the microcomputer 5 moves up and down depending on the initial set value and is adjusted to match a height of each SMD, this result may be automatically converted into a production value required for production of PCBs by a PWM output and an A/D conversion input. As a result, an alternative compressor and/ or pneumatic circuit for supporting the PCB and a control box for the same, and so forth are not required in the present invention. Accordingly, the backup jig of the present invention is preferably operated if an operator turns on a power supply to apply current to the backup jip and inputs some set values including an intial value, a delay time value and a production value in relation to a desired PCB into the backup jig. Therefore, the presnet invention does not require any additional apparatus except the backup jig and may considerably reduce an installation space for production of PCBs.

[67] After the production of PCBs is terminated, the PWM output and the A/D conversion input may send a control signal to the solenoid 10 according to a pre-determined program of the microcomputer 5 and the solenoid 10 returns at least one actuating pin 14 by the received control signal. Herein, even after the PCB production is terminated and the actuating pin 14 is returned to the original state thereof, information as to the worked set values is stored and retained in the microcomputer. Accordingly, it is not necessary to reset all values whenever starting a working process for production of PCBs, instead, reading the stored value enables continuous work in an optimum state.

[68] The microcomputer 5 fixed to the control circuit board 2 may read in a condition of the solenoid 10, as an A/D conversion value, through a current sensor 7 and may variably operate a PWM control signal. The microcomputer also continuously receives the A/D conversion value in feedback mode so as to observe the current sensor 7 so that the resulting information may be used to monitor the condition of each actuating pin 14 and the present condition of the jig via a telecommunication cable connecting the microcomputer 5 of the backup jig with an external computer 8.

Mode for the Invention

[69] Now, an exemplary embodiment of the present invention will be described in more detail in the following description, which is given for illustrative purposes only and should not be construed as limiting the spirit and scope of the invention.

[70] FIG. 6 is a partial cross-sectional view illustrating another embodiment of the backup jig for an SMD PCB according to the present invention; FIGS. 7 and 8 are a schematic exploded view and a schematic side exploded view, respectively, illustrating both a micro-motor and a lift device; and FIG. 9 is a schematic diagram of FIG. 6.

[71] According to the above exemplary embodiment of the present invention, a backup jig for an SDM PCB includes a plate and a bottom cover 1 placed therein, a control circuit board 2, a micro-motor 20, a lift device 26 and a cover 3.

[72] The plate and the bottom cover 1 placed therein are elevated to a PCB transported along a guide rail.

[73] The control circuit board 2 includes: a microcomputer 5 connected to a power supply and a computer 8, which has a program stored therein to control the overall backup jig; a driver circuit receiving a PWM output to drive a micro-motor 20; a circuit receiving a signal from a current sensor 7 and inputting the received signal into the microcomputer through an A/D conversion circuit in order to monitor the present condition of the micro-motor 20; a sensor driver circuit receiving an external actuating signal; and a telecommuncation driver circuit used for configuration and remove control of the microcomputer 5.

[74] A plurality of micro-motors 20 are aligned on a top side of the control circuit board 2 and are controlled by the same.

[75] The lift device 26 is typically fixed to each of the micro-motors 20 and is elevated by driving the micro-motor so as to support at least one SMD mounted on the PCB which in turn may horizontally support the PCB. More particularly, such a lift device 26 has a construction of: a male screw part 22 provided at the top end of a motor axis 21 of the micro-motor 20; a female screw part 24 formed around an inner circumference of the micro-motor such that the female screw part is gear coupled with the male screw part 22 on the motor axis 21; and an actuating pin 23 elevated by the male screw part 22 during rotation of the micro-motor 20, in order to support the SMD of the PCB.

[76] Such an actuating pin 23 has an elastic part 25 to prevent the SMD of the PCB from being damaged when the top end of the pin supports the SMD.

[77] The cover 3 has a plurality of holes 4 through which the actuating pins 23 are inserted and guided to move up and down.

[78] Referring to FIG. 10 which is a flow chart of FIG. 6, the following description will be given of operating the backup jig for an SMD PCB according to the present

invention.

[79] First of all, the backup jig operating process includes a set value input stage S 120 wherein an initial value of the SMD PCB, a delay time value taken until a plurality of actuating pins 23 of the backup jig are put into place to match at least one SMD, and a production value as an electric current value transmitted from the control circuit board 2 to the micro-motor 20 are input to the microcomputer 5 fixed to the control circuit board 2 and stored. In this stage S 120, a production operator may adjust a set value in response to different features based on types of the SMD PCB via a telecommunication cable, so that the set value may be properly controlled to satisfy optimum production conditions.

[80] After inputting the initial value, the delay time value and the production value, the production operator may store the set value adjusted via the telecommunication cable in a memory built in the microcomputer 5 (S 130).

[81] After storing the set value, a stage of retaining an initial condition of the micro-motor

20 (S 140) is conducted, wherein a program of the microcomputer 5 is operated to retain the initial condition of the micro-motor. In this stage, operation of the program starts according to the set value adjusted by the production operator. The actuating pins 23 of the backup jig are all retained at each minimum height in an initial state that the micro-motor 20 is not driven.

[82] After the initial condition retaining stage of the micro-motor S 140, a stage of inputting a first sensor signal S 150 is conducted, wherein a signal is received from a sensor 6 when the PCB is transported to the top of the backup jig and a plate and a bottom cover 1 placed therein are elevated, so as to determine whether the plate moves up or down. In this stage, when the SMD PCB arrives via a guide rail for production of SMD PCBs, the plate equipped with the backup jig is elevated. The microcomputer 5 receives the signal from the sensor 6 pre-mounted at an arrival position of the plate and determines whether the plate moves up and down.

[83] After the first sensor signal input stage S 150, a stage of generating a clockwise (CW)

PWM (S 160) is conducted, wherein a desired PWM output to match the set value from the microcomputer 5 fixed to the control circuit board 2 is applied to drive the micromotor 20 in a clockwise direction so that the actuating pin 23 is elevated to a contact face of the SMD. In this stage, the microcomputer 5 transmits the PWM output to the micro-motor 20 according to the set value adjusted by the production operator. A stroke and/or a velocity of the micro-motor 20 may be controlled by the PWM output and the micro-motor may elevate the actuating pins 23 up to a contact face of the SMD PCB.

[84] After the CW PWM generation stage S 160, a first comparison stage of a current A/D value of the micro-motor S 170 is conducted, wherein an A/D conversion value feed

back from each actuating pin 23 elevated by the PWM output of the microcomputer is compared to another A/D value when the actuating pin arrives at a face of the PCB, and the current A/D value is retained with reference to a difference between both the A/D values. Herein, there is a difference between the A/D conversion value feed back from each actuating pin 23 elevated by the PWM output of the microcomputer 5 and the A/D value when the actuating pin arrives at the face of the SMD PCB. The microcomputer 5 may detect a fine variation in these values and compare both the A/D values, so as to alter and/or stop the PWM output in consideration of optimum environments for production of SMD PCBs.

[85] After the first comparison stage of the current A/D value of the micro-motor S 170, a stage of stopping the CW PWM generation S 180 is conducted, wherein the PWM output is stopped to fix the height of the actuating pin 23 when a plurality of actuating pins are elevated to different heights so as to support a plurality of SMDs which in turn horizontally support the PCB.

[86] Alternatively, if a state retaining work is added to the CW PWM generation stop stage S 180, the actuating pins 23 do not return to the minimum height thereof even when the plate returns to its original condition, instead being retained at different heights corresponding to respective states. Therefore, the actuating pins 23 do not return to the original condition thereof and the initial setting is continuously retained during the repetitive process for manufacturing the same SMD PCBs, thereby permitting the production work to be directly started. Consequently, a series of works for production of SMD PCBs are reduced to around half thereof, resulting in improved production efficiency. Since the power supply is required for a jig only at the initial setting, energy efficiency is also enhanced.

[87] After the CW PWM generation stop stage S 180, a stage of inputting a second sensor signal S 190 is conducted, wherein, when the plate and the bottom cover placed therein 1 move down after the production of the PCB is terminated, the sensor 6 detects the above condition and transmits the sensed result to the microcomputer 5 so that the actuating pins 23 of the jig return to the initial condition thereof according to a predetermined program. In this stage, when the work for production of SMD PCBs is terminated, the plate equipped with the jig moves down. The microcomputer 5 recognizes descent of the plate based on whether the signal of the sensor 6 is input or not, and sends commands for returning each actuating pin 23 to an original condition according to a pre-determined program.

[88] After the second sensor signal input stage S 190, a stage of generating a counter clockwise (CCW) PWM (S200) is conducted, wherein a PWM output for reverse revolution of the micro-motor 20 is transmitted from the microcomputer 5 to the micro-motor 20 so that the actuating pins 23 of the micro-motor 20 return to a

minimum height of the backup jig. In this stage, the microcomputer 5 recognizes the signal of the sensor 6 and applies the PWM output for reverse revolution of the micromotor 20 to the same. The micro-motor 20 returns each actuating pin 23 to the minimum height of the backup jig by the PWM output.

[89] After the CCW PWM generation stage S200, the second comparison stage of the current A/D value of the micro-motor S210, wherein a variation in two A/D conversion values, one of which is feed back from each actuating pin returned by the PWM output of the microcomputer and the other being the A/D conversion value when the actuating pin reaches the minimum height, is sensed and both the A/D values are compared to each other. Herein, there is a difference between the A/D conversion value feed back from each actuating pin 23 returned by the PWM output of the microcomputer 5 and the A/D value when the actuating pin arrives at the minimum height. The microcomputer 5 may detect a fine variation in these values and compare both the A/D values, so as to alter and/or stop the PWM output.

[90] After the second comparison stage of the current A/D value of the micro-motor S210, a stage of stopping the CCW PWM generation S220 is conducted, wherein the PWM output is stopped by the actuating pin 23 returned according to the program command of the microcomputer 5.

[91] After the CCW PWM generation stop stage S220, the micro-motor 20 returns to its initial condition.

[92] So long as a power supply for the backup jig of the present invention is not turned off, the microcomputer 5 may continuously repeat production processes according to a pre-determined program command, in response to set values input by the production operator. Turning-off the power supply may stop the program operation of the microcomputer 5. If the power supply is again turned on, the most recent working state values are stored so that the production operator may alter the set values and operate the backup jig, or otherwise, may read in the stored values for the previous work and continue the same work.

[93] The backup jig for an SMD PCB described above has various advantages. More particularly, an operator may input and set desired initial values corresponding to environments for production of PCBs using a computer 8, so as to match different heights of SMDs mounted on one side of the PCB and such initial set values may be easily varied and input whenever parts mounted on the PCB are changed, thus simply rearranging the production of PCBs. Therefore, even without an alternative initial support device such as a spring, the backup jig according to the present invention including a computer, a control circuit board 2 having an initial value, a delay time value and a production value inputted therein, as well as at least one micro-motor 20 controlled by the same, may appropriately support SMDs mounted on the PCB by a

plurality of actuating pins 23 provided in the backup jig.

[94] In addition, in order to support the PCB in the optimum condition after setting an initial condition, a variation in force applied to at least one SMD over a certain period of time may be stored in a microcomputer 5, and therefore, optimum current may be applied to at least one micro-motor 20 so as to support the PCB in consideration of external factors such as vibration of equipment. Accordingly, even though the external factor such as vibration of equipment occurs in an automatic apparatus including a jig, current is optimally applied to the micro-motor 20 to be actuated and to stably support a PCB, resulting in a considerable decrease in failure rate of PCBs.

[95] Since a backup jig of the present invention is self-driven by a microcomputer 5 built in the backup jig and a micro-motor 20 fixed to a control circuit board 2, no additional control box, other than the backup jig, is required. In other words, when the micromotor 20 controlled by the microcomputer 5 moves up and down depending on the initial set value and is adjusted to match a height of each SMD, this result may be automatically converted into a production value required for production of PCBs by a PWM output and an A/D conversion input. As a result, an alternative compressor and/ or pneumatic circuit for supporting the PCB and a control box for the same, and so forth are not required in the present invention. Accordingly, the backup jig of the present invention is preferably worked if an operator turns on a power supply to apply current to the backup jig and inputs some set values including an initial value, a delay PCB into the backup jig. Therefore, the present invention does not need any additional apparatus except the backup jig and may considerably reduce an installation space for production of PCBs.

[96] After the production of PCBs is terminated, the PWM output and the A/D conversion input may send a control signal to the micro-motor according to a pre-determined program of the microcomputer 5 and the micro-motor 20 returns at least one actuating pin 23 by the received control signal. Herein, even after PCB production is terminated and the actuating pin 23 is returned to the original state thereof, information for the worked set values is stored and retained in the microcomputer. Accordingly, it is not necessary to reset all values whenever starting a working process for production of PCBs, instead, reading the stored value enables continuous work in an optimum state.

[97] The microcomputer 5 fixed to the control circuit board 2 may read in a condition of the micro-motor 20, as an A/D conversion value, through a current sensor 7 and may variably operate a PWM control signal. The microcomputer also continuously receives the A/D conversion value in feedback mode so as to observe the current sensor 7 so that the resulting information may be used to monitor the condition of each actuating pin and the present condition of the jig via a telecommunication cable connecting the microcomputer 5 of the backup jig and an external computer 8.

[98] In another aspect of the present invention, the actuating pin 23 may rotate and move along a screw thread by revolution of the micro-motor 20. Therefore, even when the plate returns to its original state, a position of the actuating pin 23 corresponding to a height and/or a shape of each SMD is continuously retained. Accordingly, it is not necessary to reset and/or adjust a position of the actuating pin 23 whenever re-starting a work for production of PCBs after the previous work is terminated. Industrial Applicability

[99] In consideration of the above results, it is understood that the present invention may considerably improve productivity in manufacturing PCBs and exhibit favorable effects in preventing an actuating pin from ageing owing to continuously repeated works and energy saving effects.

[100] Although preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.