Field of the Invention

This invention relates to the encapsulation molding of objects on a strip-type carrier or substrate and, while not limited thereto, is particularly directed to an automated system and method for the encapsulation molding of electrical or electronic circuitry previously fabricated on the carrier.

Background of the Invention

Encapsulation molding equipment of the general kind referred to is disclosed, for example, in applicant's U.S. Patent No. 5,405,255, issued April 11, 1995. As disclosed in that patent, carrier strips formed of reinforced strip material support a plurality of spaced apart circuits and/or circuit devices (hereinafter individually and collectively "circuit devices") formed on one surface of the strip and extending through the strip to small ball-type contacts on the opposite surface thereof. The '255 patent further discloses encapsulation molding equipment which comprises a portable mold bar on which strips having circuits to be encapsulated are supported. An insert plate having spaced cavities and gate and vent passages is positioned against the surface of the carrier strip

with the circuit devices in registry with the cavities. The mold bar is adapted to be resiliently supported on a platen member of a mold press of the type manufactured, for example, by the Hull Corp. of Hatboro, Pennsylvania, U.S.A. The mold platens are relatively movable toward one another so as to close upon the sandwich comprising the mold bar, the carrier strip and the cavity plate. Liquified encapsulation resin is forced through runner passages and through gate passages in the cavity plate into each of the cavities for the purpose of encapsulating the objects on the carrier strip.

Summary and Objects of the Invention

The present invention involves the provision of equipment and method which provide for automated encapsulation utilizing molding equipment incorporating certain principles of the invention disclosed in U.S. Patent No. 5,405,255 which is incorporated herein by reference.

More specifically, the invention provides molding equipment for the simultaneous encapsulation of plural circuit devices spaced in rows extending lengthwise of a carrier strip, wherein the equipment comprises a first station at which carrier strips having spaced unencapsulated circuit devices are dispensed from magazines and deposited on a planar support having oppositely disposed planar surfaces and spaced apart cavities extending from one of the planar surfaces to the other. According to the invention, the cavities are spaced apart to register with the circuit devices on the carrier strips and to receive a charge of encapsulating resin.

The invention further provides means for deposit of the carrier strips on one of the planar surfaces of the planar support member with the carrier strip interfacing with one of said surfaces and with the circuit devices in registration with the cavities. Means are provided for thereafter moving the planar support member from the first station to a molding station between a pair of relatively movable mold platens. The molding station further comprises plural resin delivery means individual to each cavity, cooperating with gate passages formed in the planar support member for delivering encapsulating resin in liquid form to each of said cavities when the mold platen members are moved to a closed position. The invention further comprises means for returning the transfer means to the first station and thereafter for removal of the carrier strips with the encapsulated circuit devices from the planar support member and delivering them to another magazine for further processing. The various functions of the equipment may be individually controlled by electric or pneumatic switches, although automatic, computer control may be readily employed.

Detailed Description of the Drawings

Figure 1 is a side elevational view, partly in section, illustrating encapsulation molding equipment incorporating the present invention;

Figure 2 is a front elevational view of the apparatus of Figure 1;

Figure 3 is a sectional view taken on lines 3-3 of Figure 1;

Figure 4 is a plan view of the invention of Figure i;

Figure 5 is a plan view similar to Figure 4 showing the transfer means of the invention in a position at the molding station;

Figure 6 is a partial sectional view taken on lines 6-6 of Figure 5;

Figure 7 is a fragmentary view similar to Figure 6, but on an enlarged scale with respect to Figure 6, illustrating the mold parts in a closed position;

Figure 8 is a view of the underside of the upper mold member of the invention; and

Figure 9 is a view illustrating the underside of the transfer plate of the present invention.

Detailed Description of the Preferred Embodiment

Figures 1 illustrates generally a mold press 10 of the kind manufactured by the Hull Corp. of Hatboro, Pennsylvania, U.S.A. Mold press 10 includes a stationary mold base 11 and a relatively movable upper mold member 12 slidably mounted on support rods 13 fixed to mold base 11. Mold base 11 carries a lower mold plate 14 positioned directly beneath upper mold member 12. Upper mold member 12 includes a first upper mold plate 15 and a second upper mold plate 16 which is yieldably mounted beneath first upper mold plate 15. Preferably, the yieldable mounting means is similar to the mounting for the mold bar in U.S. Patent No. 5,405,255 comprising bolts 17 and compression spring means 18 which are located within recesses 18a within the bottom of first upper mold plate 15 and surround the shanks of connecting bolts 17 to yieldably urge plate 16 downwardly.

Hydraulic means including piston 20 having a piston rod 21 moves the upper mold member from the position shown in full lines to a lower position,

indicated by the broken lines 21 in Figure 1, and thereafter raises the upper mold member at the conclusion of each molding cycle.

With reference particularly to Figures 4 and 5, mold base 11 also supports a rectangular frame comprising transversely extending rails 24, a cavity plate 26 bolted to the rails at one end and a cross member, not shown, joining the rails at the opposite end, as best illustrated in Figures 4 and 5. As explained further hereinafter, the frame is mounted for transverse movement by means of rollers 22 which are spring urged upwardly by springs 23 (Figure 1) .

In the preferred embodiment of the invention, cavity plate 26 is provided with two rows of spaced apart cavities 26a. A portion of the underside of the cavity plate is illustrated in Figure 9 on an enlarged scale with respect to Figures 4 and 5.

Cavities 26a each comprise an opening extending through plate 26 and are positioned to receive circuit devices to be encapsulated on the surface of a carrier strip 28. Each cavity is dimensioned to surround a circuit device and to contain a charge of resin sufficient to encapsulate the circuit device on the carrier strip. In the preferred embodiment, two carrier strips each carrying six circuit devices are adapted to be simultaneously placed on a plate 26 with the circuit devices facing downwardly into cavities 26a. In Figures 4 and 5, one such carrier strip 28 is illustrated in position on plate 26, the other being omitted for clarity of illustration in Figure 4 and in phantom in Figure 5.

Carrier strip loading means preferably comprises a pair of magazines 30 of known construction which are supported for vertical movement through rectangular

openings 30a on a table 32 to the right side of the cavity plate 26 as illustrated in Figures 2 and 4. Magazines 30 are of known construction, being provided with side walls having facing grooves 31, shown in Figure 1, which are spaced to store a stack of carrier strips out of face-to-face contact. Feed means comprising a stripper plate, not illustrated but of conventional construction, and a pair of pinch rolls 34 advance the carrier strips from each magazine one at a time with the circuit devices facing downwardly onto a pick-up platform 36 where they are positioned against a stop 37.

A reciprocating transfer means provides for picking up the carrier strips and depositing them on cavity plate 26, as is best seen upon reference to Figures 1-3. Preferably, the transfer means simultaneously picks up a strip with previously encapsulated devices from the cavity plate and places them on a support surface oppositely positioned from platform 36, as explained hereinafter.

Preferably, the transfer means comprises a horizontally extending support rail 38 mounted on a pair of uprights 38a which are in turn fixedly mounted on table 32. Rails 38 supports a vertically disposed pneumatic cylinder 39 which is mounted for movement lengthwise thereof on an angular bracket 40 and a support member 41 slidably mounted on the rail. The cylinder has a vertically downwardly projecting piston rod 42 which is affixed to a horizontally extending plate 43 on which two rows of four downwardly facing spaced apart suction cups 44 connected to a source of negative pressure are preferably located.

The transfer means further comprises a horizontally disposed second pneumatic actuating means

represented by piston rod 46 (shown in cross section in Figure 1) which is fixed to rail 38 and provides horizontal movement of the plate 43 and the suction cups 44 between the positions regulated by microswitches 45 and shown in broken lines at the left- hand side of Figure 3 and the position shown at the right-hand side in full lines in Figure 3. In operation, the suction cups at the left-hand side of Figure 3 are moved to the left on actuation of the pressure cylinder to drive piston rod 46 so as to dispose the left-hand set of suction cups over pick-up table 36, a carrier strip having been first deposited on the pick-up table and positioned by means of pinch rolls 34. Pressure cylinder 39 is then actuated to raise the carrier strip, after which second pneumatic actuating means comprising rod 46 causes horizontal movement of the suction cups so that the left-most set of suction cups (Figure 3) is now directly located over the cavity plate 26. Cylinder 39 is then activated to lower piston rod 42 downwardly until the carrier strip is deposited on the cavity plate 26 by cut off of the negative pressure supply for the suction cups when the circuit devices to be encapsulated are in registration with the cavities 27. To maintain the carrier strip in proper alignment on the cavity plate, the cavity plate is preferably provided with upwardly projecting registration pins 48 which fit within preformed openings in the carrier strips and fix the strips relative to the cavity plate during movement to and from the molding station.

As explained above, simultaneously with the pick up of a carrier strip from the pick-up table 36, the right-hand sets of suction cups 44 (as viewed in Figure 3) are interengagement with any carrier strips which

are located on cavity plate 26 and pick up that carrier strip and move the same to the right, depositing the carrier strips on a second table 50 for loading in empty magazines for subsequent processing. Once carrier strips have been deposited on the cavity plate 26 and on the table 50, the negative pressure existing within the suction devices is terminated and the suction cups are raised and traversed to the left, as viewed in Figure 3, for commencement of the next machine cycle.

The molding equipment of the invention preferably further comprises a series of bores 52, there being six such bores in the preferred embodiment in which two carrier strips each have six circuit devices to be encapsulated are provided. Each bore 52 is interfitted with a piston rod 53 independently operated by an individual hydraulic cylinder 54. During the interval when the mold is opened and prior to transfer of a cavity plate having carrier strips deposited on its surface, each bore 52 is charged with a pellet of heat softenable resin, utilizing a pellet dispensing device 55 which moves from the position shown in full lines in Figure 4 to the position shown in broken lines for deposit of resin pellets within each bore. Device 55 then retracts and drive means represented by rod 24 is activated to move rails 24 and cavity plate 26 into position between the relatively movable mold members. The position of the cavity plate for molding is illustrated in Figure 5. In this position, the bores 52 are midway between the rows of cavities in the plate 26 and cooperate with paired gates 60 leading to pairs of cavities 27a. Electric heater means, located in surrounding relationship to each bore 52, reduces the resin to liquid form prior to each molding operation.

The orientation of the gates 60 and cavities 27a is shown in Figures 6, 7 and 9, the later of which illustrates a portion of the underside of a cavity plate 26. Pairs of gate passages 60 each have a maximum cross section at the point of communication with the associated bore 52 and have an upper wall which gradually slopes downwardly to a point of minimal cross section at the entrance to each cavity 26a.

The construction of the underside of upper mold plate 15 is further illustrated in Figures 6-8. Preferably, mold plate 15 is provided with a pair of rectangular recesses 62 which are dimensioned to receive the pair of carrier strips mounted on cavity plate 26 when the cavity plate has been moved into position for molding. Upper mold plate further is provided with spaced registration apertures 63 which receive registration pins 64 which project upwardly from the cavity plate 26 through apertures in the carrier strips.

Vent passages 66 extending outwardly from each cavity 26a in the upper surface of each cavity plate 26 allow for the venting of gases from the cavities 37a as the cavities are filled with liquid resin through action of the pistons 53.

As best shown in Figure 6, when the mold is open and as the cavity insert is moved into and out of position for molding, a clearance space 68 should be maintained so as to prevent any rubbing contact between the cavity plate and the mold plate 14, creating scoring or wear to one or the other of the plate surfaces. To accomplish this, rollers 22 which support the rails 24 are supported on springs 23 and locate the cavity plate above the surface of plate 14. Upon closure of the mold, as illustrated in Figure 7,

springs 23 yield and the upper and lower mold members 14 and 15 tightly clamp the cavity insert against lower mold plate 14. The only communication with the cavities 26a is thus through the gate passages and the vent passages which allow for the escape of gases as the liquified resin is delivered to the cavities.

Figure 7 shows the position of one of the pistons 53 at the end of its upward stroke with the charge of resin expelled and filling each cavity 27, thereby encapsulating the circuit device on the surface of each carrier strip. Preferably, when the mold is closed, a pair of projections 70 in the upper mold member 15 fill knockout openings 72 to prevent the accumulation of resin in these passages during the molding process.

Once the mold is again opened, the cavity plate is shifted to the right as viewed in Figure 1, into an intermediate position in alignment with paired knockout pins 74 which project downwardly from the bottom of a plate fixed to the end of a piston rod 75 which is operated by a pressure cylinder 76 to move the pins downwardly into openings 72, pressing the resin within the gate passages downwardly until fracture occurs at the narrowest part of the gate, as indicated at 77 in Figure 7.

Following knockout of the resin within the gate passages, the cavity insert is then returned to its initial position beneath the reciprocating transfer means located at the right-hand side of Figure 1. In this position, the transfer means is activated to cause cylinder 39 to move piston rod 42 down moving the suction cups into engagement with the carrier strip having the encapsulated circuit devices. Simultaneously, the other pair of suction cups picks up a carrier strip having devices to be encapsulated from

table 36. The cylinder 39 is then actuated to raise the carrier strips following which the transfer means is moved laterally to deposit the carrier strip having the encapsulated devices on table 50 and the strip having devices to be encapsulated on the cavity insert 26. Suction is released and the cylinder 39 again activated to return the suction devices to the raised position. The molding cycle above described is then repeated.

Conveyor means of any suitable construction transfers the carrier strip having the encapsulated devices to a magazine to be filled, as indicated at 93. Carrier strips having devices to be encapsulated are simultaneously stripped from magazines 30 and delivered onto table 36 by pin rolls 34, and the cycle of operation described above is then repeated.

The apparatus is simple and reliable and produces encapsulated circuit devices without manual intervention by an operator. Contamination of the devices, as may be caused by handling with the carrier strips manually, is substantially eliminated. Production rates as contrasted with heretofore available equipment are substantially increased.