AIR SOLDERING UNIT

Technical Field

The present invention refers to an air soldereing unit, which can be particularly used for soldering automated processes. Background art

The need is known to carry out automated or semi-automated soldering jobs on printed circuits, wiring or small-sized masses.

A first known soldering technique provides for the use of automated systems for moving a laser beam emission and focussing device. These systems, although finding wide use in industry for the precision soldering on electronic circuits, are not convenient for every type of use due to their high costs.

With particular reference to carrying out spot soldering on electronic circuit boards, a second soldering technique provides for the use of soldering units comprising a first device for the emission of a flow of hot air onto an area to be heated, on the lower side of the board.

Such first device is generally composed of an air heating station to which is connected, through a pipe, a nozzle for the delivery of the flow of hot air.

Simultaneously, a second device of the soldering unit, which supports a metal material with a low casting temperature, of the tin, tin alloy type or the like, approaches the upper side of the board, until the material comes into contact with the heated area.

The heat thus transmitted by conduction leads to the material's casting, depositing onto the heated area, by a spot to be soldered. The operation is subsequently repeated for the execution of further spot soldering.

These known soldering units are not however without drawbacks, among which the fact is underlined that of the presence of two separate devices, one for the emission of the flow of hot air and one for depositing the metal material, significantly complicates the soldering process and implies, at the same time, the use of complex automation technologies to synchronise the two devices.

Another disadvantage of the known soldering units consists in the big overall

dimensions, deriving especially from the big size of the heating station used. A further disadvantage is the low level of precision achieved by such soldering units: the area heated by the flow of hot air emitted from the nozzle is, indeed, considerably larger than the effective surface to be soldered. Object of the Invention

The main aim of the present invention is to provide an air soldering unit that allows to simplify considerably the soldering process.

Within the scope of such technical aim, another object of the present invention is to reduce the overall dimensions of the equipment and devices used. Another object of the invention is to increase the precision of the soldering process compared to known air soldering units.

Another object of the invention is to cater for the above aims with a simple structure, of relatively practical implementation, safe to use and with effective operation, as well as having a relatively low cost. The above described objects are all achieved by the present air soldering unit, characterised in that it comprises a base stand for supporting at least one heating and injection device for heating and injecting at least one air flow over an area to be soldered and dosing and positioning means for dosing and positioning a castable metal material by said area to be soldered. Brief Description of the Drawings

Further characteristics and advantages of the present invention will appear even more evident from the detailed description of a preferred, but not exclusive, embodiment of an air soldering unit, illustrated by way of non limiting example in the accompanying drawings, wherein: the figure 1 is a side view, schematic and in partial section of the soldering unit according to the invention; the figure 2 is an exploded view and in partial section of a heating and injection device of an air flow of the soldering unit according to the invention; the figure 3 is a side view and in partial section of the heating and injection device of the soldering unit according to the invention; the figure 4 is a side and schematic view of the soldering unit according to the invention applied to automated means of movement.

Embodiments of the Invention

With particular reference to such figures, an air soldering unit, particularly of the type used for soldering components on printed circuits, for soldering cables and for soldering small size masses has been globally designated by reference number 1.

The soldering unit 1 comprises a substantially plate-shaped base stand 2 which can be associated with automated means of movement 3, of the robot arm type or the like, and which is the support for a heating and injection device 4 of an air flow over an area to be soldered and for dosing and positioning means 5 for dosing and positioning a material, of the metal type, which can be cast by the area to be spidered.

In particular, the heating and injection device 4 comprises a body 6 which has a substantially hollow and elongated cylindrical conformation, open at the end, which is suitable for housing a heating element 7 and which has a dispensing mouth 8 of the above mentioned air flow.

Advantageously, the heating element 7 can be composed of an incandescent spark plug of the type commonly used when starting diesel engines. The body 6 comprises an inner first chamber 9 which has the dispensing mouth 8, which houses a first section 7a of the heating element 7 suitable for generating heat and which is associated with air inlet means 10.

With particular but not limited reference to the specific enbodiment of the invention herein described, the first section 7a is housed inside the first chamber 9 at a front section of the body 6 and is made up of the metal globe of the spark plug 7. In an assembly configuration, wherein the spark plug 7 is housed inside the body 6, an interspace is defined between the inner surface of the first chamber 9 and the outer surface of the metal globe 7a; this interspace allows for the recirculation of the air introduced by the inlet means 10 around the metal globe 7a and towards the outside through the dispensing mouth 8. The body 6 also comprises an inner second chamber 11 which houses a second section 7b to be cooled of the heating element 7, which is associated with the air inlet means 10 and has an exit port 12 for the air entered. In the assembly configuration and with particular reference to the specific

embodiment herein described, an interspace is defined between the inner surface of the second chamber 11 and the outer surface of the second section 7b of the metal body of the spark plug 7; this interspace allows for the recirculation of the air introduced by the inlet means 10 around the second section 7b and towards the outside through the exit port 12 for cooling the second section 7b.

It must be pointed out the words "front" and "rear" are used in this description and in a non-exclusive way with reference to the standard arrangement of the body 6 in relation to the direction of delivery of the air flow towards the area to be soldered. Advantageously, threaded means are provided that allow for the screwing and unscrewing of the spark plug 7 inside the body 6 and which are composed of a screw 7c defined on the outer side surface at a substantially middle section of the spark plug 7 and of a corresponding nut screw 6d defined on a portion of the inner side surface of the body 6. Usefully, the dispensing mouth 8 and the exit port 12 are defined at a first and a second end 6a and 6b respectively of the body 6 opposite each other. Advantageously, a nozzle 13 can be associated removable with the first end 6a at the dispensing mouth 8. In particular, threaded means are provided which allow for the screwing and unscrewing of the nozzle 13 from the first end 6a and which are made up of a screw 6c defined on the outer side surface of such first end 6a and of a correspondant nut screw 13a defined on the inner side surface of the nozzle 13.

Different conformations of the nozzles 13 may be usefully provided which can be used according to the size of the surface to be soldered and to the precision of the soldering to be carried out.

The inlet means 10 comprise a first pipe 14 for blowing air which has an end associated with a first supply hole 15 defined through the body 6, at the first chamber 9, and the opposite end associated with compressed air generation means. A second pipe 16 for cooling has an end associated with a second supply hole 17 defined through the body 6, at the second chamber 11, and the opposite end associated with compressed air generation means.

Usefully, the inlet means 10 comprise a heat exchanger 18 which, together with the flow of cold air that goes through the second pipe 16, is suitable for levelling and controlling the temperature of the first and second pipe 14 and 16.

In particular, the first and second pipe 14 and 16 are made out of metal material and the heat exchanger 18 is made of a soldering which extends along a section between these.

The dosing and positioning means 5 comprise a spool 19 which is associated in rotation with the base stand 2 and around which is wound a wire F of castable metal material, of the tin, tin alloy type or the like. In particular, the soldering unit 1 comprises support means 20 comprising a shaft 21 fixed onto the base stand 2 and inserted inside the hole of the spool 19; the shaft 21 has a pair of centring washers 22 which can be positioned on the opposite sides of the spool 19.

The dosing and positioning means 5 also comprise a feeding device 23 of the free end of the wire F unwound from the spool 19 towards the area to be soldered.

The feeding device 23 comprises a support element 24 having a straight guide channel 25 for guiding the sliding of the wire F, of a hole, a groove type or the like which extends along a section of the support element 24. Two wheels 26 rotating in opposite directions, of which at least one is driving, are supported by the support element 24 and are arranged along a section of the channel 25, with the wire F engaged between these.

The wire F moved by the pair of wheels 26 is inserted inside a cannula 27, which has an end fixed to the support element 24, at the channel 25 and axially with respect to this, and a free end protruding with respect to the support element 24 and positionable on the area to be soldered.

The feeding device 23 also comprises at least one sensor of, for example, the infrared type for detecting the position of the free end of the wire F. Such sensor, not shown in the figures above, is associated with the support element 24, at a surface substantially opposite with respect to the surface having the channel 25.

Advantageously, the soldering unit 1 can comprise a fan 28, associated with the

base stand 2 and suitable for cooling the heating and injection device 4. For a more accurate view of the soldering process and for a more accurate control of the automated means of movement, the soldering unit 1 can comprise optical survey means 29 of the area to be soldered. As shown in the figure 3, such optical survey means 29 can be composed of a video camera (or the like) positionable on a supplementary stand 30 that extends from the base stand 2. Advantageously, the supplementary stand 30 is substantially plate-shaped and has a series of positions for fixing the video camera 29. Usefully, protection and/or cleaning means 31 are provided for the lens of the video camera 29 suitable for ensuring the integrity of the video camera 29 over time, protecting it from the effect of the poisonous gases generated by the casting of the tin wire during the soldering process. The protection and/or cleaning means 31 comprise a protection tape 32 made out of substantially transparent material, of the acetate type or the like, and actuator means for sliding the tape 32 with at least one section arranged at the outer surface of the lens of the video camera 29.

In particular, the actuator means comprise a first cylinder 33, freely turnable, arranged near one side of the video camera 29 and on which the tape 32 is at least partially wound. A second cylinder 34 turnable by means of motor means is arranged on the opposite side of the video camera 29, associated with one end of the tape 32 and suitable for dragging the tape 32. Two tensioning elements 35 are arranged on opposite sides near the lens and keep a portion of the tape 32 stretched between the first and the second cylinder 33 and 34, with one section of it arranged by the lens of the video camera 29.

The tape 32, therefore, unwinds from the first cylinder 33 and wraps around the second cylinder 34 and the reels of tape 32 used can be replaced once exhausted.

The operation of the invention is the following. The robot arm 3 moves the soldering unit 1 until it is placed together with the nozzle 13 and the cannula 27 near the area to be soldered. The input of air into the first chamber 9 through the first pipe 14 and the

simultaneous start of the spark plug 7 by incandescence of the metal globe 7a, allow to heat the air flow which is directed and oriented by the nozzle 13 towards the area to be soldered.

At the same time, the air entering the inside of the second chamber 11 through the second pipe 16 allows for the maintenance of the temperature of the heating and injection device 4 below potentially harmful temperatures. The wheels 26 of the feeding device 25 turn dragging the wire F and pushing its free end through the cannula 27, until it comes into contact with the area to be soldered. The accumulated heat of the area to be soldered together with the heat of the air flow exiting from the nozzle 13 produce the casting of a part of the metal material which composes the wire F, which is deposited on the area to be soldered. The soldering unit 1 is subsequently moved away from the soldered area and/or positioned by a new area to be soldered.

It has in practice been seen how the described invention achieves the intended objects and in particular the fact is underlined that the presence in this same soldering unit of the heating and injection device and of the dosing and positioning means considerably simplifies the soldering process. Another advantage comes from the particular conformation and from the special elements composing the heating and injection device which allow the soldering unit to be less bulky.

The presence of one or more nozzles with variable section and flow allow, moreover, for the variation and considerable increase in the precision of the soldering process.

Another advantage comes from the simple structure of the soldering unit which, together with the use of commonly used and easily available components such as, for example, the incandescent spark plug, allows for the significant reduction of the general cost of manufacturing the unit itself and, as a consequence, the general costs of the soldering process.

The invention thus conceived is susceptible of numerous modifications and variations, all of which falling within the scope of the inventive concept.

Furthermore all the details may be replaced by other elements which are technically equivalent.

In practice, the contingent shapes and dimensions may be any according to requirements without because of this moving outside the protection scope of the following claims.