Apparatus for Holding Electrial or Electronic Components During the Application of Solder

This specification relates chiefly to apparatus for holding electrical or electronic components, particularly during the application of solder. The invention is particularly concerned with the holding of dual-in-line packages (DIPs) whilst they are being soldered.

DIPs are of generally rectangular cross section in plan view and have a row of contact pins or leads along each side. The number of leads on each side is typically seven but may range from 2 to 32 to even more. DIPs contain integrated circuits and some or all of the leads are connected to respective parts of the circuits. The DIPs are designed to be inserted into circuit boards or suitable holders and may or not be soldered in place. In any event, it is desirable that the leads be given a coating of solder and in mass production this is done by means of wave soldering apparatus.

In general, a number of DIPs are loaded in a carrier, and then subjected to processing steps of e.g. cleaning, rinsing, etching, rinsing, drying, fluxing, pre-heating, wave soldering, fan drying, hot water rinsing, drying, cooling and unloading. The carriers pass along a track during these steps and in mass production the average cycle time between loading and unloading DIPs in the carrier for wave soldering is about 20 to 22 seconds with known arrangements.

The carriers must be able to withstand the temperature changes involved, particularly with repeated cycling and must permit easy access for solder to the leads of the DIPs. The carriers must be such that the DIPs will be located securely, but for commercial reasons it is desirable that as many DIPs as possible be held in a small space.

A known carrier comprises a generally rectangular frame with a number of parallel tracks, typically fourteen, for holding the DIPs. Each track consists of six parallel tungsten steel rods arranged to restrict lateral movement of the packs in any direction. During the processing steps, a gate at one end of the carrier holds the DIPs in their tracks, restricting axial movement of the rows. This gate is opened for the loading and unloading steps, the other end of the carrier being blocked permanently.

Not only is such an arrangement complex in terms of manufacture, but it is not thoroughly reliable. There is an appreciable rate of loss of DIPs possibly caused by thermally induced deformation of the tracks. The need for a gate to permit axial access to the tracks makes location of the rod ends difficult. Furthermore, the loading and unloading processes can be lengthy. In the known arrangement, unloading takes about 32 seconds and this is considerably longer than the cycle time for the processing of the DIPs. This leads to delays or to unnecessarily high numbers of carriers being required.

Viewed from one broad aspect there is disclosed in this specification a carrier for a plurality of electrical or electronic components such as dual-in-line packages or the like, comprising a frame in which is provided a plurality of parallel tracks for receiving the components, the tracks being formed by a plurality of parallel, laterally spaced, axially extending upper support members each of which defines a pair of parallel, axially extending upper rails having downwardly facing portions and by a plurality of parallel, laterally spaced, axially extending lower support members aligned with and vertically spaced from the upper support members, each of the lower support members defining a pair of parallel, axially extending lower rails having upwardly facing portions.

Thus, between any two adjacent pairs of aligned upper and lower support members there will be a track defined by four rails, one from each member. There will be two laterally spaced upper rails with downwardly facing portions and two laterally spaced lower rails with upwardly facing portions. These rails will be so arranged as to support a row of components such as DIPs and restrain vertical and horizontal movement. However, whilst effective location of the DIPs is provided, the support members themselves can be securely located whilst permitting ready axial access to the tracks.

There are a number of ways in which the four rails could support e.g. a DIP. Preferably, the DIP rests on the ends of the two lower rails. However, the rails could be stepped so as to have laterally extending but upwardly facing portions and the DIP could rest on these portions. Similarly, upwards movement could be restricted by the downwardly facing ends of the two upper rails. Preferably, however, the upper rails are stepped so as to have laterally extending, but downwardly facing portions which will restrict upwards movement of the DIP. An advantage of stepped rails, is that laterally facing portions can be used to restrict lateral movement of the DIP by engagement of its side. However, some DIPs may have inclined portions on their sides in which case engagement with the ends of the rails may restrict both vertical and lateral movement. In this case, stepped rails may not be necessary although they can be used to provide the correct spacing between the ends of adjacent rails.

In general, the configuration and vertical and lateral spacings of the rails will be chosen to adapt to the size and shape of the DIP or other component to be located, so as to provide suitable restriction against movement in any lateral or vertical direction. Preferably, a certain amount of tolerance is permitted to facilitate insertion of the DIPs into the tracks although care should be taken to ensure that thermal effects do not increase clearances to a level at which DIPs could be displaced from the tracks and drop out e.g. during a soldering operation.

In a particularly preferred embodiment, each support member is of "U" shaped cross section and in accordance with the preferred arrangement referred to above, the ends of the legs of the upper members are stepped inwardly.

In general, each support member will be secured to the frame by means disposed between the rails of the support member. Thus the space between two adjacent support members, where the track is defined for receiving e.g. DIPs, will be free of locating means. This provides easy axial access for the insertion or removal of DIPs. It is possible to use both ends by inserting the DIPs from one end and removing them from the other. Not only is there greater reliability and flexibility in the construction as a whole, but this improved ease of handling can reduce the unloading time to a level corresponding to or less than the cycle time for soldering, e.g. about 12 second.

There is disclosed herein apparatus for loading and unloading a carrier with access from both ends. The carrier itself has a gate at either end to hold the DIPs in place. The carrier is placed in the apparatus in an inclined position and means are operated to open the upper gate so that DIPs slide into the carrier. The gate is then closed and the full carrier subjected to the wave soldering process. The carrier is then placed back in the apparatus and means are operated to open the lower gate so that the DIPs slide out of the carrier. Since the DIPs can move in or out at either end, it does not matter whether or not the carrier is turned through 180.degree. between the loading and unloading operations. This dual entry concept is particularly advantageous.

The means locating the support members could include spacers positioned at the two axial ends of aligned upper and lower members although it would be possible to have continuous or semi-continuous spacer webs. It would be possible to have two aligned upper and lower support members and a spacer formed integrally. Preferably, however, they are separate and this facilitates arranging for thermal movements. In one advantageous arrangement, spacers which are integral with the frame are provided at the two axial ends and the support members are located by means of slots engaged with lugs on the spacers in such a way as to allow for axial thermal movement. The slots may have a first portion to facilitate assembly with the spacer, and a second narrower portion which locks the support member to the spacer by axial movement during assembly. The axial extent of the second portion should be such as to accommodate thermally induced axial movement without the first slot portion coming into operation and causing instability of the construction. The method of locating the support members may be of use in other contexts and need not be restricted to the particular carrier described above.

In use, the leads of a DIP supported in a track will lie inside the rail of one of the support members on either side. The arrangement should be such as to provide easy access for solder to this region and this can be achieved by providing apertures in the appropriate support members. In preferred arrangements, therefore, the lower support members will be apertured whilst the upper support members need not be.

As many tracks as are desirable may be provided in the frame. If standard elements are used throughout, there will be spare half tracks at either side of the array but manufacture will be simplified.

The components can be made from any suitable material capable of withstanding the temperatures and stresses involved. Titanium may be used, and the rails may be coated e.g. with P.T.F.E. to facilitate sliding of DIPs during loading and unloading.

An embodiment exemplifying some of the above, and other, broad aspects will now be described by way of example and with reference to the accompanying drawings in which:

FIG. 1a and 1b are upper and lower perspective views of an upper support member for use in a carrier;

FIG. 2a and 2b are upper and lower perspective views of a lower support member for use in a carrier;

FIG. 3 is a diagrammatic end view of the carrier without the support members;

FIG. 4 is an enlarged perspective view of the part of FIG. 3 marked IV;

FIG. 5 is an end view of the carrier with the support members and other components in place;

FIG. 6 is an enlarged partial end view showing a DIP in position;

FIG. 7 is a plan view of the carrier;

FIG. 8 is a diagrammatic plan view of apparatus for handling the carrier; and

FIG. 9 is a diagrammatic side view of the apparatus.

As shown in FIGS. 1a and 1b an upper support member 1 is in the form of an elongate channel of e.g. titanium coated with P.T.F.E. the cross section of the channel is generally of "U" shape but the legs, which define downwardly directed laterally spaced parallel rails 2, are stepped at 3 so that the extremities 4 are inset. At each end of the track are provided apertures 5, to be described in more detail below.

In FIGS. 2a and 2b there is shown a lower support member 6. This is again in the form of an elongate channel of e.g. titanium coated with P.T.F.E. The cross section is of "U" shape, with the legs defining upwardly directed laterally spaced parallel rails 7 with extremities 8. The width of the member 6 is substantially the same as that of the upper member 1, but the spacing between the extremities 8 is greater than that between extremities 4 of rails 2 since the rails 7 are not stepped. The member 6 is provided with apertures 9 along its length to permit easy access for solder, whilst at its axial ends there are apertures 10 corresponding to apertures 5 of the upper member.

FIG. 3 shows a portion of a frame 11 with side members 12, carrying handles 13 and cross members 14 at either end (only one being shown) carrying fifteen downwardly directed integral mounting posts 15. As shown more clearly in FIG. 4 each post is designed to provide two pairs of surfaces i.e. 16, 16' and 17, 17'. The surfaces of each pair are separated by lugs 18 and 19 respectively of reduced cross section, whilst the two pairs are separated by a spacer portion 20. This spacer portion is waisted so as to be of reduced cross section, which inter alia reduces the thermal capacity of the arrangement.

During assembly, the upper and lower support members are attached to the mounting posts 15 at either end of the frame 11. The apertures 5 and 10 have portions which are large enough to pass over the free ends and spacer portions of the posts but once positioned between the required pair of surfaces, i.e. 16,16' or 17,17', relative axial movement will cause a smaller portion of the aperture 5 or 10 in the form of a slot 5', 10' to engage lug 18 or 19 as appropriate. The support member is then locked in place but is still capable of limited axial movement relative to the supports to allow for thermal contraction and expansion, the smaller portions of apertures 5 and 10 having a greater axial extent than lugs 18 or 19.

FIG. 5 shows fifteen upper and lower support members 1,6 side by side on their respective mounting posts. The upper and lower support members are aligned and all of the members are axially parallel as shown in FIG. 7. As shown clearly in FIG. 6 between any two adjacent mounting posts 15 there is defined a track T comprising two rails 7 and two rails 2, the extremities 8 of rails 7 being closer together than those 4 of rails 2. The track can thus receive a row of DIPs, diagrammatically indicated at 200, the DIPs resting on extremities 8 of rails 7 and being restrained against upwards movement by stepped portions 3 of rails 2. There is a small amount of clearance between DIPs 200 and stepped portions 3. Horizontal lateral movement is restricted by means of the extremities 4 of rails 2 engaging slightly inclined side portions 21 of the DIPs. Leads of the DIPs, indicated at 22, lie inside of rails 7 but the apertures 9 in support members 6 will ensure free access for solder.

To restrain a row of DIPs against axial movement, gates 23 are provided at either end of the frame as shown in FIGS. 5 and 7. Side portions 24 are mounted in vertical guides 25 and the gates are movable upwardly against the action of springs 26 to permit removal or insertion of DIPs at either end. When in the rest position shown in FIG. 5, fingers 27 on the gate restrain the DIPs from movement. Adjusting screws, not shown, may be provided for the gates.

The metal used in the apparatus described above is titanium, and in general it should be a corrosion resistant material, capable of withstanding the conditions of use as regards temperature etc, and of a type which does not accept solder.

The arrangement described provides escape passages for poisonous fumes emitted in the soldering process. Furthermore, there is reduced wastage of water during the cleaning process, since runoff escapes down the pins of the DIPs, cleaning the leads and ensuring optimum use of water.

The apparatus can be manufactured in various specifications and sizes depending on the number, size and shape of the components to be carried. Any number of tracks may be provided, of any suitable length, and conveniently the tracks may be long enough to accommodate fourteen DIPs in a row.

To cope with DIPs of different width, the same support members 1 and 6 could be employed, but the mounting posts 15 would have different lateral spacings. With posts which are integral with the frame member 14, this member would be changed although other frame components could be retained. It might be possible to have movable posts 15 which could be re-positioned on the frame member 14. The gate 23 might need to be changed, depending on the positioning of the DIPs.

Referring now to FIGS. 8 and 9, there is disclosed schematically apparatus for loading and unloading a carrier such as that disclosed above, respectively before and after a wave soldering operation. The apparatus includes a base 28 carrying an inclined ramp 29. At the upper end of the ramp 29 is a loading platform 30 which can be pivoted between the position A shown in FIG. 9 and the dotted line position B, at which it is aligned with ramp 29, by means of a pneumatic actuator 31. In use, magazines of DIPs are placed on the loading platform 30 whilst it is in position A, following which the platform is raised to position B. Two gates 32 and 33 on the ramp 29 are then opened, whilst a gate 34 remains closed. DIPs from the platform 30 then slide down the ramp to occupy sections 35 and 36. The platform 30 is then lowered to position A to be reloaded with cartridges of DIPs.

A carrier, as described with reference to FIGS. 1 to 7, is then positioned on the ramp 29 below gate 34 in a locating region 37 where it is automatically latched into place by four latches. The two carrier gates 23 are closed at this stage. The upper gate 23 is then opened, gate 33 is closed, and 1.5 seconds later gate 34 is opened to allow DIPs in section 36 to slide down and fill the tracks in the carrier. When the carrier is full, and section 36 empty, gate 34 is closed, carrier gate 23 is closed, and gate 33 is opened to permit any DIPs in section 35 to slide down into section 36. The latches are then released and the carrier ejected and taken to wave soldering apparatus to be subjected to steps in a wave soldering operation.

If further carriers are to be filled, the process is repeated. A sensor switch 38 prevents platform 30 being raised to position B if there are any DIPs left in section 35, however.

The same apparatus is used to discharge soldered DIPs from a carrier. Thus, empty magazines are placed on unloading platform 39. A full carrier is placed on the ramp 29 and again latched in position. Its lower discharge gate 23 is opened and the DIPs slide down into sections 40 and 41, a gate 42 between them being opened.

The lower carrier gate 23 is then closed. If any DIPs are trapped, further operation is prevented until the blockage is cleared manually. The now empty carrier is then filled as described above, ejected, and replaced by a carrier full of soldered DIPs which are discharged as described above. When section 40 and 41 are filled with soldered DIPs, gate 42 is closed and a gate 43--previously closed--is opened so that the soldered DIPs pass down into the magazines on unloading platform 39. Once all the DIPs in section 41 have been discharged, gate 43 is closed, gate 42 opened, and the filled magazines on platform 39 removed.

The ramp 29 is provided with guides such as those indicated at 44 and 45, to ensure that the DIPs are correctly aligned in rows for the various steps of the unloading/loading process.

The process is repeated as many times as desired. It will be appreciated that the continuous processing which is possible, is brought about by the ability to open each end of the carrier as desired so that once in position it can be emptied and then filled. This in turn is a result of the novel manner of construction which provides easy axial access.

It will be appreciated that the novel loading/unloading apparatus and process could be employed with any other form of carrier which might be designed to have easy axial access at both ends.

Modifications may be possible both to the broad aspects and to the specific arrangements discussed above, whilst maintaining at least some of the advantageous results obtained by the carrier, apparatus or process described. It is intended that these modifications be encompassed by this disclosure, which is not to be limited in its technical scope by the appended claims which define in broad terms the protection sought for the time being. Furthermore, such claims are intended to encompass modifications and are not limited in scope to the specific arrangements described. For example, whilst the carrier is specifically intended for use in the wave soldering of DIPs it may have uses in other soldering operations or other fields, and for other components.

As regards broad aspects disclosed herein, attention is directed particularly to the process for wave soldering a plurality of electrical or electronic components, preferably dual-in-line packages, in which the components are located in tracks in the carrier whilst being subjected to process steps in the wave soldering operation. Attention is also directed particularly to the broad concept of apparatus for loading or unloading the carrier with two gates, including an inclined ramp having a region adapted to receive and releasably latch in place the carrier, means for selectively opening or closing the gates of the carrier when in place, a plurality of gates on the ramp to control the passage of components down the ramp, an unloading platform at the lower end of the ramp, below the region for receiving the carrier, and a loading platform at the upper end of the ramp above the region for receiving the carrier, the loading platform being selectively movable between a first position at which components can be loaded onto the platform and a second position at which components on the platform can slide down the ramp to positions at which they can be loaded into the carrier.