GB2399310A

GB2399310A - A pallet for supporting a printed circuit board during soldering

Info

Publication number: GB2399310A
Application number: GB0312150A
Authority: GB
Inventors: Enda Joseph Moran; Mark Colman Duffy
Original assignee: Hi Key Ltd
Current assignee: Hi Key Ltd
Priority date: 2003-03-11
Filing date: 2003-05-27
Publication date: 2004-09-15
Also published as: GB0312150D0

Abstract

A pallet (1) for supporting at least one (e.g. two) PCBs during soldering of electrical components to the PCB by a solder wave of a solder bath as the pallet (1) is being conveyed along the solder bath over the solder wave, comprises a base plate (15) in which at least one main locating recess (16) is formed for receiving and locating the PCB(s)(2). Communicating openings (17,18) through the main locating recess(es)(16) expose selected areas of the PCB(s) to the solder wave. Locating pins (22) may locate the PCB(s) with the selected areas aligned with the communicating openings (17,18). A retainer, preferably in the form of a top plate (30) pivotally connected to the base plate (15) by hinges (32) is pivoted between a release position and a retaining position for retaining the PCB(s) in tight abutment engagement with the main locating recess(es)(16). A latch (40) secures the top plate (30) in the retaining position. The advantage of pivotally connecting the top plate (30) to the base plate (15) is that the top plate (30) is pre-aligned with the base plate (15) and no further alignment is required, and thus by merely pivoting the top plate (30) into the retaining position and securing the top plate (30) with the latch (40) the PCBs (2) are readily easily aligned and secured in the pallet (1).

Description

"A pallet for supporting a printed circuit board during soldering and a

method for soldering a component to the printed circuit board" The present invention relates to a pallet for supporting a printed circuit board (PCB) during soldering, and in particular, during soldering of electronic components assembled on the PCB to the PCB by a solder wave. The invention also relates to a method for soldering at least one component assembled on the PCB to the PCB.

Soldering methods for soldering electronic components to a PCB are well known.

One such soldering method requires passing the PCB over a solder wave developed in a solder bath so that the solder wave impinges on the underside of the PCB, and solder from the solder wave solders the components to the PCB. This soldering method is particularly suitable for soldering electronic components to a PCB whereby the electronic components are assembled on one side, for example, a top side of the PCB, and electrical conductors from the components extend through bores in the PCB to an underside thereof. The underside of the board with the electrical conductors extending therefrom is passed over the solder wave and solder from the solder wave solders the electrical conductors to electrically conductive tracks on the underside of the PCB or electrically conductive vies through the PCB.

In general, this soldering method is generally automated, and a conveyor is provided for conveying the PCB along the solder bath over the solder wave. The conveyor in general comprises a pair of spaced apart side conveying chains located on respective opposite sides of the solder bath, and each chain is provided with a plurality of spaced apart PCB engaging lugs which extend upwardly for engaging respective PCBs for sequentially conveying the PCBs over the solder wave at a predetermined rate, sufficient for ensuring adequate soldering of the electrical conductors extending from the components to the underside of the PCBs.

s While such a soldering method is suitable for many types of PCBs, it suffers from a particularly serious disadvantage where only some of the components are to be soldered by solder from the solder wave. For example, it is now common practice to locate components on the respective opposite sides of a PCB, and thus, it is important that components on the side of the PCB which is exposed to the solder wave should not be subjected to the solder wave, since otherwise the temperature of the solder wave would damage the component.

To overcome this problem it is known to provide pallets on which the PCBs are supported while being conveyed over the solder wave. The pallets are arranged to receive the PCBs, and to mask those areas of the underside of the PCB which are not to be exposed to the solder wave. Communicating openings are provided! through the pallet for exposing those areas of the PCB which are to be subjected to the solder wave. In general, a retaining member which may be a retaining plate or other suitable retaining member secures the PCBs in position on the pallet. Such retaining members are completely releasable from the pallet for facilitating placing and removal of PCBs on the pallet, and are secured to the pallet typically by screws or other suitable fasteners.

Such pallets with such retaining members while they do mask the areas of the PCB which are not to be subjected to the solder wave, nonetheless suffer from a number of disadvantages. By virtue of the fact that the retaining member is completely separable from the pallet, alignment of the retaining member with the pallet tends to! be a relatively slow procedure and also can suffer from a lack of accuracy.

s Additionally, the alignment of the PCB with the communicating openings can be I problematical during securing of the retaining members to the pallet. If the PCB is not properly aligned with the pallet prior to securing of the retaining member, the PCB will remain misaligned during the soldering process with consequential I problems.

A further disadvantage of such known pallets is that since the retaining members are I completely separable from the pallets, they tend to be mislaid, and furthermore, tend to be mixed up with retaining members of other pallets. It will be readily apparent to those skilled in the art that specific panels are required for each different type of IS PCB. Thus, if the retaining member of one pallet becomes disassociated from that pallet and associated with a pallet for an entirely different type of PCB, the pallets are unusable. This, thus, leads to inefficiency in the use of such pallets and in particular, in the carrying out of the soldering method.

There is therefore a need for a pallet for supporting a PCB during soldering, and there is also a need for a method for soldering at least one component assembled on the PCB to the PCB.

The present invention is directed towards providing such a pallet and a method.

According to the invention there is provided a pallet for supporting a printed circuit board (PCB) having a plurality of electronic components assembled thereon, along a conveyor over a solder wave of a solder bath for selectively soldering some of the s components assembled thereon to the PCB, the pallet comprising a base plate for supporting the PCB thereon, at least one communicating opening extending through the base plate for exposing a selected area of the PCB to the solder wave, a locating means for locating the PCB on the base plate with the selected area of the PCB aligned with the communicating opening, a retaining means co-operating with the 1() PCB for retaining the PCB on the base plate with the selected area aligned with the communicating opening, the retaining means being pivotally connected to the base plate and being pivotal from a retaining position co-operating with the base plate and the PCB for retaining the PCB on the base plate with the selected area aligned with the communicating opening, and a release position for facilitating removal of the PCB from the pallet, and a securing means for releasably securing the retaining means in the retaining position.

In one embodiment of the invention the retaining means is engageable with one or more of the components of the PCB.

In another embodiment of the invention the retaining means is engageable with one or more electronic components on the PCB.

In a further embodiment of the invention the retaining means is engageable with a housing of the PCB.

Preferably, the retaining means comprises a top plate. Advantageously, the top plate is of area at least the area of the PCB. s

In one embodiment of the invention the top plate is recessed for accommodating a component of the PCB.

In another embodiment of the invention an abutment means is provided on the top plate for engaging the PCB and for urging the PCB into the locating means.

In a further embodiment of the invention the abutment means comprises an abutment member for engaging a component on the PCB. Alternatively, the abutment means comprises an abutment pin extending from the top plate for IS engaging the PCB.

Preferably, the retaining means is pivotally connected to the base plate by a hinge, the hinge defining a pivot axis about which the retaining means is pivotal between the retaining position and the release position. Advantageously, a pair of spaced apart hinges defining the pivot axis is provided.

In one embodiment of the invention the securing means comprises a latch.

Preferably, the latch is mounted on the base plate and is releasably engageable with the retaining means. Advantageously, the latch extends through a latching opening in the retaining means. Preferably, the latching opening is formed by an elongated latch accommodating slot dimensioned for accommodating the latch therethrough.

In one embodiment of the invention the latch is operable between a latched position latching the retaining means and an unlatched position disengaged from the retaining means. Preferably, the latch is pivotal about a latching axis between the latched and unlatched positions. Advantageously, the latch is pivotal about the latching axis through 90 between the latched and the unlatched positions. Ideally, the latch extends on respective opposite sides of the latch axis.

In one embodiment of the invention the locating means comprises at least one locating pin extending from the base plate for engaging a corresponding bore in the PCB for locating and aligning the selected area of the PCB with the communicating opening. Preferably, a pair of spaced apart locating pins are provided for engaging respective corresponding spaced apart bores extending through the PCB.

In one embodiment of the invention a main locating recess is provided in the base plate for locating the PCB on the base plate. Advantageously, each locating pin is provided in the main locating recess. 2()

In another embodiment of the invention at least one secondary locating recess is provided within the main locating recess for accommodating components mounted on an underside of the PCB.

In a still further embodiment of the invention a portion of the base plate acts to mask an area of the PCB which is to be protected from solder.

Preferably, a peripheral portion of the base plate extending around the communicating opening is provided for tightly abutting the PCB for preventing ingress of solder between the PCB and the base plate adjacent the communicating opening.

In one embodiment of the invention the base plate is adapted for placing on a I o conveyor for conveying the PCB over the solder wave. Preferably, the base plate is adapted for placing on a pair of spaced apart conveyors located on respective opposite sides of a solder bath in which the solder wave is generated.

Advantageously, the base plate is adapted for engaging lugs extending from the respective conveyors for conveying the PCB over the solder wave. Ideally, the base plate is adapted for engaging lugs extending from respective opposite conveying chains extending on respective opposite sides of a solder bath in which the solder wave is generated.

Additionally the invention provides a method for selectively soldering at least one of a plurality of electronic components assembled on a PCB to the PCB, the method comprising the steps of placing the PCB with the components assembled thereon on a base plate of a pallet with the PCB located by a locating means on the base plate with a selected area of the PCB exposed through a communicating opening in the base plate, retaining the PCB on the base plate with the selected area aligned with the communicating opening by a pivotally mounted retaining means, securing the retaining means in a retaining position by a securing means with the PCB retained on the base plate in alignment with the communicating opening, and passing the pallet with the PCB retained thereon over a solder wave of a solder bath for applying solder from the solder wave to the selected area of the PCB exposed through the communicating opening.

In one embodiment of the invention the pallet is passed over the solder wave on a conveying means. Advantageously, the pallet is passed over the solder wave on a conveying means formed by a pair of spaced apart side conveyors located on respective opposite sides of the solder bath. Preferably, the side conveyors on the respective opposite sides of the solder bath are chain conveyors. Ideally, the pallet is engaged with a pair of corresponding lugs extending from the respective side conveying chains.

Further, the invention provides a PCB having a plurality of electronic components assembled thereon, and at least one of the components having been soldered to the PCB by the method according to the invention.

In one embodiment of the invention the PCB is placed in and secured in the pallet according to the invention while the at least one component is being soldered to the PCB.

The invention also provides a PCB having a plurality of electronic components assembled thereon, and at least one of the components having been soldered to the PCB using the pallet according to the invention.

The advantages of the invention are many. A particularly important advantage of the s invention is that a PCB can readily easily be located and secured in the pallet with minimal effort and with maximum accuracy. By virtue of the fact that the retaining means is pivotally connected to the base plate, the retaining means is automatically accurately aligned with the base plate when pivoted into the retaining position.

Thus, there is no need for additional alignment of the retaining means with the base plate or with the PCB. Once the PCB is accurately located on the base plate by the locating means, no further alignment of the PCB with the retaining means or of the retaining means with the pallet is required. Furthermore, by virtue of the fact that the retaining means is pivotally connected to the base plate, there is no danger of the retaining means being separated from the base plate, and thus, there is no danger of t5 the retaining means being mislaid or mismatched with pallets for other PCBs.

Furthermore, by virtue of the fact that the retaining means is pivotally connected to the base plate, the securing of the retaining means in the retaining position is a simple matter of merely latching the retaining means in the retaining position by the securing means. There is no need for a fastening means such as screws, toggle clamps or the like for securing the retaining means in the retaining position which would require alignment with the retaining means and the base plate after the retaining means had been aligned with the base plate.

An additional advantage of the pallet according to the invention is that there is no danger of components on the PCB being damaged as a result of excessive force being applied to the retaining means for retaining the PCB in engagement with the base plate. By virtue of the fact that the retaining means is pivotally connected to the base plate, and a securing means is provided for securing the retaining means in s the retaining position, once the securing means is operated to secure the retaining means in the retaining position, the force applied to the PCBis controlled by dimensioning the spacing between the retaining means and the base plate when the retaining means is in the retaining position. This is determined at the design stage of the pallet. When the securing means is provided by a latch, the positioning of the to latch and the positioning of the retaining means relative to the base plate can be predetermined, thereby predetermining the force to which the PCBis subjected by the retaining means. In this way, there is no danger of over- tightening the retaining means relative to the base plate and the PCB, which can otherwise occur in pallets known heretofore.

A further advantage of the invention is that there is no danger of a PCB being incorrectly located in the locating means, since the locating means is arranged to receive the PCB in one orientation and one orientation only, namely, the correct orientation. Any attempt to enter the PCB in the locating means in an incorrect orientation is prevented by the locating means.

Accordingly, the pallet according to the invention provides a relatively simple solution to a number of problems which lead to inefficiency in the selective soldering of components on a PCB to the PCB.

The invention will be more clearly understood from the following description of a preferred embodiment thereof, which is given by way of example only, with reference to the accompanying drawings, in which: s Fig. 1 is a perspective view of a pallet according to the invention for supporting two PCBs during soldering, Fig. 2 is another perspective view of the pallet of Fig. 1, 1() Fig. 3 is an underneath plan view of the pallet of Fig. 1, Fig. 4 is a transverse cross-sectional side elevational view of the pallet of Fig. Fig. 5 is a view similar to Fig. 4 of the pallet of Fig. 1 in use, Fig. 6 is an underneath plan view of one of the PCBs for which the pallet of Fig. 1 is suitable for supporting, 2() Fig. 7 is a perspective view of a pallet according to another embodiment of the invention for supporting two PCBs during soldering, Fig. 8 is another perspective view of the pallet of Fig. 7 illustrating the two ]2 PCBs located in the pallet, and Fig. 9 is a view similar to Fig. 5 of the pallet of Fig. 7 in use.

Referring to Figs. 1 to 5 of the drawings, there is illustrated a pallet according to the invention, indicated generally by the reference numeral 1, for supporting two similar I PCBs 2 with a plurality of electronic components 3 assembled thereon along a I conveyor 4 over a solder wave (not shown) generated in a solder bath 5 for selectively soldering some of the components 3 assembled to the PCBs 2. One of the PCBs 2 is illustrated in Fig. 6 and will be briefly described below. Only a portion of the solder bath 5 is illustrated, however, such solder baths which generate a solder wave will be well known to those skilled in the art. Typically, a pair of side chain conveyors 4 located on respective opposite sides of the solder bath 5 sequentially convey the pallets 1 with PCBs located thereon over the solder bath 5.

Spaced apart lugs (not shown) extending upwardly from the respective side chain conveyors 4 engage the pallets 1 for conveying the pallets 1 over the solder bath 5.

Before describing the pallet 1, the PCB 2 will first be briefly described. In this embodiment of the invention the PCB 2 is located in one half of a housing 6, and is provided with the electronic components 2 which are to be soldered to the PCB 2 by the solder wave assembled on a top side 8 of the PCB, see Fig. 5. Electrical conductors 9 extend through the PCB 2 to an underside 10 thereof, at which the electrical conductors 9 are soldered to the PCB. However, as well as the components 3 which are to be soldered by the solder wave, the PCB 2 also comprises a plurality of surface mounted components 12 which are located on the underside 10 of the PCB 2. It is essential that the surface mounted components 12 be protected from the solder wave during soldering of the components 3 to the PCB 2 by the solder wave. The pallet 1 according to the invention fulfils this function.

The pallet 1 comprises a base plate 15 of composite Delmat material which is I adapted for engagement with the lugs (not shown) of the side conveyor chains 4 for I conveying two of the PCBs 2 over the solder wave. The composite Delmat material is sufficiently heat resistant to withstand the effects of the solder. A pair of main to locating recesses 16 are provided in the base plate 15 for receiving the respective PCBs 2. In Fig. 2 one of the PCBs 2 located in its housing 6 is illustrated in one of the main locating recesses 16. Two communicating openings 17 and 18 extend through the base plate 15 in each main locating recess 16 for exposing selected i areas 19 and 20, respectively, of the underside 10 of the PCB 2 where the electrical I S conductors 9 of the components 3 to be soldered to the PCB 2 are located. The remaining area 21 of the respective main locating recesses 16 act as a mask for protecting the remaining area of the underside 10 of the PCB from the solder wave.

Locating means for locating the respective PCBs 2 in the main locating recesses 16 with the selected areas 19 and 20 of the PCBs 2 aligned with the communicating openings 17 and 18 are provided with respective pairs of locating pins 22 which extend upwardly into the main locating recesses 16 for engaging corresponding bores 23 in the PCB 2, see Fig. 6. In this embodiment of the invention since the base plate 15 is of composite Delmat material, the locating pins 22 are of steel, and are mounted on pin carriers 25 also of steel, which are secured to the base plate 15 by screws 26. The pin carriers 25 are located in carrier recesses 28 on the underside of the base plate 15 and extend into the main locating recesses 16 through carrier accommodating slots (not shown).

A retaining means, in this embodiment of the invention a top plate 30 of glass-fibre material sold under the trade name ECP-plus, is provided for retaining the PCBs 2 on the base plate 15 located by the locating pins 22 in the main locating recesses 16. The top plate 30 is pivotally connected to the base plate 15 by a pair of spaced apart hinges 32 which are mounted on the base plate 15 by corresponding spacer mounting blocks 33. Screws 34 through the hinges 32 and the mounting blocks 33 secure the hinges to the base plate 15, while screws 35 through the hinges 32 secure the hinges 32 to the top plate 30. The top plate 30 is pivotal about a main pivot axis 36 defined by the hinges 32 between a release position illustrated in Fig. 2 I S for facilitating placing and removal of PCBs 2 on the base plate 15, and a retaining position illustrated in Figs. 1, 4 and 5 co-operating with the base plate 15, the PCBs 2 and the locating pins 22 for retaining the PCBs 2 on the base plate 15 located in the main locating recesses 16 with the selected areas 19 and 20 accurately aligned with the corresponding communicating openings 17 and 18. 2()

A securing means for releasably securing the top plate 30 in the retaining position comprises a latch 40 which is pivotally mounted on a pivot support 41 extending from a mounting member 42 secured to the base plate 31. A latching opening provided by a latch accommodating slot 44 extending through the top plate 30 accommodates the latch 40 therethrough. The latch 40 is pivotal on the pivot support 41 about a central latching axis 43 through 90 for engaging the top plate 30 adjacent respective opposite sides of the slot 44.

Component accommodating recesses 45 are formed in the top plate 30 for accommodating a projection 46 extending from the housing 6 of the PCB 2. The mounting blocks 33 of the hinges 32 and the mounting member 42, and the position of the latch 40 above the base plate 15 is such that when the top plate 30 is secured by the latch 40 in the retaining position the top plate 30 tightly abuts a top surface 47 lD of bosses 48 of the housing 6 of the PCB 2 for retaining the PCB 2 in tight secure engagement with the main locating recess 16 for preventing any danger of the PCB 2 being urged upwardly out of the main locating recess 16 by the action of the solder wave during soldering.

Secondary recesses 50 are formed in each main locating recess 16 for accommodating the surface mounted components 12 on the underside 10 of the PCB 2. Peripheral portions 52 extend completely around each communicating opening 17 and 18 in the respective main locating recesses 16 for tightly abutting the PCBs 2 adjacent the communicating openings 17 and 18 for preventing ingress of solder from the solder wave into the secondary recesses 50, which would otherwise damage the surface mounted components 12. By virtue of the fact that the mounting blocks 33 and the mounting member 42 as well as the latch 40 are dimensioned and positioned so that when the top plate 30 is in the retaining position, the top plate 30 tightly abuts the top surface 47 of the housing 6 of the PCBs 2, and thus the PCBs 2 It, are urged into tight engagement with the peripheral portions 52, thereby preventing any danger of the ingress of solder from the solder wave into the secondary recesses 50.

s A wavebreaker bar 53 of composite Delmat material extends along a leading edge of the base plate 15 to act as a barrier to any solder which might otherwise flow over the leading edge of the base plate 15. Two reinforcing bars 55 of aluminium extend along opposite side edges of the base plate 15 for reinforcing the base plate 15.

l0 In use, with the components 3 assembled on the PCBs 2, and the PCBs 2 located in their respective housings 6 and secured therein, the PCBs 2 are located in the main locating recesses 16 by engaging the bores 23 in the PCBs 2 with the corresponding pairs of locating pins 22. The top plate 30 is then pivoted from the release position in the direction of the arrow A, see Fig. 2, to the retaining position, and is secured I S therein by the latch 40. The pallet 1 is then placed on the side conveying chains 4 with the lugs (not shown) of the respective conveying chains 4 abutting the trailing end of the pallet 1, and the pallet 1 with the PCBs 2 secured therein is conveyed along the solder bath 5 over the solder wave generated therein. The electrical conductors 9 in the respective selected areas 19 and 20 of the PCBs 2 are exposed through the communicating opening 17 and 18 to the solder wave, and thus are soldered to the PCB 2.

On completion of the soldering process the latch 40 is unlatched and the top plate 30 is pivoted from the retaining position in the direction of the arrow B. see Fig. 1, to the release position, and the PCBs 2 are removed from the pallet 1, and replaced by the next pair of PCBs 2 in which the electrical conductors 9 of the components 3 are to be soldered to the PCB.

Referring now to Figs. 7 to 9, there is illustrated a pallet according to another embodiment of the invention, indicated generally by the reference numeral 70. The pallet 70 is substantially similar to the pallet 1 and similar components are identified by the same reference numerals. The main difference between the pallet 70 and the pallet 1 is that the retaining means for retaining the PCBs 2 on the base plate 15 located by the locating pins 22 in the main locating recesses 16 comprises a pair of top plates 71. The top plates 71 are each hingedly connected to the base plate 15 by a corresponding hinge 32 which is mounted on a corresponding spacer mounting block 33. Additionally, in this embodiment of the invention each top plate 71 is provided with an abutment means comprising an abutment member 72 for engaging IS a component on the PCB 2, which in this embodiment of the invention is a microprocessor 74. Latching recesses 75 are provided in each top plate 71 for accommodating a latch 40 which is similar to the latch 40 of the pallet 1, and the latch 40 is pivotal through 90 for engaging the top plates 71 adjacent the latching recesses 75 for retaining the top plates 71 in the retaining position. 2)

Otherwise, the pallet 70 and its operation is similar to that of the pallet 1 described with reference to Figs. 1 to 5.

While specific pallets have been described, it will be readily apparent to those skilled 1X in the art that the pallets according to the invention may be of any suitable design and construction, and the design of the pallets will be determined by the PCBs to be supported therein. Each pallet may be designed to support one, two or indeed, more PCBs. The number of PCBs which in general, would be supported by a pallet will be s determined by the size of the PCB.

It is also envisaged that instead of engaging a housing of a PCB or a component on a PCB, the top plate may be arranged to, or may carry an abutment member which would directly abut the PCB when the top plate is in the retaining position. 1()

It is also envisaged that the abutment means may be provided by abutment pins extending from the top plate for engaging the PCB when the top plate is in the retaining position for retaining the PCB in engagement in the main locating recess.

Such abutment pins, typically, would extend from the top plate and would terminate in their respective free ends in abutment heads which would engage the PCB. In certain cases, it is envisaged that such abutment pins may be spring loaded relative to the top plate, and the spring urging action of the abutment pins would be such as to spring urge the PCB into engagement in the main locating recess.

It will also of course be appreciated that any number of communicating openings may be provided, and the number of communicating openings, whether one or more, will be determined by the number of selected areas to be exposed to the solder wave.

Claims

Claims 1. A pallet for supporting a printed circuit board (PCB) having a

plurality of electronic components assembled thereon, along a conveyor over a solder wave of a solder bath for selectively soldering some of the components assembled thereon s to the PCB, the pallet comprising a base plate for supporting the PCB thereon, at least one communicating opening extending through the base plate for exposing a selected area of the PCB to the solder wave, a locating means for locating the PCB on the base plate with the selected area of the PCB aligned with the communicating opening, a retaining means co-operating with the PCB for retaining the PCB on the base plate with the selected area aligned with the communicating opening, the retaining means being pivotally connected to the base plate and being pivotal from a retaining position co-operating with the base plate and the PCB for retaining the PCB on the base plate with the selected area aligned with the communicating opening, i and a release position for facilitating removal of the PCB from the pallet, and a l s securing means for releasably securing the retaining means in the retaining position. 1
2. A pallet as claimed in Claim 1 in which the retaining means is engageable with one or more of the components of the PCB.
3. A pallet as claimed in Claim 1 or 2 in which the retaining means is t engageable with one or more electronic components on the PCB.
4. A pallet as claimed in any preceding claim in which the retaining means is engageable with a housing of the PCB.
5. A pallet as claimed in any preceding claim in which the retaining means comprises a top plate.
6. A pallet as claimed in Claim 5 in which the top plate is of area at least the area of the PCB.
7. A pallet as claimed in Claim 5 or 6 in which the top plate is recessed for accommodating a component of the PCB.
8. A pallet as claimed in Claim 5 or 6 in which an abutment means is provided on the top plate for engaging the PCB and for urging the PCB into the locating means.
9. A pallet as claimed in Claim 8 in which the abutment means comprises an abutment member for engaging a component on the PCB.
10. A pallet as claimed in Claim 8 in which the abutment means comprises an abutment pin extending from the top plate for engaging the PCB. 2()
11. A pallet as claimed in any preceding claim in which the retaining means is pivotally connected to the base plate by a hinge, the hinge defining a pivot axis about which the retaining means is pivotal between the retaining position and the release position.
12. A pallet as claimed in Claim 11 in which a pair of spaced apart hinges defining the pivot axis is provided.
13. A pallet as claimed in any preceding claim in which the securing means comprises a latch.
14. A pallet as claimed in Claim 13 in which the latch is mounted on the base plate and is releasably engageable with the retaining means. I
15. A pallet as claimed in Claim 14 in which the latch extends through a latching opening in the retaining means.
16. A pallet as claimed in Claim 15 in which the latching opening is formed by an elongated latch accommodating slot dimensioned for accommodating the latch therethrough.
17. A pallet as claimed in any of Claims 14 to 16 in which the latch is operable between a latched position latching the retaining means and an unlatched position disengaged from the retaining means.
18. A pallet as claimed in Claim 17 in which the latch is pivotal about a latching axis between the latched and unlatched positions. l
19. A pallet as claimed in Claim 18 in which the latch is pivotal about the latching axis through 90 between the latched and the unlatched positions.
20. A pallet as claimed in Claim 18 or 19 in which the latch extends on respective s opposite sides of the latch axis.
21. A pallet as claimed in any preceding claim in which the locating means comprises at least one locating pin extending from the base plate for engaging a corresponding bore in the PCB for locating and aligning the selected area of the lo PCB with the communicating opening.
22. A pallet as claimed in Claim 21 in which a pair of spaced apart locating pins are provided for engaging respective corresponding spaced apart bores extending through the PCB.
23. A pallet as claimed in Claim 21 or 22 in which a main locating recess is provided in the base plate for locating the PCB on the base plate.
24. A pallet as claimed in Claim 23 in which each locating pin is provided in the 2() main locating recess.
25. A pallet as claimed in Claim 23 or 24 in which at least one secondary locating recess is provided within the main locating recess for accommodating components mounted on an underside of the PCB.
26. A pallet as claimed in any preceding claim in which a portion of the base plate acts to mask an area of the PCB which is to be protected from solder.
27. A pallet as claimed in any preceding claim in which a peripheral portion of the base plate extending around the communicating opening is provided for tightly abutting the PCB for preventing ingress of solder between the PCB and the base plate adjacent the communicating opening.

lo
28. A pallet as claimed in any preceding claim in which the base plate is adapted for placing on a conveyor for conveying the PCB over the solder wave.
29. A pallet as claimed in any preceding claim in which the base plate is adapted for placing on a pair of spaced apart conveyors located on respective opposite sides of a solder bath in which the solder wave is generated.
30. A pallet as claimed in Claim 29 in which the base plate is adapted for engaging lugs extending from the respective conveyors for conveying the PCB over the solder wave. 2()
31. A pallet as claimed in Claim 30 in which the base plate is adapted for engaging lugs extending from respective opposite conveying chains extending on respective opposite sides of a solder bath in which the solder wave is generated.
32. A pallet for supporting a PCB having a plurality of electronic components assembled thereon along a conveyor over a solder wave of a solder bath for selectively soldering some of the components assembled thereon to the PCB, the pallet being substantially as described herein with reference to and as illustrated in the accompanying drawings.
33. A method for selectively soldering at least one of a plurality of electronic components assembled on a PCB to the PCB, the method comprising the steps of placing the PCB with the components assembled thereon on a base plate of a pallet with the PCB located by a locating means on the base plate with a selected area of the PCB exposed through a communicating opening in the base plate, retaining the PCB on the base plate with the selected area aligned with the communicating opening by a pivotally mounted retaining means, securing the retaining means in a retaining position by a securing means with the PCB retained on the base plate in alignment with the communicating opening, and passing the pallet with the PCB retained thereon over a solder wave of a solder bath for applying solder from the solder wave to the selected area of the PCB exposed through the communicating opening.
34. A method as claimed in Claim 33 in which the pallet is passed over the solder wave on a conveying means.
35. A method as claimed in Claim 33 or 34 in which the pallet is passed over the solder wave on a conveying means formed by a pair of spaced apart side conveyors located on respective opposite sides of the solder bath.
36. A method as claimed in Claim 35 in which the side conveyors on the respective opposite sides of the solder bath are chain conveyors.
37. A method as claimed in Claim 35 or 36 in which the pallet is engaged with a pair of corresponding lugs extending from the respective side conveying chains.
38. A method for selectively soldering at least one of a plurality of electronic lo components assembled on a PCB to the PCB, the method being substantially as described herein with reference to and as illustrated in the accompanying drawings.
39. A PCB having a plurality of electronic components assembled thereon, and at least one of the components having been soldered to the PCB by the method as claimed in any of Claims 33 to 38.
40. A PCB as claimed in Claim 39 in which the PCB is placed in and secured in the pallet according to any of Claims 1 to 32 while the at least one component is being soldered to the PCB.
41. A PCB having a plurality of electronic components assembled thereon, and at least one of the components having been soldered to the PCB using the pallet as claimed in any of Claims 1 to 32.