GB2340312A

GB2340312A - Mounting printed circuit boards in housings

Info

Publication number: GB2340312A
Application number: GB9917648A
Authority: GB
Inventors: Brent David Yohn; Robert Alan Kirker
Original assignee: Whitaker LLC
Current assignee: Whitaker LLC
Priority date: 1998-07-27
Filing date: 1999-07-27
Publication date: 2000-02-16
Also published as: GB9917648D0; CN1247450A; TW475831U

Description

2340312 SUBASSEMBLY APPARATUS

Field of the Invention

The present invention relates generally to electronic circuit assemblies and, more particularly, to subassemblies for electronic circuit assemblies which facilitate handling of the subassemblies and the assemblies.

Descrivtion of the Prior Art

A known electronic circuit assembly has a printed circuit)oard member, a housing member which supports and prot( tts the printed circuit board member and a heat sink member which conducts heat away from the printed circuit board member when the assembly is in use. Typically, the members are fastened together to provide the assembly by a plurality of threaded members which are extended through aligned holes in the heat sink member and the printed circuit board member and into threaded bores or openings in the housing member.

At times, it is desired to ship the printed circuit board member and the housing member without the heat sink member. This might occur, for example, when a customer wishes to use his own heat. sink member to satisfy special requirements he might have such as size or shape requirements. In such circumstances, it has been the practice to extend the threaded members through the holes in the printed circuit board member and into the threaded bores in the housing member to fasten the two members together for shipping without a heat sink member.

To attach a heat sink member to the apparatus so shipped, the customer must first remove the threaded members from the apparatus, mount the heat sink member and then reinsert the threaded members to complete the assembly. Besides being somewhat time consuming, the necessity of disconnecting the printed circuit board member from the housing member creates a risk of damaging the printed circuit board member.

Summarv of the Invention According to one aspect, the present invention provides a subassembly for an electronic circuit assembly. The subassembly has a circuit member and a support member which supports the circuit member, and includes a subassembly fastening mechanism on the circuit member and the support member which fastens the circuit member and the support member together to provide the subassembly. In addition, the subassembly has an assembly fastening mechanism with which the subassembly and a heat removing member are fastened together to provide the electronic circuit assembly.

According to a second aspect, the present invention provides an electronic circuit assembly which includes a subassembly comprised of a circuit member, a support member which supports the circuit member and a subassembly fastening mechanism which fastens the circuit member and the support member together to provide the subassembly. The assembly alsb has a heat removing member for removing heat from the circuit member when the assembly is in use, and an assembly fastening mechanism for fastening the subassembly and the heat removing member together to provide the electronic circuit assembly.

With the present invention, the circuit member and the support member can be quickly assembled together without the heat removing member in a subassembly which can be safely shipped and handled. To complete the assembly, it is only necessary to fasten the heat removing member to the subassembly with the assembly fastening mechanism. This can be done without disconnecting the subassembly thus reducing both labor requirements and the risk of damage to the circuit member.

According to a presently preferred embodiment of the invention, the circuit member is a printed circuit board member, the support member is a housing member which supports and protects the printed circuit board member, and the heat removing member is a heat sink member which conducts heat away from the printed circuit board member when the assembly in in use. The subassembly fastening mechanism is a latching mechanism which releasably latches the printed circuit board member to..the housing member. The latching mechanism preferably includes a plurality of latches on the housing member which are positioned to automatically latch onto the printed circuit board member when the printed circuit board member is inserted in the housing member. The latches securely retain the printed circuit board member to the housing member to protect the printed circuit board member during shipping and handling, yet permit the printed circuit board member to be easily separated from the housing member, for example, with a suitable latch- releasing tool, when required for maintenance reasons or the like.

The assembly fastening mechani-sm preferably N includes a plurality of holes in the printed circuit board member aligned with a plurality of threaded bores in the housing member. To attach the heat sink member to the subassembly to complete the electronic circuit assembly, it is only necessary to position the heat sink member on the subassembly and extend threaded members through holes in the heat sink member, the holes in the printed circuit board member and into the threaded bores in the housing member to secure the heat sink member to the subassembly. As indicated previously, it is not necessary to first disconnect the printed circuit board member from the housing member to complete the assembly.

According to a presently most preferred embodiment, the printed circuit board member has upper and lower printed circuit boards, and the plurality of holes of the assembly fastening mechanism are on the upper printed circuit board while the plurality of latches of the subassembly fastening mechanism latch onto the lower printed circuit board.

Brief Description of the Drawings

In order that the present invention may be more readily understood, reference will now be made to the accompanying drawings, in which:- Fig. 1 is an exploded view schematically illustrating an electronic circuit assembly and a subassembly therefor according to one embodiment of the present invention; Fig. 2 illustrates the electronic circuit assembly of Fig. 1 in assembled form; 20 Fig. 3 is a cross-sectional view of the subassembly fastening mechanism of Figs. 1 and 2 taken along the line 3-3 in Fig. 1; Fig. 4 illustrates a housing member of an electronic circuit assembly according to a s(.cond embodiment of the present invention; and Fig. 5 is a cross-sectional view of the subassembly fastening mechanism of Fig. 4 taken along the line 5-5 in Fig. 4.

Description of the Preferred Embodiments

Figs. 1 and 2 schematically illustrate an electronic circuit assembly and a subassembly therefor according to one embodiment of the present invention. The assembly is generally designated by reference number 10 and includes, as principal components thereof, a printed circuit board member 12, a housing member 14 and a heat sink member 16.

In the embodiment illustrated in Figs. 1 and 2, the printed circuit board member 12 includes a pair of printed circuit boards comprising an upper printed circuit board 21 and a lower printed circuit board 22. It should be understood, however, that this is intendedto be exemplary only as the printed circuit board member may comprise any appropriate number of printed circuit boards.

The printed circuit boards 21, 22 are of generally rectangulLr shape and, as is known to those skilled in the art, 6omprise suitable substrates 23, 24 having electronic circuits provided on one or both major surfaces thereof and/or embedded therein. The circuits on the two boards may be separate from one another or electrically connected, for example, by conductive pins extending between the boards. In general, the printed circuits themselves do not form a part of the present invention and thus are only schematically illustrated by dotted lines 25, 26 in Fig. 1 As best shown in Fig. 1, the printed circuit boards 21, 22 are spaced from and substantially parallel to one another and this orientation is maintained by a plurality of, for example, six pins 27 (only some of which are shown in the Fig.) extending between and soldered to the lower surface of the upper printed circuit board 21 and the upper surface of the lower printed circuit board 22. As also shown in Fig. 1, the printed circuits on the printed circuit boards 21, 22 are electrically connected to a connector 31 via flexible cable 32 extending from terminals (not shown) on the printed circuit boards to the connector 31. As is known, the connector 31 is adapted to mate with a complementary connector (not shown) to electrically connect the circuits on the printed circuit boards into an overall system in which the assembly is to be utilized.

With reference still to Fig. 1, the lower printed circuit board 22 is provided with a pair of notches or recesses 35 in the opposed side edges 36 thereof (only one side edge is visible in Fig. 1). As will be explained hereinafter, recesses 35 are positioned to receive latches provided on the housing member 14 to releasably fasten the printed circuit board member to the housing member. In addition, the upper printed circuit board 21 is provided with a plurality of holes 37 which extend through the board adjacent each corner thereof. The holes adjacent the forward edge thereof, in particular, extend through small tabs 39 which extend outwardly from the edge as shown in the Fig. As will also be explained hereinafter, the holes 37 are positioned to receive threaded elements for fastening the components of the electronic circuit assembly 10 together to provide the assembly.

Housing member 14 comprises a molded plastic member having a base 41 and lateral side walls 42. The housing member is substantially open at its forward and rearward ends 44 and 45; however, as shown in Fig. 1, a plate or ledge 46 extends across the forward."end 44 and is attached to the lateral side walls 42. The housing member 14 also includes a plurality of threaded bores or openings 47 adjacent each corner thereof extending downwardly into the housing member from its upper surface. Bores 47 are adapted to receive threaded members 48, for example, screws or bolts, to attach the heat sink member to a subassembly of the printed circuit board member and the housing member as will be explained hereinafter.

The housing member 14 also includes a plurality of latching members or latches 51. As best seen in Figs. I and 3, the latches comprise generally U-shaped members integral with the housing member which extend downwardly and inwardly from the side walls of the housing member and which include upwardly extending deflectable arms 52 adjacent the side walls. A finger 53 having an upper surface which is inclined inwardly and downwardly extends inwardly from the upper end of each arm 52 of the latches 51.

As will be described hereinafter, the latches 51 are positioned to cooperate with the recesses 35 in the lower printed circuit board 22 of printed circuit board member 12 to fasten the printed circuit board member 12 to the housing member 14.

Heat-.sink member 16 is formed of a suitable heat conductive material and comprises a substantially flat base 61 having a plurality of plates or fins 62 extending therefrom. As is well-known, the heat sink member 16 functions to conduct away heat generated when the electronic circuit assembly is in use. The heat sink member 16 also includes a plurality of holes 63 which extend through the base adjacent each corner thereof-to receive the threaded members 48 as shown in Figs. I and 2.

In accordance with the present invention, the printed circuit board member 12 an( the housing member 14 are designed to be fastened together to pro"vide a subassembly 70 of the electronic circuit assembly 10. more particularly, the printed circuit board member 12 is inserted into the housing member 14 downwardly through the open top of the housing member 14. The lower printed circuit board 22 is sized to be received within the housing member between the side walls 42 thereof and, during insertion, the lower printed circuit board 22 extends downwardly into the housing member until the upper printed circuit board 21 engages the upper surface of the housing member. During the insertion process also, the connector 31 is extended through the opening 43 in the forward end 44 of the housing member 14 below the plate 46, as shown in Fig. 2.

As the printed circuit board member 12 is inserted into the housing member 14, the back edges 71 of the recesses 35 in the side edges 36 of the lower printed circuit board 22 engage the inclined upper surfaces of the fingers 53 of the latches 51 on the housing member 14 and deflect the arms 52 thereof outwardly until the back edges clear the fingers 53. The arms then snap inwardly until the fingers extend over the top surface of the lower printed circuit board 22 to fasten the printed arcuit board member 12 to the housing member 14.

When the printed circuit board member 12 is fully inserted in the housing member 14, the latches 51 extend above the lower printed circuit board 22 and prevent it and the printed circuit board member as a whole from moving upwardly in the housing member 14. The upper printed circuit board 21 rests upon the upper surface of the housing member 14 with the holes 37 thereof in alignment with the openings 47 in the housing member. Because the printed circuit boards 21 and 22 are connected to one another by pins 27, the upper printed circuit board 21 defines and limits,.the depth to which.

the lower printed circuit board 22 may extend within the housing member 14 and defines and limits the downward movement of the printed circuit board member as a whole.

Thus the printed circuit board member is safely and securely fastened to the housing member 14.

After the printed circuit board member 12 is fastened to the housing member 14 as described above, a locking member 72 is preferably mounted on the housing member to lock the connector 31 in place within the housing member 14. As shown in the Figs., narrow recesses 73 are provided on the forward end of the housing member, and these are positioned to receive protrusions 74 formed in the sides of the locking member 72 as the locking member is inserted onto the housing member.

The subassembly 70, without the heat sink member 16 attached thereto can be safely handled and shipped while fully protecting the printed circuit board member 12 against damage. To attach the heat sink member 16 to the subassembly 70, it is only necessary to position the heat sink member 16 on the subassembly with the holes 63 thereof aligned with the holes 37 on the upper printed circuit board 21, and to then insert the threaded members 4Q through the aligned holes and into the threaded 1ores 47 in the housing member 14. In the prior art, when it was desired to ship the printed circuit board member and the housing member without the heat sink member; the printed circuit board member and the housing member were attached together with the threaded members. In such circumstances, to later fasten the heat sink member to the apparatus, it was necessary to remove the threaded members, mount the heat sink member to the apparatus and reinsert the threaded members to provide the assembly. This was time consuming and required that the printed circuit board member be disconnected from the housing member increasing the risk of damage to the printed circuit board member.

With the present invention, on the other hand, the threaded members are not used to fasten the printed circuit board member to the housing member. They can, therefore, be shipped separate from the subassembly or provided by the customer. It is also not necessary to disconnect the printed circuit board member from the housing member to fasten the heat sink member. The printed circuit board member is thus better protected against the risk of damage.

Although securely retained in the housing member 14, the printed circuit board member 12 can be readily disconnected and removed from the housing member 14 when desired for servicing or the like. This can be easily accomplished by a suitable latch-releasing tool 75 which can be extended upwardly through slots 76 provided in the base 41 of the housing member 14 in alignment with the latches 51, as shown in Fig. 1, or extended downwardly past an outer edge of circuit board 21 as shown in Fig. 4, as more fully described below. optional recesses (not shown) formed in the outer edge of circuit board 21 substantially parallel the recesses 35 to enhance access to the latches 51 by the tool 75 when the tool 75 is extended downwardly as shown in Fig.

4. The tool is used to deflect the latch arms 52 outwardly to cause the fingers 53 thereon to release the lower printed circuit board 22 to, in turn, release the printed circuit board member 12 from the housing member.

in particular, Figs. 4 and 5 illustrate a housing member 80 accordingly to a second embodiment of the present invention. The housing member 80 differs from housing member 14 primarily in the design of the latches thereon. In particular, in Figs. 4 and 5, the latches 82 comprise deflectable latch arms 3 which are integral with the sidewalls 84 of the housing member, a:nd which extend downwardly from the sidewalls of the housing member. The latch arms have an inwardly facing surface 86 which is inclined downwardly and inwardly of the housing sidewalls, and which terminate in a stepped lower edge 87.

In the embodiment of Figs. 4 and 5, as the printed circuit board member 12 is inserted into the housing member 80, the back edges 71 of the recesses 35 on the lower printed circuit board engage the inwardly facing surfaces 86 of the latch arms 83 and deflect the arms outwardly. When the lower printed circuit board clears - I I - the edges 71, the arms are released and snap inwardly such that the stepped lower edges 87 of the arms extend over the lower printed circuit board to prevent the lower printed circuit board and the printed circuit board member as a whole from moving upwardly in the housing member, thus securing the printed circuit board member to the housing member to provide the subassembly.

As in the previous embodiment, the printed circuit board member can be disconnected from the housing member by a suitable tool 75. In this embodiment and as previously described, the tool is extended downwardly into the housing member 80 along slots 88 formed in the sidewalls-84 of the housing member to deflect the latch arms 83 outwardly to release the lower printed circuit board member.

While what has been described constitute presently preferred embodiments of the invention, it should be recognized that the invention could take numerous other forms. It should be understood, therefore, that the invention is to be limited only insofar as is required by the scope of the following claims.

ell' -12

Claims

1 A subassembly for an electronic circuit assembly, said subassembly including:

a circuit member; a support member which supports said circuit member; a subassembly fastening mechanism on said circuit member and said support member which fastens said circuit member and said support member together to provide said subassembly; and an assembly fastening mechanism on said subassembly fori fasteping said subassembly and a heat removing member tofether to provide said electronic circuit assembly.

2. The subassembly of claim 1 wherein said subassembly fastening mechanism comprises a latching mechanism for releasably latching said circuit member and said support member together.

3. The subassembly of claim 2 wherein said latching mechanism comprises at least one latch on one of said circuit member and said support member which latches the other of said circuit member and said support member.

4. The subassembly of claim 3 whetein said at least one latch comprises a plurality of latches on said support member which latch said circuit member.

5. The subassembly of claim 4 wherein said plurality of latches comprise a plurality of deflectable arms on side walls of said support member, said plurality of deflectable arms each having a surface on an end thereof for extending over said circuit member for latching said circuit member.

6. The subassembly of claim 4 wherein said support member includes tool receiving portions for receiving a releasing tool for engaging said plurality of latches for disconnecting said circuit member and said support member.

7. The subassembly of claim 3 wherein said assembly fastening mechanism includes threaded member receiving structure on said subassembly which receives at least one threaded member for fastening said heat removing member and said subassembly together to provide said assembly.

8. The subassembly of claim 7 wherein said threaded member receiving structure includes a plurality of threaded bores in said support member and a plurality of holes in $aid circuit member aligned with said plurality of threadd bores in said support member for-receiving a plurality of threaded members for fastening said heat removing member and said subassembly together.

9. The subassembly of claim 4 wherein said circuit member comprises a printed circuit board member having a plurality of printed circuit boards and wherein said plurality of latches latch one of said plurality of printed circuit boards.

10. The subassembly of claim 9 wherein said printed circuit board member includes upper and lower printed circuit boards, and wherein said plurality of latches latch said lower printed circuit board and wherein said assembly fastening mechanism includes a plurality of holes in said upper printed circuit board.

11. The subassembly of claim 10 wherein said upper and lower printed circuit boards are attached together by pins extending therebetween.

12. A subassembly for an electronic circuit assembly, said subassembly including:

a printed circuit board member comprising at least one printed circuit board; a housing member for receiving and supporting said printed circuit board member; -14 a first fastening mechanism on said printed circuit board member and said housing member which releasably fastens said printed circuit board member and said housing member together to provide said subassembly; and a second fastening mechanism on said subassembly which fastens said subassembly and a heat sink member together to provide said electronic circuit assembly.

13. The subassembly of claim 12 wherein said first fastening mechanism comprises at least one releasable latching mechanism on said printed circuit board member and said housing member for fastening said printed circuit board member and said housing member together, and said second fastening mechanism comprises at least one threaded member receiving structure on said subassembly which receives at least one threaded member for fastening said heat sink member and said subassembly.

14. The subassembly of claim 13 wherein said at least one releasable latching mechanism comprises a plurality of latching mechanisms, and wherein said at least one threaded member receiving structure comprises a plurality of threaded member receiving structures.

15. The subassembly of claim 12 wherein said printed circuit board member has upper and lower printed circuit boards, and wherein said first fastening mechanism is on said lower printed circuit board and said housing member and wherein said second fastening mechanism is on said upper printed circuit board and said housing member.

16. An electronic circuit assembly comprising:

a subassembly, said subassembly including a circuit member, a support member which supports said circuit member and a subassembly fastening mechanism which fastens said circuit member and said support member together to provide said subassembly; a heat removing member which conducts heat away from said circuit member; and an assembly fastening mechanism on said subassembly and said heat removing member which fastens said heat removing member and said subassembly together to provide said assembly.

17. The assembly of claim 16 wherein said subassembly fastening mechanism comprises a latching mechanism for releasably latching said circuit member and said support member together.

18. The assembly of claim 17 wherein said latching mechanism comprises a plurality of latches on said support member which latch said circuit member.

19. The Assembly of claim 18 wherein said assembly fastenin4mechanism includes at least one threaded member for fastening said heat removing member and said subassembly together.

20. The assembly of claim 19 wherein said at least one threaded member comprises a plurality of threaded members.

21. An electronic circuit assembly constructed and arranged substantially as hereinbefore described with reference to Figures 1, 2 and 3 or Figures 4 and 5 of the accompanying drawings.

22. A subassembly for an electronic circuit assembly constructed and arranged'substantially as hereinbefore described with reference to Figures 1, 2 and N 3 or Figures 4 and 5 of the accompanying drawings.