EUROPEAN PATENT SPECIFICATION

Transcription

1 J t Europaisches Patentamt European Patent Office Office europeen des brevets (11) Publication number: B1 EUROPEAN PATENT SPECIFICATION Date of publication of patent specification : Bulletin 91/39 (51) Intel.5: H05K 7/10 21) Application number: (22) Date of filing : (Si) International application number: PCT/GB88/00183 International publication number: WO 88/ Gazette 88/22 MOUNTING ARRANGEMENT FOR A CHIP CARRIER. (30) Priority : GB GB Proprietor : Varelco Limited Exning Road Newmarket, Suffolk CB8 OBB (GB) (43) Date of publication of application : Bulletin 89/12 Inventor : SPENCER, Arthur, Thomas 28 Courtlands Drive Biggleswade Bedfordshire SG18 8PQ (GB) Publication of the grant of the patent : Bulletin 91/39 Representative : Nash, Keith Wilfrid et al ( 4) Designated Contracting States : DE GB IT KEITH W. NASH & Co. Pearl Assurance House Regent Street Cambridge CB2 1 DP (GB) CO in 9 References cited : EP-A DE-A US-A US-A US-A CO Q. UJ Note : Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement It shall not be deemed to have been filed until the opposition fee has been paid (Art 99(1) European patent convention). Jouve, 18, rue Saint-Denis, PARIS

2 ' Description, Field of the invention 5 This invention relates to an arrangement for mounting an integrated circuit chip carrier to a printed circuit board (pcb) and also to a pcb/chip carrier combination incorporating said mounting arrangement Background to the invention 10 In a mounting arrangement known from US Patent No , a socket is cemented to the pcb and receives both a contact interface member equipped with conductive interconnecting elements and the chip carrier, together with a compression spring which acts on the chip carrier to clamp the interface member between said pcb and said chip carrier with the interconnecting elements in electrical contact both with interface contacts on the chip carrier and contact pads on the pcb. In practical form the known arrangement is relatively compli- es cated and there is risk of non-uniformly distributed clamping forces acting at the electrical interfaces. A similar mounting arrangement is disclosed in European Patent Specification EP-B , in which an interface member is secured at each corner by a bolt to a pcb. An integrated circuit chip carrier is then clamped against the interface member by a resilient lid which is sprung under each bolt head. Such a mounting is, in practice, similarly complicated to the above-mentioned known arrangement 20 In US Patent No there is disclosed a further arrangement in which a chip carrier is clamped via an interface member to a pcb. However, in this arrangement the interconnecting elements of the interface member are permenently connected to the pcb by soldering. From US-A there is further known a device for housing a chip carrying package and connecting the package to a printed circuit board. The device includes a square frame, a cover and spring members. The 25 frame consists of four side walls integrally joined by corner posts and a floor, the walls and the floor defining an upwardly opened, package receiving compartment. The junction between the wall and the floor is represented by a groove, said groove receiving the downturned edges of a metal plate which provides means for attaching the device to the printed circuit board by means of a bolt extending through the printed circuit board and threadably received by the plate. Contact pressure on the spring members is maintained by hold down springs 30 on the cover. It is an object of this invention to provide an improved arrangement for mounting a chip carrier to a pcb. The invention 35 According to one aspect of the invention, there is provided a mounting arrangement for mounting an integrated circuit chip carrier to a printed circuit board (pcb), the mounting arrangement comprising a first fastener for fixedly attaching to the chip carrier, a socket moulding carrying interconnection elements for establishing electrical connection between interface contacts on the chip carrier and interface contact pads on the pcb, said socket moulding having a through aperture receiving said first fastener of the chip carrier, and a second and 40 complementary fastener for extending through an aperture in the pcb for engagement with said first fastener to clamp the socket moulding between the chip carrier and the pcb with said interface contacts and said contact pads interconnected by said interconnection elements. Desirably, the first fastener and the socket moulding are provided with means for orientating said insert and said moulding so that the interconnecting elements engage the chip carrier interface contacts. Preferably, 45 moreover, the socket moulding and the pcb are provided with means for orientating said moulding and said pcb so that the interconnecting elements engage the pcb contact pads. In one embodiment, the first fastener comprises an internally screw threaded boss externally shaped to be received in a correspondingly shaped aperture of the socket moulding in only one angular orientation of said insert and said moulding, the second fastener comprising a mounting screw. In this embodiment, the socket so moulding preferably carries one or more projecting pins to be received in one or more corresponding apertures in the pcb in only one angular orientation of said moulding and said pcb. The invention also extends to a pcb/chip carrier combination incorporating the above-described mounting arrangement. Thus, acccording to another aspect of the invention, there is provided a printed circuit board/integrated circuit chip carrier combination, including a socket moulding having slots accommodating 55 interconnecting elements which establish electrical conductive contact both with interface contacts on the chip carrier and with contact pads on the pcb, wherein the chip carrier is mounted to the pcb by means of an internally screw threaded fastener bonded to the chip carrier and received in an aperture in said socket moulding, the latter being clamped between the pcb and the chip carrier by a mounting screw which passes through an aper-

3 EP Bf ture in the pcb into threaded engagement with the fastener. If the mounting screw includes or comprises a conductive portion between the head end and the threaded shank, and the bus on the chip carrier includes a conductive element which will make contact with the conductive portion of the screw, then an electrical path will be established between the pcb and the chip carrier, when 5 the screw is inserted. This will for example allow electrical grounding of the chip carrier to a suitable point on the pcb which may for example make contact with a conductive washer, which may be spring loaded with into contact therewith, held captive below the screw head. Typically the screw will be of a conductive material as will also be at least the screw threaded region of the bus on the chip carrier. An electrical connection between the conductive path of the bus (if the whole is not 10 found from conduction material) will complete the path. Brief description of drawings The mounting arrangement in accordance with the invention will now be exemplified in the following des- 15 cription, making reference to the accompanying drawings, in which : Figure 1 is an exploded perspective view of a practical embodiment of mounting arrangement shown somewhat diamgrammatically ; Figure 2 is an exploded view of the mounting arrangement in side elevation ; and 20 Figure 3 is a side elevational view of an assembled pcb/chip carrier. Description of embodiment Referring to the drawings, a pcb 10 has on its rear face an arrangement of twenty-eight contact pads 12, 25 positioned in a generally square configuration with seven pads per side. An integrated circuit chip carrier 14 has a corresponding configuration of interface contacts 16 around its square periphery. Cemented or otherwise bonded to the central region 17 of the chip carrier 14 is a mounting fastener in the form of a lock nut 18. The nut is internally threaded at 20 within a stepped projecting boss 22, the latter having a flat 24 on its external surface. 30 Reference 26 denotes a socket moulding having a shaped central aperture 28 for receiving the boss 22 of the lock nut 18 when the chip carrier 14 and the socket moulding 26 are in a correct angular relationship, initially determined when the lock nut 18 is bonded to the chip carrier 14. The pcb 10 has an aperture 30 disposed centrally with respect to the contact pads 12, also receiving the boss 22 of the lock nut 18 after passage of the latter through the apertured socket moulding 26. Correct angular 35 orientation and positioning of the socket moulding 26 with respect to the pcb 10 is achieved by means of a pair of pins 32 on the socket moulding which engage into a pair of holes 34 formed in the pcb. The parts can be clamped together by a mounting screw 36 which passes through the aperture 30 in the pcb into threaded engagement with the nut 18. The socket moulding 26 is thus tightly sandwiched between the chip carrier 14 and the pcb The socket moulding 26 has four elongated slots 38 arranged in a square configuration which matches that of the contact pads 12 and interface contacts 16. These slots 38 accommodate elastomeric strips 40 (see Figure 2), which each have alternate conducting and non-conducting sections of which the former constitute interconnecting elements for electrically contacting both the interface contacts 16 and the contact pads 12 in order to connect corresponding such contacts and pads together, thereby electrically to connect the i.c. chip carrier with 45 the pcb on which the chip carrier is now mounted. The elastomeric strips 40 could be replaced by individual sprung contact elements, seven per elongated slot 38 in the socket moulding. It will be noted that the mounting screw 36 has an enlarged head 42 with a flat undersurface for ensuring an even distribution of clamping pressure at the spread electrical interfaces when the parts are assembled. An enlarged locking washer 44 may be interposed beneath the head, as shown in Figure 2. so Figure 3 shows the completed assembly incorporating the mounting arrangement in accordance with the invention. The mounting arrangement as described is both simple and easily practised without the need of any special tods, as only a screwdriver or the like is required to effect assembly and dis-assembly, thus facilitating servicing and maintenance. 55 Although the drawing shows four elongated slots 38 in socket moulding 26, arranged parallel to the four edges, each of the slots 38 may be sub-divided if desired, for example into two aligned slots to allow pairing. It is to be noted that screw 36 may be rendered more tamperproof by incorporating different tool engaging features in its enlarged head, and may be secured using a proprietory locking adhesive if a more permanent

4 bond is required. Various modifications of the above-described embodiment are possible within the scope of the invention as defined in the appended claims. For example, various means of correctly orientating the chip carrier, socket moulding and pcb contact pads may be employed instead of the means described, and in some instances it may be possible to use a common means for orientating both the socket moulding and the chip carrier with respect to the pcb. Claims A mounting arrangement for mounting an integrated circuit chip carrier (1 4) to a printed circuit board (1 0) the mounting arrangement comprising a first fastener (18) for fixedly attaching to the chip carrier, a socket moulding (26) carrying interconnection elements (40) for establishing electrical connection between interface contacts (16) on the chip carrier and interface contact pads (12) on the printed circuit board, said socket mould- 15 ing having a through aperture (28) receiving said first fastener of the chip carrier, and a second and complementary fastener for extending through an aperture (30) in the printed circuit board for engagement with said first fastener to clamp the socket moulding between the chip carrier and the printed circuit board with said interface contacts and said contact pads interconnected by said interconnection elements. 2. An arrangement according to claim 1, wherein said first fastener and said socket moulding are provided 20 with corresponding means for orientating said first fastener and said moulding so that the interconnecting elements engage the chip carrier interface contacts at the devised angular relationship. 3. An arrangement according to claim 1, wherein said socket moulding and said printed circuit board are provided with corresponding means (32, 34) for orientating said moulding and said printed circuit board so that the interconnecting elements engage the printed circuit board contact pads at the devised angular relationship An arrangement according to claim 2, wherein said first fastener comprises an internally screwthreaded boss (22) externally shaped to be received in the correspondingly shaped aperture (28) of the socket moulding in only one angular orientation of said first fastener and said moulding, said second fastener comprising a mounting screw. 5. An arrangement according to claim 3, wherein the socket moulding carries at least one projecting pin 30 (32) to be received in a corresponding further aperture (34) in the printed circuit board in only one angular orientation of said moulding and said printed circuit board. 6. An arrangement according to claim 1, wherein said interconnection elements are principally accomodated in further apertures (38) in the socket moulding. 7. An arrangement according to claim 6, wherein said further apertures in the socket moulding are elongate 35 slots (38) each for accomodating a plurality of the interconnection elements (40). 8. An arrangement according to claim 7, wherein each said plurality of interconnection elements (40) is formed by an elastomeric strip having alternate non-conducting and conducting sections of which the latter constitute said interconnection elements (40). 9. An arrangement according to any one of claims 4 to 8, wherein said boss is dimensioned to extend at 40 least partly through the aperture in the printed circuit board into which the mounting screw is received, the latter having an enlarged head (42) with a flat undersurface for pressing against the printed circuit board around said aperture therein either directly or through an enlarged washer. 10. A printed circuit board integrated circuit chip carrier combination, including a socket moulding (26) having slots (38) accomodating interconnecting elements (40) which establisch electrical conductive contact both 45 with interface contacts (16) on the chip carrier and with contact pads (12) on the printed circuit board, wherein the chip carrier is mounted to the printed circuit board by means of an internally screw threaded fastener (18) bonded to the chip carrier and received in an aperture (28) in said socket moulding, the latter being clamped between the printed circuit board and the chip carrier by a mounting screw (36) which passes through an aperture in the printed circuit board into threaded engagement with the fastener. 50 Patentanspruche 1. Eine Montageanordnung zum Montieren eines IC-Chiptrigers (14) auf einer Leiterplatte (1 0), wobei die 55 Befesb'gungsanordnung einen ersten Befestiger (18) zum festen Anbringen an dem Chiptriger, ein Fassungsformstuck (26) mit Verbindungselementen (40) zum Erzielen einer elektrischen Verbindung zwischen Schnittstellenkontakten (1 6) auf dem Chiptrager und Schnittstellenkontaktplittchen (1 2) auf der Leiterplatte aufweist, wobei das Fassungsformstuck zur Aufnahme des ersten Befestigers des Chiptragers eine durchgehende 6ff-

5 nung (28) aufweist, und mit einem zweiten und komplementaren Befestiger, der durch eine Offnung (30) in der Leiterplatte zwecks Anlage an dem ersten Befestiger zum Festklemmen des Fassungsformstuckes zwischen dem Chiptrager und der Leiterplatte durchtritt, wobei die Schnittstellenkontakte und die Kontaktplattchen durch die Verbindungselemente miteinander verbunden werden Eine Anordnung nach Anspruch 1, wobei der erste Befestiger und das Fassungsformstuck entsprechende Mittel zum Ausrichten des ersten Befestigers und des Formstuckes aufweisen, so dab die Verbindungselemente in der vorgesehenen Winkelbeziehung an den Chiptrager-Schnittstellenkontakten anliegen. 3. Eine Anordnung nach Anspruch 1, wobei das Fassungsformstuck und die Leiterplatte entsprechende Mittel (32, 34) zum Ausrichten des Formstuckes und der Leiterplatte aufweisen, so daft die Verbindungsele- 10 mente in der vorgesehenen Winkelbeziehung an den Leiterplatten-Kontaktplattchen anliegen. 4. Eine Anordnung nach Anspruch 2, wobei der erste Befestiger ein ein Innengewinde aufweisender Vorsprung (22) ist, derauf seiner AuEenseite so geformt ist, da& er nur in einer Winkelausrichtung des ersten Befestigers und des Formstuckes in der entsprechend geformten Offnung (28) des Fassungsformstuckes aufgenommen wird, und derzweite Befestiger eine Halteschraube ist. is 5. Eine Anordnung nach Anspruch 3, wobei das Fassungsformstuck mindestens einen in nur einer Winkelausrichtung des Formstuckes und der Leiterplatte in einer entsprechenden weiteren Offnung (34) in der Leiterplatte aufzunehmenden vorstehenden Stift (32) aufweist. 6. Eine Anordnung nach Anspruch 1, wobei die Verbindungselemente hauptsachlich in weiteren Offnungen (38) in dem Fassungsformstuck aufgenommen sind Eine Anordnung nach Anspruch 6, wobei die weiteren Offnungen in dem Fassungsformstuck Langschlitze (38) jeweils zum Aufnehmen einer Vielzahl der Verbindungselemente (40) sind. 8. Eine Anordnung nach Anspruch 7, wobei jedes aus der Vielzahl der Verbindungselemente (40) durch einen elastomeren Streifen aus abwechselnd nichtleitenden und leitenden beschnitten gebildet ist, von denen die letzteren die Verbindungselemente (40) darstellen Eine Anordnung nach irgendeinem der Anspruche 4 bis 8, wobei der Vorsprung so bemessen ist, dau er mindestens teilweise durch die Offnung in der Leiterplatte, in der die Halteschraube aufgenommen ist, durchtritt, wobei die letztere einen vergroserten Kopf (42) mit einer ebenen Unterseite zum Anpressen an die Leiterplatte urn die in dieser vorgesehene Offnung herum entweder unmittelbar oder uber eine vergroberte Unterlegscheibe aufweist Eine Kombination aus einer Leiterplatte und einem Trager eines IC-Chips mit einem Fassungsformstuck (26) mit Schlitzen (38) zur Aufnahme von Verbindungselementen (40), die elektrisch leitenden Kontakt sowohl mit Schnittstellenkontakten (16) auf dem Chiptrager als auch mit Kontaktplattchen (12) auf der Leiterplatte ergeben, wobei der Chiptrager auf der Leiterplatte mit einem Innengewinde aufweisenden Befestiger (1 8) montiert ist, der mit dem Chiptrager verbunden und in einer dffnung (28) in dem Fassungsformstuck aufge- 35 nommen ist, wobei das letztere zwischen der Leiterplatte und dem Chiptrager mit einer Halteschraube (36) eingeklemmt ist, die zum Schraubeingriff mit dem Befestiger durch eine Offnung in der Leiterplatte durchtritt. Revendications Une structure de montage pour un support de puce de circuit integre (14) sur une carte de circuit imprime (1 0), comprenant un premier element d'assemblage (1 8) destine a etre fixe sur le support de puce, une embase moulee (26) portant des elements d'interconnexion (40) pour etabiir une connexion electrique entre des contacts d'interface (16) sur le support de puce et des plots de contact d'interface (12) sur la carte de circuit 45 imprime, cette embase moulee comportant une ouverture traversante (28) qui report le premier element d'assemblage du support de puce, et un second element d'assemblage, complementaire du premier, destine a traverser une ouverture (30) dans la carte de circuit imprime pour s'adapterau premier element d'assemblage, afin de bloquer I'embase moulee entre le support de puce et la carte de circuit imprime, avec les contacts d'interface et les plots de contact interconnects par les elements d'interconnexion Une structure selon la revendication 1, dans laquelle le premier element d'assemblage et I'embase moulee comportent des moyens correspondants pourorienterle premier element d'assemblage et I'embase moulee de facon que les elements d'interconnexion viennent en contact avec les contacts d'interface du support de puce avec la relation angulaire prevue. 3. Une structure selon la revendication 1, dans laquelle I'embase moulee et la carte de circuit imprime 55 comportent des moyens correspondants (32, 34) pour orienter I'embase moulee et la carte de circuit imprime, de facon que les elements d'interconnexion viennent en contact avec les plots de contact de la carte de circuit imprime avec la relation angulaire prevue. 4. Une structure selon la revendication 2, dans laquelle le premier element d'assemblage comprend un

6 bossage filete interieurement (22), ayant une forme exterieure qui lui permet de se loger dans I'ouverture de forme correspondante (28) de I'embase moulee, dans une seule orientation angulaire du premier element d'assemblage et de I'embase moulee, tandis que le second element d'assemblage consiste en une vis de montage Une structure selon la revendication 3, dans laquelle I'embase moulee porte au moins un ergot en saillie (32) destine a se loger dans une ouverture supplemental correspondante (34) dans la carte de circuit imprime, dans une seule orientation angulaire de I'embase moulee et de la carte de circuit imprime. 6. Une structure selon la revendication 1, dans laquelle ies elements d'interconnexion sont loges principalement dans des ouvertures supplementaires (38) dans I'embase moulee Une structure selon la revendication 6, dans laquelle Ies ouvertures supplementaires dans I'embase moulee sont des fentes allongees (38), chacune d'elles etant congue pour recevoir un ensemble des elements d'interconnexion (40). 8. Une structure selon la revendication 7, dans laquelle chaque element de I'ensemble d'elements d'interconnexion (40) est constitue par une bande d'elastomere ayant des sections non conductrices et conductrices 15 altemees, parmi lesquelles ces dernieres constituent Ies elements d'interconnexion (40). 9. Une structure selon I'une quelconque des revendications 4 a 8, dans laquelle le bossage est dimensionne de facon a s'6tendre au moins partiellement a travers I'ouverture dans la carte de circuit imprim6 dans laquelle se trouve la vis de montage, cette derniere ayant une t te agrandie (42), avec une surface inferieure plane, pour exercer une pression contre la carte de circuit imprims autour de I'ouverture formee dans cette der- 20 niere, soit directement, soit par I'intermediaire d'une rondelle de plus grand diametre Une combinaison d'une carte de circuit imprime et d'un support de puce de circuit integre, comprenant une embase de montage (26) ayant des fentes (38) qui recoivent des elements d'interconnexion (40) etablissant un contact conducteur de l'electricite a la fois avec des contacts d'interface (16) sur le support de puce et avec des plots de contact (12) sur la carte de circuit imprime, dans laquelle le support de puce est monte 25 sur la carte de circuit imprime au moyen d'un element d'assemblage filete interieurement (1 8) fixe sur le support de puce et Iog6 dans une ouverture (28) dans I'embase moulee, cette derniere etant bloquee entre la carte de circuit imprim6 et le support de puce au moyen d'une vis de montage (36) qui traverse une ouverture dans la carte de circuit imprime pourse visser dans I'element d'assemblage

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8 14 I I T -18 D \ y ~ A0! i e r r ; ; 26 l \ \ \ \ \ \ K \ \ \ \ \ \ \ \ \ \ \ \ \ \ V i o ULJI ' ""'" -uu 36 l K - > F i g. 2