GB2129223A - Printed circuit boards - Google Patents
Printed circuit boards Download PDFInfo
- Publication number
- GB2129223A GB2129223A GB08309899A GB8309899A GB2129223A GB 2129223 A GB2129223 A GB 2129223A GB 08309899 A GB08309899 A GB 08309899A GB 8309899 A GB8309899 A GB 8309899A GB 2129223 A GB2129223 A GB 2129223A
- Authority
- GB
- United Kingdom
- Prior art keywords
- carriers
- packages
- laminate
- circuit board
- printed circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
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Classifications
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/18—Printed circuits structurally associated with non-printed electric components
- H05K1/189—Printed circuits structurally associated with non-printed electric components characterised by the use of a flexible or folded printed circuit
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
- H01L23/40—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs
- H01L23/4006—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
- H01L23/42—Fillings or auxiliary members in containers or encapsulations selected or arranged to facilitate heating or cooling
- H01L23/433—Auxiliary members in containers characterised by their shape, e.g. pistons
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/0201—Thermal arrangements, e.g. for cooling, heating or preventing overheating
- H05K1/0203—Cooling of mounted components
- H05K1/0204—Cooling of mounted components using means for thermal conduction connection in the thickness direction of the substrate
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
- H01L23/40—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs
- H01L23/4006—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws
- H01L2023/4037—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws characterised by thermal path or place of attachment of heatsink
- H01L2023/4043—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws characterised by thermal path or place of attachment of heatsink heatsink to have chip
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
- H01L23/40—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs
- H01L23/4006—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws
- H01L2023/4037—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws characterised by thermal path or place of attachment of heatsink
- H01L2023/4062—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws characterised by thermal path or place of attachment of heatsink heatsink to or through board or cabinet
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
- H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L2224/10—Bump connectors; Manufacturing methods related thereto
- H01L2224/15—Structure, shape, material or disposition of the bump connectors after the connecting process
- H01L2224/16—Structure, shape, material or disposition of the bump connectors after the connecting process of an individual bump connector
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/30—Technical effects
- H01L2924/35—Mechanical effects
- H01L2924/351—Thermal stress
- H01L2924/3511—Warping
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/03—Use of materials for the substrate
- H05K1/0393—Flexible materials
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/09—Shape and layout
- H05K2201/09009—Substrate related
- H05K2201/09054—Raised area or protrusion of metal substrate
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/10—Details of components or other objects attached to or integrated in a printed circuit board
- H05K2201/10227—Other objects, e.g. metallic pieces
- H05K2201/10393—Clamping a component by an element or a set of elements
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/10—Details of components or other objects attached to or integrated in a printed circuit board
- H05K2201/10613—Details of electrical connections of non-printed components, e.g. special leads
- H05K2201/10621—Components characterised by their electrical contacts
- H05K2201/10727—Leadless chip carrier [LCC], e.g. chip-modules for cards
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/0058—Laminating printed circuit boards onto other substrates, e.g. metallic substrates
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
- H05K3/341—Surface mounted components
- H05K3/3431—Leadless components
- H05K3/3442—Leadless components having edge contacts, e.g. leadless chip capacitors, chip carriers
Abstract
A multilayer printed circuit board comprises a flexible planar electrically insulating laminate (1) with an electrically conductive array (2) for connecting to electrical conductor terminals (3) on circuit or component packages or carriers (4, 4A), interconnections for the array being by electrical conductor elements at one or more planes within the laminate. The flexible laminate has holes (15) provided where the packages or carriers are to be secured. A separate rigid metallic heat sinking or spreading member (16) is applied such that protruding thermally conducting metallic pillars (17) thereon pass through the holes (15) in the laminate to contact the packages or carriers (4). One or more further rigid members (8, 10), which may also be of thermally conducting material, may be applied to the top of the packages or carriers, clips (9, 11) being arranged to secure the pillars (17) in contact with the packages or carriers. The flexibility of the laminate allows concentration of thermal expansion mismatch between the laminate and-the packages or carriers. The laminate is also able to flex or bend in regions between the packages or carriers to optimise contact between the pillars (17) and the packages or carriers (4, 4A) and to minimise risk of detachment of the latter from the board. <IMAGE>
Description
SPECIFICATION
Printed circuit board
This invention relates to multilayer printed circuit boards and more particularly to such boards arranged for supporting and electrically connecting packages or carriers accommodating electronic components or circuits. Of particular relevance in this respect are so-called chip carriers, of ceramic or plastics material, typically rectangular in shape, incorporating one or more semiconductor chips, electrical connections being provided between the chip and multiple conductor terminals on the carrier.The terminals on the package or carrier, which may constitute closely spaced tape leads or metallised areas on the outer surface of the package or carrier, are arranged to be secured and electrically connected, e.g. by solder, to an electrically conductive array on the surface of a planar electrically insulating laminate, interconnections to the array being provided by means of electrical conductor elements, e.g. of copper, arranged at one or more planes within the laminate.
With advances in technology it has become necessary to accommodate and electrically interconnect an increasing number of circuit or component packages or carriers on printed circuit boards.
Previously, a much used form of assembling and interconnecting electrical components on a printed circuit board involved mounting the components on a first side of the board with terminal leads inserted through holes in the board and secured and electrically connected by a soldering process to printed copper conductors on a second side of the board.
It has recently become known that a significant saving in the area of the board required to accommodate the necessary components can be achieved if the components are attached onto the surface of the printed circuit board. Examples include the transition from the dual-in-line package to either the leaded or leadless chip carrier and from the conventional cylindrical resistor with axial leads to the leadless rectangular chip resistor. These new components occupy significantly less area than the previous components with leads inserted into the board and call for a technique of 'surface mounting' on to the printed circuit board. Any holes previously incorporated in the board to accommodate inserted leads and also the annular conductor areas which normally surround such holes are superfluous and may be eliminated in the interests of saving space.In addition to providing important economies, this resultant space saving has offered the facility of incorporating a greater density of interconnecting elements or tracks of reduced line width and reduced intervening separation on the circuit board. These features are important in achieving economic interconnection of the required larger number of components in addition to the use of component or circuit packages or carriers each embodying a larger number of terminals than previously employed.
With these developments however, problems have been experienced in certain respects as follows. The electrically insulating laminates used hitherto for multilayer printed circuit boards adapted for this purpose have comprised a relatively rigid material, such as a glass-filled epoxy. When terminals on a chip carrier of ceramic material are soldered, or otherwise bonded, to a conductive array on a major surface of the laminate and the resulting assembly subjected to thermal cycling, the difference in thermal expansion between the laminate and the chip carrier results in mechanical strain being set up in the regions where the carrier is secured to the laminate, i.e. at the soldered connections.
After a number of cycles there is tendency for the connections to fail and the carrier becomes detached and disconnected from the circuit board laminate. A further problem may also arise in that when the circuit board with carriers or packages thereon is subsequently mounted in appropriate electrical apparatus, any flexing or bending forces applied to the relatively rigid laminate will result in mechanical strain in the connections between the carriers or packages and the laminate and there will again be a tendency for the connections to fail and for the carriers or packages to become detached from the circuit board laminate.
The surface mounting. on multilayer printed circuit boards, of a plurality of circuit or component packages or carriers has led to a further problem being encountered, namely where high power dissipation is required in the circuits or components in the packages or carriers. In cases involving high interconnection density it is necessary to introduce appropriate heat sink or spreader means to allow heat to be transferred, by conduction, from the packages or carriers. In the multilayer printed circuit boards of the prior art, embodying rigid electrically insulating laminates, it has been proposed to incorporate as a heat sink or spreader, one or more thermally conducting metal planes in the vicinity of the surface on which the packages or carriers are mounted.In some cases a layer of elastomer can be provided overlying the metal plane or planes to form an electrically insulating surface for supporting the packagees or carriers and the necessary array of surface conductor elements.
This arrangement is disadvantageous in that the package or carriers are not in intimate contact with the heat sink or spreader.
It is also known to fabricate the thermally conducting plane integrally with the circuit board but such that it provides for a direct thermal conducting path to the packages or carriers.
However with these previous arrangements the incorporation of the heat sink or spreader facility into the circuit board during the fabrication of the latter increases the complexity of the manufacturing process. It also imposes a limitation on the thickness of the metal plane which can be adopted for use as the heat sink or spreader with the result that a much less than ideal thickness may have to be employed, with consequent reduced efficiency of operation.
It is an object of the present invention to overcome or mininise the above disadvantages.
The present invention provides a multilayer printed circuit board comprising a planar electrically insulating laminate having on a major surface an electrically conductive array adapted to be secured and electrically connected to multiple electrical conductor terminals on each of a plurality of circuit or component packages or carriers, interconnections for said array being provided by means of electrical conductor elements arranged at one or more planes within said laminate, said circuit board being characterised in that said insulating laminate comprises a flexible material and has a thickness of not more than 0.5 millimetres and serves to accommodate any mismatch in thermal expansion between the laminate and said packages or carriers; flexibility of the laminate in the regions between said packages or carriers when secured and connected thereto accommodating any flexing or bending forces applied to the board during handling thereof, whereby risk of damage to said packages or carriers or detachment thereof from said conductive array is minimised or avoided.
The flexible laminate may be provided with a plurality of holes through it such that a said hole is provided at some or all locations where said circuit or component packages or carriers are to be secured and electrically connected, a substantially rigid thermally conducting metallic member being provided having protruding from a major surface thereof a plurality of thermally conducting metallic pillars, said metallic member being adapted and arranged to be applied to said flexible laminate in such a way that said pillars are insertable through said holes in said laminate to make contact with said packages or carriers when the latter are secured and electrically connected, means being provided to secure said pillars in contact with said packages or carriers, said metallic member serving as a heat sink or spreader for heat developed in said packages or carriers.
A further substantially rigid member may be provided for application on top of said packages or carriers, a suitable clamp means being provided, adapted to be applied to said metallic member and said further member to secure said pillars in contact with said packages or carriers.
Suitably said clamp means comprises one or more clips, e.g. spring clips.
The said pillars may either be formed integrally with said metallic member or fabricated separately and secured to said metallic member.
Preferably said metallic member and pillars comprise aluminium or copper, or alloys thereof.
The said further member preferably comprises a metal (e.g. aluminium or copper or alloys thereof), thereby serving as a further heat sink or spreader.
Suitably the insulating laminate comprises a flexible polyimide or polyester material.
Conveniently the said packages or carriers comprise a ceramic or plastics material.
The said packages or carriers may suitably accommodate semiconductor chips.
The said conductive array and said interconnections therefor preferably comprise copper.
The multilayer printed circuit board of the invention provided with said metallic member with protruding pillars may be arranged in stacked relationship with one or more further said multilayer printed circuit boards such that for one board, the surface of the metallic member opposite to that surface provided with the protruding pillars is located on top of the packages or carriers of another board.
The invention is advantageous in several respects. Firstly, the flexible nature of the insulating laminate allows it to yield to accept a degree of tension or compression in the plane of its major surface in order to accommodate the mismatch in thermal expansion between the packages or carriers and the laminate.
Secondly, if the laminate with the packages or carriers mounted thereon is subjected to forces which would tend to bend or flex it, the laminate is able to bend readily and preferentially in the regions between the packages or carriers and risk of the packages or carriers becoming detached is minimised or avoided since little or no stresses are imparted to their soldered connections.
Thirdly, since it is impossible to secure each package or carrier to the array of conductors on the flexible laminate such that the underneath surface of each package or carrier is exactly the same distance from the surface of the laminate and since it is also difficult to mount the packages or carriers such that their underneath surfaces are exactly parallel to the plane of the laminate, i.e.
such that there is no tilt in the mounted packages or carriers, it might be expected that it would not be possible to achieve good thermal contact between all of the pillars on the thermally conducting metallic member and their associated packages or carriers. This would certainly be the case if the laminate was rigid. We have found however, that with the use of a flexible laminate, the flexible nature of this laminate permits it to undergo the necessary contortions when clamped, with the packages or carriers mounted thereon, between the thermally conducting metallic member and the further rigid member, to bring the packages or carriers into the required state of alignment to optimise their physical contact with the pillars on the metallic member and with the further rigid member. Fourthly, as the heat sink or spreader member or members is or are formed as separate external add-on components for the circuit board, the complexity of the circuit board fabrication process itself is not increased by the provision of the heat sink or spreader. Fifthly, since the heat sink or spreader member or members is or are provided externally to the circuit board, the dimensional parameters, such as thickness, of the member or members are able to be optimised with respect to the required thermal conduction.
Lastly, as the surface of each package or carrier is not rigidly bonded to the surface of its associated protruding pillarthereis no impediment to relative lateral movement between the two and any tendency for the development of strain in the structure due to differential thermal expansion or mechanical stress effects is eliminated.
The invention is now described by way of example with reference to the accompanying drawings in which Figure 1 illustrates a side view of a multilayer printed circuit board according to the invention having circuit or component packages or carriers secured and electrically connection thereto.
Figure 2 illustrates the circuit board of Figure 1 subject to mechanical flexing or bending.
Figure 3 illustrates a sectional view of a multilayer printed circuit board according to the invention provided with heat sinking or spreading means. In order to avoid undue complexity in
Figure 3 and aid clarity, internal components or circuits of the packages or carriers and the electrical conductor elements within the flexible laminate of the circuit board have been omitted, since their inclusion is not required for an understanding of the invention. They are also well known per se.
Referring to Figure 1, a multilayer printed circuit board is provided comprising a planar electrically insulating laminate 1 of a flexible polyimide material of less than 0.5 millimetres in thickness. A suitable flexible polyimide material is manufactured by E.l. Du Pont de Nemours and Co, under the trade name Kapton (Registered trade mark). An electrically conductive array 2 of copper conductors is provided on a major surface of the laminate 1, adapted and arranged to be secured and electrically connected, by soldering, to multiple conductor terminals 3 on each of a plurality of circuit or component packages or carriers 4.
Carriers 4 may, for example, be well-known semiconductor component or integrated circuit chips accommodated in a carrier housing of ceramic or plastics material. A large number of the packages or carriers may be provided, closely spaced, e.g. in rows, on the surface of the laminate. Electrical interconnections for the array 2 are provided by means of copper electrical conductor elements or tracks arranged at one or more planes within the laminate as indicated for illustrative purposes by dotted lines 5. The techniques for producing flexible multilayer printed circuit boards comprising insulating laminates incorporating copper conductor elements at one or more planes within the laminates, and for providing through connections or vias between the copper conductor elements lying in the different planes, are well known and published in the art.
The co-efficient of thermal expansion of packages and carriers mounted on printed circuit boards is generally different from the laminate material of the board. For example, the package or carrier may be ceramic and the laminate a filled plastics material.
In the prior art arrangement where packages or carriers are mounted on rigid circuit board laminates, e.g. of glass filled epoxy material, when the resulting assembly is subjected to thermal cycling during use or test, mechanical strain occurs in the soldered connections between the packages or carriers and the conductors on the laminate, because of differential expansion between the laminate and the packages or carriers. After a number of cycles failure of the connections tends to occur and the packages or carriers become detached from the laminate. By contrast, the flexible laminate employed in the present invention is found to accommodate the thermal expansion mismatch problem because it is considerably more compliant than the rigid laminates of the prior art.It is able to yield (i.e. be stretched or compressed) as required to minimise or reduce the risk of mechanical failure of the soldered connections.
When the resulting multilayer circuit board with attached packages or carriers is mounted and supported in equipment for which it is designed, there is a risk that during handling or subsequent mounting, or in use, the laminate may be subjected to forces which would tend to bend or flex it. When this occurs with rigid laminates of the prior art, there is a tendency for the connections between the packages or carriers and the conductive array on the laminate to be subjected to mechanical strain of a severity such that the connections fail and the packages or carriers become detached. By contrast, as illustrated in Figure 2, the flexibility of the flexible laminate employed in the present invention results in the laminate bending readily and preferentially in the regions 6 between the packages or carriers and risk of the packages or carriers becoming detached is minimised or reduced.In order to conduct away or provide uniform spreading of heat generated in the packages or carriers 4 when high power is dissipated in the components or circuits therein, the arrangement illustrated in Figure 3 is provided. In Figure 3, parts common to those in
Figures 1 and 2 are given the same reference numerals as in Figures 1 and 2.
Referring to Figure 3, a multilayer printed circuit board is provided comprising a planar electrically insulating laminate 1 of a flexible polyimide material of less than 0.5 millimetres in thickness. A suitable flexible polyimide material is manufactured by E.l. Du Pont de Nemours and Co, under the trade name Kapton (Registered trade mark). An electrically conductive array 2 of copper conductors is provided on a major surface of the laminate 1, adapted and arranged to be secured and electrically connected, by soldering, to multiple conductor terminals 3 on each of a plurality of circuit or component packages or carriers 4.
Carriers 4 may, for example, be well-known semiconductor chip carriers each comprising one or more semiconductor component or integrated circuit chips accommodated in a carrier housing of ceramic or plastics material. A large number of the packages or carriers may be provided, closely spaced, e.g. in rows, on the surface of the laminate.
Electrical interconnections for the array 2 are provided by means of copper electrical conductor elements or tracks (not shown) arranged and formed by well-known techniques at one or more planes within the laminate.
The flexible laminate 1 is provided with a plurality of holes 15 through it such that a hole is formed at some or all locations where the packages or carriers 4 are secured and connected.
A substantially rigid thermally conducting number 16, suitably of aluminium or copper, is fabricated having protruding from a major surface thereof a plurality of pillars 1 7, suitably formed of the same material as the member 16. The pillars 17 may either be formed integrally with the rigid member 16 or may be fabricated separately and secured to the rigid member 16. The member 16 is applied to the laminate 1 in such a way that the pillars 17 are inserted through the holes 15 in the laminate and make contact with the underside of the packages or carriers 4.A further substantially rigid member 8, also suitably of copper or aluminium, is applied on top of the packages or carriers 4 and clamp means in the form of a spring clip 9 is applied to contact the members 1 6 and 8 and thereby provide a rigid arrangement in which the member 8 and the pillars 17 on the member 16 are secured in contact with the packages or carriers 4. Member 16, 17 and member 8 serve as heat sinks or spreaders for heat generated in the packages or carriers 4 when the latter are subjected to electrical load.
The member 8 may be constructed so as to contact the top of all the packages or carriers 4, with further clips similar to clip 9 being applied as required. If, however some packages or carriers 4A are utilised which are thicker than the other packages or carriers 4, a separate member 10 may be provided applied on top of these packages or carriers 4A. One or more clips 1 1, similar to clip 9 is or are applied to contact the members 16 and 10 in the same way as previously described for clip 9 and membes 16 and 8.
If it is not required for members 8 and 10 to contribute to the sinking or spreading of heat from the packages or carriers, these members may be fabricated from a suitably rigid non-metallic material. This arrangement of the present invention owes its successful realisation largely to the compliant nature of the flexible laminate 1. In practice it is impossible to secure each package or carrier 4 or 4A to the array of conductors 2 such that the underneath surface of each package or carrier is exactly the same distance from the surface of the laminate and such that the underneath surfaces of the packages or carriers
are exactly parallel to the plane of the laminate.
Consequently the packages may be slightly tilted when mounted. The necessary thermal contact between the pillars 17 and the packages 4 and 4A is realised and optimised by the fact that when the circuit board with the packages or carriers thereon is clamped by means of the clips 9, 11 between member 16, 17 and members 8 and 10, the flexible laminate is able to undergo the contortions necessary to bring the packages or carriers 4, 4A into the required state of alignment to optimise their physical contact with the pillars 17 and with the rigid members 8, 10.
It is not essential that the further rigid members 8 and 10 be provided. It is only necessary that means be provided to maintain the pillars 17 on the member 16 in good thermoconducting relationship with the underside of the packages or carriers 4, 4A. Although a number of techniques can be envisaged for achieving this, in the absence of rigid members 8 and 10, a convenient method would be to adhere the pillars 17 to the packages or carriers using a thin film of a flexible adhesive.
As the surface of each package or carrier is not rigidly bonded to the surface of its associated protruding pillar there is no impediment to relative lateral movement between the two and any tendency for the development of strain in the structure due to differential thermal expansion or mechanical stress effects is eliminated. Indeed, in arrangements where the flexible adhesive is not required, it is advantageous to apply a grease with high thermal conductivity (such as Electrolube
HTC 010) between the contacting surfaces of the pillars and the packages or carriers to improve thermal transfer and this also provides lubrication to faciliate any strain-relieving movement. It has been found that in any case the use of the heat sink or spreader arrangement reduces the temperature of the packages or carriers in operating conditions and thereby further reduces the tendency for thermal mismatch strains to develop.
A multilayer printed circuit board of the type illustrated in Figure 3, but without the further rigid members 8 and 10 on top of the packages or carriers 4, 4A, may be arranged in stacked relationship with one or more like boards and such that for one board, the surface 18 of the metallic member 16, (i.e. the surface opposite to that provided with the protruding pillars 17) is located on top of the packages or carriers of another board. In this way, a compact, thermally efficient and rigid assembly may be achieved, which still embodies the advantages of the flexibility of the circuit board laminate at each level of the stack.
Claims (17)
1. A multilayer printed circuit board comprising a planar electrically insulating laminate having on a major surface an electrically conductive array adapted to be secured and electrically connected to multiple electrical conductor terminals on each of a plurality of circuit or component packages or carriers, interconnections for said array being provided by means of electrical conductor elements arranged at one or more planes within said laminate, said circuit board being characterised in that said insulating laminate comprises a flexible material and has a thickness of not more than 0.5 millimetres and serves to accommodate any mismatch in thermal expansion between the laminate and said packages or carriers; flexibility of the laminate in the regions between said packages or carriers, when secured and connected thereto accommodating any flexing or bending forces applied to the board during handling thereof, whereby risk of damage to said packages or carriers or detachment thereof from said conductive array is minimised or avoided.
2. A multilayer printed circuit board according to Claim 1 in which said flexible laminate is provided with a plurality of holes through it such that a said hole is provided at some or all locations where said circuit or component packages or carriers are to be secured and electrically connected, a substantially rigid thermally conducting metallic member being provided having protruding from a major surface thereof a plurality of thermall conducting metallic pillars, said metallic member being adapted and arranged to be applied to said flexible laminate in such a way that said pillars are insertable through said holes in said laminate to make contact with said packages or carriers when the latter are secured and electrically connected, means being provided to secure said pillars in contact with said packages or carriers, said metallic member serving as a heat sink or spreader for heat developed in said packages or carriers.
3. A multilayer printed circuit board according to Claim 2 in which a further substantially rigid member is provided for application of top of said packages or carriers, clamp means being provided, adapted to be applied to said metallic member and said further member to secure said pillars in contact with said packages or carriers.
4. A multilayer printed circuit board according to Claim 3 in which said clamp means comprises one or more clips adapted to be applied around said metallic member and said further member.
5. A multilayer printed circuit board according to Claim 4 in which said clips comprise spring clips.
6. A multilayer printed circuit board according to any of Claims 2 to 5 in which said pillars are formed integrally with said metallic member.
7. A multilayer printed circuit board according to any of Claims 2 to 5 in which said pillars are fabricated separately from said metallic member and secured to said metallic member.
8. A multilayer printed circuit board according to any of Claims 2 to 7 in which said metallic member and pillars comprise aluminium or copper, or alloys thereof.
9. A multilayer printed circuit board according to any of Claims 3 to 8 in which said further member comprises a metal, thereby serving as a further heat sink or spreader.
10. A multilayer printed circuit board according to Claim 9 in which said metal of said further member comprises aluminium or copper or alloys thereof.
11. A multilayer printed circuit board according to any preceding Claim, in which said insulating laminate comprises a flexible polyimide or polyester material.
12. A multilayer printed circuit board according to any preceding Claim in which the said packages or carriers comprise a ceramic or plastics material.
13. A multilayer printed circuit board according to any preceding Claim in which said packages or carriers suitable accommodate semiconductor chips.
14. A multilayer printed circuit board according to any preceding Claim, in which said conductive array and said interconnections therefore comprise copper.
15. A multilayer printed circuit board according to any preceding Claim, in which the flexible nature of the insulating laminate allows it to yield to accept a degree of tension or compression in the plane of its major surface in order to accommodate the mismatch in thermal expansion between the packages or carriers and the laminate.
16. A multilayer printed circuit board according to Claim 2 arranged in stacked relationship with one or more further said boards, such that for one board the surface of the metallic member opposite to that surface provided with the protruding pillars is located on top of the packages or carriers of another board.
17. A multilayer printed circuit board constructed and arranged substantially as herein described and illustrated in the accompanying drawings.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08309899A GB2129223A (en) | 1982-10-09 | 1983-04-12 | Printed circuit boards |
| GB838311200A GB8311200D0 (en) | 1982-10-09 | 1983-04-25 | Printed circuit board |
| GB8400142A GB2136212B (en) | 1983-01-06 | 1984-01-05 | Cooling components on printed circuit boards |
| EP84300073A EP0116396A3 (en) | 1983-01-06 | 1984-01-05 | Electrical assembly |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8228936 | 1982-10-09 | ||
| GB838300247A GB8300247D0 (en) | 1983-01-06 | 1983-01-06 | Printed circuit board |
| GB08309899A GB2129223A (en) | 1982-10-09 | 1983-04-12 | Printed circuit boards |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8309899D0 GB8309899D0 (en) | 1983-05-18 |
| GB2129223A true GB2129223A (en) | 1984-05-10 |
Family
ID=27261789
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08309899A Withdrawn GB2129223A (en) | 1982-10-09 | 1983-04-12 | Printed circuit boards |
| GB838311200A Pending GB8311200D0 (en) | 1982-10-09 | 1983-04-25 | Printed circuit board |
Family Applications After (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB838311200A Pending GB8311200D0 (en) | 1982-10-09 | 1983-04-25 | Printed circuit board |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB2129223A (en) |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3545527A1 (en) * | 1984-12-20 | 1986-07-03 | Raytheon Co., Lexington, Mass. | FLEXIBLE ELECTRICAL CONNECTING DEVICE AND METHOD FOR THEIR PRODUCTION |
| DE3614086A1 (en) * | 1985-04-26 | 1986-10-30 | Sgs Microelettronica S.P.A., Catania | DEVICE AND METHOD FOR THERMALLY COUPLING A SEMICONDUCTOR BUILDING UNIT TO A COOLING PLATE AND FOR ELECTRICALLY COUPLING TO A CIRCUIT BOARD |
| US5008656A (en) * | 1984-12-20 | 1991-04-16 | Raytheon Company | Flexible cable assembly |
| DE4015788A1 (en) * | 1990-05-16 | 1991-11-21 | Siemens Nixdorf Inf Syst | ASSEMBLY |
| GB2247782A (en) * | 1990-09-05 | 1992-03-11 | Marconi Gec Ltd | A circuit board assembly |
| WO1992010925A1 (en) * | 1990-12-11 | 1992-06-25 | Robert Bosch Gmbh | Electrical device, in particular a switching and control device for motor vehicles |
| GB2286084A (en) * | 1994-01-28 | 1995-08-02 | Ibm | Electronic package with thermally conductive support |
| WO1998013876A1 (en) * | 1996-09-26 | 1998-04-02 | Samsung Electronics Co., Ltd. | Hybrid microwave-frequency integrated circuit |
| WO1998025306A1 (en) * | 1996-12-04 | 1998-06-11 | Samsung Electronics Co., Ltd. | High-power microwave-frequency hybrid integrated circuit |
| FR2763467A1 (en) * | 1997-05-14 | 1998-11-20 | Siemens Ag | STRUCTURE FOR CONNECTING ELECTRICAL COMPONENTS TO A CENTRAL UNIT |
| EP0938252A2 (en) * | 1998-02-18 | 1999-08-25 | Siemens Aktiengesellschaft | Electrical circuit arrangement |
| WO2003081967A1 (en) * | 2002-03-21 | 2003-10-02 | General Electric Company | Flexible interconnect structures for electrical devices and light sources incorporating the same |
| CN112738972A (en) * | 2019-10-28 | 2021-04-30 | 河北百纳信达科技有限公司 | Heat sink for circuit module and circuit module |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1476404A (en) * | 1973-06-06 | 1977-06-16 | Sharp Kk | Electronic apparatus comprising a flexible substrate and method of making such apparatus |
| GB2006534A (en) * | 1977-10-06 | 1979-05-02 | Asahi Optical Co Ltd | Multi-layer flexible printed circuit board assembly |
| GB1554882A (en) * | 1975-07-28 | 1979-10-31 | Sharp Kk | Electronic assembly including a felxible carrier and manufacture thereof |
| GB2034127A (en) * | 1978-10-13 | 1980-05-29 | Matsushita Electric Ind Co Ltd | Printed circuits and methods their manufacture |
| GB2035701A (en) * | 1978-10-19 | 1980-06-18 | Cii Honeywell Bull | Flat package for integrated circuit devices |
| GB2037489A (en) * | 1978-12-18 | 1980-07-09 | Sony Corp | Circuit Components Interconnected by Solder Layers |
| GB2047474A (en) * | 1978-10-19 | 1980-11-26 | Cii Honeywell Bull | A strip carrying devices for processing electrical signals, and a method of producing the strip |
-
1983
- 1983-04-12 GB GB08309899A patent/GB2129223A/en not_active Withdrawn
- 1983-04-25 GB GB838311200A patent/GB8311200D0/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1476404A (en) * | 1973-06-06 | 1977-06-16 | Sharp Kk | Electronic apparatus comprising a flexible substrate and method of making such apparatus |
| GB1554882A (en) * | 1975-07-28 | 1979-10-31 | Sharp Kk | Electronic assembly including a felxible carrier and manufacture thereof |
| GB2006534A (en) * | 1977-10-06 | 1979-05-02 | Asahi Optical Co Ltd | Multi-layer flexible printed circuit board assembly |
| GB2034127A (en) * | 1978-10-13 | 1980-05-29 | Matsushita Electric Ind Co Ltd | Printed circuits and methods their manufacture |
| GB2035701A (en) * | 1978-10-19 | 1980-06-18 | Cii Honeywell Bull | Flat package for integrated circuit devices |
| GB2047474A (en) * | 1978-10-19 | 1980-11-26 | Cii Honeywell Bull | A strip carrying devices for processing electrical signals, and a method of producing the strip |
| GB2037489A (en) * | 1978-12-18 | 1980-07-09 | Sony Corp | Circuit Components Interconnected by Solder Layers |
Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3545527A1 (en) * | 1984-12-20 | 1986-07-03 | Raytheon Co., Lexington, Mass. | FLEXIBLE ELECTRICAL CONNECTING DEVICE AND METHOD FOR THEIR PRODUCTION |
| GB2169750A (en) * | 1984-12-20 | 1986-07-16 | Raytheon Co | Flexible cable assembly |
| US5008656A (en) * | 1984-12-20 | 1991-04-16 | Raytheon Company | Flexible cable assembly |
| DE3614086A1 (en) * | 1985-04-26 | 1986-10-30 | Sgs Microelettronica S.P.A., Catania | DEVICE AND METHOD FOR THERMALLY COUPLING A SEMICONDUCTOR BUILDING UNIT TO A COOLING PLATE AND FOR ELECTRICALLY COUPLING TO A CIRCUIT BOARD |
| DE3614086C2 (en) * | 1985-04-26 | 1998-06-04 | Sgs Microelettronica Spa | Device for heat dissipation from a unit containing electronic components and method for thermally coupling a unit containing electronic components |
| DE4015788A1 (en) * | 1990-05-16 | 1991-11-21 | Siemens Nixdorf Inf Syst | ASSEMBLY |
| GB2247782A (en) * | 1990-09-05 | 1992-03-11 | Marconi Gec Ltd | A circuit board assembly |
| WO1992010925A1 (en) * | 1990-12-11 | 1992-06-25 | Robert Bosch Gmbh | Electrical device, in particular a switching and control device for motor vehicles |
| GB2286084B (en) * | 1994-01-28 | 1998-01-14 | Ibm | Electronic package with thermally conductive support member having a thin circuitized substrate and semiconductor device bonded thereto |
| GB2286084A (en) * | 1994-01-28 | 1995-08-02 | Ibm | Electronic package with thermally conductive support |
| WO1998013876A1 (en) * | 1996-09-26 | 1998-04-02 | Samsung Electronics Co., Ltd. | Hybrid microwave-frequency integrated circuit |
| WO1998025306A1 (en) * | 1996-12-04 | 1998-06-11 | Samsung Electronics Co., Ltd. | High-power microwave-frequency hybrid integrated circuit |
| FR2763467A1 (en) * | 1997-05-14 | 1998-11-20 | Siemens Ag | STRUCTURE FOR CONNECTING ELECTRICAL COMPONENTS TO A CENTRAL UNIT |
| EP0938252A2 (en) * | 1998-02-18 | 1999-08-25 | Siemens Aktiengesellschaft | Electrical circuit arrangement |
| EP0938252A3 (en) * | 1998-02-18 | 2001-02-14 | Siemens Aktiengesellschaft | Electrical circuit arrangement |
| WO2003081967A1 (en) * | 2002-03-21 | 2003-10-02 | General Electric Company | Flexible interconnect structures for electrical devices and light sources incorporating the same |
| CN112738972A (en) * | 2019-10-28 | 2021-04-30 | 河北百纳信达科技有限公司 | Heat sink for circuit module and circuit module |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8309899D0 (en) | 1983-05-18 |
| GB8311200D0 (en) | 1983-06-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |