Classifications

• • 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
  • H05K7/00—Constructional details common to different types of electric apparatus
  • H05K7/20—Modifications to facilitate cooling, ventilating, or heating
• • 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
  • H05K1/0206—Cooling of mounted components using means for thermal conduction connection in the thickness direction of the substrate by printed thermal vias
• • 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
• • 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
  • H01L2023/405—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 package
• • 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
  • H01L2023/4056—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 additional heatsink
• • 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
• • 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
  • H01L2023/4068—Heatconductors between device and heatsink, e.g. compliant heat-spreaders, heat-conducting bands
• • 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
  • H01L2924/0001—Technical content checked by a classifier
  • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• • 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
• • 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
  • H05K2201/02—Fillers; Particles; Fibers; Reinforcement materials
  • H05K2201/0203—Fillers and particles
  • H05K2201/0206—Materials
  • H05K2201/0209—Inorganic, non-metallic particles
• • 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
  • H05K2201/06—Thermal details
  • H05K2201/066—Heatsink mounted on the surface of the PCB
• • 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
  • H05K2201/09209—Shape and layout details of conductors
  • H05K2201/09372—Pads and lands
  • H05K2201/0949—Pad close to a hole, not surrounding the hole
• • 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
  • H05K2201/09209—Shape and layout details of conductors
  • H05K2201/095—Conductive through-holes or vias
  • H05K2201/0959—Plated through-holes or plated blind vias filled with insulating material
• • 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
  • H05K2201/09209—Shape and layout details of conductors
  • H05K2201/09654—Shape and layout details of conductors covering at least two types of conductors provided for in H05K2201/09218 - H05K2201/095
  • H05K2201/0969—Apertured conductors
• • 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
  • H05K2201/10689—Leaded Integrated Circuit [IC] package, e.g. dual-in-line [DIL]
• • 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
  • H05K2201/10734—Ball grid array [BGA]; Bump grid array
• • 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
  • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
  • H05K2203/01—Tools for processing; Objects used during processing
  • H05K2203/0104—Tools for processing; Objects used during processing for patterning or coating
  • H05K2203/0126—Dispenser, e.g. for solder paste, for supplying conductive paste for screen printing or for filling holes
• • 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
  • H05K3/40—Forming printed elements for providing electric connections to or between printed circuits
  • H05K3/4038—Through-connections; Vertical interconnect access [VIA] connections
  • H05K3/4053—Through-connections; Vertical interconnect access [VIA] connections by thick-film techniques
  • H05K3/4069—Through-connections; Vertical interconnect access [VIA] connections by thick-film techniques for via connections in organic insulating substrates

Definitions

• heat sinks are conventionally used. For efficient heat exchange to occur, it has sometimes been deemed necessary for heat sink to be intimately attached directly to a printed circuit board. However, this raises a problem in that it may be required to dismantle a printed circuit board and heat sink assembly for inspection, modification, or repair purposes and separation of the board from the heat sink may be virtually impossible without attendant destruction to one or more parts of the assembly.
• heat sinks are located on the same side of a printed circuit board as the electronic components so that the components lie between the board and the heat sink. Heat is transferred to the heat sink by a heat transfer medium compound from the electronic components. Again, there is the problem of disassembly of the parts should this be required for any reason. Further, if the compound is applied into position before assembly of the parts. This may not result in a satisfactory thermal connection between adjacent surfaces for promoting heat conduction. This latter method of assembly also is laborious and time consuming. Examples of this type of structure are to be found in U.S. Patents Nos. 4,849,856 and 4,914,551.
• the present invention seeks to provide a method of forming a printed circuit board and heat sink assembly which minimizes the above problems.
• the present invention provides a method of making a printed circuit board and heat sink structure assembly comprising:- providing a structure comprising a printed circuit board and an electronic component mounted upon a first side of the printed circuit board; providing a heat sink structure with a hole defined through the heat sink structure; relatively disposing the printed circuit board structure and the heat sink structure with a first side of the heat sink structure facing and spaced from the printed circuit board structure and with the hole having its axis extending in a direction generally towards the electronic component; and creating a heat conductive path from the heat sink structure to the printed circuit board structure by causing a flowable thermally conductive material or compound to flow through the hole so as to occupy and remain in a spatial region between and in heat conductive contact with the heat sink structure and the printed circuit board structure and in alignment with the electronic component.
• the printed circuit board and heat sink structures are assembled together into their relative positions before the thermally conductive compound is cast in position. Because the thermally conductive material or compound is caused to flow between the two structures subsequent to their assembly together, then the flowing material intimately contacts the surfaces of the two structures between which heat is to be conducted thereby maximizing the thermal conductive efficiency of the assembly.
• the thermal conductive material is not positioned upon one of the structures before the other structure is located in position and thus any slow and messy assembly steps are avoided.
• the flowable material is caused to flow through a hole in the heat sink structure, then the method is particularly suitable for use with injection apparatus, i.e.
• the resultant assembly of the printed circuit board and heat sink structures is known to optimize heat removal from components mounted upon a printed circuit board and is thus particularly relevant to removal of heat from printed circuit board structures in which the heat generated could result in electronic component failure for malfunction if not conducted away with suitable efficiency.
• the process steps may be followed with the heat sink structure facing either the first side or a second side of the printed circuit board structure.
• the thermally conductive material is caused to flow through the hole to fill a spatial region between the heat sink structure and the electronic component itself.
• the thermally conductive material is in direct heat conductive contact with the electronic component which lies closest to the heat sink structure.
• the thermally conductive material in flowing through the hole occupies a spatial region between the heat sink structure and the printed circuit board itself.
• thermally conductive material For maximizing heat conduction from the electronic component, there must be some heat conductive path from the thermally conductive material in the spatial region through the board and towards the electronic component. This is conveniently provided by causing the thermally conductive material to flow from the spatial region through at least one aperture in the printed circuit board and towards and preferably into heat conductive contact with the electronic component. In a practical method, a first mass of the thermally conductive material is caused to flow between the first side of the printed circuit board and the electronic component and a second mass of the material is then caused to flow between the side second side of the printed circuit board and the heat sink structure.
• This may be conveniently performed by inserting an injection means through the hole in the heat sink structure and into the aperture in the printed circuit board and injecting the first mass between the first side of the board and the component and subsequently withdrawing the injection means from within the aperture so that it is inserted only into the hole of the heat sink structure whereby the second mass may be caused to flow between the second side of the board and the heat sink structure.
• the first mass is caused to flow between the first side of the board and the electronic component while the two structures are separate from one another and then after the structures are assembled together the second mass is caused to flow through the hole to occupy the space between the board and the heat sink structure.
• the method of the invention may advantageously be used while enabling the heat sink itself to be removed from the printed circuit board structure thereby rendering the board or the electronic component immediately accessible for maintenance, replacement or for inspection purposes.
• This may be accomplished when the heat sink structure comprises a heat sink and a heat exchange element thermally conductively mounted upon the heat sink.
• the heat exchange element is spaced from and opposes the printed circuit board structure while facing towards the electronic component and the settable thermally conductive material is disposed between and in thermally conductive contact with the printed circuit board structure and the heat exchange element.
• the thermally conductive material has an adhesive property which provides adherence between the printed circuit board structure and the heat exchange element
• heat sink release means is provided which enables the heat sink to be removed from the heat exchange element which remains carried upon the printed circuit board structure by the adhesive nature of the thermally conductive material.
• the heat release means conveniently comprises a heat exchange pedestal in screw- threaded arrangement. This screw-threaded arrangement comprises a screw thread on the heat exchange element and a nut engageable on the end region on a side of the heat sink remote from the printed circuit board. Removal of the nut thereby enables heat sink to be detached from the assembly of the printed circuit board structure and the heat exchange element carried thereon by the thermally conductive material. Hence, the electronic component is immediately accessible as related above.
• the screw-threaded means allows for rotation of the heat exchange element within the heat sink.
• either the heat exchange element has a frangible region or the thermally conductive material is itself frangible.
• either the frangible region of the heat exchange element or the frangible thermally conductive material fails thereby enabling for detachment of the heat sink from the printed circuit board.
• the invention is particularly useful in cases in which, as is normal, a plurality of electronic components are disposed between the printed circuit board and the heat sink.
• One problem is normally caused because printed circuit boards are not absolutely planar and together with the fact that electronic components are of different shapes and heights, there is the problem of connecting each of the components to the heat sink directly in a thermally conductive manner with thermally conductive material and while minimizing stresses upon the printed circuit board, electrical components or termination leads from the components. This problem becomes aggravated during temperature fluctuations caused by in-use equipment environment.
• the present method when placing the electronic components between the board and the heat sink minimizes these problems in that while the spaces between the heat sink and the electronic components may be different from component-to-component, the thermally conductive material injected through individual holes associated with each component, will fill each spatial region as necessary to form a thermally conductive shunt from that component to the heat sink.
• a printed circuit board and heat sink structure assembly comprising:- a structure of a printed circuit board and an electronic component mounted upon a first side of the printed circuit board; a heat sink structure with a hole defined through the heat sink structure; the two structures disposed face-to-face and spaced apart with the hole extending in a direction generally towards the electronic component; and a thermally conductive material that has flowed through the hole to be disposed between the two structures and occupy a spatial region extending across the hole and in thermal conductive contact with both structures and in alignment with the electronic component.
• Figures 1, 2 and 3 are cross-sectional views showing three different stages in the manufacture of an assembly of printed circuit board and heat sink structure according to a first embodiment
• Figure 4 is a view similar to Figures 1 to 3 of the assembly of the first embodiment and showing removal of the heat sink from the assembly to render the printed circuit board and electronic components accessible;
• Figure 5 is a view similar to Figure 3 of an assembly of printed circuit board and heat exchange structures according to a second embodiment
• Figure 6 is a view similar to Figure 5 and showing two assemblies according to the second embodiment mounted together to form an overall assembly with a housing;
• Figure 7 is a view similar to Figure 6 and showing the structure of Figure 6 with one heat sink removed;
• Figures 8 and 9 are views similar to Figures 3 and
• Figure 10 is a view similar to Figure 4 of another modification to the first embodiment
• Figures 11 and 12 show two different stages in the manufacture of an assembly of printed circuit board and heat sink structures according to a third embodiment
• Figure 13 shows the completed assembly of the third embodiment
• Figure 14 relates to an alternate method to that shown in Figures 11 and 12 and shows a first of two different stages in the manufacture of the assembly of the third embodiment
• Figure 15 is a view similar to Figure 13 of a fourth embodiment
• Figure 16 is a cross-sectional view of an assembly according to a fifth embodiment
• Figure 17 is a cross-sectional view of part of the assembly according to a fifth embodiment and to a larger scale
• Figure 18 is a cross-sectional view of the part of the assembly taken along line XVIII-XVIII in Figure 17;
• Figure 19 is a view similar to Figure 18 of a modification to the fifth embodiment.
• FIG 20 is a cross-sectional view through a sixth embodiment.
• a heat sink structure comprises a heat sink 10 with a flat planar member 12 with fins 14 integrally formed from one side of the member 12.
• the heat sink structure also comprises a plurality of heat exchange elements 16 (one being shown) each comprising a wide portion 18 integrally formed with a narrow portion in the form of a cylindrical spindle 20 screw-threaded at an outer free end.
• Each of the elements 16 is assembled to the heat sink by passage through an individual clearance hole 22 in the heat sink and the location of a connecting means in the form of a nut 24 on the fin side of the planar member 12, the nut 24 screw-threadably received upon the screw-thread of the shaft 20.
• the wide portion is thus held in tight thermal- conducting contact with the heat sink.
• a film of thermally conductive grease may be disposed between the wide portion 18 and the heat sink through a dry contact is normally sufficient.
• a printed circuit board 26 is also provided ( Figure 2) .
• the printed circuit board has mounted on one side a plurality of electronic components 28 which are connected by termination leads 30 to circuitry on the board.
• the board and the heat sink are disposed in relative positions as shown in Figure 2 in which the heat sink 6 is located a spaced distance away from the printed circuit board while lying in face-to-face opposition to it by spacers 32 which are secured to the printed circuit board by securing bolts 34.
• the heat exchange elements 16 are prior positioned upon the heat sink 10 so that when assembled to the printed circuit board each of the elements 16 is located with its wide portion 18 spaced from and directly opposing a corresponding individual electronic component 28. This is clearly as shown in Figure 2.
• a settable thermally conductive viscous material which may have adhesive properties is disposed within the spatial region between each electronic component 28 and the wide portion 18 of its corresponding heat exchange element 16.
• This material may be a thermally conductive elastomeric viscous material with a low modulus of elasticity preferably below 5000 psi.
• the elements 16 are provided with holes 36 extending through the elements from side-to-side i.e. coaxially along the shaft 20 and through the wide portion 18 as indicated in Figure 2.
• the thermally conductive material is injected through each of the holes from the outside of the heat sink so as to occupy and fill the spatial regions between the wide portions and the electronic components 28 as shown at 38 in Figure 3 while possibly also intimately engaging the surfaces at each side of the space to provide an efficient heat exchange medium from the components 28 into the elements 16.
• the thermally conductive material after setting then effectively secures the wide portions 18 of the elements 16 to the electronic elements 28 as shown by Figure 3 by injecting the material 38 into the spatial regions after assembly of the printed circuit board and heat sink structures, the material flows progressively across the opposing surfaces to provide intimate engagement with those surfaces thereby ensuring maximized heat conduction from each component to the heat sink. Also, the injection process is clean, efficient and time saving.
• any heat generated by the electronic components is transferred directly with maximum efficiency through the thermally conductive adhesive 38 into the wide portions 18 of the elements 16 and into the heat sink 10 by the thermally conductive contact of the wide portions with the inside surface of the heat sink.
• This particular stage is indicated by Figure 4 in which it can be seen that each of - li ⁇
• the elements 16 remains attached to its respective electronic component 28 by the thermally conductive material 38 lying between them.
• the structure originally was built from two subassemblies, in which one of the subassemblies consisted of the heat sink with the heat exchange elements 16 attached, after the complete assembly 40 has been built, then it is necessary to disassemble the heat exchange assembly by disconnecting the heat sink from each of the elements 16.
• it is a simple matter to add the heat sink once more to complete the assembly by simply aligning the clearance holes 22 with the corresponding shafts 20 and moving the heat sink back into its assembled position as shown in Figure 3, the securing nuts 24 then being added.
• a printed circuit board and heat sink assembly is provided in which the thermally conductive material in flowable condition is easily, quickly and cleanly added by an injection procedure. Also, disassembly of the heat sink to render the printed circuit board or the electronic components accessible is an exceedingly simple matter and may be quickly accomplished without any damage occurring to any of the parts of the assembly. It is also a simple matter to replace the printed circuit board subsequently so as to reform the assembly.
• complete thermal conductive contact is created between each of the electronic components 28 and the heat sink 10 by way of the thermally conductive material 38, minimal stresses are built into the assembly although differences in distance exist between the electronic components and the heat sink. For example, stresses created by temperature expansion differences between the heat sink and printed circuit board.
• the distances between the elements 16 and the components 28 may vary widely, but such variation is unimportant because any spatial region that is created between elements 16 and the corresponding components 28 is easily filled with material 38 while ensuring that thermal conductive contact is ensured. Minimal stresses are built into the assembly therefore between the heat sink and the printed circuit board which could create problems after the assembly has been built.
• a heat sink comprised of a material which has a temperature coefficient of expansion reasonably matched to the printed circuit board, preferably within ⁇ 3X10 ⁇ 6/°C.
• a material which has a temperature coefficient of expansion reasonably matched to the printed circuit board, preferably within ⁇ 3X10 ⁇ 6/°C.
• alloys of copper, or composites or alloys of aluminum and silicon are inexpensive, yet work well.
• a printed circuit board 26 is formed into a printed circuit board structure with a plurality of the electronic components 28 as described in the first embodiment.
• a heat sink 52 has a planar member 54 similar to that of the first embodiment and also has integrally formed spaced parallel fins 56 extending from one side of it.
• this heat sink is also provided with elements 16 as in the first embodiment, these elements being positioned so that in the complete assembly 50 the wide portions 18 of the elements are spaced from and oppose the electronic components 28.
• Thermally conductive material 38 is disposed between the electronic components and the elements 16 in the manner described in the first embodiment.
• the assembly 50 differs from the assembly of the first embodiment in that the heat sink 52 has side walls 58 extending from the four marginal edges of the planar member 54 and outwardly from one side of the plane of the member 54. These side walls have a planar engagement surface 60 facing outwardly and this surface engages an edge region of the printed circuit board 26 so as to hold the printed circuit board a fixed distance away from the planar member 54 of the heat sink preparatory to the material 38 being injected between the components 28 and the elements 16.
• the assembly 50 is particularly useful when combined with a similarly built assembly 50 as shown in Figure 6 when the two assemblies are disposed together in mutually reversed positions so that the walls 58 cooperate from one assembly to the other to form a housing for containing printed circuit board structures.
• the two side walls 58 are provided with means for assembling the side walls together, this means in this instance being in the form of outwardly projecting flanges 62 which abut together for assembly purposes and may be held in position either by brackets (not shown) or by screw-threaded structures to hold against an elongate seal 64.
• each assembly 50 having a printed circuit board mounted thereon, the printed circuit boards in the finished assembly are spaced apart from each other and the electronic components 28 are secured to the elements 16 by the thermally conductive material 38.
• a heat exchange element 70 is similar to the heat exchange element 16 described above except that at the junction of the narrow portion 72 with the wide portion 74 of the element a narrowing neck 76 of the narrow portion is provided to render it frangible.
• Figure 8 shows the complete assembly of the modification and differs from the above embodiments in that the narrow portion 72 is screw- threadably received within a screw-threaded hole 78 in the planar member 12 of the heat sink.
• the set thermally conductive material 38 itself is frangible so that upon insertion of a screw driver into the end slot 80 of the heat exchange element 70, the thermal compound 38 fractures to enable the heat sink 12 to be removed together with the whole of the heat exchange element.
• the heat sink 10 has one or more heat exchange elements mounted upon it in the manner described in the first embodiment.
• the printed circuit board structure is reversed in position so that the electronic components 28 are separated from the heat sink by the printed circuit board 26.
• Figure 11 shows the state of the structure with the heat sink spaced apart from the printed circuit board at a first stage in the application of the settable thermally conductive material 38.
• a plurality of apertures 82 are provided through the printed circuit board to a position beneath each electronic component 28.
• a substantially centrally located aperture 84 is approximately in alignment with the hole 36 through each associated heat exchange element 16.
• a thermally conductive material 38 is applied in two separate masses 38a and 38b (see Figure 12) .
• the first mass 38a in each case, is applied by inserting an injection means in the form of an injection nozzle 86 through a hole 36, the nozzle being sufficiently long to extend into the corresponding aperture 84 as shown by Figure 11.
• the mass 38a is then injected in the spatial region between the printed circuit board 26 and the electronic component 28. This mass moves progressively beneath the component 28 and intimately engages the surface of the component and the surface of the printed circuit board. As shown by Figure 12, the nozzle 86 is then retracted to a position in which its outlet end lies in the aperture 36.
• the second mass 38b of the thermally conductive material 38 is then injected into the spatial region between the printed circuit board and the wide portion 18 of the heat exchange element 6 so as to intimately engage the opposite surface of the printed circuit board and the end surface of the wide portion 18.
• the aperture 84 should be substantially filled with the material 38.
• the apertures 82 should be at least partly filled with compound 38 from each side of the board and preferably the compound should continue through each of the apertures 82 to interconnect the two masses 38a and 38b.
• the apertures 82 may have been pre-filled by solder 88 or by some other thermally conductive material such as copper to assist in transferring the heat from the mass 38a to the mass 38b and then through the heat exchange element 6 into the heat sink.
• each mass 38a is located between its associated electronic component 28 and the printed circuit board 26 before the printed circuit board structure is assembled onto the heat sink structure. With this method, the injection nozzle 86 is passed into the aperture 84 and the mass 38 is injected into the spatial region beneath the component 28. When all of the masses 38a are in position the printed circuit board structure with the masses 38a is completed and is assembled onto the printed circuit board structure.
• the mass 38b is then formed between the printed circuit board and the heat sink 12 in the manner described above with reference to Figure 12.
• the completed construction is again as shown by Figure 13.
• a substantially large aperture 90 provided beneath each component 28 mounted on the printed circuit board 26 there is a substantially large aperture 90 provided.
• This aperture may be elongate or of other shape so as to extend substantially beneath the shape of the associated component 28.
• the nozzle 86 is inserted into each hole 36 and by a single injection operation, a single complete mass of the thermally conductive material 38 is injected into a spatial region extending between the end surface of the wide portion 18 of the heat exchange element to the opposing surface of the associated electronic component 28, the mass 38 passing through the aperture 90 to achieve direct thermal conductive contact from the component to the wide portion 18 of the heat exchange element.
• this particular arrangement is applicable with advantages for extracting heat from electronic components, e.g. of planar configuration and with terminal connections to the printed circuit board by means of ball grid arrays.
• a planar electronic component 92 is disposed on the side of the printed circuit board 26 remote from the heat sink 10 with spacers 32 located in place as described in the above embodiments.
• a heat exchange element is again employed and is disposed with its wide portion 18 facing in a direction towards its corresponding electronic component 92 and with the printed circuit board 26 positioned in between.
• the thermally conductive material 38 occupies the spatial region between the board and the wide portion of each of the heat exchange elements and also passes into apertures 94 in the printed circuit board.
• the apertures 94 are in the form of vias and have conductive footprints 96 on the remote side of the board.
• the footprints 96 are connected to the terminals of the electronic components by solder balls 98 applied in known manner for forming the terminal connections.
• the apertures 94 are provided with linings 100 of conductive material, e.g. copper for connecting each of the terminals of the electronic components to circuitry within the board.
• the viscous thermally conductive material 38 extends into each of the apertures 94 so as to be in direct heat conductive contact with the linings 100 for removal of heat from the electronic components.
• the Thermally conductive material may also be permitted to flow in the space defined by 92, 96.
• additional apertures 102 pass through the printed circuit board between the footprints 96 and these apertures 102 are themselves filled with the thermally conductive material 38 which may also extend through and fill a space between each of the electronic components 92 and the printed circuit board.
• a heat sink structure comprises a heat sink 110 which is formed with holes 112 for alignment with the electronic component 28 mounted upon a printed circuit board 26. Thermal conductive material 38 is injected through the holes 112 to occupy spatial regions between each component 28 and the opposing heat sink surface so as to transfer heat directly from the component to the heat sink.

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• Engineering & Computer Science (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Computer Hardware Design (AREA)
• Power Engineering (AREA)
• Thermal Sciences (AREA)
• Cooling Or The Like Of Electrical Apparatus (AREA)
• Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)

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• 1996
  • 1996-01-19 AU AU44283/96A patent/AU697409B2/en not_active Ceased
  • 1996-01-19 CN CN96191600A patent/CN1114338C/zh not_active Expired - Fee Related
  • 1996-01-19 JP JP8522512A patent/JP2908881B2/ja not_active Expired - Fee Related
  • 1996-01-19 WO PCT/CA1996/000028 patent/WO1996023397A1/en not_active Application Discontinuation
  • 1996-01-19 EP EP96900483A patent/EP0807372A1/de not_active Withdrawn
  • 1996-01-19 KR KR1019970705036A patent/KR19980701642A/ko not_active Application Discontinuation

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