CA1244683A - Heat sink mounting - Google Patents
Heat sink mountingInfo
- Publication number
- CA1244683A CA1244683A CA000404261A CA404261A CA1244683A CA 1244683 A CA1244683 A CA 1244683A CA 000404261 A CA000404261 A CA 000404261A CA 404261 A CA404261 A CA 404261A CA 1244683 A CA1244683 A CA 1244683A
- Authority
- CA
- Canada
- Prior art keywords
- heat sink
- circuit board
- stud
- shaft portion
- flange
- 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.)
- Expired
Links
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- Cooling Or The Like Of Electrical Apparatus (AREA)
Abstract
HEAT SINK MOUNTING
ABSTRACT OF THE DISCLOSURE
Disclosed are methods and apparatus for attaching a heat sink mounted semiconductor case to a circuit board employing a stud with a flange near one end. The longer shank is threaded and at least the shorter shank or head stud is tin-plated. The stud may be swaged into a mounting hole in the heat sink and the heat sink and semiconductor case pre-assembled. The pre-assembled unit may then be mounted and soldered to the circuit board along with other circuit components.
ABSTRACT OF THE DISCLOSURE
Disclosed are methods and apparatus for attaching a heat sink mounted semiconductor case to a circuit board employing a stud with a flange near one end. The longer shank is threaded and at least the shorter shank or head stud is tin-plated. The stud may be swaged into a mounting hole in the heat sink and the heat sink and semiconductor case pre-assembled. The pre-assembled unit may then be mounted and soldered to the circuit board along with other circuit components.
Description
~4683 This invcntiOn relates to mcthods and app~ratus or asscmbly of componcnts on circuit board~ and the like.
More particularly, it relates to methods and apparatus for asscmbly and mounting of semiconductor devices and heat sinks for semiconductor devices and the like on printed circuit boards or other mounting substrates.
Many semiconauctor devices generate heat during operatio which must be dissipated to a~oid aamage to the de~ice. In some devices the heat generated is dissipated sufficiently by the enclosure, header or leads. Other devices may be mounted j on heat sinks comprising bodies of thermally conductive materials i such as copper, aluminum or the like which dissipate the heat ¦ generated by the devices lnto the surrounding environment. Such ¦ heat sinks may be extruded or sheet metal bodies incluaing heat ! dissipating fins or the like.
! In many applications it is customary to mount a heat I sink between the semiconductor header or case and ~le substrate ¦ on which the case is mounted, such as a circuit board ¦ or the like, so that the case and heat sink may be held in I intimate broad-area contact to aid in conduction of thermal ! energy from the case to the heat sin~ and so that the case may ! be electrically connected to the mounting substrate by soldering ! or other means, if desired. Conventionally, a circuit employing a plurality of components, some of which utilize heat sinks, is ! pre-assembled with the individual components which do not emplov
More particularly, it relates to methods and apparatus for asscmbly and mounting of semiconductor devices and heat sinks for semiconductor devices and the like on printed circuit boards or other mounting substrates.
Many semiconauctor devices generate heat during operatio which must be dissipated to a~oid aamage to the de~ice. In some devices the heat generated is dissipated sufficiently by the enclosure, header or leads. Other devices may be mounted j on heat sinks comprising bodies of thermally conductive materials i such as copper, aluminum or the like which dissipate the heat ¦ generated by the devices lnto the surrounding environment. Such ¦ heat sinks may be extruded or sheet metal bodies incluaing heat ! dissipating fins or the like.
! In many applications it is customary to mount a heat I sink between the semiconductor header or case and ~le substrate ¦ on which the case is mounted, such as a circuit board ¦ or the like, so that the case and heat sink may be held in I intimate broad-area contact to aid in conduction of thermal ! energy from the case to the heat sin~ and so that the case may ! be electrically connected to the mounting substrate by soldering ! or other means, if desired. Conventionally, a circuit employing a plurality of components, some of which utilize heat sinks, is ! pre-assembled with the individual components which do not emplov
-2- î
6~3 heat sinks positioned on the circuit board. Thereafter, the components are attached to the c;rcuit board by convent~onal wave soldering of the leads to the circuit pads. After cleaning and tr;mming, the circu~t board ls inspected and the heat s~nk and semiconductor device are hand mounted on loose hardware such as bolts or the like wh;ch pass through the circuit board. The leads from each heat sink mounted component must then be hand soldered to the c;rcuit board, the mounting hardware installed, and the clean;ng, tr;mming and ;nspection steps repeated.
In accordance with the present invention all the circuit components, including those mounted with heat sinks as well as the heat s;nk ;tself, may be pre-assembled on a circuit board or the like and soldered to the circu;t board ;n a single solder;ng opérat;on. Ac-cordingly, the additional steps of hand mounting and solder;ng, etc., of heat sink mounted components is el;m;nated, result;ng in a sub-stantial t;me sav;ng and reliability improvement.
In accordance with one aspect of the present invent;on, a novel mount;ng stud ;s employed ;n combinat;on with a heat sink.
The stud compr;ses an elongate shaft, preferably threaded at its first end, hav;ng a radially enlarged port;on, such as a flange, extend;ng outwardly between its ends. The second or head end of the shaft is coated w;th a solder-promot;ng material, such as tin. The first end of the stud extends through a hole in the flat base portion of the heat sink. The shank of the threaded end of the shaft is preferably knurled or serrated adjacent the flange so that the stud may be swaged or force-f;tted ;nto the heat sink mount;ng hole. As a result of this arrangement, the sem;conductor case may be pre-assembled on the heat s;nk with the leads extending through holes ;n the heat sink. The pre-assembled semiconductor device and heat s;nk assembly may then be 46~
1 positioned on the circuit board and the semiconductor device leads 2 and the mounting stud holding the heat sink and case together soldered
6~3 heat sinks positioned on the circuit board. Thereafter, the components are attached to the c;rcuit board by convent~onal wave soldering of the leads to the circuit pads. After cleaning and tr;mming, the circu~t board ls inspected and the heat s~nk and semiconductor device are hand mounted on loose hardware such as bolts or the like wh;ch pass through the circuit board. The leads from each heat sink mounted component must then be hand soldered to the c;rcuit board, the mounting hardware installed, and the clean;ng, tr;mming and ;nspection steps repeated.
In accordance with the present invention all the circuit components, including those mounted with heat sinks as well as the heat s;nk ;tself, may be pre-assembled on a circuit board or the like and soldered to the circu;t board ;n a single solder;ng opérat;on. Ac-cordingly, the additional steps of hand mounting and solder;ng, etc., of heat sink mounted components is el;m;nated, result;ng in a sub-stantial t;me sav;ng and reliability improvement.
In accordance with one aspect of the present invent;on, a novel mount;ng stud ;s employed ;n combinat;on with a heat sink.
The stud compr;ses an elongate shaft, preferably threaded at its first end, hav;ng a radially enlarged port;on, such as a flange, extend;ng outwardly between its ends. The second or head end of the shaft is coated w;th a solder-promot;ng material, such as tin. The first end of the stud extends through a hole in the flat base portion of the heat sink. The shank of the threaded end of the shaft is preferably knurled or serrated adjacent the flange so that the stud may be swaged or force-f;tted ;nto the heat sink mount;ng hole. As a result of this arrangement, the sem;conductor case may be pre-assembled on the heat s;nk with the leads extending through holes ;n the heat sink. The pre-assembled semiconductor device and heat s;nk assembly may then be 46~
1 positioned on the circuit board and the semiconductor device leads 2 and the mounting stud holding the heat sink and case together soldered
3 to the circuit board in a single wave soldering operation along the other
4 components. Accordingly, the conventional subsequent steps of mounting the heat sink with loose hardware, hand soldering and subsequent cleaning, 6 trimming and inspection are totally eliminated. Pre-assembly of the heat 7 sink and semiconductor case in accordance with the invention thus results 8 in vast time savings in circuit board assembly operations, eliminates g tedious hand assembly of circuit boards with loose hardware , and eliminates hand soldering. Thus not only is a vast saving in assembly time realized, 11 bur reliability of solder connections and uniformity of the soldering 12 assembly process is vastly improved.
13 Broadly stated, the invention is a mounting stud, for use 14 in connection with mounting components to a circuit board, comprising: an elongated cylindrical shaft having a flange extending outwardly and radially 16 therefrom between its ends to define first and second shaft portions; the 7 end of said second shaft portion being adapted to fit in a hole formed in 18 the circuit board and to be soldered to the circuit board; and a coating 13 of solder-promoting material covering the end of said second shaft portion.
Other features and advantages of the invention will become 21 more readily understood from the following detailed description when 22 taken in connection with the appended claims and attached drawings in 23 which:
24 Figure 1 is an exploded view of a heat sin~ mounting assembly on a c;rcuit board employing the methods and apparatus of the invention;
Figure 2 is an elevational view of one embodiment of the novel mounting stud of the invention; and Figure 3 is an elevational view of an alternative embodi-ment of the novel mounting stud of the invention.
Assembly of a semiconductor device case and heat sink on a circuit board or the like in accordance with the principles of the invention is illustrated in Figure 1. While the invention is disclosed with particular reference to assembly of a semi-conductor device encapsulated in a standard TO-3 type header and employs a single broad-base heat sink, it will be readily - 4a -lZ446E13 apparent that the principles of the inVentiOn are equally applicable to assembly of circuits employing various othe~
encapsulation cases a~d other forms of heat sinks. 1, As illustrated in FIGURE 1, a conventional printed circuit board 10 (shown only in p~rtion) is employed for mounting and electrically interconnecting a plurality of discrete semiconductor components to form a circuit. conventioAally, the printed circuit board 10 is a non-conductive material having a conductive pattern (not shown) printed on the underside thereof.
Semiconductor devices are positioned on the top surface of the board with their leads extending through holes 11. In the assembly operation, the semiconductor devices are positioned on the top surface of circuit board 10 with the leads 12 extending l through the holes 11 and the leads electrically connected to the l printed conductive cir~uit on the underside of the board by ¦conventional wave soldering methods. The design, fabrication ¦ and assembly of circuit boards and circuit co~ponents is well `
¦ known to those skilled in the art and therefore will not be I described in detail herein.
¦ When the circuit to be fabricated includes components which generate excess thermal energy, it is frequently necessary ¦ to interpose a heat dissipating device, known as a heat sink, between the semiconductor case and the circuit board.
Conventionally, the devices which do not employ heat sinks are first placed on the circuit board ànd their leads solaered to the circuit board by a first wave soldering operation. Thereafter the devices employing heat sinks are attached to the heat sinks by conventional hardware such as screws, bolts or the like - which pass through the circuit board. This is usually accomplishe 1 by posi`tioning the semiconductor case on the heat sinX with the 1 .
II _5_ I
~244~83 semiconductor leads extending through the heat sink and into the I printed circ~it board eyelets. The semiconductor component leads j are then hand soldered to the printed circuit and the heat sink ! and case attached ~o the board with loose hardware. rZrequently, additional hardware or soldering is used to assure electrical contact between the case and the circuit ~oard. Obviously, since the heat sink mounted devices are attached to the heat sink and ¦ the circuit board after the other components have been soldered ¦ thereto, the attachment of heat sink mounted devices is very ! time-consuming and risks damage to the already partially assembled ¦ circuit. Furthermore, since the soldering operation for the other components has been completed, the leads from the heat sink mounted component must be hand soldered to the circuit board. Such hand soldering is not only time-consuming but results in less reliable electrical connections and possible damage to the previously soldered components.
As illustrated in FIGIIRE 1, the heat sink and semiconductor c~ponent may be pre-as~embled employing thè novel mounting stud illustrated in FIGURE 2. Accordingly, the pre-assembled heat sink and semiconductor case assembly may be positioned on the printed circuit board along with the other components and soldered to the circuit board in a single soldering i operation which attaches the assembly to the board, solders the ! leadsj and provides electrical contact with the case.
~As illustrated in FIGURES 1 and 2, the mounting stud 20 ¦! of the invention compriseslan elongated cylindrical shaft having I a relatively `thin flange 21 radially extending therefrom, ! preferably near one end thcreof. Ad]acent the flange 21 and 1. ``' ` `
.
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on the side thereof adjacent the longer portion of the shaft 20 Iis provided a slightly expanded and knurled or serrated base 22.
¦The remainder of the longer portion of the shaft 20 is threaded ¦with standard threads to accept standard nuts or the like. The !entixe stud 20, or at least the head stud portion 23r is preferabl! r tin-plated to aid in forming solder connections thereto.
The stud 20 is force fitted or swaged into a hole 25 in the flat base portion 26 of a heat sink 27. The heat sink may ,~
¦be of various types such as that illustrated in FIGURE 1.
incluaing heat aissipated fins or various other conventional heat sink bodies. The tin-plated stud 20 and the heat sink 27 may i be pre-assembled by suitable machine operations, thus eliminating tedious hand assembly of screws, bolts and the like. A standard ¦semiconductor case 28 is then mounted on the heat sink with the studs 20 passing through mounting holes 29 and the semiconductor device leads 12 extending through holes 30 in the flat base portion 26 of the heat sink. Nuts 31 and lock washers 32 are posi~tioned on the studs 20 and the pre-assembled case and heat slnk is t~en ready for attachment to the circuit board 10.
Since the pre-assem~led heat sink and case is to be attached to the circuit board by soldering, the pre-assembled unit may be treated in exactly the same manner as other circuit components. The components are simply positioned with their leads extenaing thro~gh the -appropriate holes in the board anA
the pre-assembled unit is positioned with the tin-plated heads 23 extendi tnrough e hole6 35 provided for attaching the heat sinj.
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-7- i :IZ~46~33 S;nce the head 23 of the stud 20 ;s pre-tinned, the pre-assembled unit is soldered to the circuit board in the same soldering operation used to solder the leads of the other components.
Therefore, the conventional post-assembly and hand soldering operations are totally elim;nated.
It should be noted that although the heat sink is attached to the circuit board when the head 23 is soldered, the nuts 31 are on the top surface. Accordingly the case 28 may be removed for replacement without removing the heat s;nk. Therefore, servicing and ma;ntenance of circuit boards using the heat sink mounting of the invention ;s quite convenient.
Not only does the assembly process of the invention result in a major time saving; elimination of hand soldering operations improves reliability of the completed c;rcuit boards.
Any hand soldering operation conducted after partial assembly of the circuit board may result in accidental damage to the previously soldered connections. Furthermore, manual handling of the partially assembled boards to attach heat sinks thereto with conventional loose hardware also increases the risk o~ accidental damage. By soldering all the components in a single operation, the risks of post-soldering hand operations are totally eliminated.
The use of tin-plated studs also aids in permitting soldering o~ the heat sink mounting hardware to the circuit board.
While the ;nvention is described herein in terms of t;n-plated components, it will be understood that those skilled in the art that the terms "tin-plated", "pre-tinned" and the like are used herein in the broadest sense to include coatings of conventional solder and solder-aiding or solder-promoting compositions such as tin, tin-lead alloys, fluxes and the like, regardless of the actual composition of the coating or the method by which it is applied.
It will be observed that employing a mounting stud 20 with a thin flange 21 as shown in Figures 1 and 2 results in mounting the flat base portion 26 of the heat sink 27 closely adjacent or even in contact with the circuit board surface. In some situations it is preferrable to mount the heat sink 27 parallel to but spaced from the surface of the circuit board 10.
In such cases, the stud 20 may be manufactured with an axially thickened flange 21. Alternatively, where relatively large spacing between the base 26 of the heat sink and the surface of the circuit board 10 is requ;red, such as for better circulation of cooling air around the heat sink or to permit cleaning under the heat sink or the like, the stud 20 may include a stand-off shank as illustrated in Figure 3.
In the alternative embodiment illustrated in Figure 3, the stud 20 comprises an elongated cylindrical shaft having a relatively thin flange 21 radially extending therefrom. In this embodiment, however, the flange 21 may be near the central portion of the shaft. A slightly enlarged knurled or serrated base 22 is provided on the shaft adjacent one side of the flange 21 and the remainder of the shaft on the same end as the knurled base 22 is provided with standard threads or the like to accept standard nuts. Obviously, other means for securing the semiconductor case to the shaft 20 such as swage clasps or the like may be employed instead of the threaded connections shown. A stand-off shank 40 which is radially enlarged with respect to the head end 42 is interposèd between the flange 21 and the head 42. Since the stand-o~f shank 40 is radially enlarged with respect to the head 42, _ g _ 46~33 a shoulder 41 is provided which rests on the top surface of the circuit board 10 when the head 42 is inserted in the mounting holes 35 in the circuit board. Accordingly, the base 26 of the heat sink 27 is spaced from the circuit board 10 by the axial length of stand-off shank 40. Therefore the stud 20 of Figure 3 may be manufactured with the axial length of stand-off shank 40 of any lenyth des;red to provide the required spacing between the circuit board and the heat sink.
It will be readily appreciated that the funct;ons of flange 21 and stand-off shank 40 can be accomplished by a single radially enlarged shaft or axially thickened flange. It will be further appreciated that the radial dimensions of the stand-off shank are determined by the diameter of the mounting holes 35 in the circuit board. Accordingly, the diameter of the shank 40 need not necessarily be the same as th~t of the remainder of the shaft 20 as shown, but may be larger than that of the remainder of the shaft, depending upon the diameter of the mounting holes 35 in which the stud is to be mounted, so that a shoulder 41 is provided between the head 42 and the stand-off shank 40. Further-more, since only the head 42 will be soldered to the circuit board, only the head 42 need be coated or pre-tinned with a solder-promoting material. If desired, however, the entire stud 20 may be pre-tinned.
While the invention has been described with particular reference to specific embodiments thereof, it is to be understood that the forms of the invention described in detail are to be taken as preferred embodiments thereof, and that various changes and modificat;ons may be resorted to without departing from the spirit and scope of the invention as defined by the appended claims.
13 Broadly stated, the invention is a mounting stud, for use 14 in connection with mounting components to a circuit board, comprising: an elongated cylindrical shaft having a flange extending outwardly and radially 16 therefrom between its ends to define first and second shaft portions; the 7 end of said second shaft portion being adapted to fit in a hole formed in 18 the circuit board and to be soldered to the circuit board; and a coating 13 of solder-promoting material covering the end of said second shaft portion.
Other features and advantages of the invention will become 21 more readily understood from the following detailed description when 22 taken in connection with the appended claims and attached drawings in 23 which:
24 Figure 1 is an exploded view of a heat sin~ mounting assembly on a c;rcuit board employing the methods and apparatus of the invention;
Figure 2 is an elevational view of one embodiment of the novel mounting stud of the invention; and Figure 3 is an elevational view of an alternative embodi-ment of the novel mounting stud of the invention.
Assembly of a semiconductor device case and heat sink on a circuit board or the like in accordance with the principles of the invention is illustrated in Figure 1. While the invention is disclosed with particular reference to assembly of a semi-conductor device encapsulated in a standard TO-3 type header and employs a single broad-base heat sink, it will be readily - 4a -lZ446E13 apparent that the principles of the inVentiOn are equally applicable to assembly of circuits employing various othe~
encapsulation cases a~d other forms of heat sinks. 1, As illustrated in FIGURE 1, a conventional printed circuit board 10 (shown only in p~rtion) is employed for mounting and electrically interconnecting a plurality of discrete semiconductor components to form a circuit. conventioAally, the printed circuit board 10 is a non-conductive material having a conductive pattern (not shown) printed on the underside thereof.
Semiconductor devices are positioned on the top surface of the board with their leads extending through holes 11. In the assembly operation, the semiconductor devices are positioned on the top surface of circuit board 10 with the leads 12 extending l through the holes 11 and the leads electrically connected to the l printed conductive cir~uit on the underside of the board by ¦conventional wave soldering methods. The design, fabrication ¦ and assembly of circuit boards and circuit co~ponents is well `
¦ known to those skilled in the art and therefore will not be I described in detail herein.
¦ When the circuit to be fabricated includes components which generate excess thermal energy, it is frequently necessary ¦ to interpose a heat dissipating device, known as a heat sink, between the semiconductor case and the circuit board.
Conventionally, the devices which do not employ heat sinks are first placed on the circuit board ànd their leads solaered to the circuit board by a first wave soldering operation. Thereafter the devices employing heat sinks are attached to the heat sinks by conventional hardware such as screws, bolts or the like - which pass through the circuit board. This is usually accomplishe 1 by posi`tioning the semiconductor case on the heat sinX with the 1 .
II _5_ I
~244~83 semiconductor leads extending through the heat sink and into the I printed circ~it board eyelets. The semiconductor component leads j are then hand soldered to the printed circuit and the heat sink ! and case attached ~o the board with loose hardware. rZrequently, additional hardware or soldering is used to assure electrical contact between the case and the circuit ~oard. Obviously, since the heat sink mounted devices are attached to the heat sink and ¦ the circuit board after the other components have been soldered ¦ thereto, the attachment of heat sink mounted devices is very ! time-consuming and risks damage to the already partially assembled ¦ circuit. Furthermore, since the soldering operation for the other components has been completed, the leads from the heat sink mounted component must be hand soldered to the circuit board. Such hand soldering is not only time-consuming but results in less reliable electrical connections and possible damage to the previously soldered components.
As illustrated in FIGIIRE 1, the heat sink and semiconductor c~ponent may be pre-as~embled employing thè novel mounting stud illustrated in FIGURE 2. Accordingly, the pre-assembled heat sink and semiconductor case assembly may be positioned on the printed circuit board along with the other components and soldered to the circuit board in a single soldering i operation which attaches the assembly to the board, solders the ! leadsj and provides electrical contact with the case.
~As illustrated in FIGURES 1 and 2, the mounting stud 20 ¦! of the invention compriseslan elongated cylindrical shaft having I a relatively `thin flange 21 radially extending therefrom, ! preferably near one end thcreof. Ad]acent the flange 21 and 1. ``' ` `
.
! - ` ` .
,. .
, I!
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lZ~46~33 , . .
on the side thereof adjacent the longer portion of the shaft 20 Iis provided a slightly expanded and knurled or serrated base 22.
¦The remainder of the longer portion of the shaft 20 is threaded ¦with standard threads to accept standard nuts or the like. The !entixe stud 20, or at least the head stud portion 23r is preferabl! r tin-plated to aid in forming solder connections thereto.
The stud 20 is force fitted or swaged into a hole 25 in the flat base portion 26 of a heat sink 27. The heat sink may ,~
¦be of various types such as that illustrated in FIGURE 1.
incluaing heat aissipated fins or various other conventional heat sink bodies. The tin-plated stud 20 and the heat sink 27 may i be pre-assembled by suitable machine operations, thus eliminating tedious hand assembly of screws, bolts and the like. A standard ¦semiconductor case 28 is then mounted on the heat sink with the studs 20 passing through mounting holes 29 and the semiconductor device leads 12 extending through holes 30 in the flat base portion 26 of the heat sink. Nuts 31 and lock washers 32 are posi~tioned on the studs 20 and the pre-assembled case and heat slnk is t~en ready for attachment to the circuit board 10.
Since the pre-assem~led heat sink and case is to be attached to the circuit board by soldering, the pre-assembled unit may be treated in exactly the same manner as other circuit components. The components are simply positioned with their leads extenaing thro~gh the -appropriate holes in the board anA
the pre-assembled unit is positioned with the tin-plated heads 23 extendi tnrough e hole6 35 provided for attaching the heat sinj.
;'~'' ...,.` ,' '' '.
.' ., ~, , , . ` i.
-7- i :IZ~46~33 S;nce the head 23 of the stud 20 ;s pre-tinned, the pre-assembled unit is soldered to the circuit board in the same soldering operation used to solder the leads of the other components.
Therefore, the conventional post-assembly and hand soldering operations are totally elim;nated.
It should be noted that although the heat sink is attached to the circuit board when the head 23 is soldered, the nuts 31 are on the top surface. Accordingly the case 28 may be removed for replacement without removing the heat s;nk. Therefore, servicing and ma;ntenance of circuit boards using the heat sink mounting of the invention ;s quite convenient.
Not only does the assembly process of the invention result in a major time saving; elimination of hand soldering operations improves reliability of the completed c;rcuit boards.
Any hand soldering operation conducted after partial assembly of the circuit board may result in accidental damage to the previously soldered connections. Furthermore, manual handling of the partially assembled boards to attach heat sinks thereto with conventional loose hardware also increases the risk o~ accidental damage. By soldering all the components in a single operation, the risks of post-soldering hand operations are totally eliminated.
The use of tin-plated studs also aids in permitting soldering o~ the heat sink mounting hardware to the circuit board.
While the ;nvention is described herein in terms of t;n-plated components, it will be understood that those skilled in the art that the terms "tin-plated", "pre-tinned" and the like are used herein in the broadest sense to include coatings of conventional solder and solder-aiding or solder-promoting compositions such as tin, tin-lead alloys, fluxes and the like, regardless of the actual composition of the coating or the method by which it is applied.
It will be observed that employing a mounting stud 20 with a thin flange 21 as shown in Figures 1 and 2 results in mounting the flat base portion 26 of the heat sink 27 closely adjacent or even in contact with the circuit board surface. In some situations it is preferrable to mount the heat sink 27 parallel to but spaced from the surface of the circuit board 10.
In such cases, the stud 20 may be manufactured with an axially thickened flange 21. Alternatively, where relatively large spacing between the base 26 of the heat sink and the surface of the circuit board 10 is requ;red, such as for better circulation of cooling air around the heat sink or to permit cleaning under the heat sink or the like, the stud 20 may include a stand-off shank as illustrated in Figure 3.
In the alternative embodiment illustrated in Figure 3, the stud 20 comprises an elongated cylindrical shaft having a relatively thin flange 21 radially extending therefrom. In this embodiment, however, the flange 21 may be near the central portion of the shaft. A slightly enlarged knurled or serrated base 22 is provided on the shaft adjacent one side of the flange 21 and the remainder of the shaft on the same end as the knurled base 22 is provided with standard threads or the like to accept standard nuts. Obviously, other means for securing the semiconductor case to the shaft 20 such as swage clasps or the like may be employed instead of the threaded connections shown. A stand-off shank 40 which is radially enlarged with respect to the head end 42 is interposèd between the flange 21 and the head 42. Since the stand-o~f shank 40 is radially enlarged with respect to the head 42, _ g _ 46~33 a shoulder 41 is provided which rests on the top surface of the circuit board 10 when the head 42 is inserted in the mounting holes 35 in the circuit board. Accordingly, the base 26 of the heat sink 27 is spaced from the circuit board 10 by the axial length of stand-off shank 40. Therefore the stud 20 of Figure 3 may be manufactured with the axial length of stand-off shank 40 of any lenyth des;red to provide the required spacing between the circuit board and the heat sink.
It will be readily appreciated that the funct;ons of flange 21 and stand-off shank 40 can be accomplished by a single radially enlarged shaft or axially thickened flange. It will be further appreciated that the radial dimensions of the stand-off shank are determined by the diameter of the mounting holes 35 in the circuit board. Accordingly, the diameter of the shank 40 need not necessarily be the same as th~t of the remainder of the shaft 20 as shown, but may be larger than that of the remainder of the shaft, depending upon the diameter of the mounting holes 35 in which the stud is to be mounted, so that a shoulder 41 is provided between the head 42 and the stand-off shank 40. Further-more, since only the head 42 will be soldered to the circuit board, only the head 42 need be coated or pre-tinned with a solder-promoting material. If desired, however, the entire stud 20 may be pre-tinned.
While the invention has been described with particular reference to specific embodiments thereof, it is to be understood that the forms of the invention described in detail are to be taken as preferred embodiments thereof, and that various changes and modificat;ons may be resorted to without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A mounting stud for use in connection with mounting com-ponents to a circuit board comprising:
an elongated generally cylindrical shaft having a flange ex-tending radially outwardly therefrom between its ends to define first and second shaft portions;
the end of said second shaft portion being adapted to fit in a hole formed in the circuit board; and a coating of solder-promoting material covering the end of said second shaft portion.
an elongated generally cylindrical shaft having a flange ex-tending radially outwardly therefrom between its ends to define first and second shaft portions;
the end of said second shaft portion being adapted to fit in a hole formed in the circuit board; and a coating of solder-promoting material covering the end of said second shaft portion.
2. The mounting stud as set forth in claim 1 comprising:
a base member extending radially outwardly from said first shaft portion adjacent the flange for tightly engaging an opening in a heat sink to be mounted on said circuit board.
a base member extending radially outwardly from said first shaft portion adjacent the flange for tightly engaging an opening in a heat sink to be mounted on said circuit board.
3. A mounting stud for connecting a semiconductor case and heat sink on a circuit board comprising:
an elongated generally cylindrical shaft having a flange extending radially outwardly therefrom between its ends to define first and second shaft portions, said flange forming the largest diameter of said stud;
said first shaft portion being externally threaded and sized to extend through an opening in the case;
a base member extending radially outwardly from said first shaft portion adjacent the flange for tightly engaging an opening in the heat sink;
said second shaft portion being adapted to fit in a hole formed in the circuit board; and a coating of solder-promoting material covering the end of said second shaft portion;
whereby the second shaft portion may be soldered to the circuit board, the flange will limit axial movement of the stud into the circuit board or heat sink, the base member will tightly inter-connect the heat sink with the stud, and the threaded shaft portion is available to have a nut affixed thereto to interconnect the case with the stud.
an elongated generally cylindrical shaft having a flange extending radially outwardly therefrom between its ends to define first and second shaft portions, said flange forming the largest diameter of said stud;
said first shaft portion being externally threaded and sized to extend through an opening in the case;
a base member extending radially outwardly from said first shaft portion adjacent the flange for tightly engaging an opening in the heat sink;
said second shaft portion being adapted to fit in a hole formed in the circuit board; and a coating of solder-promoting material covering the end of said second shaft portion;
whereby the second shaft portion may be soldered to the circuit board, the flange will limit axial movement of the stud into the circuit board or heat sink, the base member will tightly inter-connect the heat sink with the stud, and the threaded shaft portion is available to have a nut affixed thereto to interconnect the case with the stud.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000404261A CA1244683A (en) | 1979-01-31 | 1982-06-01 | Heat sink mounting |
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US803279A | 1979-01-31 | 1979-01-31 | |
| US8,032 | 1979-01-31 | ||
| US9328179A | 1979-11-13 | 1979-11-13 | |
| US93,281 | 1979-11-13 | ||
| CA343,286A CA1130466A (en) | 1979-01-31 | 1980-01-07 | Heat sink mounting |
| CA000404261A CA1244683A (en) | 1979-01-31 | 1982-06-01 | Heat sink mounting |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1244683A true CA1244683A (en) | 1988-11-15 |
Family
ID=27166540
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000404261A Expired CA1244683A (en) | 1979-01-31 | 1982-06-01 | Heat sink mounting |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1244683A (en) |
-
1982
- 1982-06-01 CA CA000404261A patent/CA1244683A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |