CA1162324A - Heat sink mounting - Google Patents
Heat sink mountingInfo
- Publication number
- CA1162324A CA1162324A CA000404263A CA404263A CA1162324A CA 1162324 A CA1162324 A CA 1162324A CA 000404263 A CA000404263 A CA 000404263A CA 404263 A CA404263 A CA 404263A CA 1162324 A CA1162324 A CA 1162324A
- Authority
- CA
- Canada
- Prior art keywords
- circuit board
- heat sink
- shaft
- flange
- stud
- 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
Landscapes
- 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
~ 162324 This invention relates to mcthods and apparatus for asscmbly of componcnts on circuit boards and the like.
More particularly, it relates to methods and apparatus for assembly and mounting of semiconductor de~ices and heat sinks for semiconductor devices and the like on printed circuit boards or other mounting substrates.
Many semiconductor devices generate heat during operatio which must be dissipated to avoid damage to the device. In some devices the heat generated is dissipated sufficiently by the enclosure, header or leads. Other devices may be mounted on heat sinks comprising boaies of thermally conductive m~terials such as copper, aluminum or-the like which dissipate the heat generated by the devices into the surrounding environment. Such heat sinks may be extruded or sheet metal ~odies including heat dissipating fins or the like.
In many applications it is customary to mount a heat sink between the semiconauctor header or case and the 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 intimate broad-area contact to aid in conduction of thermal energy from the case to the heat sink and so that the case may be electrically connected to the mounting substrate by soldering or other means, if desired. Conventionally, a circuit employin~
a plurality of components, some of which utilize heat sinks, is pre-assembled with the individual co~ponents whicb do not emplo~ ¦
More particularly, it relates to methods and apparatus for assembly and mounting of semiconductor de~ices and heat sinks for semiconductor devices and the like on printed circuit boards or other mounting substrates.
Many semiconductor devices generate heat during operatio which must be dissipated to avoid damage to the device. In some devices the heat generated is dissipated sufficiently by the enclosure, header or leads. Other devices may be mounted on heat sinks comprising boaies of thermally conductive m~terials such as copper, aluminum or-the like which dissipate the heat generated by the devices into the surrounding environment. Such heat sinks may be extruded or sheet metal ~odies including heat dissipating fins or the like.
In many applications it is customary to mount a heat sink between the semiconauctor header or case and the 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 intimate broad-area contact to aid in conduction of thermal energy from the case to the heat sink and so that the case may be electrically connected to the mounting substrate by soldering or other means, if desired. Conventionally, a circuit employin~
a plurality of components, some of which utilize heat sinks, is pre-assembled with the individual co~ponents whicb do not emplo~ ¦
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-~ 1 16232~
heat sinks positioned on the circuit board. Thereafter, the components are attached to ~he circuit board by convent~onal wave soldering of the leads to the circuit pads. After cleaning and trimming, the circuit board is inspected and the heat sink and semiconductor device are hand mounted on loose hardware s~ch-as bolts or the like which pass through the circuit board. The leads from each heat s;nk mounted component must then be hand soldered to the circuit board, the mounting hardware installed, and the cleaning, trimming and ;nspection steps repeated.
In accordance with the present invention all the circuit components, including those mounted with heat sinks as well as the hea~
s;nk itself, may be pre-assembled on a circuit board or the l;ke and soldered to the circuit board in a single soldering operat;on. Ac-cordingly, the additional steps of hand mounting and soldering, etc., of heat sink mounted components is el;m;nated, resulting in a sub-stantial time saving and rel;ability improvement.
In accordance with one aspect of the present invention, a novel mounting stud is employed ;n combination with a heat sink.
The stud compr;ses an elongate shaft, preferably threaded at its first end, having a radially enlarged portion~ such as a flange, extending outwardly between its ends. The second or head end of the shaft is coated with a solder-promoting material, such as tin. The first end of the stud extends through a hole ;n 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 swaQed or force-f;tted into the heat sink mounting hole. As a result of this arrangement, the sem;conductor case may be pre-assembled on the heat sink with the leads extend;ng through holes in the heat s;nk. The pre-assembled semiconductor device and heat sink assembly may then be - I 16232~
positioned on the circuit board and the semiconductor device leads and the mounting stud holding the heat sink and case together soldered to the circuit board in a single wave soldering operation along the other components. Accordingly, the conventional subsequent steps of mounting the heat sink with loose hardware, hand soldering and subsequent cleaning, trimming and inspection are totally el;minated. Pre-assembly of the heat sink and semiconductor case in accordance with the invention thus results in vast time savings in circuit board assembly operations, eliminates ted;ous hand assembly of circuit boards with loose hard-ware, and eliminates hand soldering. Thus not only is a vast saving in assembly time realized, but reliability of solder connections and uniformity of the soldering assembly process is vastly improved.
Broadly stated, the invention is a mounting stud, for use in connection with a circuit board and heat sink, comprising: (a) an elongated shaft with an enlarged flange extending radially therefrom ;ntermediate the ends thereof defining a shaft with a first portion extending in a first direction from said flange and a second portion extending in the opposite direction from said flange, said flange forming the largest diameter of said stud; (b) the end of said second portion of said shaft being adapted to fit in a hole formed in the circuit board and to be soldered to said circuit board; and (c) part of said second portion of said shaft, between said flange and said end portion thereof adapted to fit within the hole in said circuit board, being enlarged with respect to said end, thereby forming a shoulder for resting on the surface of said circuit board to space said flange from the surface of said circuit board~
Other features and advantages of the invention will become more readily understood from the following detailed description when taken in connection with the appended claims and attached drawings in which:
Figure 1 is an exploded view of a heat sink mounting assembly on a circuit 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 -` ` I 162324 Figure 3 is an elevational view of an alternative embodiment 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 semiconductor device encapsulated in a standard TO-3 type header and employs a single broad-base heat sink, it will be readily , ~, .
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.' .
apparent that the principles of the invention are equally applicable to assembly of circuits employing ~arious other encapsulation cases and other forms of heat sinks.
As illustrated in FIGURE 1, a conve~tional printed circuit board 10 (shown only in portion) 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-conauctive 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 extçnding 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 through the holes 11 and the leads electrically connected to the printed conductive circuit on the underside of the board by conventional wave soldering methods. The design, fabrication and assembly of circuit boards and circuit components is well known to those skilled in the art and therefore will not be described in aetail 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 and their leads soldered to the circuit board by a first wave soldering operation. Thereaft~
the devices employing heat sinks are attached to the heat sinks by convent~onal hardware such as screws, bolts or the like . which pass through the circuit board. This is bsually accomplis;
by positioning the semiconductor case on the heat sink with the . `' , ,.
t l6232 i I. .
semiconductor leads extending through the heat sin~ and into the printed circuit board eyelets. The semiconductor comp~nent leads are then hand soldered to the printed circuit and the heat sink land case attached ~o the board with loose hardware. ~requently, additional hardware or soldering is used to assure electrical contact between the case and the circuit board. Obviously, since the heat sink mounted devices are attached to the heat sink and the circuit board after the other components ha~e been solaered ¦ thereto, the attachment of heat sink mounted de~ices is very ¦ time-consuming and risks damage to the already partially assembled ¦ circuit. Furthermore, since the soldering operation for the i other components has been completed, the leads from the heat sink mounted component must be hand solaered 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 FIGURE 1, ~he heat sink and semiconductor c~ponent may be pre-as~emblea employing the novel mounting stud illustrated in FIG~RE 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 operat~on which attaches the assembly to thé board, solders the leadsj and provides electrical contact with the case~
`As illustrated in FIGURES 1 and 2, the mounting stud 20 I of the invention comprises an elongated cylindrical shaft having I a relatively thin flange 21 radially extending therefrom, ¦ preferably near one end thereof. Ad~acent the flange 21 and . .' , . ' `, ~ .
. ~ ., .
I, .
- ~ 116232~ ;
on the side thereof adjacent the longer portion of the shaft 20 is 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 entire stud 20, or at least the head stud portion 23, is preferabl~ , tin-plated to aid in forming solder connections thereto.
The stud 20 is force fittea 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 be pre-asseJ~led 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 hase portion 26 of the heat sink. Nuts 31 and lock washers 32 are pos~tioned on the studs 20 and the pre-assembled case and heat sink is then reaay for attachment to the circuit board 10.
Since the pre-assem~led heat sinX and case is to be attac~ed to the circùit board by soldering, the pre-assembled ~' uni~t may be treated in exactly the same manner as other circuit components. The components are simply positioned with,their leads extenaln~ through the appropriate holes in the board and the pre-assembled unit is positioned with the tin-plated heads 23 e~tending through the holes 35 provided for attaching the heat sin~
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I lB232~
~ince the head 23 of the stud 20 is pre-tinned, the pre-assembled unit is soldered to the circuit board in the same soldering operat;on used to solder the leads of the other components.
Therefore, the convent;onal post-assembly and hand solder;ng operations are totally eliminated.
It should be noted that although the heat s;nk ;s attached to the c;rcuit 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, servic;ng and maintenance of circuit boards using the heat sink mounting of the invent;on ;s ~u;te convenient.
Not only does the assembly process of the invention result in a ma~or time saving; elimination of hand solder;ng operat;ons ;mproves 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 of accidental damage. By soldering all the components in a single opération, the risks of post-soldering hand operations are totally eliminated.
The use of tin-plated studs also aids in permitting soldering of the heat sink mount;ng hardware to the circuit board.
While the invention is descr;bed herein in terms of tin-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 ;n the broadest sense to include coatings of conventional solder and solder-aid;ng or solder-promot;ng compos;t;ons such t 162324 as tin, tin-lead alloys, fluxes and the like, regardless of the actual composition of the coating or the method by ~hich it is applied.
It will be observed that employing a mounting stud 20 with a thin ftange 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 spac;ng between the base 26 of the heat sink and the surface of the circuit board 10 is required, such as for better circulation of cooling air around the heat sink or to perm;t 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 radialiy 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 sha~t 20 such as swage clasps or the l;ke 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 int~rposed ~etween the flange 21 and the head 42. Since the stand-, off shank 40 is radially enlarged with respect to the head 42, l 16232~
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 length desired to provide the reguired 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 s;ngle radially enlarged shaft or axially thickened flange. It will be further apprec;ated 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 inYention has been described with particular reference to specific embodiments thereof, ;t 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 modifications may be resorted to without departing from the spirit and scope of the invention as defined by the appended claims.
-~ 1 16232~
heat sinks positioned on the circuit board. Thereafter, the components are attached to ~he circuit board by convent~onal wave soldering of the leads to the circuit pads. After cleaning and trimming, the circuit board is inspected and the heat sink and semiconductor device are hand mounted on loose hardware s~ch-as bolts or the like which pass through the circuit board. The leads from each heat s;nk mounted component must then be hand soldered to the circuit board, the mounting hardware installed, and the cleaning, trimming and ;nspection steps repeated.
In accordance with the present invention all the circuit components, including those mounted with heat sinks as well as the hea~
s;nk itself, may be pre-assembled on a circuit board or the l;ke and soldered to the circuit board in a single soldering operat;on. Ac-cordingly, the additional steps of hand mounting and soldering, etc., of heat sink mounted components is el;m;nated, resulting in a sub-stantial time saving and rel;ability improvement.
In accordance with one aspect of the present invention, a novel mounting stud is employed ;n combination with a heat sink.
The stud compr;ses an elongate shaft, preferably threaded at its first end, having a radially enlarged portion~ such as a flange, extending outwardly between its ends. The second or head end of the shaft is coated with a solder-promoting material, such as tin. The first end of the stud extends through a hole ;n 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 swaQed or force-f;tted into the heat sink mounting hole. As a result of this arrangement, the sem;conductor case may be pre-assembled on the heat sink with the leads extend;ng through holes in the heat s;nk. The pre-assembled semiconductor device and heat sink assembly may then be - I 16232~
positioned on the circuit board and the semiconductor device leads and the mounting stud holding the heat sink and case together soldered to the circuit board in a single wave soldering operation along the other components. Accordingly, the conventional subsequent steps of mounting the heat sink with loose hardware, hand soldering and subsequent cleaning, trimming and inspection are totally el;minated. Pre-assembly of the heat sink and semiconductor case in accordance with the invention thus results in vast time savings in circuit board assembly operations, eliminates ted;ous hand assembly of circuit boards with loose hard-ware, and eliminates hand soldering. Thus not only is a vast saving in assembly time realized, but reliability of solder connections and uniformity of the soldering assembly process is vastly improved.
Broadly stated, the invention is a mounting stud, for use in connection with a circuit board and heat sink, comprising: (a) an elongated shaft with an enlarged flange extending radially therefrom ;ntermediate the ends thereof defining a shaft with a first portion extending in a first direction from said flange and a second portion extending in the opposite direction from said flange, said flange forming the largest diameter of said stud; (b) the end of said second portion of said shaft being adapted to fit in a hole formed in the circuit board and to be soldered to said circuit board; and (c) part of said second portion of said shaft, between said flange and said end portion thereof adapted to fit within the hole in said circuit board, being enlarged with respect to said end, thereby forming a shoulder for resting on the surface of said circuit board to space said flange from the surface of said circuit board~
Other features and advantages of the invention will become more readily understood from the following detailed description when taken in connection with the appended claims and attached drawings in which:
Figure 1 is an exploded view of a heat sink mounting assembly on a circuit 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 -` ` I 162324 Figure 3 is an elevational view of an alternative embodiment 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 semiconductor device encapsulated in a standard TO-3 type header and employs a single broad-base heat sink, it will be readily , ~, .
- 4a -I 16232~
.' .
apparent that the principles of the invention are equally applicable to assembly of circuits employing ~arious other encapsulation cases and other forms of heat sinks.
As illustrated in FIGURE 1, a conve~tional printed circuit board 10 (shown only in portion) 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-conauctive 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 extçnding 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 through the holes 11 and the leads electrically connected to the printed conductive circuit on the underside of the board by conventional wave soldering methods. The design, fabrication and assembly of circuit boards and circuit components is well known to those skilled in the art and therefore will not be described in aetail 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 and their leads soldered to the circuit board by a first wave soldering operation. Thereaft~
the devices employing heat sinks are attached to the heat sinks by convent~onal hardware such as screws, bolts or the like . which pass through the circuit board. This is bsually accomplis;
by positioning the semiconductor case on the heat sink with the . `' , ,.
t l6232 i I. .
semiconductor leads extending through the heat sin~ and into the printed circuit board eyelets. The semiconductor comp~nent leads are then hand soldered to the printed circuit and the heat sink land case attached ~o the board with loose hardware. ~requently, additional hardware or soldering is used to assure electrical contact between the case and the circuit board. Obviously, since the heat sink mounted devices are attached to the heat sink and the circuit board after the other components ha~e been solaered ¦ thereto, the attachment of heat sink mounted de~ices is very ¦ time-consuming and risks damage to the already partially assembled ¦ circuit. Furthermore, since the soldering operation for the i other components has been completed, the leads from the heat sink mounted component must be hand solaered 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 FIGURE 1, ~he heat sink and semiconductor c~ponent may be pre-as~emblea employing the novel mounting stud illustrated in FIG~RE 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 operat~on which attaches the assembly to thé board, solders the leadsj and provides electrical contact with the case~
`As illustrated in FIGURES 1 and 2, the mounting stud 20 I of the invention comprises an elongated cylindrical shaft having I a relatively thin flange 21 radially extending therefrom, ¦ preferably near one end thereof. Ad~acent the flange 21 and . .' , . ' `, ~ .
. ~ ., .
I, .
- ~ 116232~ ;
on the side thereof adjacent the longer portion of the shaft 20 is 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 entire stud 20, or at least the head stud portion 23, is preferabl~ , tin-plated to aid in forming solder connections thereto.
The stud 20 is force fittea 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 be pre-asseJ~led 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 hase portion 26 of the heat sink. Nuts 31 and lock washers 32 are pos~tioned on the studs 20 and the pre-assembled case and heat sink is then reaay for attachment to the circuit board 10.
Since the pre-assem~led heat sinX and case is to be attac~ed to the circùit board by soldering, the pre-assembled ~' uni~t may be treated in exactly the same manner as other circuit components. The components are simply positioned with,their leads extenaln~ through the appropriate holes in the board and the pre-assembled unit is positioned with the tin-plated heads 23 e~tending through the holes 35 provided for attaching the heat sin~
. . -. . ' ,,. ' " - ., ''`
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I lB232~
~ince the head 23 of the stud 20 is pre-tinned, the pre-assembled unit is soldered to the circuit board in the same soldering operat;on used to solder the leads of the other components.
Therefore, the convent;onal post-assembly and hand solder;ng operations are totally eliminated.
It should be noted that although the heat s;nk ;s attached to the c;rcuit 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, servic;ng and maintenance of circuit boards using the heat sink mounting of the invent;on ;s ~u;te convenient.
Not only does the assembly process of the invention result in a ma~or time saving; elimination of hand solder;ng operat;ons ;mproves 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 of accidental damage. By soldering all the components in a single opération, the risks of post-soldering hand operations are totally eliminated.
The use of tin-plated studs also aids in permitting soldering of the heat sink mount;ng hardware to the circuit board.
While the invention is descr;bed herein in terms of tin-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 ;n the broadest sense to include coatings of conventional solder and solder-aid;ng or solder-promot;ng compos;t;ons such t 162324 as tin, tin-lead alloys, fluxes and the like, regardless of the actual composition of the coating or the method by ~hich it is applied.
It will be observed that employing a mounting stud 20 with a thin ftange 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 spac;ng between the base 26 of the heat sink and the surface of the circuit board 10 is required, such as for better circulation of cooling air around the heat sink or to perm;t 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 radialiy 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 sha~t 20 such as swage clasps or the l;ke 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 int~rposed ~etween the flange 21 and the head 42. Since the stand-, off shank 40 is radially enlarged with respect to the head 42, l 16232~
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 length desired to provide the reguired 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 s;ngle radially enlarged shaft or axially thickened flange. It will be further apprec;ated 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 inYention has been described with particular reference to specific embodiments thereof, ;t 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 modifications may be resorted to without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (3)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A mounting stud, for use in connection with a circuit board and heat sink, comprising:
(a) an elongated shaft with an enlarged flange extending radially therefrom intermediate the ends thereof defining a shaft with a first portion extending in a first direction from said flange and a second portion extending in the opposite direction from said flange, said flange forming the largest diameter of said stud;
(b) the end of said second portion of said shaft being adapted to fit in a hole formed in the circuit board and to be soldered to said circuit board; and (c) part of said second portion of said shaft, between said flange and said end portion thereof adapted to fit within the hole in said circuit board, being enlarged with respect to said end , thereby forming a shoulder for resting on the surface of said circuit board to space said flange from the surface of said circuit board.
(a) an elongated shaft with an enlarged flange extending radially therefrom intermediate the ends thereof defining a shaft with a first portion extending in a first direction from said flange and a second portion extending in the opposite direction from said flange, said flange forming the largest diameter of said stud;
(b) the end of said second portion of said shaft being adapted to fit in a hole formed in the circuit board and to be soldered to said circuit board; and (c) part of said second portion of said shaft, between said flange and said end portion thereof adapted to fit within the hole in said circuit board, being enlarged with respect to said end , thereby forming a shoulder for resting on the surface of said circuit board to space said flange from the surface of said circuit board.
2. The mounting stud as set forth in claim 1 including means for attaching a semiconductor case to said first portion of said shaft.
3. The mounting stud as set forth in claim 1 or claim 2 wherein at least part of the end of said second portion is associated with solder-promoting material to facilitate the connection with the circuit board and the first portion of the shaft comprises means for locking the shaft with a heat sink.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000404263A CA1162324A (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 |
| CA000404263A CA1162324A (en) | 1979-01-31 | 1982-06-01 | Heat sink mounting |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1162324A true CA1162324A (en) | 1984-02-14 |
Family
ID=27426214
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000404263A Expired CA1162324A (en) | 1979-01-31 | 1982-06-01 | Heat sink mounting |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1162324A (en) |
-
1982
- 1982-06-01 CA CA000404263A patent/CA1162324A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |