WO1994013014A1

WO1994013014A1 - Disc-formed, heat producing electronic element

Info

Publication number: WO1994013014A1
Application number: PCT/SE1993/001004
Authority: WO
Inventors: Waldemar Belwon; Gösta HESSLOW; Tomas Melberg
Original assignee: Asea Brown Boveri Ab
Priority date: 1992-11-24
Filing date: 1993-11-22
Publication date: 1994-06-09
Also published as: WO1994013012A1; SE9203533L; SE500281C2; SE9203533D0

Abstract

The invention relates to a heat-generating electronic circuit board, comprising a board substrate (12) of electrically non-conducting material with at least one circuit pattern (14) formed thereon, on which semiconductors are mounted. The circuit pattern (14) has a section (B) with terminals (16) for contacts. The substrate is divided into a substrate portion (24) supporting semiconductors and a substrate portion (22) separated therefrom and supporting terminals (16) of the circuit pattern, said substrate portions being flexibly held together by the circuit pattern (18) therebetween. The invention also relates to a process for manufacturing such an electronic circuit board, whereby a score (20) is made on one side of the substrate along a portion thereof separating the terminal portion (22) from the semiconductor portion (24), whereafter the substrate is broken along the score and the substrate portions are pulled apart with the portions held at an angle to each other so that freed bridges (18) are formed in the circuit pattern, said bridges flexibly connecting the terminal substrate portion (22) with the semiconductor substrate portion (24).

Description

DISCFOR ED, HEAT PRODUCING ELECTRONIC ELEMENT

The present invention relates to a heat-generating electronic circuit board, comprising a board substrate of electrically non-conducting material with at least one circuit pattern laid thereon, on which semiconductors, in particular power semiconductors, are mounted, said circuit pattern having a section with terminals for contacts. The invention also relates to processes for manufacturing such heat-generating electronic circuit boards.

When installing heat-generating electronic circuit boards of the type described by way of introduction, it is in certain cases desirable to make possible a certain amount of movement between, on the one hand, the contact-supporting portion of the circuit on the substrate board and, on the other hand, the portion of the substrate board supporting the heat-gene¬ rating electronic elements, especially power semiconductors. One example is when such power electronics boards are to be mounted in a heat sink, where the connecting and disconnect¬ ing of external contacts with the contact-supporting portion of the circuit should not affect the position of the semi¬ conductor-supporting portion of the board and where movements of materials due to temperature variations of the various electrical components should be able to be taken up between the contact portion and the semiconductor portion of the circuit board. Furthermore, it is desirable to achieve such an electronic circuit board which facilitates installation of the same inside a hollow heat sink.

For this purpose, the electronic circuit board described by way of introduction is characterized, according to the in¬ vention in its broadest sense, in that the substrate is divided into a semiconductor-supporting substrate portion and at least one substrate portion separate therefrom and sup¬ porting terminals of the circuit pattern, said substrate portions being flexibly connected by the circuit pattern therebetween.

According to a preferred embodiment of the invention, the substrate portions are flexibly connected by the circuit pattern by means of circuit pattern bridges freed from at least one of the opposing edge portions of the substrate por¬ tions. The contact portion of the substrate supporting the terminals is thus given greater freedom in its positioning in a heat sink, e.g. of the type described in our Swedish Patent Application ΞE-A-9203533-6 , it being possible to insert this contact board portion into a groove in the heat sink, there receiving the contact pins of a contact means which can be inserted into the heat sink and at the same time keeping the semiconductor-supporting portion of the board fixed against a wall of the heat sink.

According to an alternative embodiment, the substrate por¬ tions can be separated from each other by an intermediate strip of substrate material broken therefrom. In such an embodiment, it is not necessary to pull the substrate por¬ tions apart in order to free the bridges of the circuit between the substrate portions. The freedom of movement of the contact portion is, however, somewhat limited in compari- son with the embodiment without the intermediate substrate strip. By removing the strip of substrate material, the freedom of movement can, however, be increased between the substrate portions.

The present invention suggests also a process for manufactur¬ ing heat-generating circuit boards, comprising a board sub¬ strate of electrically non-conductive material with at least one circuit pattern formed thereon, on which semiconductors, in particular power semiconductors, are mounted, said circuit pattern having a section with terminals for contacts, in which process a score is formed on one side of the substrate along a portion thereof which separates the portion with the terminals from the portion of the circuit pattern supporting the semiconductors, whereafter the substrate is broken along the score, whereupon the substrate portions are pulled apart with the portions at an angle to each other, so that freed bridges are formed in the circuit pattern, said bridges flexibly connecting the terminal substrate portion with the semiconductor substrate portion.

Alternatively, it is possible to make two parallel scores on one side of the substrate along a portion thereof, which separates the terminal portion from the semiconductor portion of the circuit board, whereafter the substrate is broken in two along the scores, so that the substrate portions are held ovably together via a bridge of the circuit with a strip of substrate material adhering thereto.

The scores can suitably be formed by laser scoring and can be prescored on the substrate board, i.e. before the circuit is laid on the other side of the substrate board.

The invention will be described in more detail below with reference to the accompanying drawings,, of which

Fig. 1 shows a plan view of a board substrate with a cir¬ cuit etched thereon with a terminal zone and a semi¬ conductor-supporting zone;

Fig. 2a is a cross section through a circuit board according to Claim 1, which is divided along a score on the underside of the substrate;

Fig. 2b is a cross section through a circuit board according to Fig. 1, which has been divided along two parallel scores; and

Fig. 3 is a schematic cross section through a heat sink in the form of a hollow profile with a circuit board according to Fig. 2a mounted therein with a signal electronics unit connected thereto. In Fig. 1, 10 generally designates an electronic circuit board in the form of a circuit 14 applied to a board sub¬ strate 12 of electrically non-conducting material, such as A1_0_, said circuit being etched from a metallic layer of copper for example. The circuit 14 lies within an area A, within which i.a. heat-generating semiconductors, such as power semiconductors (not shown) are mounted, and an area B within which the circuit terminals 16 for contacts are placed. An area C between areas A and B has conducting brid- ges 18 which connect the terminals 16 in area B to the cir¬ cuit pattern and the semiconductors in area A.

According to a preferred example of the electronic circuit board according to the invention, a score, e.g. in the form of a laser score 20, is made on the underside of the board substrate 12 and extends the length of area C. After contacts (not shown in Fig. 1) have been fixed to the terminals 16 in area B and heat-generating semiconductors have been mounted on the circuit portion of area A, the substrate board 12 is snapped along the score 20, whereafter the freed substrate portions 22 and 24 are pulled apart at an angle to each other so that the circuit 14 separates from the lateral edges of the respective substrate portions 22,24 within area C in Fig. 1, so that conducting bridges 18 are exposed between the sub- strate portions 22,24, forming a hinge, as indicated by the arrow 26 in Fig. 2a. This gives the contact-supporting sub¬ strate portion 22 (the contact portion) relatively great freedom of movement in relation to the semiconductor support¬ ing substrate portion 24 (the semiconductor portion) , which is designed to be fixed securely in a heat sink for example, as will be described in more detail below.

According to an alternative embodiment of the electronic cir¬ cuit board according to the invention, two parallel scores, in the form of laser scores 28,30 (Fig. 1) for example, are made on the underside of the substrate board, said scores defining area C for the conducting bridges 18. As is shown in Fig. 2b, the substrate board 12 is broken along these scores 28 and 30, and the contact supporting substrate portion 22 is still connected with the semiconductor portion 24 via the conducting bridges 18, to the underside of which a strip 32 adheres of the area C substrate. In this example, the sub¬ strate portion 22 can be moved relative to the substrate por¬ tion 24 with the portion 18,32 forming a hinge between the substrate portions 22,24, even if the freedom of movement is more limited than in the embodiment in Fig. 2a. It is also possible to remove the strip 32, thus increasing the freedom of movement between the substrate portions 22 and 24.

Fig. 3 shows a heat sink 34 preferably in the form of an extruded aluminum hollow profile of essentially rectangular cross sectional shape. The profile 34 has an inner space 38, and three of its four sides are provided with heat dissi- pating fins 40. The upper side 42 of the hollow profile in Fig. 3 is a mounting flange for the heat sink 34 on a sup¬ porting component (not shown) . The heat sink 34 is intended to hermetically enclose an electronics unit 44, which in the example shown consists of power semiconductor elements mount- ed on the board substrate portion 24, a contact portion 22 including the terminals 16 and contacts 46, and a control or signal electronics unit 48 with a contact 50 and legs 52 connecting the control electronics unit 48 with the power semiconductors on the board 24.

The power electronics portion 24 of the board is designed to be clamped with even contact pressure against the wall 54 of the cavity 38 so that heat generated in the power semiconduc¬ tor portion 24 can be effectively conducted to the heat sink 34 and its heat dissipating fins 40. In order to provide a protective hermetic seal of the entire electronics unit 44 in the cavity 38 of the heat sink 34, the openings of the cavity 38 can be sealed by means of end covers (not shown) . The end covers are preferably made in the manner described in more detail in our Swedish patent application SE-A-9203532-8 and they have the double function of fixing the position of the semiconductor portion 24 with even force against the cavity wall 54 and hermetically sealing the end openings of the cavity 38 by seals on the peripheral edge of the cover. Prior to insertion of the clamping and fixing covers, in order to facilitate the insertion of the power electronics portion 24 and its contact portion 22 through one end opening of the cavity 38, the cavity can be provided with grooves or shoulders 56 and 58.

The heat sink 34 also has an opening 60 in its mounting flange side 42 for a contact plug 62 of insulating material, which has embedded contact pins 64 and 66 for power connec- tion to the corresponding contacts 46 of the contact portion 22 and to the contacts 50 of the control electronics unit 48. The contact plug 62 has a peripheral seal 70 to seal against a shoulder 72. A lock ring 74 is arranged to be inserted into a groove 76 to fix the contact plug 62 in the heat sink 34, compressing the seal 70.

The contact portion 22 is thus made as a circuit board, which is somewhat movably mounted relative to the ridgedly fixed semiconductor portion 24 and is joined thereto via flexible conducting bridges 18. The flexible conductors 18 permit the contact portion 22 to move somewhat in its own plane and axially as the contact plug 62 is inserted into its opening 60, when the contact pins 64 are centered in their associated contacts 46, without affecting the position of the fixed semiconductor portion 24. Furthermore, the material movements due to temperature variations of the various electronics com¬ ponents are absorbed by this flexible mounting of the contact portion 22. The contact pins 66 extend freely through through-holes 78 (Fig. 1) in the contact portion 22 to con- tact with the corresponding contacts 50 on the control elec¬ tronics unit 48.

The installation of an electronics unit 44 in a heat sink 34 serving at the same time as a casing is done as follows:

A pretested and assembled electronics unit 44, consisting of the power semiconductor portion 24 mounted on a substrate, the contact portion 22 and the control electronics unit 48, is inserted into the cavity 38 through one end opening there- in to its intended position, where the semiconductor portion 24 is in contact with one of the cavity walls 54. The contact plug 62 is then placed in the opening 60, and the assembly 22,24,48 is correctly positioned in the cavity 38 with the aid of contact pins 64,66. The two end covers with their clamping elements can then be inserted into the cavity 38 at either end thereof to seal the cavity 38 and at the same time securely clamp and fix the substrate 24 with its power semi¬ conductor components against the cavity wall 54. If the cavity 38 is to be filled with a coolant fluid, which also protects the semiconductor board portions against any aggres¬ sive substances, the contact plug 62 is removed, and the cavity 38 is filled with said fluid through the opening 60. Finally, the contact plug 62 is reinserted.

The invention provides a power electronics circuit board which is particularly suited to heat sinks. The connecting portion (the contact board 22) is flexibly joined to the semiconductor portion 24 by means of flexible conductors 18 to obtain a firmly fixed power semiconductor portion 24 and a contact portion 22 somewhat movable relative thereto.

Claims

1. Heat-generating electronic circuit board, comprising a board substrate (12) of electrically non-conducting material with at least one circuit pattern (14) laid thereon, on which semiconductors, in particular power semiconductors, are mounted, said circuit pattern (14) having a section (B) with terminals (16) for contacts, c h a r a c t e r i z e d in that the substrate is divided into a semiconductor-supporting substrate portion (22) and at least one substrate portion (22) separate therefrom and supporting terminals (16) of the circuit pattern (14), said substrate portions (22,24) being flexibly connected by the circuit pattern (18) therebetween.

2. Electronic circuit board according to Claim 1, c h a r a c t e r i z e d in that the substrate portions (22,24) are flexibly connected by the circuit pattern by means of circuit pattern bridges (18) freed from at least one of the opposing edge portions of the substrate portions.

3. Electronic circuit board according to Claim 1, c h a r a c t e r i z e d in that the substrate portions (22,24) are separated from each other by an intermediate strip (32) of substrate material broken therefrom.

4. Electronic circuit board according to one of Claims 1-3, c h a r a c t e r i z e d in that the substrate portions

(22,24) are oriented at an angle to each other in the posi¬ tion of use of the electronic circuit board (10) .

5. Electronic circuit board according to Claim 4, c h a r a c t e r i z e d in that the angle is about 90°.

6. Electronic circuit board according to one of Claims 1-5, c h a r a c t e r i z e d in that the suostrate portion (22) supporting the terminals (16) of the circuit pattern (14) are provided with through-holes (78) in portions of the substrate free of metal coating for the passage of contact pins (66) of an external contact plug (62) .

7. Electronic circuit board according to one of Claims 1-6, c h a r a c t e r i z e d in that a signal electronics unit (48) in board-form and with its own signal-transmitting contact (50) is connected to the semiconductor portion (24) by means of contact pins (52) .

8. Electronic circuit board according to Claim 7, c h a r a c t e r i z e d in that the portion (22) support¬ ing the terminals is provided with holes (78) for the passage of signal-transmitting contact pins (66) between the contact plug (62) and the contact (50) of the signal electronics unit (48) .

9. Electronic circuit board according to Claim 8, c h a r a c t e r i z e d in that the power electronics portion (24) and the portion (22) supporting the terminals, and the signal electronics unit (48) are made as a prefabri¬ cated unit (44) designed to be inserted in situ and fixed in the cavity (38) of a heat sink.

10. Process for the manufacture of heat-generating electronic circuit boards (10) , comprising a board substrate (12) of electrically non-conductive material with at least one cir¬ cuit pattern (14) formed thereon, on which semiconductors, in particular power semiconductors, are mounted, said circuit pattern (14) having a section (B) with terminals (16) for contacts (46) , c h a r a c t e r i z e d in that a score (20) is formed on one side of the substrate (12) along a portion (C) thereof which separates the portion (22) with the terminals (16) from the portion (24) of the circuit pattern supporting the semiconductors, and that the substrate (12) is broken along the score (20) , whereupon the substrate portions (22,24) are pulled apart with the portions at an angle to each other, so that freed bridges (18) are formed in the circuit pattern, said bridges flexibly connecting the termi¬ nal substrate portion (22) with the semiconductor substrate portion (24) .

11. Process according to Claim 10, c h a r a c t e r i z e d in that the score (20) is formed by laser scoring.

12. Process for the manufacture of a heat-generating elec- tronic circuit board (10) , comprising a board substrate (12) of electrically non-conducting material with at least one circuit pattern (14) formed thereon, on which semiconductors, in particular power semiconductors, are mounted, said circuit pattern (14) having a section (B) with terminals (16) for contacts (46), c h a r a c t e r i z e d in that two paral¬ lel scores (28,30) are formed on one side of the substrate (12) along a portion (C) thereof which separates the portion (22) supporting terminals (16) from the portion (24) of the circuit pattern supporting the semiconductors, and that the substrate (12) is broken along the scores (28,30) , so that the substrate portions (22,24) are held flexibly together via a bridge (18) of the circuit pattern with a strip (32) of the substrate material adhering thereto.

13. Process according to Claim 12, c h a r a c t e r i z e d in that the strip (32) is removed from the conductor bridges (18) .

14. Process according to Claim 12, c h a r a c t e r i z e d in that the scores (28,30) are formed by laser scoring.