METHOD OF ASSEMBLING A SEMICONDUCTOR POWER MODULE COMPONENT AND A SEMICONDUCTOR POWER MODULE WITH SUCH A MODULE COMPONENT AND MANUFACTURING SYSTEM THEREFOR

Abstract

A method of assembling a semiconductor power module component 30 and a manufacturing system comprising such a semiconductor power module component and a pressing apparatus 20 for manufacturing a semiconductor power module component are described. The semiconductor power module component 30 comprises at least a first element 1, a second element 2 and a third element 3 arranged in a stack 10. The first element 1 and the second element 2 are joined by sintering in a sintering area 4 and the second element 2 and the third element 3 are joined by soldering in a soldering area 6. The sintering and the soldering are simultaneously executed, wherein the soldering area 6 is heated to a temperature of soldering and the sintering area 4 is heated to a temperature of sintering, the temperature of soldering and the temperature of sintering being harmonized to each other. Pressure is being applied to the stack 10, comprising the at least one soldering area 6 and the at least one sintering area 4 with stabilizing means 7 being arranged in the soldering area 6.

Claims

1. A method of assembling a semiconductor power module component comprising at least a first element, a second element and a third element arranged in a stack wherein the first element and the second element are joined by sintering in a sintering area and the second element and the third element are joined by soldering in a soldering area and wherein the sintering and the soldering are simultaneously executed, wherein the soldering area is heated to a temperature of soldering and the sintering area is heated to a temperature of sintering, the temperature of soldering and the temperature of sintering being harmonized to each other, and wherein pressure is applied to the stack comprising the soldering area and the sintering area with stabilizing means being arranged in the soldering area.

2. The method according to claim 1, wherein the pressure is applied to a complete area of the module component comprising at least the first element, the second element and the third element being component parts to be assembled together.

3. The method according to claim 1, wherein the stabilizing means are bumps on a surface of the second element facing the third element or on a surface of the third element facing the second element.

4. The method according to claim 1, wherein the stabilizing means remains solid during soldering.

5. The method according to claim 1, wherein the stabilizing means is solid spacer means placed between the second element and the third element.

6. The method according to claim 5, wherein the solid spacer means is incorporated with soldering material to form a solder preform.

7. The method according to claim 4, wherein the solder preform comprises substantially spherical bodies made of metal, in particular made of copper, glass or ceramics or comprises a wire mesh, in particular made of metal, in particular copper.

8. The method according to claim 1, wherein the second element is a DCB substrate and/or the third element is a base plate.

9. The method according to claim 1, wherein additional component parts are sintered onto the first element and/or the second element simultaneously with the sintering and the soldering of the stack.

10. A manufacturing system comprising a semiconductor power module component having at least a first element, a second element and a third element assembled as a stack, and a pressing apparatus having a heating and a pressing component, wherein the first element and the second element are joined by soldering in a soldering area of the stack and the second element and the third element are joined by sintering in a sintering area of the stack, wherein a heating component for heating to soldering temperature and to a sintering temperature is provided, the temperatures being harmonized to each other, and the pressing apparatus for applying pressure by a soft cushion-like element surrounding component parts of the module completely is provided, wherein soldering and sintering within the stack are carried out simultaneously.

11. The manufacturing system according to claim 10, wherein the soft cushion-like element is housed in an external and an internal boundary element which are displaceable against each other when pressed onto the stack to compress the soft cushion-like element.

12. The manufacturing system according to claim 10, wherein the semiconductor power module component comprises a stabilizing means within the soldering area for taking up the pressure exerted by the pressing apparatus and preventing solder material from being squeezed out of the soldering area.

13. A method of assembling a semiconductor power module comprising a semiconductor power module component assembled according to claim 1.

14. A method of assembling a semiconductor power module component for semiconductor power module with the following steps: a) apply a sintering paste to a substrate or a chip by printing or by spraying or by painting; b) pick and place the chip onto the sinter paste on the substrate; c) apply the preassembled substrate to a stack of base plate and solder with included stabilizing means in the form of spacers; d) supply heat energy to the stack to temperature of sintering and temperature of soldering, these temperatures being harmonized to each other; e) feed the stack of base plate and preassembled substrate into the sintering-soldering processing press; and f) carry out simultaneous sintering and soldering at the respective temperature and at the pressure applied by the process press.

15. The method according to claim 14, wherein preassembling comprises adding other component parts.

16. The method according to claim 14, wherein the steps a) to f) are carried out after the stack has been provided with a thermal buffer.

17. The method according to claim 14, in which step f) takes place in a process atmosphere comprising an inert gases such as nitrogen, process gases such as formic acid or a combination thereof.

18. The method according to claim 14, in which the step f) takes place at a pressure of 10 mbar to 1.5 bar.

19. A method of assembling a semiconductor power module comprising a semiconductor power module component as claimed in claim 1, and wherein connections are made to the upper face of the substrate, in particular DCB substrate, using wire bonds and in which the semiconductor power module component is encapsulated using a mold compound or attached to a frame with a lid and with a silicone protective filling.

20. The method according to claim 2, wherein the stabilizing means are bumps on a surface of the second element facing the third element or on a surface of the third element facing the second element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Further details of inventive embodiments are described in the subsequent drawing wherein:

[0053] FIG. 1 illustrates the inventive method according to a first embodiment in its simplest form (FIG. 1a) to FIG. 1e));

[0054] FIG. 2 shows a similar embodiment of the invention with a DCB substrate comprising a ceramic center (FIG. 2a) to FIG. 2f));

[0055] FIG. 3 illustrates a similar process of FIGS. 1 and 2 with additionally a thermal buffer on the semiconductor chip (FIG. 3a) to FIG. 3e));

[0056] FIG. 4 shows a pressing apparatus for the soldering and sintering step (FIG. 4a) to FIG. 4b));

[0057] FIG. 5 shows a further embodiment of a fully assembled module after the soldering and sintering step;

[0058] FIG. 6 illustrates a stabilizing means with bumps at the substrate prior to (FIG. 6a)) and after soldering (FIG. 6b));

[0059] FIG. 7 represents stabilizing means in the form of separate space elements prior to (FIG. 7a)) and after soldering (FIG. 7b));

[0060] FIG. 8 shows an embodiment for a soldered preform and how it is assembled (FIG. 8a) and FIG. 8b));

[0061] FIG. 9 shows two embodiments of a semiconductor power module; and

[0062] FIG. 10 shows a flow chart reflecting the method steps for manufacturing the semiconductor power module component according to the invention.

DETAILED DESCRIPTION

[0063] FIG. 1 illustrates the method according to the invention in its simplest form.

[0064] In FIG. 1a) a substrate 2 is represented onto which according to which FIG. 1b) sintering paste 5 is applied onto the upper surface of the substrate 2 which represents the sintering area 4.

[0065] FIG. 1c) shows the way a semiconductor chip 1 is placed on top of the sintering paste the pre-applied to the substrate 2. It would also be possible to apply the sintering paste to the semiconductor chip initially and then place the chip 1 onto the top of the substrate 2. The arrow in FIG. 1c) stands for placing the semiconductor chip 1 which represents the first element of a stack 10 onto the sintering paste 5.

[0066] FIG. 1d) shows the substrate 2 with the sintering paste on top thereon with the semiconductor chip 1 placed onto the sintering paste 5. The substrate 2 is placed onto a base plate 3 with a stabilizing means 7 in the form of a solder preform 8 between the second element 2 in the kind of the substrate and in the third element 3 in the form of a base plate. The solder preform 8 is formed from a metallic mesh within a soldering material. The solder preform 8 can be tailored to the required size of the substrate to be attached to the base plate. Once this structure (stack 10) consisting of the first element 1 to be the semiconductor chip, the sintering paste 5, the second element 2 in the form of the substrate, the stabilizing means 7 in the form of a solder preform 8 and the third element 3 in the form of the base plate is placed into a sintering/soldering press and heated whilst pressure is applied vertically through the structure (see arrow 9), sintering and soldering take place.

[0067] FIG. 1e) represents the structure after the soldering and sintering process for the joins (the sinter join and solder join) are completed. This structure can also be referred to as the soldered and sintered stack 10.

[0068] FIG. 2 shows a similar embodiment as represented in FIG. 1 with the difference that the second element 2 in form of the substrate is a DCB substrate comprising a ceramic center 2a) as an insulating layer with a top copper layer 2b) and a bottom copper layer 2c) on the upper side of the substrate and the lower side of the substrate, respectively. The top copper layer 2b) is broken up into circuit elements to form conducting tracks as required by the defined topology of the power module.

[0069] FIG. 2a) represents the substrate in the form of a ceramic centered layer with a top copper layer 2b) and a bottom copper layer 2c).

[0070] FIG. 2b) represents the partial structure 2 according to FIG. 2a) with a sintering area 4 on top of the middle part of the DCB substrate with sintering paste 5 applied on the upper side of the middle part of the DCB substrate, the complete substrate being comprised of the ceramic insulating layer 2a), the top copper layer 2b) and the bottom copper layer 2c).

[0071] FIG. 2c) corresponds to FIG. 2b) with the first element 1 in the form of a semiconductor chip just about to be placed on top of the sintering paste 5.

[0072] FIG. 2d) shows additional components 15 just about to be placed on other parts of the upper tracks of the DCB substrate with sintering paste 5 therebetween. When the sintering process takes place the semiconductor chip 1 and the additional component parts 15 are each sintered together onto the respective tracks of the top copper layer 2b) of the DCB substrate 2. These additional component parts 15 may be resistors, capacitors, inductors, diodes etc. That means electronical component parts required by the circuitry on the upper surface of the DCB substrate. It is advantageous for these additional component parts 15 to be sintered in place as well since sintering is highly reliable and can take place simultaneously with joining of the other component parts in the power module component;

[0073] FIG. 2e) is similar to the described method according to FIG. 1, however, with the DCB substrate 2 having placed thereon additional component parts 15 and meant for soldering to the base plate 3 with a solder preform 8 therebetween. This arrangement of the stack 10 is prepared for sintering and soldering to be carried out simultaneously under the pressure exerted by the pressing apparatus (not shown here).

[0074] FIG. 2f) shows the structure after temperature and pressure were applied when sintering and soldering joins are completed.

[0075] FIG. 3 represents a similar process as the one according to FIG. 2, but with a thermal buffer 14 as an additional component part just about to be placed on top of the semiconductor chip 1 with a sintering layer 5 therebetween. The sintering paste 5 for sintering the thermal buffer 14 onto the semiconductor chip 1 can be placed onto the surface of the thermal buffer 14 facing to the semiconductor chip 1 or can also be placed thereinstead onto the upper surface of the semiconductor chip 1 facing to the lower side of the thermal buffer 14. The entire stack 10 just about to be sintered and soldered by means of applying pressure 9 and heat, represented by the arrows, is represented in FIG. 3d). And finally, FIG. 3e) shows the complete structure after soldering and sintering step have taken place simultaneously.

[0076] FIG. 4 shows a pressing apparatus 20 prior to and during the soldering and sintering step. The press 20 consists of an open configuration with a size being as big as overlapping the entire assembled structure just about to be subjected to pressure. The lower die 22 of the pressing apparatus 20 comprises a heating element 19 in order to be able to supply heat energy to the stack 10 of assembled component parts to be sintered and soldered simultaneously. The lower die 22 receives the base plate 3 with the DCB substrate to be soldered on the base plate and with the semiconductor chip 1 placed on top of the DCB substrate with a sintering paste 5 there between. The upper die 21 of the pressing apparatus 20 consists of an external boundary element 21a and an internal boundary element 21b which are displaceable against each other when pressure is applied onto the stack 10 that means when the upper die 21 is displaced onto the lower die 22. Within the open structure of the upper die 21 there is a soft cushion-like element 23 which is gently enough not to impose any harm to the component parts of the stack 10 to be sintered and soldered and which to a certain extent represents when being compressed a hydrodynamic pressing means. Pressing is indicated by the arrows 9.

[0077] Heating of the component parts is carried out during the process. The pressure exerted by the soft cushion-like element 23 is a quasi-hydrostatic pressure on the assembled component parts during the soldering and sintering step. The soft cushion-like material may comprise silicone rubber or any other suitable material known in the field.

[0078] FIG. 4b) shows the pressing apparatus 20 in a closed configuration, that means in a configuration overlapping the entire stack, that means the entire module structure, during the soldering and the sintering step of the process. The soft cushion-like element 23 completely surrounds the assembled component parts, that means the stack 10, and subjects the stack 10 to a quasi-hydrostatic pressure over the complete area of the assembled component parts. This enables the sintering to take place under the influence of the heated element. And the heat also allows the solder in the solder preform to melt and to form the solder join between the DCB substrate 2 and the base plate 3. Once the sintering process has been accomplished, the pressing apparatus opened and the assembled structure is cooled down, the solder material solidifies and forms the join between the DCB substrate and the base plate 3.

[0079] FIG. 5 shows an embodiment in a fully assembled form after soldering and sintering step have been successfully completed with the difference to FIG. 4b) in that the structure of the base plate has cooling channels 18 within it which are suitable for the passage of a fluid coolant for extracting heat generated by the semiconductor chip 1 when in use.

[0080] FIG. 6 shows another embodiment in a simplified form which illustrates just a substrate 2 and a base plate 3 with the substrate 2 having stabilizing means 7 in form of bumps 16 facing towards the upper side of the base plate.

[0081] FIG. 6a) shows the state just about before soldering without even the soldering layer between the two components.

[0082] FIG. 6b) illustrates the complete join where the solder lays between the substrate 2 and the base plate 3 as soldering layer 11. The bumps 16 ensure when the pressure is supplied for sintering and soldering process step that the space between the substrate 2 and the base plate 3 is just about as thick as the soldering layer 11 is supposed to be so that the high quality strength and other properties can be guaranteed.

[0083] FIG. 7 shows a similar embodiment as the one of FIG. 6, however, instead of bumps arranged on the substrate 2 separate spacer elements as stabilizing means 7 are arranged within the soldering layer 11 between the substrate 2 and the base plate 3. The spacer elements ensure the sufficient distance between the substrate 2 and the base plate 3 when the soldering process step takes place to guarantee the required thickness of soldering layer 11 (see FIG. 7b)).

[0084] FIG. 8 shows an example of a solder preform 8 and how it is assembled.

[0085] FIG. 8a) illustrates a wire mesh, for example, made of copper wires. This metal wire mesh 17 represents the stabilizing means 7 to guarantee a proper spacing between the substrate 2 and the base plate (not shown) for ensuring the correct thickness of the soldering layer.

[0086] FIG. 8b) shows how this wire mesh is incorporated into a solder preform 8 which then can be inserted between the substrate and the base plate as described before.

[0087] FIG. 9 shows two embodiments of a semiconductor power module with a semiconductor power module component according to FIG. 3.

[0088] The assembling of the power module 40 would be completed by the addition of connections 24 to the upper face of the DCB substrate and the various additional component parts thereon, using, as it is known in the prior art, wire bonds 25 or other mechanical connectors. Finally, this structure as represented in FIG. 3f) would be, for example, encapsulated using a mold compound (FIG. 9a)) or attached to a frame 27 but inbuilt connections (FIG. 9b)) to complete the power module, with a lid covering the power module component 30 together with the frame 27 and with a silicone protective filling 29.

[0089] FIG. 9a represents a molded semiconductor power module with the semiconductor power module component embedded in a molding compound, whereas FIG. 9b) represents a frame-based semiconductor power module with the semiconductor power module component embedded in a silicone gel protective filling.

[0090] FIG. 10 shows a principal flow chart for the method of manufacturing an inventive semiconductor power module component.

[0091] The meanings of the various reference characters are:

[0092] START: Start

[0093] A: Applying sinter paste to a substrate or a chip which could be carried out by printing or by spraying or painting;

[0094] B: picking and placing the chip onto the sinter paste on the substrate;

[0095] C: preassembling of the substrate, if required, wherein preassembling comprises adding other components parts or other connections;

[0096] D: applying the preassembled substrate to a stack of base plate and solder with included stabilizing means in the form of spacers;

[0097] E: supplying heat energy to the stack to temperature of sintering and temperature of soldering, these temperatures being harmonized to each other;

[0098] F: feeding the stack of base plate and preassembled substrate into the sintering-soldering processing press and carrying out sintering and soldering at the respective temperature according to e).

[0099] G: For a module requiring a thermal buffer, such a stack with a thermal buffer can be placed by applying paste to the chip or the buffer and placing this kind of stack on the chip before carrying out step A or after step B.

[0100] END: End.

[0101] While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.