METHOD FOR MANUFACTURING AN ELECTRONIC POWER MODULE

Abstract

The invention relates to a method for manufacturing a power electronic module (1) by additive manufacturing, characterized in that it comprises the steps of: making or fixing preforms (15) of polymer material on at least one face of an insulating substrate (2a) covered with at least one layer of metal (2b, 2c), referred to as a metallized substrate (2), depositing a first metal layer (17) on the preform (15), depositing by electroforming a second metal layer (18) on the first metal layer (17).

Claims

1.-7. (canceled)

8. A method for manufacturing a power electronic module (1) by additive manufacturing, characterized in that it comprises the steps of: making or fixing preforms (15) of polymer material on at least one face of an insulating substrate (2a) covered with at least one layer of metal (2b, 2c), referred to as a metallized substrate (2), depositing a first metal layer (17) on the preform (15), depositing by electroforming a second metal layer (18) on the first metal layer (17).

9. The method according to claim 8, characterized in that it comprises a step of dissolving the preforms of polymeric material (15) by chemical or thermal means.

10. The method according to claim 9, characterized in that it comprises a step of assembling active components, such as semiconductor power components (3), on the metallized substrate (2a).

11. The method according to claim 8, characterized in that it comprises a step of assembling active components, such as semiconductor power components (3), on the metallized substrate (2a).

12. The method according to claim 8, characterized in that it comprises a step of protecting at least one zone of the metallized substrate (2a) before deposition of the first metal layer (17).

13. The method according to claim 9, characterized in that it comprises a step of protecting at least one zone of the metallized substrate (2a) before deposition of the first metal layer (17).

14. The method according to claim 8, characterized in that the metallized substrate (2) comprises at least one insulating layer (2a) of ceramic.

15. The method according to claim 9, characterized in that the metallized substrate (2) comprises at least one insulating layer (2a) of ceramic.

16. The method according to claim 8, characterized in that the first metal layer (17) has a thickness of less than 5 microns, preferably less than 1 micron.

17. The method according to claim 9, characterized in that the first metal layer (17) has a thickness of less than 5 microns, preferably less than 1 micron.

18. The method according to claim 8, characterized in that the power electronic module (1) comprises a housing (7) in which the metallized substrate (2) and the active component (3) are housed, the method comprising a step of filling the housing, at least in part, with an electrically insulating material (10).

19. A method for manufacturing a power electronic module by additive manufacturing, comprising: making or fixing preforms of polymer material on at least one face of an insulating substrate covered with at least one layer of metal, referred to as a metallized substrate, depositing a first metal layer on the preform, depositing by electroforming a second metal layer on the first metal layer, dissolving the preforms of polymeric material by chemical or thermal means, assembling active components, such as semiconductor power components, on the metallized substrate, attaching a housing to the metallized substrate, and filling the housing, at least in part, with an electrically insulating material.

20. A method according to claim 19, characterized in that it comprises a step of protecting at least one zone of the metallized substrate (2a) before deposition of the first metal layer (17).

21. A method according to claim 19, characterized in that the metallized substrate (2) comprises at least one insulating layer (2a) of ceramic.

22. The method according to claim 19, characterized in that the first metal layer (17) has a thickness of less than 5 microns, preferably less than 1 micron.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0042] FIG. 1 is a schematic view illustrating a power electronic module of the prior art,

[0043] FIG. 2,

[0044] FIG. 3,

[0045] FIG. 4,

[0046] FIG. 5 and

[0047] FIG. 6 illustrate various steps of a method of manufacturing a power electronic module according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0048] FIGS. 2 to 6 schematically illustrate the various manufacturing steps of a power electronic module 1 according to one embodiment of the invention.

[0049] In a first step illustrated in FIG. 2, preforms 15 of polymeric material are made by additive manufacturing on two opposite sides of a metallized substrate 2. The preforms 15 may be made directly on the metallized substrate 2 or may be attached to said metallized substrate 2 after the preforms 15 have been made. In the latter case, the preforms 15 may be bonded to the metallized substrate 2.

[0050] The metallized substrate 2 comprises an electrically insulating layer 2a of ceramic material coated on each of its opposite sides with a metal layer 2b, 2c, for example of copper. The metal layers 2b, 2c of the metallized substrate 2 can be joined to the insulating layer 2a by Active Metal Brazing (AMB), Direct Bonded Copper (DBC), or Direct Bonded Aluminium (DBA).

[0051] The metal layers 2b, 2c may form separate tracks from each other.

[0052] A protective film 16 of polymeric material may cover at least a portion of the conductor tracks of the top layer 2b.

[0053] Alternatively, the electrically insulating layer 2a may be made of a polymeric material (in the case of an Insulated Metal Substrate—IMS).

[0054] As shown in FIG. 3, a first metal layer 17, for example of copper, is then deposited on the preforms 15, for example by chemical reduction via spraying. The first layer 17 has a thickness of less than 1 micron for example.

[0055] A second metal layer 18, for example copper, is then deposited on the first metal layer 17, as shown in FIG. 4. Such a deposition can be made by electroforming.

[0056] The second layer 18 may have a thickness of between a few microns and a few millimetres, as required. The thickness of the second layer 18 can be varied as a function of the applied voltage and bias time applied during the electroforming deposition step.

[0057] During electroforming, all or part of the metallized substrate 2 and the first metal layer 17 is immersed in an electrolytic bath comprising metal ions, for example copper in ionic form. The bath may be a low temperature bath, i.e. at a temperature below 100° C. An electrode is electrically connected to the first metal layer 17, an electrical potential being applied to said electrode so as to deposit the filler metal of the electrolytic bath on the first metal layer 17. The non-metallic areas of the substrate 2 that are not at electrode potential are then not covered with filler metal. According to one embodiment, at least a portion of the first metal layer 17 is covered with a protective film so as to prevent deposition of the second metal layer 18 in the covered area.

[0058] The second metal layer 17 may in particular delimit connectors 5, housing parts 7 or cooling channels 19 of a heat sink or radiator 11.

[0059] As shown in FIG. 5, the preforms 15 are then removed in a chemical or thermal dissolution step.

[0060] In the case of chemical dissolution, ABS preforms 15 can be dissolved in an acetone bath at a temperature of 50° C. using ultrasound.

[0061] Alternatively, in order to dissolve PLA preforms 15, a 35% soda bath can be used at a temperature of 60° C. and stirring can be carried out to promote dissolution.

[0062] It is thus possible to create recessed areas, connectors 5 or channels 19 intended to facilitate heat exchange for the purpose of cooling the assembly, for example by means of a flow of air or a liquid coolant.

[0063] The films 16 may also be removed in the dissolving step.

[0064] The power semiconductor components 3 are then joined to the corresponding tracks of the metallized substrate 2 via an electrical and/or mechanical interconnect joint 4, as seen in FIG. 6. The power components 3 are then electrically interconnected with each other and/or with the connectors 11 by means of wiring wires 6. The housing 7 is then filled with an electrical encapsulant or insulator 10, such as a gel or epoxy, to provide mechanical and electrical protection for the power components 3 and the wiring wires 6.

[0065] Such a process provides the following advantages: [0066] good thermal performance due in particular to the reduction of the interfaces between the semiconductor components 3 and the heat sink 11 and to the possibility of producing a heat sink 11 with complex geometric shapes, [0067] possibility of use at very high temperatures, —improvement in reliability by eliminating soldering on large surfaces, [0068] increase in the mass power density of the converters due to the reduction in the mass of the heat sink 11, [0069] reduction of the number of manufacturing steps and of the manufacturing time, [0070] reduction of the residual stresses compared with the same production by additive manufacturing techniques requiring very high local temperatures for the melting or sintering of metal powders, [0071] sealing of the channels 19 of the heat sink 11 thanks to the absence of porosity and gaps in the electro-deposited material 18, [0072] high precision of the electroforming, in terms of the reproducibility of the surface state. This allows a great freedom of surface texturing via the use of polymer preforms 15 with complex geometries obtained by additive manufacturing, thus strongly increasing the exchange surfaces and thus the performance in terms of thermal dissipation, [0073] obtaining a unitary assembly at low temperature (<80° C.) and in a single phase including several functions (heat sink 11, housing 7, connectors 5) on both sides of the metallized insulating substrate 2 without the need for additional joints.