Fixing material for electronic components

Abstract

The present invention relates to fixing material for electronic components, configured for electrically connecting a first component with a second component, wherein the fixing material is pasty and electrically conductive, and wherein the fixing material comprises a photochemically curable material which is configured to stiffen the fixing material in such a way that a relative position between the first and second electronic component is pre-fixed.

Description

State of the art

[0001] The present invention relates to a fixing material for fixing electronic components, an electronic arrangement, in particular a power module, and a method for manufacturing an electronic arrangement.

[0002] In electronic arrangements, such as power modules of control units or the like, electrically conductive connections must be established. These connections can be made between two components or between a component and electrical conductors or the like. It is known to produce such electrical connections by means of soldering or sintering processes. DE 10 2019 126 505 B4 also discloses an adhesive bonding method for producing an electrically conductive connection in which ultrasonic energy is applied to electronic components during sintering.However, during the production of such electronic assemblies, a problem can arise: a component positioned on a fixing material for electrical connection may be displaced from its originally correct position during transport to the next processing station due to external influences, such as vibrations during transport. In such cases, an electrical connection between the component and another component may no longer be established. This leads to a relatively high scrap rate in the production of such electronic assemblies. Disclosure of the invention

[0003] The fixing material according to the invention for electronic components with the features of claim 1 has the advantage that a temporary pre-fixation of an electronic component to be connected with the fixing material is possible. This eliminates the risk that, particularly during further transport or handling of the component, a defined position of the component will change, and in extreme cases, a defective part will be produced. The solution according to the invention for the fixing material is particularly compelling due to its simple implementation. No established manufacturing steps need to be changed with regard to the production process for manufacturing an electronic arrangement. The fixing material can still be in a paste-like form and possess the necessary electrical conductivity. According to the invention, this is achieved by the fixing material additionally comprising a photochemically curable material.The photochemically curable material is designed to stiffen the fixing material in such a way that a relative position between a first and a second component to be electrically connected is temporarily pre-fixed. Final fixing by the fixing material occurs at a later time. The photochemically curable material thus only serves to temporarily pre-fix the components to be electrically connected. The photochemically curable material is a material that can be cured by electromagnetic radiation.

[0004] The invention can be implemented simply by providing a source of electromagnetic radiation during the manufacturing process after the electronic component to be joined has been arranged. Since, in particular, curing only on the surface of the fixing material is sufficient for pre-fixing the electronic component, this can be easily integrated into the manufacturing process without requiring any changes to the manufacturing process.

[0005] The invention can be used in the connection of electronic components such as chips or the like, and also in the connection of an electronic component with a conductor track or a substrate or a circuit board or the like.

[0006] The dependent claims describe preferred embodiments of the invention.

[0007] The photochemically curable material is preferably a material that can be crosslinked using ultraviolet radiation (UV) or a material that can be crosslinked using visible light. Preferably, the photochemically curable material is a plastic, in particular a photopolymer.

[0008] According to a particularly preferred embodiment, the photochemically curable material is designed to be broken down and, in particular, completely decomposable by heating, especially by temperatures greater than or equal to 200°C. This ensures that the photochemically curable material is completely removed from the fixative material during the final fixation step for fixing the electronic components. As a result, there are no disadvantages to the fixative material with regard to its electrically conductive properties.

[0009] The photochemically curable material preferably comprises a proportion of less than or equal to 5 wt.%, particularly less than or equal to 2 wt.%, and particularly less than or equal to 1 wt.% in the fixative. Preferably, the proportion of photochemically curable material in the fixative increases with the proportion of metallic materials in the fixative. Particularly preferably, the weight fraction of the photochemically curable material is equal to the weight fraction of the metallic material in the fixative.

[0010] Preferably, the fixing material contains a metallic component, in particular tin and / or copper and / or silver, such that the metallic component acts as a shield for the photochemically curable material present within the pasty fixing material. This ensures that, during the photochemical curing process for pre-fixing the electronic components, only the outer surface of the fixing material hardens, and that no curing of the photochemically curable material occurs within the fixing material. In the subsequent final fixing step for fixing the components together, all photochemically curable material, whether hardened or unhardened, can then be broken down and, in particular, completely decomposed by heating.

[0011] Preferably, the fixing material is a soldering material, in particular a lead-free soldering material. The soldering material preferably comprises a metal or a metal alloy and a flux. Alternatively, the fixing material is a sintered material. With a sintered material as the fixing material, a releasable pre-fixation of the components to be electrically connected preferably takes place before a pre-sintering process or before an actual sintering process.

[0012] The invention further relates to an electronic arrangement, in particular a power module, comprising a plurality of electronic components. The electronic components can be substrates, AMB (Active Metal Brazing) substrates, or other types of substrates. In principle, the fixing material according to the invention can be used for the electrical connection of all types of necessary electrical connections in electronic arrangements. The invention is particularly preferred in high-performance electronics, especially controllers for inverters in the field of electromobility.

[0013] Furthermore, the present invention relates to a method for manufacturing an electronic assembly, in particular a power module. The method comprises the steps of applying a pasty fixative material, which contains a proportion of photochemically curable material, to create an electrically conductive connection between a first and a second electronic component. The pasty fixative material can be applied by various methods, for example, by spraying, printing, or coating. In a next step, the electronic component to be fixed is positioned on the fixative material. Subsequently, electromagnetic radiation, in particular ultraviolet radiation or visible light, is applied to the fixative material, causing the photochemically curable material in the fixative material to crosslink, at least on the outer surface of the fixative material.The remaining components of the fixative remain in a paste-like consistency. The cross-linking of the photochemically curable material pre-fixes the position of the electronic component to be fixed. Subsequently, particularly after further transport, a final and permanent fixing of the electronic component can be carried out, especially by means of heat, to establish permanent electrical conductivity between the first and second electronic components.

[0014] Furthermore, the present invention relates to another alternative method for manufacturing an electronic assembly, in particular a power module. This alternative method comprises the steps of applying a pasty fixative material that does not contain any photochemically curable material. The fixative material is configured to establish an electrical connection between a first and a second electronic component. In a next step, a photochemically curable material is applied to the pasty fixative material. Thus, the photochemically curable material is located exclusively on the top surface of the pasty fixative material. In a further step, the second electronic component to be fixed is positioned on the photochemically curable material, and ultraviolet radiation or radiation in the visible range is applied to the photochemically curable material.This process cross-links photochemically curable components, while the fixative itself remains pasty. The curing of the photochemically curable material applied to the fixative results in a pre-fixation of the second electronic component to the first. This is sufficient even though the fixative, which does not contain any photochemically curable material, is still pasty. Finally, the second electronic component is permanently fixed to the first to create a lasting, electrically conductive connection. Thus, in the alternative method, the photochemically curable material is applied as an additional layer on top of the actual pasty fixative and is not part of the pasty fixative itself.It should be noted that it is of course also possible for the pasty fixing material to contain a certain proportion of photochemically curable material. However, providing the photochemically curable material as a layer on top of the fixing material ensures improved pre-fixation of the second electronic component.

[0015] The crosslinking of the photochemically curable material preferably occurs exclusively on one surface of the fixative, whereby any photochemically curable material located within the fixative remains uncrosslinked. This is sufficient for pre-fixing many, especially small, electronic components. Alternatively, complete crosslinking of the photochemically curable material is achieved, including the material located within the fixative.

[0016] Preferably, during the final fixing of the pre-fixed electronic component by means of heat, the cross-links of the photochemically curable material are broken down. Particularly preferably, the photochemically curable material is completely decomposed.

[0017] Preferably, the fixing material is a solder paste and the final fixing step is a soldering process, in particular a reflow soldering process.

[0018] Alternatively, the fixing material is preferably a sintering paste and the final fixing is a pre-sintering process or a sintering process. Brief description of the drawings

[0019] Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings. The drawing shows: Fig. 1 a schematic side view of an electronic arrangement with a fixing material according to a first embodiment of the invention and Fig. Figures 2 to 5 schematic representation of the implementation of a method according to the invention for the manufacture of an electronic arrangement. Preferred embodiments of the invention

[0020] The following refers to the Fig. 1 to 5 describe in detail a fixing material and an electronic arrangement 1 as well as a method for manufacturing the electronic arrangement 1.

[0021] Fig. Figure 1 schematically shows the structure of an electronic arrangement 1 according to the present invention. The electronic arrangement 1 comprises an AMB (Active Metal Brazing) substrate on which first electronic components 2, for example electrically conductive silicon or copper traces, are arranged. A second component 3 is to be fixed to the first components 2.

[0022] The electronic arrangement 1 includes a fixing material 4.

[0023] Fixing material 4 is an electrically conductive, pasty material. Fixing material 4 comprises a photochemically curable component. The proportion of the photochemically curable component is very small, in particular less than or equal to 1% by weight of the fixing material.

[0024] The function of the photochemically curable material in the fixing material 4 is to cure, in particular to cross-link, by the action of visible light and / or by the action of UV radiation, so that the second component 3 to be fixed is securely placed on the fixing material 4 and is pre-fixed.

[0025] This pre-fixation ensures that, during transport of the electronic arrangement 1, a defined position in which a secure electrical connection of the components is possible is maintained, for example, due to slippage or similar issues. Final fixing of the second component 3 to be fixed takes place in a later process step. The pre-fixation of the second component 32 to be fixed is thus achieved by photochemical curing, preferably only on the surface of the fixing material.

[0026] In a final fixing step, which takes place at a later time, the pre-fixation can then be reversed and, in particular, a complete decomposition of the photochemically curable material can be achieved.

[0027] The Fig. Figures 2 to 5 schematically show the method according to the invention.

[0028] As a first step, as in Fig. Figure 2 shows that a fixative 4, which contains a proportion of photochemically curable material, is applied to the first electronic components 2 on an AMB substrate 5. The fixative can be applied by a person skilled in the art using common methods such as spraying, printing, or the like. The addition of photochemically curable material to the fixative does not require any technical modification of the application method of the fixative 4.

[0029] In this embodiment, the fixing material is a soldering material with a photochemically curable material component, and the photochemically curable material is preferably a photopolymer.

[0030] In Fig. The second component 3 to be fixed is positioned on the fixing material 4 according to the desired specifications. The fixing material 4 is still in a pasty form, i.e., in the same pasty consistency as after application. Here, there is a risk that the second component 3 to be fixed may be moved from its predefined position to the next production step, for example, due to movement processes in a production line.

[0031] In Fig. Step 4 now provides an additional step, which takes place immediately after the placement of the second component 3 to be fixed. Depending on the specific properties of the photochemically curable material, the photochemically curable component can now be cured, in particular cross-linked, by means of a light source 6 if the photochemically curable material is a light-sensitive photochemical material activatable by visible light, or a UV radiation source if the photochemically curable material is a material curable by UV radiation. Preferably, the cross-linking of the photochemically curable material, which is normally evenly distributed throughout the pasty fixer material, occurs exclusively on the surface of the fixer material. This is sufficient to securely fix the second component 3 in the Fig. To hold and pre-fix the desired position shown in the 3 diagrams.

[0032] Since the hardening of the fixing material only takes a few seconds, this additional process step can be easily integrated into the manufacturing process. Preferably, the step begins immediately after the second component 3 to be fixed has been placed on the fixing material.

[0033] In Fig. Figure 4 schematically represents the electromagnetic radiation 7 emitted by the light source 6. The fixing material that has hardened on the surface is designated by the reference symbol 4'.

[0034] In the next step, the second component 3 is permanently fixed using the fixing material 4. For this purpose, heat is applied, as described in Fig. 5, indicated by arrows 8, is applied for a soldering process, so that a secure electrical connection between the first and second electronic components 2, 3 is permanently formed by the fixing material. The fixing material, which has hardened after the soldering step, is in Fig. 5 with the reference symbol 4".

[0035] During the application of heat 8, at higher temperatures, particularly temperatures above 200°C, the hardened structures of the photochemically curable material break down. A thermal threshold is preferably selected such that all components of the photochemically curable material in the fixative 4 are destroyed. This ensures that the addition of photochemically curable material to the solder paste does not impair the electrical connection in any way. The temperature for this purpose is preferably chosen to be greater than or equal to 350°C.

[0036] It should be noted that if the fixing material is a pasty sintering material, the same process steps apply as in the Fig. 2 to 5 can be executed, with the difference that instead of the one in Fig. In the soldering process shown in section 5, a pre-sintering process or a sintering process is carried out for the final permanent hardening of the fixing material 4.

[0037] Thus, according to the present invention, a fixing material 4 can be used which, by adding a photochemically curable material, in particular a photopolymer, enables secure pre-positioning and pre-fixation of electronic components 2, 3 to be joined, which in a final fixing step, by soldering or sintering, results in a permanent final fixation of the components. In particular, in the last fixing step, the photochemically curable material can preferably be completely decomposed, especially if it is an organic photochemically curable material.

[0038] Alternatively, according to the present invention, fixing material without a photochemically curable component can also be used if a photochemically curable material is applied as a layer, for example by spraying, onto the pasty fixing material. This is sufficient for the reliable pre-positioning and pre-fixing of electronic components to be joined. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 126 505 B4

[0002]

Claims

[1] Fixing material for electronic components, designed to electrically connect a first component (2) to a second component (3), - wherein the fixing material is pasty and electrically conductive, and - wherein the fixing material comprises a photochemically curable material which is configured to stiffen the fixing material in such a way that a relative position between the first and second electronic component is pre-fixed. [2] Fixing material according to claim 1, wherein the photochemically curable material is a material that can be crosslinked by ultraviolet radiation or a material that can be crosslinked by visible light. [3] Fixing material according to any of the preceding claims, wherein the photochemically curable material is a photopolymer. [4] Fixing material according to one of the preceding claims, wherein the photochemically curable material is arranged to be broken down by heating, in particular heating above 200°C, so that the fixing material is again pasty and in particular the photochemically curable material is completely decomposable. [5] Fixing material according to one of the preceding claims, wherein the photochemically curable material comprises a proportion of less than or equal to 5 wt.%, in particular less than or equal to 2 wt.% and further in particular less than or equal to 1 wt.% of the fixing material. [6] Fixing material according to any of the preceding claims, wherein the fixing material comprises a metal such that the metal acts as a shield for photochemically curable material present inside the fixing material, so that the photochemically curable material does not stiffen. [7] Fixing material according to any of the preceding claims, wherein the fixing material is a pasty soldering material. [8] Fixing material according to any one of claims 1 to 6, wherein the fixing material is a pasty sintered material. [9] Electronic arrangement, in particular power module, comprising a fixing material according to any of the preceding claims. [10] Method for manufacturing an electronic arrangement (1), in particular a power module, comprising the steps: - Applying a pasty fixing material (4) with a proportion of photochemically curable material, wherein the fixing material is configured to establish an electrical connection between a first electronic component (2) and a second electronic component (3), - Arranging the second electronic component (3) to be fixed onto the fixing material (4), - Applying ultraviolet radiation or radiation in the visible range to the fixative material (4) such that cross-linking of photochemically curable components of the fixative material is achieved, with the remaining components of the fixative material remaining pasty, and a defined relative position between the first and second electronic component is pre-fixed, and - Final fixing of the second component (3) to the first component (2) to create a permanent electrically conductive connection between the first and second components. [11] Method for manufacturing an electronic arrangement (1), in particular a power module, comprising the steps: - Applying a pasty fixing material (4), wherein the fixing material is configured to establish an electrical connection between a first electronic component (2) and a second electronic component (3), - Application of a photochemically curable material to the pasty fixing material, in particular by spraying, - Arranging the second electronic component (3) to be fixed onto the photochemically curable material, - Applying ultraviolet radiation or radiation in the visible range to the photochemically curable material, such that cross-linking of photochemically curable components is achieved, whereby the fixative material remains pasty and a defined relative position between the first and second electronic component is pre-fixed, and - Final fixing of the second component (3) to the first component (2) to create a permanent electrically conductive connection between the first and second components. [12] Method according to claim 10 or 11, wherein in the final fixing step the cured photochemically curable material is broken up or completely decomposed. [13] Method according to claim 10 or 11 or 12, wherein the fixing material (4) is a solder paste and the final fixing is a soldering process. [14] Method according to claim 10 or 11 or 12, wherein the fixing material is a sintering paste and the final fixing is a pre-sintering process or a final sintering process. [15] Method according to any one of claims 10 to 14, wherein in the pre-fixing step the fixing material is cured only on one surface.

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