Method and device for producing a substrate provided with a hardenable encapsulation compound

Abstract

The invention relates to a method for producing a substrate (10) provided with a curable encapsulation material (14), the substrate having an electrical component (12) on the substrate top side (18), wherein the encapsulation material (14) is applied in an uncured state (22) in an encapsulation region (20) and the electrical component (12) is covered by the encapsulation material (14), wherein the substrate (10) is bent about at least one spatial axis (x, y, z) and a bend (28) is performed in the direction of the encapsulation material (14).

Description

Technical Field

[0001] The invention relates to a method for producing a substrate provided with a hardenable encapsulation compound and to a device according to the invention for carrying out the method. The substrate has, in particular, electrical components on the substrate top side, which are covered by the encapsulation compound. Background Art

[0002] It is known that electrical components and their conductor tracks on a substrate can be protected from environmental influences by means of a hardenable encapsulation compound. The encapsulation compound can be hardened chemically and / or thermally, wherein the encapsulation compound can shrink during the hardening process. Shrinkage can lead to warping of the substrate and thereby damage the electrical components or cause disadvantages in subsequent use, for example due to changed installation dimensions or changed heat conduction.

[0003] A person skilled in the art knows from DE 94 07 927 U1 a method for producing a substrate provided with a curable encapsulation material, the substrate having electrical components on the substrate top side. During the production process of the substrate, the substrate is reinforced by further components or material layers in such a way that the substrate does not warp after the encapsulation material has hardened. For this purpose, for example, components compensating for the warping are applied to the top side of the encapsulation material. Summary of the invention

[0004] The method according to the invention for producing a substrate provided with a hardenable encapsulation material having the features of claim 1 has the advantage that the method prevents warping of the substrate after the encapsulation material has hardened without the use of additional components or material layers. To this end, the teaching of the invention in its most general form provides that the substrate is bent at least temporarily about at least one spatial axis before the encapsulation material reaches a hardened state and at least about at least one spatial axis until the encapsulation material reaches a hardened state and the bending is carried out in the direction of the encapsulation material.

[0005] The invention has been recognized that the curvature of the substrate can compensate for the warping caused by the hardening of the encapsulation material, thereby producing a preferably flat substrate. The method is characterized by particularly simple production steps and does not require complex steps, such as applying further components or material layers. The method according to the invention thus avoids, for example, that the possible approaches to or arrangements of the electronic components are restricted by additional components or material layers. In addition, the method according to the invention is particularly suitable for mass production.

[0006] Advantageous developments of the method according to the invention for producing a substrate provided with a curable encapsulation compound are listed in the dependent claims.

[0007] There are many possibilities for the specific implementation of the method, some of which are preferably provided below: The bending of the substrate is thus implemented in the phase change of the encapsulating material from the unhardened state to the hardened state. In the unhardened or still fluid state, the encapsulating material can flow around the electrical component, while in the hardened state, the encapsulating material is completely cross-linked. In the phase change, which is also known to those skilled in the art as gelling of the encapsulating material, the encapsulating material no longer flows and the substrate advantageously has no warpage. In addition, the thickness of the encapsulating material is advantageously not affected by the bending of the substrate.

[0008] In an alternative embodiment of the method, the substrate is bent in the uncured state of the encapsulation material and before the already described phase change of the encapsulation material. In this case, the encapsulation material can flow into a less curved region, for example into the edge region of the encapsulation region, corresponding to the bending of the substrate. As a result, the thickness of the encapsulation material can be greater in the edge region of the encapsulation region than in the central region of the encapsulation region.

[0009] Particularly preferably, in an alternative embodiment of the method, when equipping the substrate, electrical components with a low structural height are arranged in the central region of the packaging region, and electrical components with a higher structural height than the low electrical components are arranged in the edge region of the packaging region. This arrangement ensures that all electrical components are covered with the least amount of packaging material possible.

[0010] Particularly preferably, in the method, when equipped in the manner already mentioned, the bending of the substrate is carried out in such a way that the upper side of the higher electrical components is at or below the level of the upper side of the lower electrical components in the central region of the encapsulation region. Thus, all higher electrical components as well as the lower electrical components are also covered by the encapsulation compound.

[0011] Independently of the above-mentioned embodiments, it can be provided that the bending of the base plate is carried out by means of at least one mechanical element.

[0012] The invention further relates to a device for carrying out the method according to the invention described above, wherein the substrate holder is designed to fix the substrate in at least one clamping position outside the encapsulation area and has means designed to bend the substrate about at least one spatial axis.

[0013] In a further development, it is provided that the component is designed as at least one machine element and that the material of the at least one machine element has a higher coefficient of thermal expansion than the material of the substrate holder.

[0014] In order to be able to use base plates with different dimensions or tolerances, it is particularly preferred if at least one machine element is mounted adjustably on the rail.

[0015] Alternatively, the device may be configured to adjust the screw in order to bend the substrate.

[0016] Particularly preferably, the means are arranged within and / or outside the at least one clamping point. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Further advantages and details of the invention are apparent from the following description of preferred embodiments of the invention and with the aid of the accompanying drawings.

[0018] Figure 1 shows a perspective view of a rectangular substrate provided with a hardenable encapsulation compound, the substrate having electrical components on the upper side of the substrate,

[0019] Figure 2a to Figure 2e The four method steps in chronological order are shown respectively. Figure 1 A view of a substrate in plane II-II, wherein the substrate is bent during the hardening of the encapsulation material,

[0020] Figure 3a to Figure 3d according to Figure 2a to Figure 2e 1 and 2 show views of a substrate in three method steps in chronological order, wherein the substrate is bent before the encapsulation material hardens,

[0021] Figure 4a A longitudinal sectional view of a device according to the invention is shown for moving a substrate according to Figure 2c or Figure 3b Curved,

[0022] Figure 4b Shown according to Figure 4a A longitudinal cross-sectional view of a device, wherein the substrate is bent from the underside of the substrate,

[0023] Figure 5a Shows Figure 4a A longitudinal cross-sectional view of an alternative device,

[0024] Figure 5b Shown according to Figure 5a A longitudinal cross-sectional view of a device, wherein the substrate is bent from the side of the substrate,

[0025] Figure 6a Shown according to Figure 5a A longitudinal sectional view of a device, wherein the mechanical element is supported on a rail,

[0026] Figure 6b Shows that according to Figure 6a Transverse cross-sectional view of section B of the track. DETAILED DESCRIPTION

[0027] In the figures, identical elements or elements having the same function are provided with the same reference symbols.

[0028] exist Figure 1 1 shows a rectangular substrate 10 provided with a hardenable encapsulation material 14, which has an electrical component 12 on a substrate upper side 18, wherein the encapsulation material 14 covers the electrical component 12 in an encapsulation region 20. The encapsulation region 20 is defined by a support structure 16, wherein the encapsulation material 14 covers the electrical component 12. The support structure 16 serves to prevent uncontrolled flow of the encapsulation material 14 in the unhardened state 22.

[0029] The support structure 16 and the encapsulation material 14 can be applied automatically, for example, by a dispenser (not shown). In this case, the support structure 16, which consists, for example, of a highly viscous or partially cross-linked polymer, is first applied, and then the encapsulation material 14 is applied in the encapsulation region 20. Advantageously, before the application of the support structure 16 and the application of the encapsulation material 14, the substrate 10 is flat, so that the dispenser can be moved at a small distance from the substrate top side 18 and the electrical component 12 can be precisely encapsulated.

[0030] The encapsulation material 14 can be chemically and / or thermally hardened. For example, the encapsulation material 14 can contain material components that can chemically react with each other and harden, wherein the reaction is triggered and / or accelerated by means of thermal energy (e.g. in a furnace) or radiation energy (e.g. by means of ultraviolet radiation).

[0031] Depending on the hardening method or the encapsulation material 14, a warping of the substrate 10 due to chemical and / or thermal shrinkage may occur, wherein the warping is caused by a reduction in volume of the encapsulation material 14 which is connected to the substrate top side 18 on one side. If the encapsulation material 14 and the substrate 10 have different coefficients of thermal expansion, thermal shrinkage may result. In particular, in thermal hardening methods, thermal shrinkage occurs during cooling to the initial temperature.

[0032] exist Figure 2a to Figure 2e 1 and 1 , respectively, during the production process of the substrate 10 in four steps in chronological order according to Figure 1 In the first step, the encapsulation material 14 is formed from the substrate 10. Figure 2a In the unhardened state 22 to Figure 2b The substrate 10 is hardened by a phase transition 24 between an unhardened state 22 and a hardened state 26. In the phase transition 24, which can also be understood as gelling of the encapsulation material 14, the encapsulation material 14 is stabilized, but only crosslinked to 50% to 70%. The encapsulation material 14 no longer flows, and the substrate 10 advantageously does not warp. The moment of the phase transition 24, also referred to as the gel point, can be determined, for example, by means of rheometer measurements.

[0033] In the second step, Figure 2cIn the embodiment, the bending 28 of the substrate 10 is performed during the phase change 24 of the encapsulant 14 from the unhardened state 22 to the hardened state 26. Since the encapsulant 14 no longer flows during the phase change 24, the thickness of the encapsulant 14 does not change in the bent state of the substrate 10.

[0034] The bend 28 is implemented about the spatial axis x and / or about the spatial axis y and in the direction of the encapsulation material 14, wherein Figure 2c Only the curvature 28 about the spatial axis x is shown in FIG. In the case of the curvature 28 about both spatial axes x and y, the base plate 10 is preferably curved spherically.

[0035] The bending 28 of the substrate 10 can be achieved by means of forces 30, 30' perpendicular to the substrate upper side 18, wherein the force 30 or force 30' is respectively an action force or a reaction force and cancels each other out. Alternatively, the bending 28 can be implemented by means of a force 32 acting on the side of the substrate 10.

[0036] As in Figure 2d , in a third step, the substrate 10 is bent 28 until a hardened state 26 is reached, wherein the encapsulation material 14 is stable and completely cross-linked in the hardened state 26. If the encapsulation material 14 is thermally hardened, the hardened state 26 is understood to mean that the initial temperature has been reached and any thermal shrinkage of the encapsulation material 14 has ended.

[0037] exist Figure 2d The height a and shape of the bend 28 in the embodiment are advantageously designed so that the warping of the substrate 10 is precisely compensated by the hardening of the encapsulation material 14 and a Figure 2e Thus, the height a of the meander 28 is advantageously close to zero or advantageously does not exceed a value of 0.35% of the width of the substrate 10 .

[0038] Figure 3a to Figure 3d Shows that already Figure 2a to Figure 2e An alternative embodiment of the method is shown in , in which the bending 28 of the substrate 10 is carried out in the uncured state 22 of the encapsulation material 14. Figure 3b As shown in FIG. 1 , the encapsulation material 14 may flow into a region of a smaller bend 28 corresponding to the bend 28, for example, into an edge region 38 of the encapsulation region 20. Therefore, the thickness of the encapsulation material 14 in the edge region 38 of the encapsulation region 20 is greater than the thickness of the encapsulation material 14 in the central region 40 of the encapsulation region 20. Figure 3c and Figure 3d As shown in , after curing of the encapsulation compound 14 , the different thicknesses of the encapsulation compound 14 corresponding to the bends 28 remain.

[0039] Therefore, it is particularly preferred that, when equipping the substrate 10, the electrical components 12 having a low structure height 42 are arranged in the central region 40 of the packaging region 20, and the electrical components 12 having a higher structure height 44 than the low electrical components 12 are arranged in the edge region 38 of the packaging region 20. This arrangement ensures that all electrical components 12 are covered by the smallest possible amount of packaging material 14.

[0040] Furthermore, the bend 28 of the substrate 10 can be implemented in such a way that the upper sides 36 of the taller electrical components 12, 44 are in or below the level of the upper sides 34 of the lower electrical components 12, 42 located in the central region 40 of the encapsulation region 20. Thus, the encapsulation material 14 also covers all the taller electrical components 12, 44 together with the lower electrical components 12, 42.

[0041] The bending 28 of the substrate 10 in the method described above can be carried out in various ways with the aid of the device 100. Preferably, the bending 28 of the substrate 10 is carried out with the aid of at least one mechanical element 52. Alternatively, the bending 28 can also be carried out with the aid of pneumatically or hydraulically acting elements.

[0042] exist Figure 4a 1 shows a device 100, wherein a substrate holder 46 holds a substrate 10 outside the encapsulation region 20 along a spatial axis y in two clamping positions 48 and has a structure configured to hold the substrate 10 about a spatial axis z according to Figure 2c or Figure 3b Bendable device. Here, the device is constructed as a mechanical element 52 in the form of a mechanical element 54, which has a higher thermal expansion coefficient than the material of the substrate support 46 and / or is constructed as a mechanical element 52 in the form of an adjusting screw 56. The mechanical element 54 is especially made of plastic or aluminum, and the substrate support 46 is made of steel. The mechanical element 54 and the adjusting screw 56 are arranged within the clamping position 48 and in the base plate 58, wherein the mechanical element 54 is connected to the base plate 58 in a form-fitting manner. The clamping part 62 at the side element 60 of the device 100 fixes the substrate 10 on the base plate 58 at the clamping position 48, so that the substrate 10 does not slip during the application of the encapsulation material 14 and the substrate 10 is as flat as possible. Preferably, one of the clamping parts 62 is implemented as a roller so that the bend 28 is not restricted.

[0043] exist Figure 4b In the embodiment, the relative movement of the mechanical device relative to the clamping portion 62 is implemented according to Figure 2cThe mechanical element 54 can expand by means of temperature changes in the device 100, for example during the thermal curing of the encapsulation material 14. The passive mechanical element 54 makes the method particularly simple to implement, since no active adjustment or active adjustment mechanism is required. In contrast, the adjustment screw 56 must be actively adjusted at the desired time or method step during the execution of the production method.

[0044] In an alternative embodiment, the hold-down 62 can also be used in combination with the side elements 60 as the mechanical element 52, wherein the bending 28 of the base plate 10 can be performed by means of the relative movement of the hold-down 62 relative to the base plate 58. In this case, the base plate 58 must be provided with a recess so that the bending 28 can be performed, for example, at the edge of the recess.

[0045] The pressing portion 62 can also be arranged along the spatial axis x, in order, for example, to implement the spherical bend 28 in combination with the pressing portion 62 along the spatial axis y. Furthermore, the pressing portion 62 can be formed in an annular shape in the xy plane and, for example, interact with the mechanical element 52 in the middle of the packaging area 20. Furthermore, a plurality of pressing portions 62 can also form point-shaped and / or line-shaped clamping locations 48.

[0046] exist Figure 5a In the embodiment shown, the mechanical element 54 is arranged in the substrate holder 46 to the side of the substrate 10 and outside the clamping point 48 and is advantageously in positive contact with the base plate 58 and the side elements 60 .

[0047] exist Figure 5b The mechanical element 54 is shown in a deformed state, so that the base plate 10 is relatively Figure 5a The illustration in FIG. 1 is clamped between the mechanical element 54 and the two side elements 60 and is thus bent in the direction of the encapsulation material 14 .

[0048] exist Figure 6a and according to Figure 6b Detailed view B in Figure 6a The mechanical element 54 is movably supported on the rail 64, wherein the screw 66 can fix the mechanical element 54 on the rail 64. By means of this embodiment of the device 100, different substrates 10 with different sizes or tolerances can be produced in the same device 100. In a possibly manual or automatic production process, the defined spacing between the side of the substrate 10 and the mechanical element 54 can be adjusted so that the bend 28 of the substrate 10 is achieved with the desired height a during the subsequent thermal curing of the encapsulation material 14. In addition, substrates 10 with different materials can be used, and the height a of the bend 28 can be adjusted simply and without replacing the mechanical element 54. The rail 64 is oriented in such a way that the mechanical element 54 can be pressed against the side area of ​​the substrate 10 with force in order to cause the substrate to bend.

[0049] The device 100 described here can be changed or modified in many ways without departing from the concept of the invention. Thus, for example, it is also conceivable to use an adjusting screw 56 that acts on the base plate 10 laterally and perpendicularly to the bend 28, or to combine the mechanical element 52 with a pneumatic and / or hydraulic element.

Claims

1. A method for producing a substrate (10) provided with a hardenable encapsulation material (14), the substrate having an electrical component (12) on a substrate top side (18), wherein: The encapsulation material (14) is applied in an uncured state (22) in an encapsulation region (20) and the electrical component (12) is covered by the encapsulation material (14), characterized in that before the encapsulation material (14) reaches a cured state (26), the substrate (10) is at least temporarily bent about at least one spatial axis (x, y, z) and at least until the cured state (26) is reached, the substrate (10) is bent about at least one spatial axis (x, y, z) and a bending (28) is performed in the direction of the encapsulation material (14), wherein the bending (28) of the substrate (10) is performed by means of a component that is movable relative to a base plate (58) that accommodates the substrate (10), wherein the component has a higher coefficient of thermal expansion than the material of a substrate holder (46) that is designed to fix the substrate (10) in at least one clamping point (48) outside the encapsulation region (20), wherein the component is arranged in the base plate (58), wherein the relative movement of the component is caused by a temperature change.

2. The method according to claim 1, characterized in that: The substrate (10) is bent (28) during a phase change (24) of the encapsulation material (14) from an uncured state (22) to a cured state (26).

3. The method according to claim 1, characterized in that: The substrate (10) is bent (28) in an uncured state (22) of the encapsulation compound (14).

4. The method according to claim 3, characterized in that When the substrate (10) is equipped, an electrical component (12) having a low structural height (42) is arranged in a central area (40) of the packaging area (20), and an electrical component (12) having a higher structural height (44) than the lower electrical components (12, 42) is arranged in an edge area (38) of the packaging area (20).

5. The method according to claim 4, characterized in that The substrate (10) is bent (28) so that the upper side (36) of the higher electrical components (12, 44) is located in or below the horizontal plane (34) of the upper side of the lower electrical components (12, 42) in the central area (40) of the packaging area (20).

6. The method according to any one of claims 1 to 5, characterized in that The bending (28) of the base plate (10) is performed by means of at least one mechanical element (52).

7. A device (100) for performing the method according to any one of claims 1 to 6, characterized in that: The substrate holder (46) is configured to fix the substrate (10) in at least one clamping position (48) outside the packaging area (20), and has a device configured to bend the substrate (10) around at least one spatial axis (x, y, z), the device being movable relative to a base plate (58) accommodating the substrate (10), wherein the device has a higher coefficient of thermal expansion than the material of the substrate holder (46) and is arranged in the base plate (58), wherein the relative movement of the device is caused by temperature changes.

8. The device according to claim 7, characterized in that The device is configured as at least one mechanical element (52, 54), and the material of the at least one mechanical element (52, 54) has a higher coefficient of thermal expansion than the material of the substrate support (46).

9. The device according to claim 8, characterized in that The at least one machine element (52, 54) is mounted adjustably on a rail (64).

10. The device according to claim 7, characterized in that The device is designed as an adjusting screw (56).

11. The device according to any one of claims 7 to 10, characterized in that The device is arranged within the at least one clamping point (48) and / or outside the at least one clamping point (48).

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