Partially overmolded printed circuit board, use of the printed circuit board, and production of the printed circuit board

Abstract

The invention relates to a partially overmolded printed circuit board (10) comprising: a substrate (12) having at least one electrically conductive conductor track; an electrically conductive contact element (14) which is connected to the conductor track and extends beyond an end edge (16) of the substrate (12); and a mold material (18) which is applied onto the substrate (12) and the contact element (14), wherein the mold material (18) directly surrounds at least areas of the substrate (12) and directly surrounds only portions of the electrically conductive contact element (14).

Description

[0001] Description

[0002] Partially overmolded PCB, use of the PCB and manufacturing of the PCB

[0003] The invention relates to a partially overmolded printed circuit board with a substrate and a contact element, wherein the contact element is guided over a terminal edge of the substrate. The substrate and the contact element are encapsulated or overmolded with a molding material. The contact element can thus be easily formed as an integral connector connected to the printed circuit board. The invention also relates to the use of the printed circuit board in a transmission control unit or in an electrification unit. Another subject of the invention is the production of the printed circuit board.

[0004] Printed circuit boards are generally well known. Printed circuit boards typically comprise a substrate. A connector, which typically includes a contact element formed within a housing, can be arranged on the substrate. It is also known for the connector and the printed circuit board to be overmolded. The disadvantage of this is that the connector and the overmold of the printed circuit board are generally made of different materials, which must be taken into account thermally to avoid stress cracks and subsequent leaks. Furthermore, the printed circuit board is larger in the area where the connector and the printed circuit board are overmolded, which can increase both the installation space and the weight of the printed circuit board. Multiple and different materials generally also result in higher costs.

[0005] It is an object of the invention to provide a printed circuit board with an integrated connection contact, which can be manufactured inexpensively, has a reduced installation space and can also have increased media tightness.

[0006] The object is achieved by the subject matter of the independent patent claims. Preferred developments of the invention are the subject matter of the dependent patent claims, the following description and the drawings. Each feature can represent an aspect of the invention both individually and in combination, unless something to the contrary explicitly arises from the description. In a first aspect, the invention relates to a partially overmolded printed circuit board, comprising a substrate having at least one electrically conductive conductor track, an electrically conductive contact element connected to the conductor track and extending beyond a terminal edge of the substrate, and a molding material applied to the substrate and the contact element, wherein the molding material surrounds the substrate directly and at least in regions, and surrounds the electrically conductive contact element directly and exclusively in sections.

[0007] In other words, according to the first aspect of the invention, it is provided that a partially overmolded printed circuit board is provided, preferably for a transmission control unit or an electrification unit, which can preferably be, but not limited to, an inverter or a DC / DC converter.

[0008] The printed circuit board comprises a substrate, wherein the substrate has at least one electrically conductive conductor track. The electrically conductive conductor track is usually formed within the substrate, on a top side of the substrate and / or on a bottom side of the substrate. Consequently, multiple conductor tracks can be arranged and / or formed in the substrate at a distance from one another. The substrate can therefore be a multilayer substrate. An electrically conductive contact element is directly or indirectly connected to the conductor track. Direct means that the contact element is directly connected to the conductor track, for example, in a materially bonded, positively bonded, or non-positively bonded manner. Indirect, on the other hand, means that the contact element is directly connected to an electrical component arranged on the printed circuit board, which component, in turn, is in electrically conductive contact with the conductor track.The electrical component may preferably be, but not limited to, a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated-gate bipolar transistor (IGBT).

[0009] The contact element extends beyond a terminal edge of the substrate. The terminal edge can also be referred to as an edge of the substrate. The contacting section extending beyond the terminal edge is intended for electrically connecting the circuit board with another contact element.

[0010] The substrate is directly encapsulated or overmolded with a molding material, at least in certain areas. "At least in certain areas" means that only a portion of the substrate is overmolded with the molding material, or the entire substrate is overmolded with the molding material. "Directly overmolded" means that the molding material is applied directly to the substrate, thus forming a material bond with the substrate, at least in certain areas. This allows for increased media impermeability.

[0011] The contact element is overmolded or surrounded with the molding material only in sections. Thus, the circuit board can be electrically connected via the exposed section of the overmolded contact element, which is preferably formed in a contacting section extending beyond the end edge. The contact element is also directly overmolded with the molding material. This means that the molding material is in direct contact with the electrically conductive contact element.

[0012] This allows the contact element to be formed integrally with the circuit board. Since only one molding material is used to overmold the circuit board and the contact element, thermal stresses can be minimized, which can have a positive effect on media tightness. Furthermore, the installation space and weight of the circuit board can be reduced, as the molding material is arranged not only directly on the substrate but also on the contact element. A separate plastic housing for the contact element is thus no longer necessary. This can also have a beneficial effect on the cost of the circuit board.

[0013] An advantageous development of the invention is that the electrically conductive contact element is fixed to the substrate. Fixing the contact element to the substrate ensures that the contact element is securely positioned before overmolding the substrate and the contact element. This can simplify the manufacturing process and reduce tolerances.

[0014] The fixation on the substrate can be a material-to-material, form-fitting, and / or force-fitting fixation. The material-to-material fixation can preferably be a soldered connection or an adhesive connection, in particular an electrically conductive adhesive connection. The force-to-material and / or form-fitting connection can preferably be a screw connection, a rivet connection, and / or a clamp connection. In this way, options for simple and inexpensive fixation of the contact element on the substrate are provided. An advantageous development of the invention lies in the fact that the electrically conductive contact element is electrically connected to the conductor track by means of a surface contact or a through-hole connection. It is therefore also conceivable for the fixation to be a surface connection between the contact element and the conductor track.Thus, the fixation of the contact element can simultaneously provide an electrically conductive connection to the conductor track. This can save work steps and thus also costs. However, the electrically conductive connection can also be a through-hole connection, if necessary. In this case, one end of the contact element is guided through an opening in the substrate and electrically connected to the conductor track, preferably via a material-to-material, form-fitting, and / or force-fitting connection.

[0015] In a preferred embodiment of the invention, the molding material completely surrounds a contact element top side of the contact element, and the contact element has an at least partially exposed contact surface on a contact element bottom side facing away from the contact element top side. It goes without saying that the exposed section is arranged in a region of the contact element that projects beyond the end edge and / or the edge region of the substrate. The contact element top side is preferably aligned and / or formed parallel to a plane of the substrate. The molding material thus functions as insulation, in particular as contact protection. A corresponding contact element for contacting the circuit board can act against the contact element bottom side.

[0016] According to an advantageous development of the invention, the contacting section of the contact element extending beyond the end edge has a fastening opening. The fastening opening is preferably a closed-edge opening that completely penetrates the contact element. Particularly preferably, the longitudinal direction of the opening runs in a direction perpendicular to the plane of the substrate. In this way, the contact element can be electrically connected in a simple manner, preferably via a screw connection, to another contact element for supplying power to the circuit board.

[0017] The molding material is preferably a plastic material. The plastic material can be a thermoplastic or a thermosetting plastic, or can comprise a thermoplastic or a thermosetting plastic. Particularly advantageously, the plastic material is formed from an epoxy-based thermosetting material or comprises an epoxy-based thermosetting material. Such a material exhibits increased thermal stability for applications up to, preferably, 200°C. Likewise, increased media impermeability for corrosive media can be provided. Furthermore, the material is dimensionally stable in the application area. Furthermore, the epoxy-based thermosetting material can provide an electrically insulating sheath, which can also exhibit high electrical breakdown power.

[0018] An advantageous embodiment of the invention is that the molding material is a plastic material that has a filler. In other words, the molding material comprises a filler in addition to a plastic material. The filler can increase the rigidity of the molding material. The increased rigidity can have a beneficial effect on the circuit board if it is preferably only overmolded or overmolded on one side. Bending of the circuit board and possible damage to the conductor tracks can thus be avoided. In addition, the installation space can be reduced because the material thickness of the molding material can be reduced due to the filler. Likewise, the molding material can increase the rigidity of the overmolded contact element, so that it can have increased positional accuracy.

[0019] In this context, a preferred development of the invention is that the filler is a glass-based filler. The glass-based filler is preferably, but not limited to, a silicate glass. The filler preferably has a grain size between 5 pm and 300 pm, particularly preferably between 8 pm and 200 pm, and most preferably between 10 pm and 100 pm, the limits being included. A filler content of greater than 50 mass% and less than 90 mass% is advantageous, particularly preferably greater than 60 mass% and less than 90 mass%, and most preferably greater than 70 mass% and less than 90 mass%, the limits being included. The filler in the plastic material acts like reinforcement. In other words, an overmolding can be realized in this way that is particularly rigid and dimensionally stable. This can be advantageous if the circuit board is only overmolding on one side or.The plastic material is applied only on one side. Furthermore, the overmolding formed with the filler can have a reduced thickness, which can have a beneficial effect on the weight and dimensions of the circuit board.

[0020] In a second aspect, the invention relates to a use of the circuit board according to the invention in a transmission control unit or in an electrification unit.

[0021] In other words, according to the second aspect of the invention, it is provided that the printed circuit board is preferably used in a motor vehicle. In this case, it is particularly preferably provided that the printed circuit board is a component of a transmission control unit. Transmission control units are arranged in a transmission of a motor vehicle and are thus at least partially surrounded by oil. The molding material acts as a media-tight seal between the printed circuit board and the oil. An additional housing can therefore be dispensed with, which can have an advantageous effect on the manufacturing costs, the installation space, and the weight of the printed circuit board. However, it is also conceivable for the printed circuit board to be a component of an electrification unit. The electrification unit is preferably, but not limited to, an inverter or a DC / DC converter. This electrification unit is preferably cooled.The coolant can thus be applied directly to the mold material to cool it. The mold material protects the substrate and the circuit trace from liquid damage.

[0022] In this way, a printed circuit board is provided for both a transmission control unit and an electrification unit that can be manufactured inexpensively, has a reduced installation space and can also have increased media tightness.

[0023] In a third aspect, the invention relates to a method for producing the printed circuit board according to the invention, comprising the steps:

[0024] - Providing a substrate;

[0025] - Connection of an electrically conductive contact element to a conductor track of the substrate;

[0026] - Encapsulating and / or overmolding the substrate and the contact element with a molding material, wherein the molding material directly and at least partially surrounds the substrate and directly and exclusively surrounds the electrically conductive contact element. In other words, according to the third aspect of the invention, a substrate is first provided. The substrate has at least one conductor track. The conductor track can preferably be arranged and / or formed on a top side of the substrate, within the substrate, or on a bottom side of the substrate.

[0027] In a second step, the electrically conductive contact element is electrically connected to the conductor track. The electrically conductive connection can be a direct connection or an indirect connection, as described in this disclosure of the printed circuit board.

[0028] In a third step, the substrate and the contact element are overmolded with a molding material. The molding material is intended to surround the substrate directly and at least partially. Directly means that the molding material is in direct contact with the top side of the substrate and forms a material-to-material connection with it, at least in part. The molding material can be applied to one side of the substrate. However, it is also conceivable for the molding material to completely surround the substrate. The contact element is only partially overmolded with the same molding material in order to leave a contact area free in the contacting section. For this reason, the circuit board as a whole is only partially overmolded. The molding material is sprayed directly onto the contact element.

[0029] This allows the contact element to be formed integrally with the circuit board. Since only one molding material is used to overmold the circuit board and the contact element, thermal stresses can be minimized, which can have a positive effect on media tightness. Furthermore, the installation space and weight of the circuit board can be reduced, as the molding material is arranged not only directly on the substrate but also on the contact element. A separate plastic housing for the contact element is thus no longer necessary. This can also have a beneficial effect on the manufacturing costs of the circuit board.

[0030] An advantageous development of the invention is that the molding material is applied to the substrate and the contact element simultaneously and / or simultaneously in an overmolding process and / or molding process. In other words, the substrate and contact element are overmolded in one manufacturing process. This can have a beneficial effect on production time and thus also on production costs.

[0031] It should be noted that all features described above and below with respect to one aspect of the present invention equally apply to any other aspect of the present invention. In particular, all features of the circuit board can also be features of the use and method. This also applies vice versa.

[0032] Further features and advantages of the present invention emerge from the dependent claims and the following exemplary embodiments. The exemplary embodiments are not limiting, but rather are to be understood as examples. They are intended to enable the skilled person to implement the invention. The applicant reserves the right to make individual and / or several of the features disclosed in the exemplary embodiments the subject of patent claims or to incorporate such features into existing patent claims. The exemplary embodiments are explained in more detail with reference to drawings.

[0033] In these show:

[0034] Fig. 1 shows a detailed section of a three-dimensional view of a partially overmolded printed circuit board with a substrate and a contact element in a first embodiment;

[0035] Fig. 2 shows a longitudinal section through the circuit board in the region of the contact element according to the first embodiment;

[0036] Fig. 3 shows a longitudinal section through the circuit board in the region of the contact element according to a second embodiment;

[0037] Fig. 4 shows a longitudinal section through the circuit board in the region of the contact element according to a third embodiment;

[0038] Fig. 5 shows a method for manufacturing the printed circuit board;

[0039] Fig. 6 a motor vehicle with a transmission control unit and a use of the circuit board in the transmission control unit.

[0040] Fig. 1 shows a detailed section of a three-dimensional view of a partially overmolded printed circuit board 10 with a substrate 12 and a contact element 14 in a first embodiment. The substrate 12 has at least one electrically conductive conductor track. The electrically conductive conductor track is usually formed within the substrate 12 on a substrate top side 24 and / or a substrate bottom side 32 of the substrate 12. The conductor track is usually formed from a metallization layer. Consequently, several conductor tracks can also be arranged and / or formed spaced from one another in the substrate 12. The substrate 12 can therefore be a multilayer substrate. In the present exemplary embodiment, the electrically conductive contact element 14 is directly connected to the conductor track. "Directly" means that the contact element 14 is connected directly to the conductor track, for example, in a materially bonded, positively bonded, or force-fitted manner.

[0041] The contact element 14 extends beyond a terminal edge 16 of the substrate 12. The terminal edge 16 can also be referred to as an edge of the substrate 12. The contacting section of the contact element 14 extending beyond the terminal edge 16 is intended for electrically contacting the circuit board.

[0042] The substrate 12 is directly cast or overmolded, at least in some areas, with a molding material 18. At least in some areas means that only a portion of the substrate 12 is overmolded with the molding material 18, or the entire substrate 12 is overmolded with the molding material 18. In the present exemplary embodiment, only one side of the substrate 12 is overmolded with the molding material 18. Directly overmolded means that the molding material 18 is applied directly to the substrate 12 and thus forms a material bond with the substrate 12, at least in some areas.

[0043] The contact element 14 is overmolded or surrounded by the molding material 18 exclusively in sections. Thus, the circuit board 10 can be electrically connected via the exposed section of the overmolded contact element 14, which is formed in the contacting section extending beyond the end edge 16. The contact element 14 is also directly overmolded with the molding material 18. This means that the molding material 18 is in direct contact with the electrically conductive contact element 14.

[0044] Thus, the contact element 14 can be formed integrally with the circuit board 10. Since only one molding material 18 is used to overmold the circuit board 10 and the contact element 14, thermal stresses can be minimized, which can have a positive effect on media tightness. Furthermore, the installation space and weight of the circuit board 10 can be reduced because the molding material 18 is arranged not only directly on the substrate 12, but also on the contact element 14. A separate plastic housing for the contact element 14 can thus be dispensed with. This can also have a beneficial effect on the cost of the circuit board 10.

[0045] The electrically conductive contact element 14 is fixed to the substrate 12. Fixing the contact element 14 to the substrate 12 ensures that the contact element 14 is securely positioned before overmolding the substrate 12 and the contact element 14. This can simplify the manufacturing process and reduce tolerances.

[0046] In the present embodiment, the contact element 14 is secured to the substrate 12 by a positive and / or force-locking fixation. A clamping connection 20 securely holds the contact element 14 on the substrate 12 both before and after overmolding with the molding material 18. This provides a simple and cost-effective way to secure the contact element 14 to the substrate 12.

[0047] The contact element 14 has a fastening opening 22 in the contacting section. The fastening opening 22 is preferably a closed-edge opening that completely penetrates the contact element 14. A longitudinal direction of the opening runs in a direction perpendicular to the plane of the substrate 12. In this way, the contact element 14 can be electrically connected in a simple manner, preferably via a screw connection 23, to another contact element for supplying power to the circuit board 10, as shown in Fig. 2.

[0048] Fig. 2 also shows that the electrically conductive contact element 14 is electrically connected to the conductor track by means of a surface contact. Such a connection can also be referred to as a surface-mounted device (SMD) connection. Consequently, the SMD connection preferably allows the substrate 12 and the contact elements 14 to be populated from one side, which can have a beneficial effect on the manufacturing process and the manufacturing costs of the printed circuit board 10.

[0049] Fig. 3 shows a longitudinal section through the circuit board 10 in a second embodiment. In contrast to the first embodiment, as known from Figs. 1 and 2, the contact element 14 in the contacting section differs in that it does not have a fastening opening 22. Rather, the contact element 14 is formed continuously in the contacting section. The molding material 18 is formed on a substrate upper side 24 and on a contact element upper side 26. The substrate upper side 24 and the contact element upper side 26 are aligned in the same direction. A contact element lower side 28, which is formed on a side facing away from the contact element upper side 26, is free of molding material 18, so that this side is a contacting surface. The molding material 18 thus functions as insulation, in particular as contact protection.As can be seen, an end face 30 of the contact element 14, which is spaced apart from the end edge 16, is also overmolded with molding material 18. A corresponding contact element can act against the contact element underside 28 for contacting the circuit board 10.

[0050] In this exemplary embodiment, the molding material 18 is a plastic with a filler, in particular a glass-based filler, and most preferably a silicate glass. This molding material 18 has increased rigidity, so that the contacting section is dimensionally and positionally stable.

[0051] Fig. 4 shows a longitudinal section through the circuit board 10 in a third embodiment. In contrast to the third embodiment, the contact element 14 for connecting to the conductor track of the substrate 12 is designed as a through-hole plating element. This may be necessary if the corresponding conductor track for contacting the contact element 14 is not formed on the substrate top side 24, on which the contact element 14 is also arranged. On a substrate bottom side 32, at least the through-hole plating area is overmolded with the molding material 18 in order to seal the connection area in a media-tight manner.

[0052] Fig. 5 shows a method for producing a partially overmolded printed circuit board 10. In a first step 100, a substrate 12 is provided. The substrate 12 has at least one conductor track. The conductor track can preferably be arranged and / or formed on a substrate top side 24 of the substrate 12 or within the substrate 12.

[0053] In a second step 110, the electrically conductive contact element 14 is electrically conductively connected to the conductor track. The electrically conductive connection can be a direct connection or an indirect connection, as described in this disclosure of the printed circuit board 10. In a third step 120, the substrate 12 and the contact element 14 are overmolded or over-molded with a molding material 18. It is provided that the molding material 18 surrounds the substrate 12 directly and at least in some areas. "Directly" means that the molding material 18 is in direct contact with the substrate top side 24 and forms a material-to-material connection therewith, at least in some areas. The molding material 18 can be applied to one side of the substrate 12. However, it is also conceivable for the molding material 18 to completely surround the substrate 12.The contact element 14 is only partially overmolded with the same molding material 14 in order to leave a contact area free. Therefore, the printed circuit board 10 as a whole is also only partially overmolded. The molding material 18 is molded directly onto the contact element 14. This allows the contact element 14 to be formed integrally with the printed circuit board 10. Since only one molding material 18 is used to overmold the substrate 12 and the contact element 14, thermal stresses can be minimized, which can have a positive effect on media tightness. In addition, the installation space and weight of the printed circuit board 10 can be reduced because the molding material 18 is arranged not only directly on the substrate 12, but also on the contact element 14. A separate plastic housing for the contact element 14 can therefore be dispensed with. This can have a beneficial effect on the manufacturing costs of the printed circuit board 10.

[0054] Fig. 6 shows a motor vehicle 34 with a transmission control unit 36, wherein the circuit board 10 is arranged in the transmission control unit.

Claims

Patent claims 1. Partially overmolded printed circuit board (10), comprising a substrate (12) having at least one electrically conductive conductor track, an electrically conductive contact element (14) connected to the conductor track and extending beyond a terminal edge (16) of the substrate (12), and a molding material (18) applied to the substrate (12) and the contact element (14), wherein the molding material (18) surrounds the substrate (12) directly and at least in regions, and surrounds the electrically conductive contact element (14) directly and exclusively in sections.

2. Printed circuit board according to claim 1, characterized in that the electrically conductive contact element (14) is fixed on the substrate (12).

3. Printed circuit board according to one of the preceding claims, characterized in that the electrically conductive contact element (14) is electrically conductively connected to the conductor track by means of a surface contact or a through-contact.

4. Printed circuit board according to one of the preceding claims, characterized in that the molding material (18) completely surrounds a contact element upper side (26) of the contact element (14), and the contact element (14) has a contact surface which is at least partially exposed on a contact element lower side (28) facing away from the contact element upper side (26).

5. Printed circuit board according to one of the preceding claims, characterized in that the contacting section of the contact element (14) extending beyond the end edge (16) has a fastening opening (22).

6. Printed circuit board according to one of the preceding claims, characterized in that the molding material (18) is a plastic material which comprises a filler.

7. Printed circuit board according to one of the preceding claims, characterized in that the filler is a glass-based filler.

8. Printed circuit board according to one of the preceding claims, characterized in that a filling degree of the filler is greater than 50 mass% and less than 90 mass%, the limits being included.

9. Use of a printed circuit board (10) according to one of the preceding claims in a transmission control unit (36) or in an electrification unit.

10. A method for producing a printed circuit board (10) according to one of claims 1 to 8, comprising the steps: - providing a substrate (12); - connecting an electrically conductive contact element (14) to a conductor track of the substrate (12); - Overmolding and / or overmolding the substrate (12) and the contact element (14) with a molding material (18), wherein the molding material (18) surrounds the substrate (12) directly and at least in regions, and surrounds the electrically conductive contact element (14) directly and exclusively in sections.

11. The method according to claim 10, characterized in that the molding material (18) is applied to the substrate (12) and the contact element (14) at the same time and / or simultaneously in an overmolding process and / or molding process.

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