Manufacturing process of a semiconductor module

Abstract

A manufacturing process for a semiconductor module is proposed, comprising the following steps: providing a substrate with an electrically conductive top layer; in case A): connecting one or more threaded sleeves to the top layer, the threaded sleeve having a length longer than the thickness of the mold to be applied subsequently; inserting a screw into the threaded sleeve before or after it is connected to the top layer; placing the system of substrate, threaded sleeve, and screw into a molding device; and performing a molding process, wherein the molding device has indentations formed and arranged such that a screw head can be placed in each indentation, each indentation having a minimum depth such that the screw head is not surrounded by mold after the molding process; and after the molding process is complete, unscrewing the screw from the threaded sleeve.so that part of it remains in the threaded sleeve, and cutting off the screw head so that part of the pin remains free from the mold, or completely unscrewing the screw from the threaded sleeve.

Description

The present invention relates to a manufacturing method by which a better pin connection for semiconductor modules is achieved.In a current power electronics application, as illustrated in FIG. 1, one or more semiconductor modules 100 are connected to a driver board 3. Each of the semiconductor modules 100 comprises one or more power semiconductor chips 101 arranged on a substrate 10, which normally comprises three layers 11, 12, 13. The top layer 10, on which the semiconductor chips 101 are arranged, consists of an electrically conductive material and is structured in islands in order to provide different electrical connection possibilities. Under this layer is an electrically insulating layer 12, followed by a metallic heat sink 13, which may have a heat-dissipating fin structure (not shown) on the opposite side of the insulating layer 12. The heat sink 13 is electrically grounded. The system of substrate 10 with the semiconductor chips 101 (and terminals and optional components) is processed, e.g. by a molding process, to house (seal) the system in an electrically insulating material that also seals the interior of the system from the external environment. Only the heat sink 13 is not completely sealed by the mold (the shell) to provide a heat dissipating surface on the outside of the case 2. The pins 14 are also only partially sheathed, since they produce the electrical connection between the housing interior, i.e. the semiconductor chips 101, and the outer side, more precisely the driver board 3. In practice, the pins 14 are bent to be connected to the driver board 3 to be connected to the driver board 3 so that the package 2 (the semiconductor chips 101) is parallel to the driver board 3.Due to the structure of the module, the pins 14 are rather long, resulting in a high inductance. The air gap 5 between the pins 14 and the cooling body 13 is also short, so that an insulation problem can occur. These problems are solved in the prior art by separate insulation parts 4, as indicated in FIG. 1. However, there is still an optimization potential of the design of the pins 14, so that they become shorter and the air gap 5 becomes larger.In order to achieve this object, a manufacturing method for a semiconductor module is proposed, comprising the steps of: providing a substrate having an electrically conductive top layer. In case A): joining one or more threaded sleeves to the top layer, the threaded sleeve having a length that is longer than the thickness of the mold to be applied subsequently, and inserting a screw into the threaded sleeve before or after it is joined to the top layer, inserting the substrate, threaded sleeve and screw system into a molding device and carrying out a molding process, the molding device having indentations that are formed and arranged such that a screw head can be arranged in each indentation, each indentation having at least one depth such that the screw head is not surrounded by mold after the molding process, and after the molding process is finished, unscrewing the screw from the threaded sleeve such that a part thereof remains in the threaded sleeve, and cutting off the screw head such that a part of the screw protrudes from the mold as a pin, or fully unscrewing the screw from the threaded sleeve. Alternatively, in case B): connecting one or more screw heads of a screw to the top layer, a part of the open end of the screw having a length such that it protrudes from the mold to be applied later, and applying a threaded sleeve to the open end of the screw before or after it is connected to the top layer, the threaded sleeve having a length equal to or shorter than the open end of the screw protruding from the mold to be applied later, and inserting the substrate, screw and threaded sleeve system into a molding apparatus and performing a molding process, the molding apparatus having indentations formed and arranged such that each threaded sleeve fits into an indentation, each indentation having a depth such that, the threaded sleeve not being surrounded by the mold after the molding process, and after the molding process is finished, removing the threaded sleeve from the screw.In one embodiment, the threaded sleeve and / or the screw and / or the top layer are made of copper.In one embodiment, the part of the pins of the semiconductor module that protrudes from the mold is connected to corresponding through holes of a driver board.In one embodiment, the threaded sleeve or the screw head are connected to the uppermost layer by means of soldering or sintering or welding.In one embodiment, the substrate is a DBC or an AMB or an IMS.Furthermore, a semiconductor module produced by the method is provided.For a better understanding of the invention, the invention will now be described in detail with reference to the accompanying drawings. The detailed description illustrates and describes what are considered to be preferred embodiments of the invention. It is to be understood that various modifications and changes in form or detail may be readily made without departing from the spirit of the invention. It is therefore intended that the invention not be limited to the exact form and details shown and described herein, nor to any extent less than the entire invention disclosed and claimed herein. Furthermore, the features described in the description, the drawings and the claims of the invention may be essential for the invention alone or in combination. In particular, all reference numerals in the claims should not be interpreted as limiting the scope of the invention.The appended figures show: FIG. 1 shows a semiconductor module according to the prior art connected to a driver board; FIG. 2 shows a substrate with a screw and threaded sleeve according to a first embodiment of the invention; FIG. 3 shows the molding method of the substrate according to the first embodiment of the invention; FIG. 4 shows the molded and moved screw substrate according to the first embodiment of the invention; FIG. 5 shows the connection between the substrate and the driver board according to the first embodiment of the invention; FIG. 6 shows a threaded sleeve and screw substrate according to a second embodiment of the invention; FIG. 7 shows the molding method of the substrate according to the second embodiment of the invention; FIG. 8 shows the substrate with the mold and the threaded sleeve moved according to the second embodiment of the invention; FIG. 9 shows the connection between substrate and driver board according to the second embodiment of the invention.While the present disclosure is subject to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described herein in detail. The invention should be understood not to be limited to the particular forms disclosed, but, on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure.In all embodiments, the substrate includes a top layer 11 (of metal) that is electrically conductive because the pins 14 are electrically connected to the top layer 11 at one end thereof. They can be connected to the driver board 3 by their other end. Preferred substrates 10 are DCB (direct copper bond), AMB (active metal bond), IMS (insulated metal substrate). All substrates are at least three layers and have a top layer 11 (made of metal) made of electrically conductive material such as copper, an insulating layer 12 and a bottom layer which functions as a heat sink 13. The top layer 11 may be processed to have multiple islands electrically isolated from each other to provide different electrical connectivity.FIGS. 2 to 5 show a first embodiment, also referred to as case A), of a method for producing a semiconductor module 100 having a new pin design 14. As can be seen in FIG. 2, in this case at least one threaded sleeve 6 is connected (electrically and mechanically) to the uppermost layer 11 of the substrate 10. Further, an open end of a screw 7 is inserted (by turning) into the threaded sleeve 6. The screw has a screw head 71 at its end opposite to the open end. Preferably, the screw 7 has a length (y direction) which corresponds to the length of the shank of the threaded sleeve 6, i.e. the screw 7 can be screwed completely into the threaded sleeve 6, so that the screw head 71 closes the shank of the threaded sleeve 6. This is preferred since no mold is to penetrate into the shaft in the subsequent molding process.After the threaded sleeve 6 is connected to the uppermost layer 11 and the threaded sleeve 6 and the screw 7 are connected, the system thus produced (substrate 10, threaded sleeve 6 and screw 7) is introduced into a molding device 8, as can be seen in FIG. 3. The molding device 8 comprises indentations 81 at the areas where the threaded sleeve 6 is placed with the screw 7. The indentations 81 are configured such that each can receive one of the screw heads 71. Thus, an alignment of the entire system can take place in the molding device 8. Since as little molding material as possible is to be used, but all components to be sealed must be covered, and since the screw 7 must be removed as easily as possible after the molding process, the depth of the indentations 81 is additionally selected accordingly. Thus, the depth of each indentation 81 corresponds at least to the length of the screw head 71, but is preferably slightly longer, so that the transition region between the threaded sleeve 6 and the screw 7 is also within the indentation 81. The screw head 71 advantageously contacts the lower wall of the indentation 81, which has the advantage that the upper side of the screw head 71 is not covered by the mold. In FIG. 3, a process is shown in which the molding apparatus 8 has an upper part and a lower part. The lower part can be moved (marked with the arrows) in such a way that the system is pressed against the upper part. However, the process is not limited to the shown process.In Fig. 4 the remolded system is shown. That is, the housing 2 is now completed. Now, the pins 14 must be completed. As shown, the mold (corresponding to the package 2) covers all components to be encapsulated (sealed) on the top sheet 11, specifically the semiconductor chips 101 and their electrical connections. The heat sink 13 (parts thereof) is not sheathed. Also, at least the screw head 71 is not sheathed. Thus, the screw 7 can be turned and thus turned off the threaded sleeve 6 until it has a predetermined length. In case mold is present, this may be removed before the screw 7 is turned.Then, after the desired length is reached, the screw head 71 is cut off (indicated by the broken line in Fig. 4), thereby producing a pin 14 protruding from the housing 2. Of course, the lengths of the threaded sleeve 6 and the screw 7 are chosen such that a good part of the screw 7 still remains in the threaded sleeve 6 after it has been unscrewed to the desired length. In addition, the desired length is selected so that the pin 14 can be inserted into a through hole 30 of the drive board 3 to which the semiconductor module 100 (corresponding to the packaged / over-molded system) is to be connected.Alternatively, the screw 7 can be fully unscrewed from the threaded sleeve 6, so that e.g. a press pin can be introduced in order to connect the components on the uppermost layer 11 like the semiconductor chips 101 to the driver board 3.The completed semiconductor module 100 can now be connected to a driver board 3 by inserting the pins 14 into a corresponding through hole 30 of the driver board 3.By providing the threaded sleeve 6 and the screw 7 on the uppermost layer 11, it is no longer necessary to bend the pins 14. Thus, the pins 14 are shorter and thus have a lower inductance. Also, the pins 14 are no longer as close to the heat sink 13, even if the mold (the housing 2) is not thicker, resulting in a larger air gap.It should be noted that the screw 7 can also be introduced into the threaded sleeve 6 if this is already connected to the uppermost layer 11. Alternatively, the screw 7 is then introduced.FIGS. 6 to 9 show a second embodiment, also referred to as case B), of an alternative production method of a semiconductor module 100 having a new pin design 14. As can be seen in FIG. 6, in this case at least one screw 7 is fastened (electrically and mechanically) by its screw head 71 on the uppermost layer 11 of the substrate 10. Furthermore, a threaded sleeve 6 is connected to the free end of the screw 7 (by screwing on). Preferably, the screw 7 has a length (y direction) longer than the thickness of the mold to be applied later so that a part of the free end of the screw 7 protrudes from the housing 2 (the mold). The length (y-direction) of the threaded sleeve 6 preferably corresponds to the length of the part of the screw 7 which protrudes from the housing 2.After the screw 7 is connected to the top layer 11 and the threaded sleeve 6 and the screw 7 are combined, the system thus produced (substrate 10, threaded sleeve 6 and screw 7) is introduced into a molding device 8, as can be seen in FIG. 7. The molding device 8 includes indentations 81 at the portions where the threaded sleeve 6 is placed with the screw 7, as seen in FIG. 7. The indentations 81 are configured such that each can receive one of the threaded sleeves 6. Thus, an alignment of the entire system can take place in the molding device 8. Since as little molding material as possible is to be used, but all components to be sealed must be covered, and since the threaded sleeve 6 must be removed as simply as possible after the molding process, the depth of the indentations 81 is additionally selected accordingly.Thus, the depth of each indentation 81 corresponds at least to the length of the threaded sleeve 6, but is preferably slightly longer, so that the transition region between the threaded sleeve 6 and the screw 7 is also within the indentation 81. The upper part of the threaded sleeve 6 advantageously contacts the inner walls of the molding device 8, and the heat sink 13 also contacts the inner walls of the molding device 8, In FIG. 7, a process is shown in which the molding device 8 has the indentations 81 at an upper part thereof. A side wall has an inlet 82 for the molding material (e.g., resin). However, the process is not limited to the shown process.In FIG. 8, the completed semiconductor module 100 (corresponding to the packaged / over-molded system) is shown. That is, the housing 2 is now completed. Now, the pins 14 must be completed. As shown, the mold (corresponding to the package 2) covers all components to be encapsulated (sealed) on the top sheet 11, specifically the semiconductor chips 101 and their electrical connections. The heat sink 13 (parts thereof) is not sheathed. Also, at least the threaded sleeve 6 is not sheathed. Thus, the threaded sleeve 6 can be rotated and thus turned off from the free end of the screw 7. Thus, a pin 14 is produced which protrudes from the housing 2 formed by the mold. In the case that mold is present on the threaded sleeve 6, this can be removed before the threaded sleeve 6 is removed.The semiconductor module 100 can now be connected to a driver board 3 by the pins 14 being inserted directly into a corresponding through hole 30 of the driver board 3. Of course, the lengths of the screw 7 and the threaded sleeve 6 are selected such that the part of the screw 7 protruding outside the mold can be inserted into the through hole 30 of the driver board 3 so that the pin 14 can be fixed to the driver board 3.By providing the threaded sleeve 6 and the screw 7 on the uppermost layer 11, it is no longer necessary to bend the pins 14. Thus, the pins 14 are shorter and thus have a lower inductance. Also, the pins 14 are no longer as close to the heat sink 13, even if the mold (the housing 2) is not thicker, resulting in a larger air gap.It should be noted that the threaded sleeve 6 may already be mounted on the screw 7 when it is connected to the uppermost layer 11. Alternatively, the threaded sleeve 6 is then introduced.In all embodiments, the screw 7 and the threaded sleeve 6 are formed from an electrically conductive material such as copper or any suitable alloy, which can preferably be joined to the top layer 11 by means of a standard process such as soldering, welding or sintering.The molding process is a standard molding process as known to those skilled in the art.Reference numerals denote reference numerals100 Semiconductor module 101 Semiconductor chips 10 Substrate 11 Uppermost layer 12 Electrically insulating layer 13 Heat sink 14 Pins 2 Housing / mold 3 Driver board 30 Through hole 4 Insulation part 5 Air gap 6 Threaded sleeve 7 Screw 71 Screw head 8 Molding device 81 Indentations 82 Inlet

Claims

Manufacturing method for a semiconductor module (100), comprising the steps of: - providing a substrate with an electrically conductive top layer (11), and - in case A): - connecting one or more threaded sleeves (6) to the top layer (11), the threaded sleeve (6) having a length that is longer than the thickness of the mold (2) to be applied subsequently, and - inserting a screw (7) into the threaded sleeve (6) before or after it is connected to the top layer (11), - inserting the system of substrate, threaded sleeve (6) and screw (7) into a molding device (8) and carrying out a molding process, wherein the molding device (8) has indentations (81) formed and arranged such that a screw head (71) can be arranged in each indentation (81), wherein each indentation (81) has at least one depth such that the screw head (71) is not surrounded by mold (2) after the molding process, and - after the molding process is finished, unscrewing the screw (7) from the threaded sleeve (6) such that a part thereof remains in the threaded sleeve (6) and cutting off the screw head (71) such that a part of the screw (7) protrudes from the mold (2) as a pin (14), or completely unscrewing the screw (7) from the threaded sleeve (6), or - in case B): - connecting one or more screw heads (71) of a screw (7) to the uppermost layer (11), wherein a part of the open end of the screw (7) has a length such that it protrudes from the mold (2) to be applied later, and - applying a threaded sleeve (6) to the open end of the screw (7) before or after it is connected to the top layer (11), wherein the threaded sleeve (6) has a length which is equal to or shorter than the open end of the screw (7) which protrudes from the mold (2) to be applied later, and - introducing the system of substrate, screw (7) and threaded sleeve (6) into a molding device (8) and carrying out a molding process, wherein the molding device (8) has indentations (81) which are formed and arranged such that each threaded sleeve (6) fits into an indentation (81), wherein each indentation (81) has a depth such that the threaded sleeve (6) is not surrounded by the mold (2) after the molding process, and - after the molding process is finished, Removal of the threaded sleeve (6) from the screw (7).Method according to claim 1, wherein the threaded sleeve (6) and / or the screw (7) and / or the uppermost layer (11) are made of copper.Method according to claim 1 or 2, wherein the part of the pins (14) of the semiconductor module (100) protruding from the mold (100) is connected to corresponding through holes (30) of a driver board (3).Method according to one of the preceding claims, wherein the threaded sleeve (6) or the screw head (71) are connected to the uppermost layer (11) by means of soldering or sintering or welding.The method of any preceding claim, wherein the substrate is a DBC or an AMB or an IMS.Semiconductor module (100) produced by a method according to one of the preceding claims.

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