JP7432075B2 - power semiconductor module - Google Patents

Description

The present invention relates to a method of forming a power semiconductor module. The invention further relates to a power semiconductor module. The invention particularly relates to power semiconductor modules with improved connection of terminals to substrate metallization.

Power semiconductor modules are generally well known in the art. There are different connection techniques for respectively connecting a terminal to a conductive structure such as a substrate or substrate metallization.

Ultrasonic welding (USW) is a known technique for connecting terminals to substrate metallization that can be used for high reliability and high temperature power electronics modules. In particular, ultrasonic welding is widely used to join copper terminals to ceramic substrates with copper metallization. This is primarily due to the fact that both the copper terminal and the copper metallization are annealed copper with low hardness, such as in the Vickers hardness range of about 50.

However, in the advanced design of power semiconductor modules, the welding of dissimilar materials, for example the welding of copper terminals to the aluminum metallization of a ceramic substrate, or the welding of a copper terminal to a ceramic substrate with a copper metallization, using a push pin auxiliary made from CuNiSi It is also known that welding of hard copper terminals such as terminals is necessary. When using ultrasonic welding to connect dissimilar materials, the harder material is likely to be forced into or deform the softer material. As an alternative, it is known to use laser welding to join the terminal to the substrate or substrate metallization, respectively. However, considering this technology, there is a risk of forming brittle intermetallic phases when connecting dissimilar materials.

Therefore, there may be room for improvement regarding the connection of dissimilar materials, especially when considering connecting terminals to the substrate metallization of the substrate.

JP2009302579 shows that the front side electrode of the semiconductor chip and the lead frame are formed of the same material, the tip of the lead frame is processed into a convex shape, and the corresponding surface film of the semiconductor chip and the lead frame face each other. By applying ultrasonic vibration while applying pressure, the same metals formed on the outermost surface diffuse into each other, allowing direct metal joining without using solder. Therefore, we are focusing on the connection between semiconductor chips and lead frames. No mention is made of the means for connecting the terminal to the conductive structure.

However, this step is not comparable to fixing the terminals to the substrate, since this step is a completely different process. In this regard, according to the prior art, in the case of wire bonding on semiconductor electrodes, a maximum of 100 mW is applied, whereas in the case of ultrasonic welding of terminals, up to the kW range is applied.

JP2008042039A describes dividing a wiring member into two parts, an electrode plate that functions as a heat spreader, and a lead frame, and brazing the electrode plate to the main surface of a semiconductor chip without being bonded to the lead frame. Then, the joint end of the lead frame is overlapped on the extending portion extending laterally from the periphery of the electrode plate, and locally heated by laser welding, electron beam welding, or the like.

JP 2012 039018 A describes that before ultrasonic bonding, one surface of a connecting portion to be bonded to a wiring pattern of a lead is curved into a convex shape, and the convex surface is directed toward the wiring pattern. The ultrasonic wave applying means is pressed against the surface opposite to the convex surface and applies ultrasonic waves to ultrasonically bond the leads and the wiring pattern.

CN104241209 relates to a special power module for outdoor power supply, including lead frame, control chip, thermistor, power chip, diode and metal wire as a dedicated power integration module. A heat dissipation board is located at the bottom of the package. The thermistor, power chip and diode are soldered to the board. The power chip and the diode are connected to the lead frame by ultrasonic bonding, the lead frame is distributed on both sides of the heat dissipation board, and metal wires connect the control chip and the lead frame.

WO 2007/033829 describes a method for manufacturing a power semiconductor module, in which a contact is formed in the form of an ultrasonic welding contact between a contact area and a contact element, and the sonotrode used for the ultrasonic welding process The present invention relates to a method which is also used to assemble the area with the contact end and thereby also to assemble the contact part with the base area.

JP 2011061105 A includes the following in order to provide a highly reliable connection technology that achieves sufficient connection strength and suppresses pad damage when connecting lead terminals to pads on a substrate using ultrasonic waves. It is written as follows. A coating layer that is harder than the pad and lead terminal is formed on the metal base material and the pad on the insulating film. During ultrasonic connection, the ultrasonic tool applies ultrasonic waves to destroy the coating layer, and the plastic flow directly connects the lead terminals and pads on both sides of the coating layer.

US2014/021620 A1 describes that, according to embodiments, a power device includes a semiconductor structure having a first surface facing a second surface, a top electrode, and a bottom electrode. The top electrode includes a first contact layer on the first surface of the semiconductor structure and a first bonding pad layer on the first contact layer formed of a metal containing nickel (Ni). May include. The lower electrode includes a second contact layer located under the second surface of the semiconductor structure, and a second bonding pad layer located under the second contact layer and made of a metal containing Ni. May include.

However, there is still room for improvement in the above-mentioned document, especially with regard to the gentle and reliable connection of terminals to substrates in power semiconductor modules.

SUMMARY OF THE INVENTION It is therefore an object of the invention to provide a solution to at least partially overcome at least one drawback of the prior art. In particular, it is an object of the invention to provide a solution for a reliable and gentle connection of a terminal to a substrate.

These objects are at least partially solved by a method for connecting terminals to a substrate to form a power semiconductor module with the features of claim 1. These objects are furthermore solved at least partially by a power semiconductor module having the features of independent claim 13. Advantageous embodiments are shown in the dependent claims, the further description and the drawings, and the embodiments described, alone or in any combination of the respective embodiments, characterize the invention, unless expressly excluded. can be provided.

Described is a method of connecting a terminal to a substrate to form a power semiconductor module, the terminal having a first connection region formed from a first material, the substrate having a second the first material has a first hardness, the second material has a second hardness, and the first hardness has a second hardness. 2, such a first connection area or a second connection area with a higher hardness forms a connection partner area, and such a first connection area or a second connection with a lower hardness The area forms a connection base area, and the terminal is connected to the substrate by ultrasonic welding or laser welding, and before connecting the terminal to the substrate, the method includes forming a connection base area from a material having a hardness corresponding to the hardness of the connection partner area. providing a connection layer having a surface sublayer formed, the connection layer being provided on the connection base region, the surface sublayer facing the connection partner region;

Such a method offers significant advantages over prior art solutions, in particular with regard to reliably and safely connecting the terminal to the substrate or substrate metallization, respectively.

The invention therefore relates to a method for connecting terminals to a substrate to form a power semiconductor module. The method is therefore suitable for and intended for implementation in the manufacturing process of power semiconductor modules, and in particular deals with connecting a terminal to a substrate and thus in particular to a substrate metallization. .

The terminal may have a generally L-shape and its lower part is connected to the substrate at its first connection area, such as a weld area. A terminal in the sense of the invention may have a thickness of 600 μm or more, illustratively 1000 μm or more, and a width of 2 mm or more. Furthermore, the connection area, such as the weld area, may have dimensions of 2 mm x 2 mm or more. The cross-section of the terminal may be rectangular and the angle between the two differently aligned parts of the L-shape may be rectangular or greater than 90°. Additionally, the terminal may be non-flexible.

In contrast to terminals, typical parameters for wire bonds include a diameter of 400 μm or less and a connection area, such as a weld area of 0.5 mm x 1 mm or less. The angle between the connecting region and the adjacent part may be oblique, much more than 90 degrees, and the cross section may be circular. Additionally, the wire bond may be flexible, ie, bendable.

Additionally, for ribbons as opposed to terminals, typical parameters include a thickness of 300 μm or less, a width of 2 mm or more, and a connection area such as a weld area of 0.5 mm x 2 mm or less. The angle between the connecting region and the adjacent part may be oblique, much more than 90 degrees, and the cross section may be rectangular. Additionally, the ribbon may be flexible or bendable.

Connection in the sense of the invention shall therefore mean mechanically and/or electrically connecting the terminal to the substrate or to the substrate metallization, respectively.

In this regard, power semiconductor modules may generally have such functionality as is known in the art. For example, the power semiconductor module to be manufactured comprises a metallization that is adapted to electrically connect the terminals to be connected to the metallization with the respective power semiconductor device.

Power semiconductor devices are also arranged on the substrate metallization. Such power semiconductor devices may generally be formed as known in the art and may each include transistors or switches, such as MOSFETs and/or IGBTs, among others, and/or the plurality of power semiconductor devices may include diodes, diodes, etc. can be provided. The power semiconductor devices may each be interconnected and therefore in electrical contact, such as in galvanic contact with the metallization.

Regarding the terminals and the metallizations to be connected to each other, the terminals have a first connection area formed from a first material, the substrate has a second connection area formed from a second material, and the substrate has a second connection area formed from a second material; One material has a first hardness, the second material has a second hardness, and the first hardness is different from the second hardness.

The first connection area is therefore the area of the terminal intended to be connected to the substrate metallization, and correspondingly the second connection area is the area of the terminal intended to be connected to the substrate metallization. or each area of substrate metallization. In many applications, the first connection region and the second connection region may be formed from different materials and therefore have different hardnesses. The first material and therefore the material provided in the first connection area may have a higher hardness than the second material and therefore the material provided in the second connection area; In some cases, the hardness is higher than that of other materials.

According to the above method, such a first connection area or a second connection area with a higher hardness forms a connection partner area and such a first connection area or a second connection area with a lower hardness The regions form connected base regions.

Indeed, it is also known that advanced designs of power semiconductor modules require welding of dissimilar materials. By way of example, it is known to connect copper-based terminals to aluminum metallization of ceramic substrates. Furthermore, it may be necessary to connect hard copper terminals, such as CuNiSi push pin auxiliary terminals, on ceramic substrates with copper metallization.

Independent of the particular first and second materials, it is often desirable to connect the terminal to the substrate by using ultrasonic or laser welding. This may be due to the fact that these techniques are known for connecting terminals to substrates to form reliable high temperature power electronics modules. In particular, ultrasonic welding is widely used, for example, for joining terminals made of copper to ceramic substrates with copper metallization. This is primarily due to the fact that both the copper terminal and the copper metallization are annealed copper with low hardness, such as in the Vickers hardness range of about 50.

However, using these welding techniques may present drawbacks, especially when the first material has a different hardness compared to the second material. When using ultrasonic welding to connect dissimilar materials, the harder material can be forced into or deform the softer material, thus damaging it.

In order to overcome this shortcoming of the prior art, according to the method described herein, before connecting the terminal to the substrate, a connecting layer is provided, which layer corresponds to the hardness of the connecting partner area. the connecting layer is provided on the connecting base region, and the surface layer faces the connecting partner region.

Regarding the connection layer, the connection layer may consist of surface sublayers or may include more layers than surface sublayers as described below. When it is referred to only from the connecting layer, the term may also describe the surface sublayer when the connecting layer consists of a surface sublayer.

This step of providing the connecting layer as described above ensures that the surfaces that are in contact when connecting the terminal to the conductive structure by ultrasonic or laser welding are in particular made of a first material having a higher hardness and a second material having a higher hardness. It is possible to have a corresponding hardness depending on the material of the material. Corresponding hardness in the sense of the invention shall in particular mean the same hardness or having the same hardness with a tolerance of +/−30% for higher hardness values.

Thus, the disadvantages referring to different hardnesses that can occur with the prior art may be avoided.

Therefore, the possibility of a harder material being forced into or deforming a softer material may be avoided, especially when using ultrasonic or laser welding to connect dissimilar materials. . Therefore, it is possible to prevent materials with low hardness from being damaged during the connection process.

A very high quality metallurgical bond at the interface between the first material and the connecting layer or between the second material and the connecting layer can thus be achieved.

A very reliable connection of the respective surfaces may thus be achieved, which may enable a high operating capacity of the power semiconductor module, which may avoid damage due to poor quality joints.

Apart from that, the power semiconductor module can operate with high safety due to the stable and reliable connection between the terminals and the substrate or substrate metallization.

Apart from the above, the possibility of cracking of the ceramic substrate during ultrasonic welding and reducing or even shorting the metallization gap can be further avoided. This may be due to the fact that the method described above allows a gentle and effective connection technique between the terminal and the substrate.

Providing a connecting layer may include a step of cold gas spraying (CGS). For CGS, this process is a coating deposition method. A solid powder is accelerated to high velocity in a supersonic gas jet. During the collision with the material to be coated, it undergoes plastic deformation and adheres to the surface. According to this method, the connecting layer can be applied in a particularly reliable and flexible manner, for example with respect to the thickness and the materials used. Alternatively, the method can be carried out irrespective of the geometry of the respective first and second connection regions.

Cold gas atomization can generally be used independently of the first material and the second material.
However, as a non-limiting example, this embodiment may be used with a combination of copper and aluminum as the first and second materials. In this regard, AI/AlN/Al substrates are preferred for high voltage power modules as they have high cycle reliability and do not exhibit silver ion migration problems compared to active metal brazed Cu/AlN/Cu substrates. There are many. However, according to the prior art, it is very difficult to weld copper-based terminals on these types of AI/AIN/AI substrates. This may be due to the fact that aluminum metallization is much softer than copper as the material of the terminal, so copper-based terminals can be forced into the aluminum metallization. Moreover, in this case the ceramic material AIN of the substrate is very susceptible to cracking.

Therefore, cold gas atomization is a very effective embodiment for providing a connecting layer for connecting copper and aluminum by welding.

Therefore, an additional copper layer may be provided by CGS on the existing aluminum metallization of the substrate in selective areas, where the terminal bonding takes place, ie in the second connection area. This copper cladding area allows ultrasonic or laser welding of copper terminals on the aluminum metallization by protecting the aluminum metallization and the ceramic AlN substrate by a connecting layer.

Furthermore, cryogenic gas atomization may be replaced by other methods, for example selective laser melting (SLM) or multilayer cryogenic gas atomization, e.g. the composition of the layers such that the material changes gradually from aluminum to copper. may be used with variations in This will be explained in more detail below.

Additionally, providing the connection layer may include metal plating. Here, metal plating is a surface coating process that deposits metal onto a conductive surface. This includes, for example, both electroplating and electroless plating.

Metal plating can generally be used independently of the first material and the second material.
However, as a non-limiting example, this embodiment may be used to connect a press-fit terminal to the metallization of a substrate such as a ceramic substrate, in particular aluminum metallization or especially copper metallization.

Press-fit terminals are widely used as auxiliary terminals in power module packaging due to their high reliability, high temperature performance, and simplicity during assembly, such as inverter assemblies. However, press-fit terminals must be hard copper alloys, such as those formed from CuNiSi, so that they can form a metallurgical bond during assembly and keep the contact reliable even at high operating temperatures. . According to the prior art, ultrasonic welding of press-fit terminals on copper metallization is very difficult, especially since the joining legs of the auxiliary terminals are typically small and the Cu metallization of the substrate is CuNiSi. This is because it is much softer than alloys.

The use of plating allows a very simple manufacturing process and, moreover, very thin layers can be formed as connection layers. Particularly in this embodiment it is possible to provide the copper metallization with a connection layer, the connection layer or at least its surface sublayer comprising an alloy or layer, such as a NiAg alloy, to increase the hardness compared to the copper metallization. It is formed from a multilayer structure with the arrangement Ni/Au or Ni/Cu. This allows for stronger friction at the interface during welding, which in turn results in a stable and reliable metallurgical bond.

As mentioned above, the method can be very effective if, for example, a press-fit auxiliary terminal is to be connected to the substrate metallization as a conductive structure, since in that case different materials This is because they often have to be welded together. The invention thus makes it possible to form high temperature and high power semiconductor modules with welded auxiliary press-fit terminals.

According to the above, the terminal may be an auxiliary press-fit terminal. In this regard, press-fit terminals are used to enable permanent electrical and mechanical terminal-to-PCB connections, which are made from different materials, usually hard Cu alloys, namely CuNiSi, CuSn alloys. be able to.

Additionally, providing a connection layer may include bonding a preformed layer onto the connection base region. This can be done, for example, by sintering.

This embodiment makes it possible to provide a connection layer with a large thickness, which may show advantages when harsh welding conditions are to be used and when the power module operates at high powers and high temperatures. .

As a non-limiting example, according to this embodiment, a copper plate having a small thickness or a large thickness or a plate made from a copper alloy, such as a CuNiSi alloy, is placed on a first connection area, such as on a terminal, e.g. It may be sintered at the same time and therefore in the same process step of chip attachment. This also allows both the ultrasonic welding of copper terminals on aluminum metallization and the ultrasonic welding of press-fit terminals, including copper alloys, on copper or aluminum metallization.

Thus, in particular, the step of providing the connection layer may include the step of sintering a pre-formed layer on the connection base region. In particular with respect to sintering the preformed layer on the first connection area or on the second connection area, this step achieves the above-mentioned advantages by providing the preformed layer as a connection layer. A durable and reliable connection can be provided so that there is no risk of offset.

Additionally, the terminals may be connected to the substrate using ultrasonic welding. In particular, by using ultrasonic welding, a relatively softer material is damaged by a relatively harder material, or in other words, a relatively harder material is damaged by a relatively softer material as described above. It has been found that problems can arise where the The advantages as described are therefore particularly effective if the terminal is connected to the substrate, and thus in particular to the substrate metallization, by ultrasonic welding.

Furthermore, the first material comprises, such as consists of, a copper alloy, thus in particular a hard copper alloy, and the second material comprises, such as consists of, or the second material consists of, or , a copper alloy, and thus in particular a hard copper alloy, and the first material may consist of, for example, a copper alloy, in particular a soft copper alloy. In this regard, in more detail, soft copper is soft annealed copper having, by way of example and by no means by way of limitation, a hardness in the range of 50 to 70 HV; can be determined according to DIN EN ISO 6507-1:2018 to 6507-4:2018. For example, substrate metallization, such as ceramic substrates, is often formed from such soft annealed copper. Further, with respect to high hardness copper alloys, it may have a hardness within the exemplary and non-limiting range of, for example, 120-200 HV. This may include or consist of a CuNiSi alloy, and it may be the material in the auxiliary terminal, such as a press-fit terminal, for example.

Further, the first material is made of or includes aluminum, the second material is made of or includes copper, or the first material is made of or includes copper, and the second material is It may be made of or contain aluminum. According to this embodiment, again, copper and aluminum are materials with different hardness, so connecting these materials by ultrasonic or laser welding can lead to problems as described. Therefore, once again, the method can be very effective.

Such embodiments may exist and may be implemented, for example, in high voltage power modules that include AI/AIN/AI substrates. Such a substrate may be suitable for high voltage applications because it has high cycle reliability and avoids silver ion migration when using active metal brazing (AMB), for example. , as opposed to, for example, a Cu/ceramic/Cu substrate. However, welding copper-based terminals onto relatively soft aluminum metallization is difficult because the copper material can be forced into the aluminum metallization as described above.

Furthermore, the connection layer is formed such that in addition to the surface sublayer it includes a base sublayer, the surface sublayer comprising the material of the connection partner region and the base sublayer comprising the material of the connection base region. may be located directly adjacent to the connection base region.

In other words, the surface sub-layer forms the surface of the connection layer after attachment of the connection layer to the connection base region, ie the first or second connection region with lower hardness. Thus, after attaching the connection layer to the connection base area, the surface sublayer faces the connection partner area and therefore the first or second connection area with higher hardness.

Such a configuration may also be referred to as a multilayer structure or a multilayer configuration, in particular if it has a plurality of more than two layers, thus more than a base sublayer and a surface sublayer, respectively. It is therefore possible to change its composition, either directly in a two-layer configuration or gradually in a configuration with more than two layers, so that the first material of the terminal is connected to the same material of the connecting layer and Correspondingly, the second material of the substrate metallization can be connected to the same material of the connection layer. Therefore, the material change exists in the direction from the terminal towards the conductive structure.

Such an embodiment may allow a particularly reliable and stable connection of the terminal to the substrate. The advantages of the invention described may therefore be particularly pronounced according to this embodiment.

Thus, the connecting layer may continuously change its composition from the first material to the second material.

Furthermore, the connecting layer may be provided continuously on the substrate metallization and on the body of the substrate adjacent to the substrate metallization. According to this embodiment, therefore, a continuous connection layer is provided which is arranged on the substrate, ie both on the substrate body and on the substrate metallization. This may be done, for example, by a CGS or an SLM. According to this embodiment, the terminal can be positioned at least partially, for example completely, next to the metallization and thus at least partially or completely on the substrate body. However, the continuous connection layer still allows connections for transferring current or signals from the terminal to the metallization.

This embodiment makes it possible to provide a terminal without having an underlying soft layer, such as an aluminum layer. This can widen the process window for ultrasonic or laser welding. A particularly reliable connection of the terminal to the electrically conductive structure can then be provided. The described advantages of the invention may therefore be particularly pronounced according to this embodiment.

Regarding further advantages and technical features of the method, reference is made to the power semiconductor module, the drawing and the further description.

Further described is a power semiconductor module in contact with a power semiconductor device, comprising a substrate metallization for contacting a terminal, and comprising a terminal disposed on the substrate metallization, the terminal comprising a first the substrate has a second connection region formed from a second material, the first material has a first hardness; the second material has a second hardness, the first hardness is different from the second hardness, and the terminal is connected to the substrate at its first connection area and at its second connection area. such a first connection area or a second connection area with a higher hardness forming a connection partner area and such a first connection area or a second connection area with a lower hardness forming a connection A connecting layer is provided between the first connecting area and the second connecting area, the connecting layer forming a base area, the connecting layer comprising a surface sub-layer formed from a material having a hardness corresponding to the hardness of the connecting partner area. layer, the surface layer facing the connection partner area.

The terminals are preferably auxiliary press-fit terminals. Such terminals are typically formed from a hard copper alloy such as CuNiSi, whereas the substrate metallization is typically formed from very soft annealed copper. Particularly when connecting such parts by ultrasonic or laser welding, this can lead to damage by cracks of the softer materials, ie the metallization or the substrate body.

Such a power semiconductor module offers significant advantages over the prior art, which are explained in detail with respect to the present method. In summary, by providing a connecting layer, power semiconductor modules can be manufactured without the risk of damaging softer materials during ultrasonic or laser welding processes. Instead, it can provide a very stable and reliable electrical connection between the terminal and the conductive structure, which ensures safe, reliable and high-performance operating behavior of the power semiconductor module. It becomes possible.

To summarize the above, the present invention solves the important objective of how to weld two dissimilar materials with different harnesses, thus enabling advanced power module designs.

For further advantages and technical features of the power semiconductor module, reference is made to the method, the drawings and the further description.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention will become apparent from and be elucidated with reference to the embodiments described below. Individual features disclosed in the embodiments can constitute aspects of the invention alone or in combination. Features of different embodiments may be carried over from one embodiment to another.

1 is a partially cutaway sectional side view of a first embodiment of a power semiconductor module according to the invention; FIG. FIG. 3 is a partially cutaway sectional side view of a second embodiment of a power semiconductor module according to the invention; FIG. 3 shows a partially cutaway sectional side view of a third embodiment of a power semiconductor module according to the invention;

DESCRIPTION OF THE EMBODIMENTS FIG. 1 shows a power semiconductor module 10 . Power semiconductor module 10 includes a substrate 12 having a substrate body 14, which may be formed from a ceramic, such as aluminum nitride, and a substrate metallization 16, which may be formed from copper, such as annealed soft copper. Furthermore, the substrate body 14 is connected to the base plate 18 by a further copper layer 20, which layer 20 may be described as a bottom metallization. Such a substrate 12 is therefore a Cu/ceramic/Cu substrate or a Cu/AlN/Cu substrate.

Substrate metallization 16 forms a conductive structure and serves, among other things, to connect power semiconductor devices (not shown as such) to terminals 22, such as power terminals 24 and auxiliary terminals 26. Terminals 22, particularly auxiliary terminals 26, may be formed from a hard copper alloy such as CuNiSi.

Each terminal 22 includes a first connection region 28 formed from a first material, and the substrate 12 has a second connection region 30 formed from a second material, the first material being a first material. 1 and the second material has a second hardness, the first hardness being different than the second hardness.

This is primarily due to the materials as described above for terminals 22 and substrate metallization 16.

Ultrasonic or laser welding is used to connect the terminals 22 to the substrate 12, ie, the substrate metallization 16. Connecting the terminals 22 to the substrate 12 is done by means of a connecting layer 32, since the respective connecting areas 28, 30 are formed from different materials, which may introduce drawbacks due to welding steps.

More particularly, the terminals 22, and in particular the auxiliary press-fit terminals 26 according to the embodiment of FIG. 1, are connected to the substrate 12 by using ultrasonic or laser welding. In this regard, a welding tool 34, such as a sonotrode, is shown.

Furthermore, before connecting the terminals 22 to the substrate 12, a connection layer 32 is provided, which has a surface sublayer, which is the only layer of the connection layer 32 in the figure. The connection layer 32 is formed from a material with a hardness that corresponds to the hardness of the connection partner region, ie the connection region 28, 30, which has a higher hardness. A connecting layer 32 is provided on the connecting region 28, 30 with lower hardness, which is the connecting base region, ie the second connecting region 30 in FIG. The material of the connection layer 32 and therefore its hardness therefore corresponds to the hardness of the copper alloy of the auxiliary terminal 26.

A connection layer 32 is therefore provided on the second connection area 30, the connection layer 32 being formed from a material having a hardness corresponding to the hardness of the first material, ie the copper alloy of the auxiliary terminal 26.

Providing the connection layer 32 may include at least one of a cold gas spraying step, a metal plating step, and bonding a preformed layer onto the second connection region 30.

A further embodiment is shown in FIG. 2, in which the same or equivalent components are defined by the same reference numerals compared to FIG.

According to FIG. 2, the same generally applies compared to FIG.
However, according to FIG. 2, the substrate is an Al/ceramic/AlN substrate, or more particularly an Al/AlN/Al substrate. The power semiconductor module 10 thus comprises a substrate 12 having a substrate body 14, which may be formed from aluminum nitride, and a substrate metallization 16, which may be formed from aluminum. Furthermore, the substrate body 14 is connected to the base plate 18 by a further aluminum layer as layer 20 and thus as bottom metallization.

Therefore, in order to realize ultrasonic welding of the terminals 22 to the substrate 12, a respective connection layer 32 is provided here again on the second connection layer 30.

However, since the substrate metallization 16 is formed from aluminum, a connection layer 32 is also provided between the power terminals 24 and the substrate 12, since by using ultrasonic welding, the aluminum and the copper of the power terminals are This is because the combination may also lead to problems.

A connection layer 32 is provided on the second connection area 30, the connection layer 32 being made of a first material, namely a material having a hardness corresponding to the hardness of the copper alloy of the auxiliary terminal 26 or the copper of the power terminal, respectively. It is formed.

A further embodiment is shown in FIG. 3, in which the same or equivalent components are defined by the same reference numerals compared to FIG.

According to FIG. 3, compared to FIG. 2, the substrate is an Al/ceramic/AlN substrate, or more specifically an Al/AlN/Al substrate. The power semiconductor module 10 thus comprises a substrate 12 having a substrate body 14, which may be formed from aluminum nitride, and a substrate metallization 16, which may be formed from aluminum. Furthermore, the substrate body 14 is connected to the base plate 18 by a further aluminum layer as layer 20 and thus as bottom metallization.

Therefore, in order to realize ultrasonic welding of the terminals 22 to the substrate 12, a respective connection layer 32 is provided here again on the second connection layer 30.

However, since the substrate metallization 16 is formed from aluminum, a connection layer 32 is also provided between the power terminals 24 and the substrate 12, since by using ultrasonic welding, the aluminum and the copper of the power terminals are This is because the combination may also lead to problems.

A connection layer 32 is provided on the second connection area 30, the connection layer 32 being made of a first material, namely a material having a hardness corresponding to the hardness of the copper alloy of the auxiliary terminal 26 or the copper of the power terminal, respectively. It is formed.

However, in addition to FIGS. 2 and 1, a connecting layer 32 is provided continuously on the metallization 16 and on the substrate body 14 adjacent to the substrate metallization. This may be realized, for example, by CGS or SLM.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative and not restrictive, and the invention The present invention is not limited to the embodiments described above. Other variations to the disclosed embodiments will be understood and may be practiced by those skilled in the art from a consideration of the drawings, this disclosure, and the claims in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting the scope.

10 Power semiconductor module 12 Substrate 14 Body 16 Metallization 18 Base plate 20 Layer 22 Terminal 24 Power terminal 26 Auxiliary terminal 28 First connection area 30 Second connection area 32 Connection layer 34 Welding tool

Claims (14)

A method of connecting terminals (22) to a substrate (12) to form a power semiconductor module (10), wherein said terminals (22) are connected to a first connection region (28) formed from a first material. ), the substrate (12) has a second connection region (30) formed from a second material, the first material has a first hardness, the second has a second hardness, said first hardness being different from said second hardness such that said first connection region (28) or said second connection region (28) has a higher hardness. 30) forms a connection partner area, such a first connection area (28) or a second connection area (30) with lower hardness forms a connection base area, said terminal (22) Connected to said substrate (12) by sonic welding or laser welding, before connecting said terminal (22) to said substrate (12), said method comprises: providing a connection layer (32) having a surface sublayer formed, said connection layer (32) being provided on said connection base region, said surface sublayer facing said connection partner region; A method characterized by: Method according to claim 1, characterized in that the step of providing the connecting layer (32) comprises a step of cold gas atomization or selective laser melting. Method according to claim 1 or 2, characterized in that the step of providing the connecting layer (32) comprises a step of metal plating. 4. A method according to any one of claims 1 to 3, characterized in that the step (32) of providing the connection layer comprises the step of bonding a pre-formed layer on the connection base area. 5. Method according to claim 4, characterized in that the step (32) of providing the connection layer comprises the step of sintering a pre-formed layer on the connection base region. 6. Method according to any one of claims 1 to 5, characterized in that the terminal (22) is connected to the substrate (12) by using ultrasonic welding. The first material includes a copper alloy and the second material includes copper, or the first material includes copper and the second material includes a copper alloy. The method according to any one of Items 1 to 6. 1 . The first material comprises aluminum and the second material comprises copper, or the first material comprises copper and the second material comprises aluminum. 7. The method according to any one of 7. 9. Method according to any one of claims 1 to 8, characterized in that the terminal (22) is a press-fit auxiliary terminal (26). Said connection layer (32) is formed in such a way that in addition to said surface sublayer it comprises a base sublayer, said surface sublayer comprising the material of said connection partner region and said base sublayer comprising: 10. A method according to any one of claims 1 to 9, characterized in that it is placed directly adjacent to the connection base region so as to include the material of the connection base region. 11. Method according to claim 10, characterized in that the connecting layer (32) changes its composition continuously from the first material to the second material. Claim 1, characterized in that the connecting layer (32) is provided continuously on the metallization (16) and on the body (14) of the substrate (12) adjacent to the metallization (16). 12. The method according to any one of items 11 to 11. A power semiconductor module (10) comprising a substrate metallization (16) for contacting a power semiconductor device and for contacting a terminal (22), the terminal for being disposed on said substrate metallization (16). (22), said terminal (22) having a first connection region (28) formed from a first material, and said substrate (12) having said substrate metallization (16) having a second connection region (28) formed from a first material. a second connection region (30) formed from a material, said first material having a first hardness, said second material having a second hardness, said first 1 hardness differs from said second hardness, said terminal (22) being connected by its first connection area (28) to said substrate (12) by its second connection area (30). and such a first connection area (28) or a second connection area (30) of higher hardness forms a connection partner area, and such a first connection area (28) or of a lower hardness forms a connection partner area. a second connection area (30) forms a connection base area, and between said first connection area (28) and said second connection area (30) a connection layer (32) is provided; The connection layer (32) is characterized in that it has a surface sublayer formed from a material having a hardness corresponding to the hardness of the connection partner area, and the surface sublayer faces the connection partner area. , power semiconductor module (10). Power semiconductor module (10) according to claim 13, characterized in that the terminal (22) is a press-fit auxiliary terminal (22).

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