Patent Description:
Power semiconductor module arrangements often include at least one semiconductor substrate arranged in a housing. A semiconductor arrangement including a plurality of controllable semiconductor elements (e.g., two IGBTs in a half-bridge configuration) is arranged on each of the at least one substrates. Each substrate usually comprises a substrate layer (e.g., a ceramic layer), a first metallization layer deposited on a first side of the substrate layer and a second metallization layer deposited on a second side of the substrate layer. The controllable semiconductor elements are mounted, for example, on the first metallization layer. The second metallization layer may optionally be attached to a base plate. The controllable semiconductor devices are usually mounted onto the semiconductor substrate by soldering or sintering techniques.

The components of the semiconductor module arrangement are usually protected from mechanical damage or other environmental impacts by means of a housing. The housing needs to be securely mounted either to the substrate or to the base plate, for example. A seal may be arranged between the housing and the substrate or base plate in order to prevent particles or gases from entering the inside of the housing.

Document <CIT> discloses a package having a cavity to be sealed by a lid. The package includes a heat sink having a coefficient of thermal expansion of <NUM> ppm/° C. or more and <NUM> ppm/° C. or less from <NUM> ° C. to <NUM> ° C. and a frame disposed on the heat sink, made of ceramics, and surrounding the cavity in plan view. An outer edge of the frame includes a first linear portion extending along a first direction, a second linear portion extending along a second direction orthogonal to the first direction, and a chamfer connecting the first linear portion and the second linear portion in plan view.

Document <CIT> discloses an optical device enclosed within a package or module having an optically transmissive or transparent cover that is sealed with an adhesive preform that has been pre-applied onto the bonding areas of the cover. The adhesive preforms are formed of a wet adhesive deposited on a sheet of optically transmissive or transparent material as a preform in predetermined locations and are B-staged or dried to form dry solid adhesive preforms. The preforms may be continuous or have one or more small gaps therein. The sheet of optical material is diced or singulated to produce individual optical covers having an adhesive preform thereon.

There is a need for a semiconductor module arrangement that offers protection for the semiconductor components arranged therein such that the overall lifetime of the power semiconductor module arrangement is increased.

In the following detailed description, reference is made to the accompanying drawings. The drawings show specific examples in which the invention may be practiced. It is to be understood that the features and principles described with respect to the various examples may be combined with each other, unless specifically noted otherwise. In the description as well as in the claims, designations of certain elements as "first element", "second element", "third element" etc. are not to be understood as enumerative. Instead, such designations serve solely to address different "elements". That is, e.g., the existence of a "third element" does not require the existence of a "first element" and a "second element". An electrical line or electrical connection as described herein may be a single electrically conductive element, or include at least two individual electrically conductive elements connected in series and/or parallel. Electrical lines and electrical connections may include metal and/or semiconductor material, and may be permanently electrically conductive (i.e., non-switchable). A semiconductor body as described herein may be made from (doped) semiconductor material and may be a semiconductor chip or be included in a semiconductor chip. A semiconductor body has electrically connecting pads and includes at least one semiconductor element with electrodes.

Referring to <FIG>, a cross-sectional view of a power semiconductor module arrangement <NUM>, that does not fall within the scope of the claimed invention, is illustrated. The power semiconductor module arrangement <NUM> includes a housing <NUM> and a substrate <NUM>. The substrate <NUM> includes a dielectric insulation layer <NUM>, a (structured) first metallization layer <NUM> attached to the dielectric insulation layer <NUM>, and a (structured) second metallization layer <NUM> attached to the dielectric insulation layer <NUM>. The dielectric insulation layer <NUM> is disposed between the first and second metallization layers <NUM>, <NUM>.

Each of the first and second metallization layers <NUM>, <NUM> may consist of or include one of the following materials: copper; a copper alloy; aluminum; an aluminum alloy; any other metal or alloy that remains solid during the operation of the power semiconductor module arrangement. The substrate <NUM> may be a ceramic substrate, that is, a substrate in which the dielectric insulation layer <NUM> is a ceramic, e.g., a thin ceramic layer. The ceramic may consist of or include one of the following materials: aluminum oxide; aluminum nitride; zirconium oxide; silicon nitride; boron nitride; or any other dielectric ceramic. For example, the dielectric insulation layer <NUM> may consist of or include one of the following materials: Al<NUM>O<NUM>, AlN, SiC, BeO or Si<NUM>N<NUM>. For instance, the substrate <NUM> may, e.g., be a Direct Copper Bonding (DCB) substrate, a Direct Aluminum Bonding (DAB) substrate, or an Active Metal Brazing (AMB) substrate. Further, the substrate <NUM> may be an Insulated Metal Substrate (IMS). An Insulated Metal Substrate generally comprises a dielectric insulation layer <NUM> comprising (filled) materials such as epoxy resin or polyimide, for example. The material of the dielectric insulation layer <NUM> may be filled with ceramic particles, for example. Such particles may comprise, e.g., SiO<NUM>, Al<NUM>O<NUM>, AlN, or BN and may have a diameter of between about <NUM> and about <NUM>. The substrate <NUM> may also be a conventional printed circuit board (PCB) having a non-ceramic dielectric insulation layer <NUM>. For instance, a non-ceramic dielectric insulation layer <NUM> may consist of or include a cured resin.

The substrate <NUM> is arranged in a housing <NUM>. In the example illustrated in <FIG>, the substrate <NUM> forms a ground surface of the housing <NUM>, while the housing <NUM> itself solely comprises sidewalls and a cover. This is, however, only an example. It is also possible that the substrate <NUM> is mounted on a base plate. In some power semiconductor module arrangements <NUM>, more than one substrate <NUM> is arranged on a single base plate. A base plate may form a ground surface of the housing <NUM>, for example. That is, the sidewalls of the housing <NUM> may be attached to the base plate, thereby covering the at least one substrate <NUM>.

One or more semiconductor bodies <NUM> may be arranged on the at least one substrate <NUM>. Each of the semiconductor bodies <NUM> arranged on the at least one substrate <NUM> may include a diode, an IGBT (Insulated-Gate Bipolar Transistor), a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), a JFET (Junction Field-Effect Transistor), a HEMT (High-Electron-Mobility Transistor), or any other suitable controllable or non-controllable semiconductor element.

The one or more semiconductor bodies <NUM> may form a semiconductor arrangement on the substrate <NUM>. In <FIG>, only two semiconductor bodies <NUM> are exemplarily illustrated. The second metallization layer <NUM> of the semiconductor substrate <NUM> in <FIG> is a continuous layer. It is, however, also possible to omit the second metallization layer <NUM>. It is also possible that the second metallization layer <NUM> is a structured layer. The first metallization layer <NUM> is a structured layer in the example illustrated in <FIG>. "Structured layer" in this context means that the first metallization layer <NUM> is not a continuous layer, but includes recesses between different sections of the layer. Such recesses are schematically illustrated in <FIG>. The first metallization layer <NUM> in this example includes three different sections. Different semiconductor bodies <NUM> may be mounted on the same or to different sections of the first metallization layer <NUM>. Different sections of the first metallization layer may have no electrical connection or may be electrically connected to one or more other sections using, e.g., bonding wires <NUM>. Electrical connections <NUM> may also include bonding ribbons, connection plates or conductor rails, for example, to name just a few examples. The one or more semiconductor bodies <NUM> may be electrically and mechanically connected to the substrate <NUM> by an electrically conductive connection layer <NUM>. Such an electrically conductive connection layer may be a solder layer, a layer of an electrically conductive adhesive, or a layer of a sintered metal powder, e.g., a sintered silver powder, for example.

The power semiconductor module arrangement <NUM> further includes terminal elements <NUM>. The terminal elements <NUM> are electrically connected to the first metallization layer <NUM> and provide an electrical connection between the inside and the outside of the housing <NUM>. The terminal elements <NUM> may be electrically connected to the first metallization layer <NUM> with a first end, while a second end <NUM> of the terminal elements <NUM> protrudes out of the housing <NUM>. The terminal elements <NUM> may be electrically contacted from the outside at their second end <NUM>. Such terminal elements <NUM>, however, are only an example. The components inside the housing <NUM> may be electrically contacted from outside the housing <NUM> in any other suitable way. For example, terminal elements <NUM> may be arranged closer or adjacent to the sidewalls of the housing <NUM>. It is also possible that terminal elements <NUM> protrude vertically or horizontally through the sidewalls of the housing <NUM>. It is even possible that terminal elements <NUM> protrude through a ground surface of the housing <NUM>.

The semiconductor bodies <NUM> each may include a chip pad metallization, e.g., a source, drain, anode, cathode or gate metallization. A chip pad metallization generally provides a contact surface for electrically connecting the semiconductor body <NUM>. The chip pad metallization may electrically contact a connection layer <NUM>, a terminal element <NUM>, or an electrical connection <NUM>, for example. A chip pad metallization may consist of or include a metal such as aluminum, copper, gold or silver, for example. The electrical connections <NUM> and the terminal elements <NUM> may also consist of or include a metal such as copper, aluminum, gold, or silver, for example.

The power semiconductor module arrangement <NUM> further includes a casting compound <NUM>. The casting compound <NUM> may consist of or include a silicone gel, a silicone, polyurethane, epoxy, or polyacrylate based isolation material, or may be a rigid molding compound, for example. The casting compound <NUM> may at least partly fill the interior of the housing <NUM>, thereby covering the components and electrical connections that are arranged on the substrate <NUM>. The terminal elements <NUM> may be partly embedded in the casting compound <NUM>. At least their second ends <NUM>, however, are not covered by the casting compound <NUM> and protrude from the casting compound <NUM> through the housing <NUM> to the outside of the housing <NUM>. The casting compound <NUM> is configured to protect the components and electrical connections inside the power semiconductor module <NUM>, in particular inside the housing <NUM>, from certain environmental conditions and mechanical damage. The casting compound <NUM> may be formed by dispensing a material, for example, an uncured dielectric gel, into the housing <NUM>, after the housing <NUM> has been mounted to a substrate <NUM> or to a base plate, and then curing the material.

The housing <NUM> encloses the arrangement and provides further protection from certain environmental conditions and mechanical damage. As has been described above, the housing <NUM> may be attached to the substrate <NUM> or, if the substrate <NUM> is arranged on a base plate, the housing <NUM> may be attached to the base plate, for example. In order to prevent the casting compound <NUM> from leaking out between the housing <NUM> and the substrate <NUM> or base plate, and to prevent contaminants or gasses (e.g., corrosive gasses) from entering the inside of the housing <NUM>, a seal <NUM> may be arranged between the housing <NUM> and the substrate <NUM> (or between the housing <NUM> and the base plate). Referring to <FIG>, a semiconductor module arrangement <NUM> not falling within the scope of the claimed invention, and comprising a seal <NUM> between the substrate <NUM> and the housing <NUM> is schematically illustrated.

In order to form the seal <NUM>, the material of the seal <NUM> may be applied on the substrate <NUM> (or base plate) or to the housing <NUM> in a liquid or viscous form. The housing <NUM> may then be arranged on the substrate <NUM> (or base plate), with the material of the seal <NUM> arranged between the housing <NUM> and the substrate <NUM> (or base plate). The material of the seal <NUM> may then be cured, e.g., by heating the arrangement. During the curing process, the presence of contaminants may cause the formation of air bubbles and unwanted cavities in the seal <NUM> which may decrease the sealing abilities of the seal <NUM>. Measurements to avoid unwanted bubble formation lead to higher costs due to additional process steps and/or longer cycle times. Furthermore, components of the viscous seal <NUM> can interact with other module components, especially during heating, until solidification which can have an adverse impact on the module negative, e.g., through reduced cycle times.

In addition, there is a risk that contaminants in the material forming the seal will interfere with the curing process such that non-solidified (non-cured) material remains between the housing and the cured parts of the seal <NUM>. This may also result in reduced sealing abilities of the seal <NUM>. For example, corrosive gasses may be able to enter the housing <NUM> through a non-solidified layer of sealing material.

It is therefore important to prevent air from penetrating into the material <NUM>, so the seal <NUM> is free of any unwanted air bubbles or cavities. Even further, any fluids or moisture that may be present in the housing <NUM> should be prevented from penetrating into the seal <NUM>. The seal <NUM>, therefore, should also be free of any unwanted air bubbles and uncured material. Measurements to avoid unwanted bubble formation lead to higher costs due to additional process steps and/or longer cycle times.

Now referring to <FIG>, a conventional process that does not fall within the scope of the claimed invention, for forming a seal is schematically illustrated. The liquid or viscous material <NUM> (illustrated inside the box at the top of <FIG>) is dispensed on the respective surface of the substrate <NUM>, base plate, or housing <NUM> (step 301A), and, once the housing <NUM> has been arranged on the substrate <NUM> or base plate, with the material <NUM> arranged therebetween, the material <NUM> is cured (step 302A). The material <NUM> generally comprises a matrix material <NUM>, e.g., a silicone-based matrix material, and an adhesion promoter <NUM>. Adhesion promoters, often also referred to as coupling agents, are chemicals that act at the interface between two different materials (e.g., an organic polymer such as the matrix material, and an inorganic material such as the housing, substrate and base plate) to enhance adhesion between the two materials. Organic and inorganic materials are very different in many ways, for example, compatibility, chemical reactivity, surface properties, and coefficient of thermal expansion, such that forming a strong adhesive bond between each of these two dissimilar materials and the matrix material <NUM> is difficult. An adhesion promoter <NUM> acts effectively at the interface between the matrix material <NUM> and each of the organic and inorganic materials (e.g., the interface between matrix material <NUM> and housing <NUM>, and the interface between matrix material <NUM> and substrate <NUM> or base plate) to chemically and physically wed each of these dissimilar materials with the matrix material <NUM> via a strong cohesive bond structure.

The curing process is usually performed at temperatures that are high enough and applied for a sufficient duration to solidify (cure) the matrix material <NUM> and activate the adhesion promoter <NUM>. That is, during the curing process, a crosslinking process occurs and the adhesion promoter <NUM> is activated, resulting in certain adhesion properties of the resulting seal <NUM>. Once activated, the adhesion promoter is consumed, such that it becomes unreactive, i.e. it cannot be activated again at a later time.

Now referring to <FIG>, a method according to one embodiment falling within the scope of the claimed invention, is schematically illustrated. A material <NUM> comprising a silicone based matrix material <NUM> and an adhesion promoter <NUM> are provided. The material <NUM> may be the same or similar to the material <NUM> described with respect to <FIG>. In a first step (step 301B), the material <NUM> is heated to a first temperature. The first temperature, however, is lower than the temperature that is required to activate the adhesion promoter <NUM>, or is applied for a duration that is too short (insufficient) to fully consume the adhesion promoter <NUM>. That is, the material <NUM> (the matrix material <NUM>) is cured (crosslinking process occurs) while ensuring that a sufficient amount of adhesion promoter <NUM> remains in the pre-seal <NUM> after curing. The resulting intermediate product (pre-seal <NUM>) is solid (cured/hardened) but has limited adhesive properties, which is to say that while it might be slightly sticky, it cannot be durably attached to a surface. This makes the pre-seal <NUM> easy to handle. The step 301B which is illustrated above the dashed line in <FIG> may be performed at a supplier of the pre-seal <NUM>, for example. The pre-seal <NUM> may then be shipped to a manufacturer of the power semiconductor module arrangement <NUM>. A surface on which the pre-seal <NUM> is formed, therefore, may be a suitable working surface and the resulting pre-seal <NUM> may be removed from the working surface for further handling.

Different adhesion promoters <NUM> may usually be suitable to be used in a seal <NUM>. Each adhesion promoter <NUM> may have a different specific activation time-temperature budget. In other words, heating a given adhesion promoter <NUM> at a given temperature for a given period of time will lead to activation and consumption of that adhesion promoter <NUM>. On the other hand, heating that same adhesion promoter <NUM> at a higher temperature for a shorter time, or at a lower temperature for a longer time, can also lead to activation and consumption of that adhesion promoter <NUM>. Many adhesion promoters <NUM> have an activation temperature of between <NUM> and <NUM>, and activation times of between <NUM> minutes and <NUM> minutes. That is, the temperature and time during which the first step 301B is performed depends on the specific activation time-temperature budget of the adhesion promoter <NUM> present in the material <NUM>. In any case, however, the first step 301B is performed for a duration and at a temperature that is lower than the activation time-temperature budget of the adhesion promoter <NUM> that is used for the seal <NUM>. The matrix material <NUM> that is used for a silicon based seal <NUM>, for example, generally cures at temperatures that are significantly lower than the activation temperature of the adhesion promoter <NUM>. The curing may even occur at relatively low temperatures such as, e.g., between <NUM> and <NUM>. According to one example, a curing step (step 301B) may be performed at <NUM> for <NUM> hours, at <NUM> for <NUM> hour, or at <NUM> for <NUM> minutes. As noted, however, the specific temperatures and durations generally depend on the specific materials and may vary.

The resulting pre-seal <NUM> may be shipped and may then be arranged on a surface of a substrate <NUM>, base plate or housing <NUM>, and the housing <NUM> may be arranged on the substrate <NUM> or base plate with the pre-seal <NUM> arranged therebetween (step 302B). A second heating step may follow during which the arrangement, and in particular the pre-seal <NUM>, is heated to temperatures which correspond to or are even higher than the activation temperature of the adhesion promoter <NUM> (step 303B). For example, heat may be applied to the side of the substrate <NUM> or base plate opposite the side to which the pre-seal <NUM> is mounted, effecting activation of the adhesion promoter <NUM>, and causing the resulting seal <NUM> to securely attach to both the housing <NUM> and the substrate <NUM> or base plate. That is, the resulting seal <NUM> securely attaches the housing <NUM> to the substrate <NUM> or base plate and, in addition, seals the inside of the housing <NUM>.

Conventional non-adhesive seals such as gaskets and o-rings can also be used to seal power modules. However, such gaskets and o-rings require use of external fasteners to provide a compressive force to maintain a seal between the housing <NUM> and substrate <NUM> or base plate at all times, both before and after curing of the casting compound <NUM>. Again, the adhesive properties of the adhesive seal <NUM> according to embodiments of the disclosure mean that no additional fasteners are required after the adhesion promoter is activated so as to secure the housing <NUM> to the substrate <NUM> or base plate.

The steps 302B and 303B, as described with respect to <FIG> above, are again illustrated by means of <FIG>, <FIG>. As is schematically illustrated in <FIG>, a pre-produced pre-seal <NUM> may be arranged on a substrate <NUM>. A housing <NUM> may be arranged on the substrate <NUM>, with the pre-seal <NUM> arranged between the substrate <NUM> and the housing <NUM>, as is illustrated in <FIG>. A heating step follows during which the adhesion promoter that is present in the pre-seal <NUM> (but which has not yet been activated) is activated, resulting in a seal <NUM> which has sealing properties as well as adhesion properties. That is, the resulting seal <NUM> has strong adhesion forces and securely attaches the housing <NUM> to the substrate <NUM>.

The pre-seal <NUM> may have any suitable form. According to one example, the pre-seal <NUM> forms a closed loop, as is schematically illustrated in <FIG>, for example. The shape and size of the pre-seal <NUM> may depend on the shape and size of the housing <NUM>, for example. The pre-seal <NUM> may have the exact same shape and dimensions as the housing <NUM> such that it may be arranged between the housing <NUM> and the substrate <NUM> or base plate to attach the housing <NUM> to the substrate <NUM> or base plate and seal the inside of the housing <NUM>. Many substrates <NUM>, base plates and housings <NUM> have a rectangular or square shape. Other shapes, however, are generally possible. The size of the pre-seal <NUM> may be slightly smaller than the size of the respective substrate <NUM> or base plate such that, when it is arranged on the substrate <NUM> or base plate, it extends along its edge. When the housing <NUM> is arranged on the pre-seal <NUM>, the pre-seal <NUM> extends along the entire circumference of the housing <NUM> (i.e., along the lower surface of the sidewalls of the housing <NUM> that face towards the substrate <NUM> or base plate).

Alternatively, the pre-seal <NUM> may be arranged on a surface of the housing <NUM> first. The housing <NUM> with the pre-seal <NUM> arranged thereon may then be arranged on a substrate <NUM>. The heating step may follow as has been described above with respect to <FIG> to form the final seal <NUM>. If the substrate <NUM> is arranged on a base plate, the housing <NUM> may be arranged on the base plate, with the pre-seal <NUM> arranged between the base plate and the housing <NUM>.

It is possible to manufacture and ship the pre-seal <NUM> independently. According to another embodiment falling within the scope of the present invention, however, it is also possible to form the pre-seal <NUM> on the housing <NUM> and ship the housing <NUM> together with the pre-seal <NUM> formed thereon. This is schematically illustrated in <FIG>. In a first step, the material <NUM> including the (silicone based) matrix material and the adhesion promoter is applied to the housing <NUM> (e.g., on a lower surface of the sidewalls of the housing <NUM> that face towards the substrate <NUM> or base plate when the housing <NUM> is arranged on the substrate <NUM> or base plate). This is schematically illustrated in <FIG>. A heating step is performed to cure the matrix material without activating or without fully consuming the adhesion promoter, thereby forming the pre-seal <NUM> (<FIG>). The housing <NUM> with the pre-seal <NUM> formed thereon may then be arranged on a substrate <NUM> or base plate and the final seal <NUM> may be formed by performing the second heating step as has been described above.

The lower surface of the sidewalls of the housing <NUM> may be a flat or essentially flat surface, as is schematically illustrated in <FIG>, for example. In this case, the pre-seal <NUM> is required to have certain adhesive properties in order to remain attached to the flat lower surface. It is, however, also possible that the lower surface of the sidewalls is formed to have at least one recess or undercut <NUM>, for example. This is schematically illustrated in <FIG>. When the material <NUM> is applied to the lower surface of the housing <NUM>, the material <NUM> fills the recess <NUM> formed in the sidewall of the housing <NUM>, and further forms a layer of material <NUM> that extends from the lower surface in a vertical direction y. Once the material <NUM> has been cured and the pre-seal <NUM> is solid, it is securely attached to the lower surface of the housing <NUM> without having any adhesive properties yet, or having only limited adhesive properties. The specific form of the recess <NUM> illustrated in <FIG> is merely an example. A recess or undercut <NUM> may generally have any suitable form. In this case, the pre-seal <NUM> remains attached to the sidewall of the housing without having any adhesive properties.

A similar effect may be achieved if the lower surface of the housing <NUM> comprises a protrusion <NUM>, and the material <NUM> is applied to the lower surface of the housing <NUM> such that it forms a layer of material <NUM> that extends from the lower surface in a vertical direction y and entirely encloses the protrusion <NUM>, as is exemplarily illustrated in <FIG>. The recess <NUM> or protrusion <NUM> may be a continuous recess <NUM> or protrusion <NUM> along the entire circumference of the housing <NUM>. It is, however, also possible, that a plurality of recesses <NUM> and/or protrusions <NUM> is arranged along the circumference of the housing <NUM>.

When forming a pre-seal <NUM> (either independently or on a lower surface of the housing, for example), the curing step at a temperature below the activation temperature of the adhesion promoter <NUM> may be carried out in a vacuum chamber, for example. This prevents air from penetrating into the material <NUM>. The resulting pre-seal <NUM> as well as the final seal <NUM>, therefore, are free of any unwanted air bubbles or cavities. Even further, any fluids or moisture that may be present in the housing <NUM> may be prevented from penetrating into the material <NUM>. The resulting pre-seal <NUM> as well as the final seal <NUM>, therefore, are also free of any unwanted fluids.

According to another example, a housing <NUM> with a pre-attached pre-seal <NUM> may be formed in a two-shot (<NUM>) injection molding process, for example. Techniques that are known as <NUM> injection molding allow to form injection-molded parts comprising two different materials in the same mold. A first material (e.g., the material forming the housing <NUM>) may be filled into a mold by means of at least one injection. At least one second injection is used to fill a second material (e.g., the material <NUM> forming the pre-seal <NUM>) into a mold containing the housing <NUM>, where the mold has defined locations adjacent the housing <NUM>. The two materials, in this way, may be connected to each other. It is important that during the second step of the <NUM> processes, e.g., during formation of the pre-seal <NUM>, that the temperature be held sufficiently high and for a sufficient time to allow curing of the second material <NUM> but at a low enough temperature and/or for a time that is short enough to prevent the adhesion promoter from being fully consumed during the curing process. The <NUM> injection molding process can be a manual two-step process, or a fully automated process using a rotary injection molding form, for example. The two materials may be filled into the mold in any suitable order, as long as the temperature can be held low enough or for an amount of time insufficient to allow full consumption of the adhesion promoter in the pre-seal material <NUM>.

According to this example, the housing/pre-seal assembly <NUM>, <NUM> may be mounted to a substrate <NUM> by placing it on the substrate <NUM> with the pre-seal <NUM> arranged between the housing <NUM> and the substrate <NUM> and by pressing the housing <NUM> toward the substrate. The pre-seal <NUM> is then heated in order to activate the adhesion promoter remaining in the pre-seal material <NUM>, for example, by heating the other side of the substrate <NUM>. Pressure may be removed from the housing <NUM> and the heat may be removed once the adhesion promoter is fully activated and the pre-seal <NUM> seal is fully adhered to the substrate <NUM>.

Claim 1:
A method for forming a pre-seal (<NUM>) for a power semiconductor module arrangement (<NUM>), the method comprising:
applying a first material (<NUM>) to a first surface, the first material (<NUM>) comprising a matrix material (<NUM>) and an inactive adhesion promoter (<NUM>) wherein the matrix material (<NUM>) is configured to cure when heated to a defined temperature for a defined period of time, and wherein the adhesion promoter (<NUM>) is configured to be activated when heated to a temperature that is higher than the defined temperature and/or for a period of time that is longer than the defined period of time; and
heating the first material (<NUM>) to the defined temperature for the defined period of time such that the matrix material (<NUM>) cures and the adhesion promoter (<NUM>) remains inactive, thereby forming a pre-seal (<NUM>), wherein the pre-seal (<NUM>), when the adhesion promoter (<NUM>) is inactive, comprises no or only limited adhesive properties such that it cannot be durably attached to the surface, and wherein the pre-seal (<NUM>), when the adhesion promoter (<NUM>) is activated, comprises adhesive properties such that it can be durably attached to the surface.