Patent Description:
Document <CIT> discloses a semiconductor device and a method of manufacturing the same, in particular, a power semiconductor device having a power semiconductor element resin-sealed inside a case.

Semiconductor components are usually packaged and then mounted to a printed circuit board. The semiconductor components may further be coupled to a heat sink, wherein the heat sink is configured to dissipate heat produced by the semiconductor component. Several different ways are known of how a semiconductor component may be mounted to a heat sink. Such mounting methods, however, are often expensive, require a lot of space, and require one or more additional process steps for mounting the component to the heat sink. There is a need to provide a semiconductor component that may be easily mounted to another component, such as a heat sink, at reduced costs and with reduced effort.

One example relates to a method. The method includes providing a heat sink, wherein the heat sink is embedded in an encapsulation material of a package, wherein a metallic surface of the heat sink is not covered by the encapsulation material, forming a wall around the perimeter and/or circumference of the heat sink such that the wall extends in a vertical direction from a plane formed by the metallic surface of the heat sink, wherein the wall is placed only at least on portions of the top surface (<NUM>) of the package (<NUM>), or on at least portions of the top surface (<NUM>) of the package (<NUM>) and a portion of the metallic surface (<NUM>); depositing a filler material in a walled area on the metallic surface, wherein the filler material is a ceramic material, depositing a plastic material on the filler material, wherein the plastic material is a crosslinking material, and performing a vacuum treatment of the filler material and the plastic material thereby forming a matrix composite layer disposed on the metallic surface.

Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and on viewing the accompanying drawings.

Examples are explained below with reference to the drawings. The drawings serve to illustrate certain principles, so that only aspects necessary for understanding these principles are illustrated. In the drawings the same reference characters denote like features.

In the following detailed description, reference is made to the accompanying drawings. The drawings form a part of the description and by way of illustration show specific embodiments in which the invention may be practiced. It is to be understood that the features of the various embodiments described herein may be combined with each other, unless specifically noted otherwise.

Several methods are known for mounting a semiconductor component to a second component such as a heat sink, for example. Attaching semiconductor components to heat sinks removes the waste heat that is generated during operation of the semiconductor components. <FIG> shows one known possibility for attaching a semiconductor component <NUM> to a heat sink <NUM>. The semiconductor component <NUM> comprises a package <NUM>. One or more semiconductor dies (not illustrated in <FIG>) may be arranged within the semiconductor package <NUM>. The package <NUM> may comprise one or more pins or leads <NUM> for mounting the semiconductor component <NUM> to a printed circuit board <NUM> and for providing an electrical connection between the semiconductor die(s) in the package <NUM> and the surrounding circuitry (e.g., on the printed circuit board <NUM>). The semiconductor component <NUM> is further coupled to a heat sink <NUM>. An isolation foil <NUM> is arranged between the semiconductor component <NUM> and the heat sink <NUM>. The isolation foil <NUM> is configured to dissipate heat from the semiconductor component <NUM> to the heat sink <NUM>. The use of isolation foils <NUM>, however, is usually rather expensive. A further drawback of isolation foils <NUM> is that additional process steps are required. This is because the semiconductor component <NUM>, the heat sink <NUM> and the isolation foil <NUM> have to be purchased separately and subsequently have to be assembled by an end user. The isolation foil <NUM> is first laminated to the heat sink <NUM> and then the semiconductor component <NUM> is attached to the isolation foil <NUM>. The isolation foil <NUM> may be a ceramic foil, for example. The isolation foil <NUM> generally may be electrically non-conductive and thermally conductive.

Generally, the creepage distances in the arrangement in <FIG> are rather large. This is schematically illustrated in <FIG> which illustrates a top view of the arrangement of <FIG>. The creepage distances are schematically indicated by arrows in <FIG>.

<FIG> illustrates another example of a known method for mounting a semiconductor component <NUM> to a heat sink <NUM>. In the example of <FIG>, the heat sink <NUM> and the semiconductor component <NUM> each comprise a hole <NUM>, <NUM>. A screw <NUM> may be inserted into the holes <NUM>, <NUM> to fix the semiconductor component <NUM> to the heat sink <NUM>. A compression washer <NUM> may be inserted between the screw <NUM> and the semiconductor component <NUM>. This method, however, also has several drawbacks. For example, the thermal conductivity depends on a filler material (usually Silicon) that acts as a thermal dissipator and the resulting Silicon/Resin ratio is usually limited/balanced by the moldability performance. Other mechanical fasteners are known for attaching a semiconductor component <NUM> to a heat sink <NUM>, including nuts and bolts or spring clips with either greased mica or thermally-enhanced silicone pads, for example.

A further known method is illustrated in <FIG>. The semiconductor component <NUM> is mounted on a substrate <NUM>, in particular a direct copper bonded (DCB) substrate <NUM>. The DCB substrate comprises a ceramic dielectric insulator layer <NUM>. Pure copper layers <NUM> are applied and bonded to the ceramic layer <NUM> on both sides using great adhesive strength in a high temperature melting and diffusion process. The semiconductor component <NUM> is then soldered to a first side of the DCB substrate <NUM> using a solder layer <NUM>. The heat sink <NUM> may be coupled to the second side of the DCB substrate <NUM> opposite the first surface. A heat spreader <NUM> may be inserted between the DCB substrate <NUM> and the heat sink <NUM>. For example, the DCB substrate <NUM> may be soldered to the heat spreader <NUM> by means of a solder layer <NUM>. A thermal grease layer <NUM> may be arranged between the heat spreader <NUM> and the heat sink <NUM>.

The heat spreader <NUM> may be a copper baseplate or aluminium baseplate. However, especially in the lower power range, arrangements without a baseplate are also frequently used. In such an arrangement the second solder layer <NUM> and heat spreader <NUM> may be omitted and the DCB substrate <NUM> may be coupled to the heat sink <NUM> via the thermal grease layer <NUM>. Even though an arrangement including a DCB substrate <NUM> has several advantages such as a high mechanical strength and mechanical stability, good adhesion and corrosion resistance, and a very good thermal conductivity, it also has some drawbacks. The drawbacks include high costs. Furthermore, several additional process steps are required during assembly of the arrangement and the isolation is rather thick (e.g., minimum of <NUM>).

<FIG> illustrates a first exemplary embodiment of a semiconductor component <NUM> according to the present invention. The semiconductor component <NUM> comprises a semiconductor package <NUM>. A first thermally conductive layer <NUM> is arranged on an outer surface of the semiconductor package <NUM>. The first thermally conductive layer <NUM> formed on the outer surface of the semiconductor package is configured to be mounted to an external heat sink <NUM>. Correspondingly, the semiconductor component <NUM> with the first thermally conductive layer <NUM> arranged on the outer surface of the semiconductor component <NUM> is configured to be mounted to an external heat sink <NUM> such that the first thermally conductive layer <NUM> faces the heat sink <NUM>.

A method for producing a semiconductor component <NUM> comprises forming a first thermally conductive layer <NUM> on an outer surface of a semiconductor package <NUM>. The first thermally conductive layer <NUM> formed on the outer surface of the semiconductor package <NUM> is configured to be mounted to an external heat sink <NUM>.

In one example, the semiconductor component <NUM> includes at least one semiconductor die <NUM> (see <FIG>) that is arranged within the semiconductor package <NUM>. The first thermally conductive layer <NUM> may be arranged on a first outer surface or external surface of the semiconductor package <NUM>. The first outer surface of the semiconductor package <NUM> may comprise an electrically conductive surface <NUM> such as a heat sink or exposed die pad (see <FIG>), for example. The electrically conductive surface <NUM> may comprise an electrically conductive material such as a metal, for example. The semiconductor package <NUM> may comprise a casing made of plastic, glass or ceramic, for example. The casing may comprise an opening on one side, e.g. bottom side or top side. The electrically conductive surface <NUM> may be arranged within this opening such that it forms a part of the respective outer surface of the semiconductor package <NUM>.

The semiconductor component <NUM> may comprise pins or leads <NUM> (see <FIG>) for mounting the semiconductor component <NUM> to a printed circuit board (PCB) or a DCB <NUM>, for example. The pins or leads <NUM> may be inserted in through holes of a PCB or may be surface mounted to a PCB, for example. The electrically conductive surface <NUM> of the semiconductor component <NUM> may be thermally coupled to an external heat sink <NUM> by means of the first thermally conductive layer <NUM>. This means that the first thermally conductive layer <NUM> is arranged between the semiconductor component <NUM> and the external heat sink <NUM>. The external heat sink <NUM> may comprise a thermally conductive material and is configured to dissipate heat from the semiconductor component <NUM>. The external heat sink <NUM> may comprise fins, as is illustrated in <FIG>, to increase the surface area of the external heat sink <NUM>. In this way, more heat may be delivered to a surrounding medium such as air, or any other suitable cooling fluid (not illustrated in <FIG>). A heat sink <NUM> comprising fins, however, is only an example.

The first thermally conductive layer <NUM> is formed on the semiconductor package <NUM> before the package <NUM> is mounted to the external heat sink <NUM>, in particular before the semiconductor component <NUM> is sold to a final customer. The thermally conductive layer <NUM>, together with the semiconductor component <NUM>, may then be mounted to an external heat sink <NUM> such that the thermally conductive layer faces the external heat sink <NUM> and is arranged between the semiconductor component <NUM> and the external heat sink <NUM>.

The first thermally conductive layer <NUM> may comprise a ceramic material, for example. However, any other materials may be used, for example any materials providing sufficient electrical isolation and good thermal conductivity. As the first thermally conductive layer <NUM> is formed on the semiconductor component <NUM> before the semiconductor component <NUM> is delivered to the end customer, the mounting process for the end customer becomes much more convenient. The end customer only needs to purchase the semiconductor component <NUM> with the thermally conductive layer <NUM> already applied thereon. The end customer can easily mount the semiconductor component <NUM> to the external heat sink <NUM>.

The semiconductor package <NUM> in the example of <FIG> may be a so-called TO-<NUM> package. This is, however, only an example. Any other packages having an electrically conductive surface such as an exposed heat sink or exposed die pad, for example, arranged at an outer surface of the semiconductor package <NUM> are generally suitable such as DPAK or split leadframe packages, for example.

According to one example, a method comprises forming a first thermally conductive layer <NUM> on an outer surface of the semiconductor package <NUM>. The thermally conductive layer <NUM> is formed before mounting the semiconductor package <NUM> to an external heat sink <NUM>. The thermally conductive layer <NUM> formed on the semiconductor package <NUM> is configured to be mounted to an external heat sink <NUM>.

<FIG> illustrates a further example of a method for producing a semiconductor component <NUM>. The method may comprise two successive steps, for example. In a first step, a first material <NUM> may be deposited on the electrically conductive surface (e.g., heat sink or exposed die pad) <NUM> of the semiconductor package <NUM>. The first material <NUM> may be or may include boron nitride, in particular hexagonal boron nitride, for example. The first material <NUM> may be a ceramic based material and may include an oxide, carbide or nitride combination. The first material <NUM> may include aluminium oxide, silicon carbide or silicon dioxide, for example. The first material <NUM> (e.g., the boron nitride) may be provided in the form of droplets or platelets, for example. The first step may comprise an electrophoretic deposition process, for example. Electrophoretic deposition (EPD) is a term used for a broad range of industrial processes including electrocoating, cathodic electrodeposition, anodic electrodeposition, electrophoretic coating and electrophoretic painting, for example. A characteristic feature of this process is that colloidal particles suspended in a liquid medium migrate under the influence of an electric field (electrophoresis) and are deposited onto an electrode. Generally, all colloidal particles that can be used to form stable suspensions and that can carry a charge can be used in an electrophoretic deposition process. This includes materials such as polymers, pigments, dyes, ceramics and metals, for example.

The semiconductor package <NUM> has a semiconductor die <NUM> arranged inside. An electrically conductive surface (e.g., heat sink or exposed die pad) <NUM> at least partially forms one of the outer surfaces of the semiconductor package <NUM>. The electrically conductive surface <NUM> is electrically coupled to at least one pin or lead <NUM>. The at least one pin or lead <NUM> is configured to electrically contact the semiconductor die <NUM> within the semiconductor package <NUM> and to electrically couple the semiconductor die <NUM> to any surrounding circuitry and any other components that may be arranged on the same printed circuit board, for example. The electrical connection between the pin or lead <NUM> and the electrically conductive surface <NUM> may be formed via the semiconductor die <NUM> within the semiconductor package <NUM>.

The at least one pin or lead <NUM> may be coupled to a power supply so as to apply a direct current to the electrically conductive surface <NUM> of the semiconductor package <NUM>. In one example, a voltage of between <NUM> and <NUM> V is applied to the electrically conductive surface <NUM>. The semiconductor component <NUM> may be submerged into a container or vessel, for example, which holds the coating bath or solution. One or more so-called counter-electrodes may be used to complete the circuit (not illustrated in <FIG>).

The general principle of an arrangement for electrophoretic deposition is schematically illustrated in <FIG>. The arrangement comprises a container or vessel <NUM>. A coating bath or solution is held in the container or vessel <NUM>. The electrically conductive surface <NUM> that is to be coated as well as at least one counter-electrode <NUM>, are immersed into the coating bath or solution within the container <NUM>. The electrically conductive surface <NUM> and the counter-electrode <NUM> are each connected to terminals, namely a terminal for providing a positive potential and a terminal for providing a negative potential, respectively. For example, if the electrically conductive surface <NUM> is coupled to a terminal for a negative potential (-), the counter-electrode <NUM> is coupled to a terminal for a positive potential (+), as is illustrated in <FIG>, or vice versa. During the EPD process, a direct current is applied to the electrically conductive surface <NUM> and to the counter-electrode <NUM>, and, therefore, also to the solution or colloidal suspension within the container <NUM>. The solution or colloidal suspension may comprise ionizable groups.

There are generally two different types of E102PD processes, namely anodic and cathodic. In the anodic process, negatively charged material is deposited on the positively charged electrode, or anode. In the cathodic process, positively charged material is deposited on the negatively charged electrode, or cathode. When an electric field is applied, the charged particles within the solution or suspension migrate by the process of electrophoresis towards the electrode with the opposite charge. There are several mechanisms by which the material can be deposited on the electrode, including charge destruction and the resultant decrease in solubility, concentration coagulation, and salting out, for example. Such EPD processes are generally known in the art and will not be described in further detail herein. The so-called dippingmethod of <FIG> is further exemplarily illustrated in <FIG>.

<FIG> illustrates a semiconductor component <NUM> with a semiconductor package <NUM> that is immersed into the solution or suspension <NUM> in the container <NUM>. Although the arrow in <FIG> indicates that the semiconductor component <NUM> is being immersed into the solution <NUM>, a first layer <NUM> is illustrated on an outer surface of the semiconductor package <NUM>. The first layer <NUM> may be formed on an electrically conductive surface of the semiconductor component <NUM> during the EPD process.

Again referring to <FIG>, a first layer <NUM> is formed on the outer surface of the semiconductor package <NUM> by depositing the first material <NUM> and, after depositing the first material <NUM>, in a second step depositing a second material <NUM> on the first material <NUM> or on a pre-layer formed by the first material <NUM>. The second material <NUM> may be a thermally conductive material with or without fillers. For example, the second material <NUM> may be or may include a polymer. The polymer may be an epoxy or a silicon based polymer. The polymeric material may be a soft polymeric material (flexible type polymer) or the polymeric material may be hardened. The second material <NUM> may be provided in the form of droplets or platelets, for example. The second step may comprise an electrophoretic deposition process, as has been described above with respect to the first step, or a dispensing method, for example.

The general principle of such a dispensing method is schematically illustrated in <FIG>. Instead of a dispensing method as is illustrated in <FIG>, an electrostatic spraying method may be used, for example. During a dispensing or electrostatic spraying method, a liquid flow emerging from a tip or thin tube <NUM> under the influence of a strong electric field breaks up into small droplets due to a charging of the dielectric liquid. If a polymer material is dissolved in the liquid, this technique may be utilized to produce a polymer layer on an electrode. In the example of <FIG>, the electrode is formed by the electrically conductive surface <NUM> with the first pre-layer <NUM> (formed in step <NUM>) deposited thereon. As has been described with reference to <FIG>, the at least one pin or lead <NUM> of the semiconductor component <NUM> may be coupled to a power supply. Instead of a wet solution that is broken up into small droplets, it is also possible to apply a dry powder including the second material <NUM>, for example a polymer, to the first material <NUM> or the first pre-layer. The particles in the dry powder may be electrically charged and may be attracted by the electrically conductive surface <NUM> when coupled to a power supply. The charged particles in the liquid or the powder are initially projected towards the electrically conductive surface <NUM> and may be accelerated towards the electrically conductive surface <NUM> by an electrostatic charge provided by the power supply. Depending on the charge of the particles, the electrically conductive surface <NUM> may be coupled to the positive (negatively charged particles) or the negative terminal (positively charged particles) of the power supply.

A polymer may alternatively be deposited on the electrically conductive surface <NUM> using a polymer coating process or so-called e-coating method. Polymer coating processes generally include extrusion/dispersion coating or solution application techniques, for example. E-coating methods include immersing the electrically conductive surface in a bath that consists of a water-based solution, for example. An electric current is then used to attract the particles that are suspended in the liquid solution and deposit them onto the surface of the substrate. The e-coating, therefore, is very similar to the electrophoretic deposition.

After completing the second step, the first layer <NUM> includes both the first material <NUM> and the second material <NUM>. In some examples the first step is followed by a sintering process before performing the second step. Such a sintering process, however, is optional. Sintering generally is the process of compacting and forming a solid mass of material by applying heat or pressure, without melting the material to the point of liquefaction. The sintering may enhance properties such as strength and thermal conductivity, for example. If the first material includes ceramic, the sintering process at a high temperature may fuse the ceramic particles together.

Referring to <FIG>, an example of a method for producing a semiconductor component <NUM> is illustrated. In a first step, illustrated in <FIG>, a first material <NUM> is deposited on an electrically conductive surface <NUM>. The first step may comprise an electrophoretic deposition process, as has been described with respect to <FIG>. An optional sintering step may follow (not illustrated in <FIG>). In a second step, illustrated in <FIG>, a second material <NUM> is deposited on the first material <NUM> already arranged on the electrically conductive surface <NUM>. The second step may comprise an electrophoretic deposition process or a dispensing method, as has been described with respect to <FIG> above. The second material <NUM> may be deposited on the surface of a pre-layer that is formed by the first material <NUM>. However, as this pre-layer includes droplets or platelets of the first material <NUM>, the pre-layer may be porous with empty spaces or cavities between the separate droplets or platelets (as illustrated in <FIG>), the second material <NUM> may at least partially fill the empty spaces or cavities of the porous pre-layer between the droplets or platelets of the first material <NUM>, as is schematically illustrated in <FIG>.

The first material <NUM> may be or may include hexagonal boron nitride. The deposited first material <NUM> may form a hexagonal boron nitride pre-layer on the electrically conductive surface <NUM>. The second material <NUM> may be or may include a polymer and may form a polymer coating on the first material <NUM>. The resulting first layer <NUM> comprises the first material <NUM> as well as the second material <NUM>. The second step may optionally be followed by a third step during which the first layer <NUM> comprising the first material <NUM> and the second material <NUM> is exposed to a vacuum and/or high temperatures. The temperatures may be room temperature (typically between <NUM> and <NUM>), up to <NUM>, up to <NUM>, up to <NUM> or up to <NUM>, for example. The third step is exemplarily illustrated in <FIG>. While heating and/or exposing the first layer <NUM> to a vacuum, the first layer <NUM> may be polymerized. Generally, during polymerization monomer molecules are reacted together in a chemical reaction to form polymer chains or three-dimensional networks. There are generally many forms of polymerization. During this third polymerization step, the first material <NUM> (e.g., hexagonal boron nitride) may be crosslinked with the second material <NUM> (e.g., polymer). The first material <NUM> may be, so to speak, held in place by the second material <NUM>. The structure of the first material <NUM> and/or the second material <NUM> may be altered during the third step, as is schematically illustrated in <FIG>. In particular, the connections between the first material <NUM> and the second material <NUM> may be altered. This may provide very good mechanical properties to the first layer <NUM>.

The first layer <NUM> may have a mass fraction of ><NUM> wt% and provide a dense layer <NUM> of boron nitride and polymer on the electrically conductive surface <NUM>. When high temperatures are used, a sintered boron nitride layer may be formed on the electrically conductive surface <NUM>. The suspension that is used during the first electrophoretic deposition process may be water based, and may include a binder (e.g., cationic binder, anionic binder or uncharged binder) on a <NUM> - <NUM> wt% BN weight basis, for example. The electropohoretic deposition process using an aqueous based solution for depositing a hexagonal boron nitride filler on the electrically conductive surface <NUM> may be followed by a polymer coating step. For example, a method may comprise an EPD (electropohoretic deposition process) boron nitride deposition followed by (i) conformal coating (dispensing or dipping), (ii) e-coating, or (iii) sintering. If options (i) or (ii) are used, an electrically isolating but thermally conductive (ceramic) layer may be formed on the electrically conductive surface <NUM>. If option (iii) is used, a sensor coating, corrosion protection and/or mould realizing coating may be formed on the thermally conductive surface <NUM>.

The thickness of an electrically non-conducting thin ceramic layer of hexagonal boron nitride may be in the range of about <NUM>- <NUM>, <NUM> - <NUM>, <NUM> - <NUM> or <NUM> - <NUM>, for example. A ceramic layer of hexagonal boron nitride of such a thickness may provide electrical isolation for voltages from about <NUM>- <NUM> kV/s. Generally, the electrical isolation depends on the thickness of the first material <NUM> (e.g., ceramic) deposited on the outer surface of the semiconductor, the first material <NUM> being coated by the second material <NUM> (e.g., polymer). A thermal conductivity of about 2W/mK, 10W/mK or 20W/mK may be achieved with the proposed solution, for example.

<FIG>) shows a method for forming a matrix composite layer on a heat sink according to an embodiment.

In a first step, illustrated in <FIG>, a heat sink <NUM> is provided. The heat sink <NUM> may be embedded in an encapsulation material of a package <NUM>. The heatsink <NUM> may comprise a heat sink metal such as copper, nickel, tin, gold etc. The encapsulation material of the package <NUM> may include plastic, glass or ceramic, etc. In the next step, illustrated in <FIG>, a top surface <NUM> of the heat sink <NUM> is roughened so that the previously smooth surface of the heat sink <NUM> is now rough. Rough means that the surface of the heat sink includes small irregular notches, recesses or indents <NUM>. The top surface <NUM> may have a roughness of less than <NUM> (Ra < <NUM> (or alternatively Ra < <NUM>, < <NUM>, < <NUM> or < <NUM>), i.e., the arithmetical mean height is less than <NUM>. The surface roughness may be, however, larger than <NUM> (Ra > <NUM>, > <NUM> or > <NUM>).

In the next step, illustrated in <FIG>, a dam or wall <NUM> is formed or attached around the heat sink surface or a package <NUM> (embedding the heat sink) <NUM>. The dam <NUM> may be placed around the perimeter and/or circumference of the heat sink <NUM>. The dam <NUM> may be placed on the package <NUM> as shown in <FIG> making the entire top surface <NUM> of the heatsink <NUM> (and maybe portions of the top surface of the package <NUM>) available for deposition or dispense of the filler and plastic materials. The dam <NUM> is used for containing the later deposited or dispensed materials. The dam <NUM> may be placed only on (portions) of the top surface <NUM> of the package <NUM> material or on the (portion) of the top surface <NUM> of the package <NUM> and a portion of the top surface <NUM> of the heat sink <NUM>. The dam <NUM> may be placed directly next to the perimeter of the heat sink <NUM> or may be laterally spaced apart from the perimeter of the heat sink <NUM> on the top surface <NUM> of the package <NUM> (as shown in, e.g., <FIG>). The dam <NUM> may comprise a crosslinking material such as an epoxy material or a polymer material. In various embodiments, the dam may include silicon, acrylic, etc. The crosslinking material of the dam and the plastic material <NUM> may be the same material or a different material.

The dam <NUM> may be pre-formed and adhered to the heat sink <NUM>/package <NUM>. Alternatively, the epoxy or polymer material is dispensed and then crosslinked by ambient temperature, heat or ultraviolet light (UV) light. The dam <NUM> may be about <NUM> high. Alternatively, the dam may have a high of <NUM> to <NUM>, <NUM> to <NUM> or <NUM> to <NUM>. The height of the dam <NUM> may depend on the height of the matrix composite layer to be deposited or dispensed.

<FIG> shows a top view of the heat sink <NUM> with the dam <NUM>. In this particular example, the dam <NUM> is placed around the perimeter of the heatsink <NUM> and around the circumference of the inner hole <NUM>. The dam <NUM> around the perimeter and the circumference of the inner hole <NUM> may include the same thickness and the same height. Alternatively, the dam <NUM> may comprise different thicknesses and/or heights.

In the next step, illustrated in <FIG>, a first material <NUM> such as a filler material is formed on the roughened surface <NUM> of the heat sink <NUM> within the and bordered by the dam <NUM>. The filler material <NUM> may be a ceramic material. The ceramic material may include nitride, oxide and a carbide base material. The ceramic material may include (hexagonal) boron nitride, alumina oxide or alumina nitride, boron carbide. The filler material may be the same as previously disclosed. The deposition method may a dispensing method wherein the filler material <NUM> is dispensed by a dispenser. Alternatively, the same or similar deposition methods as previously disclosed can be used. The filler material <NUM> may be ceramic filler with or without surface coating. The filler material <NUM> (e.g., ceramic filler material) may be pretreated so that it can crosslink with a polymer. The filler material <NUM> is filled up to the height of the dam <NUM> or to a height lower than that of the dam <NUM>.

In the next step, illustrated in <FIG>, a second material <NUM> such as a plastic material is deposited or formed on the filler material <NUM>. The plastic material <NUM> may a crosslinking material such an epoxy material or a polymer material. Alternatively, the plastic material <NUM> may be the same as previously disclosed. In various embodiments, the crosslinking material <NUM> may be a silicone or an acrylic. The deposition method may a dispensing method wherein the plastic material <NUM> is dispensed by a dispenser. Alternatively, the same or similar deposition methods as previously disclosed can be used. The plastic material <NUM> may be the same or may be different to the material used for the dam <NUM>.

Then, a matrix composite layer <NUM> is formed by exposing the filler material <NUM> and the plastic material <NUM> to vacuum/ and or temperature so that the matrix composite layer <NUM> is formed on the roughened heat sink surface <NUM>. The material depositions <NUM>/<NUM> may be cured at room temperature or at a higher temperature. A high or higher temperature can be a temperature in the temperature ranges of <NUM> to <NUM> OC, <NUM> OC to <NUM> OC or <NUM> OC to <NUM> OC. The material depositions <NUM>/<NUM> may be exposed to vacuum. Typical vacuum level ranges are provided in the following table:
<IMG>.

The matrix composite layer <NUM> disposed on the heat sink <NUM>, is shown in <FIG>. The dam <NUM> may remain on the heat sink <NUM>.

Alternatively, the exposure to vacuum may not be performed as a separate additional step after depositing the filler and plastic materials <NUM>, <NUM> (<FIG> and <FIG>) but rather while the filler material and the epoxy material are deposited. The temperature may be applied during these steps (together with the exposure to vacuum) or separately afterwards. The exposure to vacuum may remove air bubbles and/or other chemical additives. It is advantageous to form the matrix composite layer <NUM> on a roughened heat sink surface because it adheres and connects better to the heat sink <NUM>.

<FIG>) shows a method for forming a matrix composite layer on a heat sink according to another embodiment.

The method of <FIG> is the same as the one in <FIG> with the exception of an additional step inserted between method steps <FIG>/ <FIG> and <FIG>/<FIG>. Accordingly, <FIG> show roughening the heat sink surface <NUM> and building a dam <NUM> around the perimeter and/or the circumference of the heat sink <NUM>/package <NUM>.

After building the dam <NUM>, a third material <NUM> such a (plastic) crosslinking material, e.g., an epoxy material or a polymer material (crosslinking polymer material) is deposited or dispensed within the perimeter/circumference of or inside the dam <NUM>. The third material <NUM> is dispensed in order to cover the rough surface <NUM> of the heat sink <NUM>. This is shown in <FIG>. This is advantageous because it provides a (air) bubble free rough top surface <NUM> and provides good adhesion for the matrix composite layer <NUM>. The crosslinking material <NUM> may also be a silicone or an acrylic. The deposition method may be a dispensing method wherein the third material <NUM> is dispensed by a dispenser. Alternatively, the same or similar deposition methods as previously disclosed can be used. The third material <NUM> may be dispensed up to a height <NUM> to <NUM> or, alternatively, <NUM>µ to <NUM>.

In the next steps, illustrated in <FIG>, the filler material <NUM> and the plastic material <NUM> are deposited (e.g., dispensed) and the matrix composite layer <NUM> is formed similar to the method disclosed in <FIG>. Again, the deposition (e.g., dispense) of the filler and plastic materials <NUM>, <NUM> can be performed under vacuum conditions or the deposited layer can be exposed to a vacuum and/or temperature after they are deposited. The third material <NUM>, the plastic material <NUM> and the crosslinking material of the dam <NUM> may comprise the same materials or different materials.

<FIG>) shows a method for forming a matrix composite layer on a heat sink according to yet another embodiment.

In a first step, illustrated in <FIG>, a roughened heat sink <NUM> is provided. The heat sink <NUM> may be embedded in an encapsulation material of the package <NUM>. The heatsink <NUM> may comprise a heat sink metal such as copper, nickel, tin, gold, etc. The encapsulation material of the package <NUM> may include plastic, glass or ceramic, etc. The heat sink <NUM> may be roughened according to a procedure discussed in <FIG>.

In the next step, illustrated in <FIG>, a clamper <NUM> such as a side wall clamper grabs or grasps the heatsink <NUM> or clamps to the package <NUM> surrounding the heat sink <NUM>. The clamper <NUM> may grab, grasp or clamp to the heat sink <NUM> at a sidewall of the heat sink <NUM> or at the sidewall of the package <NUM>. The clamper <NUM> may be a jig clamper (prefix jig from side or top package to create required shape). Other clampers <NUM> may be used. The clamper <NUM> may grab or grasps the heat sink/package <NUM>/<NUM> in an angle between equal or more than <NUM>° degree and equal or less than <NUM>°. Alternatively, the clamper <NUM> may grab or grasps the heat sink/package <NUM>/<NUM> in an angle between equal or more than <NUM>° degree and equal or less than <NUM>°. Clamping the heat sink/package <NUM>/<NUM> with an angle is advantageous because the clamper <NUM> can be easier released compared to a clamper having not such an angle.

The clamper <NUM> may clamp to the outer sidewall and the inner hole <NUM> of the heat sink/package <NUM>/<NUM> at the same time so that so that walls are formed similar to that of the dam <NUM>. The clamper <NUM> is used for containing the later deposited or dispensed materials. In the next steps, illustrated in <FIG>, the filler material <NUM> and the plastic material <NUM> deposited (e.g., dispensed) and the matrix composite layer <NUM>/<NUM> is formed similar to the method disclosed in <FIG>. Again, the deposition (e.g., dispensing) of the filler and plastic materials <NUM>/<NUM> can be performed under vacuum conditions or the deposited (e.g., dispensed) layers can be exposed to vacuum and/or temperature after they are deposited. In a further variation, an epoxy material <NUM> can be deposited similar to that shown in <FIG>.

<FIG> show different types of filler materials in the matrix composite layer disposed on the heat sink.

<FIG> and <FIG> illustrate matrix composite layers <NUM>/<NUM> disposed on the heat sink <NUM>, wherein the filler materials <NUM>/<NUM> comprise individual spherical filler particles or individual platelet filler particles (e.g., ceramic particles). The filler particles may be circular or oval, ball shaped or ellipsoid. Alternatively, the filer particles may be a polygon platelet or a three dimensional polygon. The filler particles <NUM> may comprise substantially the same size as shown in <FIG> or different sizes as shown in <FIG>. The particles may be aligned in specific direction, or randomly or irregularly distributed (no main direction). For example, <FIG> shows oval or ellipsoid particles <NUM> having the substantially the same size aligned with their main direction parallel to the top surface <NUM> of the heat sink <NUM>. In contrast, <FIG> shows ball shaped/circular and ellipsoid/oval particles <NUM> of different sizes randomly distributed with no particular preferred alignment.

<FIG> illustrates a matrix composite layer <NUM> having a filler material <NUM> of agglomerated spherical/platelet filler particles (e.g., ceramic particles). The agglomerated particles <NUM> may be disposed such that their main direction is aligned and that they are aligned sphere or round shape to the top surface <NUM> of the heat sink <NUM>. Again, the agglomerated particles <NUM> themselves may comprise substantially the same size or different size. Similarly, the particles in the agglomerated particles <NUM> may comprise substantially the same size or different sizes.

<FIG> illustrates a matrix composite layer <NUM> having agglomerated spherical/platelet filler particles <NUM> (e.g., ceramic particles) and individual filler particles <NUM>/<NUM>. Any combination of these different particles is possible. For example, aligned individual filler particles can be combined with aligned agglomerated filler particles (e.g., aligned orthogonal to each other), aligned agglomerated filler particles can be combined randomly distributed individual filler particles (having, e.g., the same or different sizes), etc. The agglomerated filler particles <NUM> may be disposed on certain regions <NUM> on the surface <NUM> of the heat sink <NUM> and the individual filler particles <NUM>/<NUM> may be disposed on other regions <NUM> of the surface <NUM> of the heat sink <NUM>. By providing the agglomerated filler particles <NUM> in certain regions <NUM> and the individual filler particles <NUM>/<NUM> in other regions <NUM> the thermal conductivity and/or the electrical insolation of the matrix composite layer <NUM> can be configured. For example, the thermal conductivity and/or electrical isolation of the matrix composite layer <NUM> in the regions <NUM> where the individual filler particles <NUM>/<NUM> are disposed may be higher than the thermal conductivity of the matrix composite layer <NUM> in regions <NUM> where the agglomerated particles <NUM> are located (or vice versa). Alternatively, the thermal conductivity and/or electrical isolation of the matrix composite layer <NUM> in the regions <NUM> where the filler particles are aligned <NUM> may be higher than the thermal conductivity and/or electrical isolation of the matrix composite layer <NUM> in regions <NUM> where the filler particles <NUM> are not aligned (or vice versa). Accordingly, the matrix composite layer <NUM> can be configures or arranged such that the regions where a package <NUM> is attached to the heat sink <NUM> has a high thermal conductivity and a high electrical isolation while areas where no package is attached to the heat sink <NUM> has a high thermal conductivity and an electrically conductive, for example.

In various embodiments, the embodiment methods for forming a matrix composite layer on a heat sink <NUM> can also be performed to form a matrix composite layer on the heat sink <NUM> of the package <NUM>.

In various further embodiments, the matrix composite layer is a layer with a high filler content. For example, the filler content may be equal or more than <NUM> wt%, equal or more than <NUM> wt%, equal or more than <NUM> wt%, or equal or more than <NUM> wt%.

In various other embodiments, the electrical isolation of the matrix composite layer depends on the thickness of the layer, i.e., the thicker the layer the better the electrical isolation.

Alternately stated, disclosed herein is a method wherein a thermally conductive layer is formed on an outer surface of a semiconductor package, by depositing a first material on the outer surface of the semiconductor package, and depositing a second material on the first material after depositing the first material. The first thermally conductive layer may be formed by an electrophoretic deposition process. Depositing the first material may form a porous pre-layer on the outer surface of the semiconductor package. The porous pre-layer may comprise cavities and depositing the second material on the first material may at least partially fill the cavities of the pre-layer. The first material may be deposited by an electrophoretic deposition process. The first material may comprise at least one of boron nitride, aluminium oxide, silicon carbide, silicon dioxide, or a ceramic material including an oxide or nitride combination. The second material may be deposited on the first material by at least one of an electrophoretic deposition process, an e-coating process, a dispensing method, an electrostatic spraying method or a dipping method. The second material may be a thermally conductive material with or without fillers or a polymer. The first material may be sintered after being deposited. After depositing the second material, the first and the second material may be heated and/or exposed to a vacuum. The thermal conductivity of the first thermally conductive layer may be dependent on the first thickness of the first material. The outer surface of the semiconductor package may be electrically conductive, and may take the form of a heat sink or a die pad of the semiconductor package. The first thermally conductive layer may be formed by applying a direct current to the electrically conductive surface, and may be configured to be mounted to an external heat sink.

Alternately stated, disclosed herein is a semiconductor component having a semiconductor package with an outer surface, and a first thermally conductive layer arranged on the outer surface. The first thermally conductive layer may include a first material comprising a porous pre-layer disposed on the outer surface of the semiconductor package and a second material disposed over the first material. The porous pre-layer may comprises cavities and the second material may at least partially fill the cavities of the porous pre-layer. The first material may include at least one of boron nitride, aluminium oxide, silicon carbide, silicon dioxide, or a ceramic material including an oxide or a nitride combination. The second material may be a polymer, or a thermally conductive material with or without fillers. The outer surface of the package may include an electrically conductive surface, which may take the form of a heat sink or a die pad of the semiconductor component. The semiconductor component may be configured to be mounted to an external heat sink such that the first thermally conductive layer faces the external heat sink.

Alternately stated, disclosed herein is a method wherein a wall is formed around a metallic surface such that the wall extends in a vertical direction from a plane formed by the metallic surface of a workpiece. A filler material is deposited in the walled area on the metallic surface, a plastic material is deposited on the filler material, and a vacuum treatment is performed on the filler material and the plastic material thereby forming a matrix composite layer disposed on the metallic surface. The vacuum treatment may be performed while or after the filler material and the plastic material are deposited. The filler material may be deposited by dispensing the filler material, and plastic material may be deposited by dispensing the plastic material. The metallic surface may be roughened, and a crosslinking material may be directly formed on the roughened metallic surface before the filler and plastic materials are deposited. The matrix composite layer may have a filler content of equal or more than <NUM> wt%. The plastic material may be a crosslinking material, and the filler material may be a ceramic filler material. The ceramic filler material may include nitride or oxide, and a carbide base material. The filler material may include two or three dimensional particles, platelets, agglomerated particles or a combination thereof. The workpiece may be a heat sink.

Alternately stated, disclosed herein is a method wherein sidewalls of a workpiece are clamped with a clamper, a filler material is deposited on a metallic surface of the workpiece, a plastic material is deposited on the filler material, and a vacuum treatment is performed on the filler material and the plastic material thereby forming a matrix composite layer disposed on the metallic surface. The vacuum treatment may be performed while or after the filler material and the plastic material are deposited. The filler material may be deposited by dispensing the filler material, and the plastic material may be deposited by dispensing the plastic material. The metallic surface may be roughened, and a crosslinking material may be directly deposited on the roughened metallic surface of the workpiece before the filler and plastic materials are deposited. The matrix composite layer may have a filler content of equal or more than <NUM> wt%. The plastic material may be a cross linking material, and the filler material may be a ceramic filler material. The ceramic filler material may include nitride or oxide, and a carbide base material. The filler material may include three dimensional particles, platelets, agglomerated particles or a combination thereof. The workpiece may be a heat sink.

Alternately stated, disclosed herein is an arrangement including a heatsink with a roughened metallic surface and a matrix composite layer disposed on the roughened metallic surface. The matrix composite layer includes a ceramic filler material and a plastic material, and the ceramic filler material includes two or three dimensional particles, platelets, agglomerated particles or a combination thereof.

Although various exemplary embodiments of the invention have been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention. It will be obvious to those reasonably skilled in the art that other components performing the same functions may be suitably substituted. It should be mentioned that features explained with reference to a specific figure may be combined with features of other figures, even in those cases in which this has not explicitly been mentioned. Further, the methods of the invention may be achieved in either all software implementations, using the appropriate processor instructions, or in hybrid implementations that utilize a combination of hardware logic and software logic to achieve the same results. Such modifications to the inventive concept are intended to be covered by the appended claims.

Spatially relative terms such as "under," "below," "lower," "over," "upper" and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to those depicted in the figures. Further, terms such as "first," "second" and the like, are also used to describe various elements, regions, sections, etc. and are also not intended to be limiting. Like terms refer to like elements throughout the description.

Claim 1:
A method comprising:
providing a heat sink (<NUM>), wherein the heat sink (<NUM>) is embedded in an encapsulation material of a package (<NUM>), wherein a metallic surface (<NUM>) of the heat sink (<NUM>) is not covered by the encapsulation material (<NUM>);
forming a wall (<NUM>) around the perimeter and/or circumference of the heat sink (<NUM>) such that the wall (<NUM>) extends in a vertical direction from a plane formed by the metallic surface (<NUM>) of the heat sink (<NUM>), wherein the wall (<NUM>) is placed only at least on portions of the top surface (<NUM>) of the package (<NUM>), or on at least portions of the top surface (<NUM>) of the package (<NUM>) and a portion of the metallic surface (<NUM>);
depositing a filler material (<NUM>) in a walled area on the metallic surface (<NUM>), wherein the filler material (<NUM>) is a ceramic material;
depositing a plastic material (<NUM>) on the filler material (<NUM>), wherein the plastic material (<NUM>) is a crosslinking material; and
performing a vacuum treatment of the filler material (<NUM>) and the plastic material (<NUM>) thereby forming a matrix composite layer (<NUM>) disposed on the metallic surface (<NUM>).