KR20050086589A - Method and structures for enhanced temperature control of high power components on multilayer ltcc and ltcc-m boards - Google Patents

Abstract

A multilayer ceramic circuit board comprises a core of high conductivity material such as metal and an overlying layer of electrically insulating ceramic having an outer surface. In accordance with the invention, a circuit board for receiving a high power component is provided with a thermal spreading layer on or near the outer surface and one or more thermal vias through the ceramic to thermally couple the spreading layer to the core. The vias and the spreading layer comprise electrically insulating thermally conductive materials. The resulting structure provides rapid heat dissipation for a high power component formed or mounted on or near the spreading layer.

Description

METHOD AND STRUCTURES FOR ENHANCED TEMPERATURE CONTROL OF HIGH POWER COMPONENTS ON MULTILAYER LTCC AND LTCC-M BOARDS}

The present invention relates to methods and structures for improved temperature control of power devices mounted on or on a multilayer ceramic circuit board. More specifically, the present invention relates to methods and structures for forming or mounting high power devices on low temperature cofired ceramic circuit boards (LTCC substrates).

The multilayer ceramic circuit board consists of layers of green ceramic tape. The green tape consists of a specific glass composition and optional ceramic powder that is mixed with an organic binder and a solvent and cast and cut to form the tape. Wiring patterns are screen printed on the tape layers to perform various functions. Vias are filled with the conductive ink formed on the tape to connect the wiring on the green tape to the wiring on another green tape. The tapes are then aligned, laminated and calcined to remove organic material, sinter the metal pattern and crystallize the glass. This is generally carried out at temperatures up to about 1000 ° C., preferably from about 750-950 ° C. The composition of the glass determines the coefficient of thermal expansion, dielectric constant and suitability of the multilayer ceramic circuit board for various electronic devices.

Recently, metal support substrates (metal substrates) have been used to support green tape. The metal substrate provides strength to the glass layers. In addition, the green tape layers can be mounted on both sides of the metal substrate and can be attached to the metal substrate with suitable laminated glass, so that the metal substrate enables enhanced complexity and density of circuits and devices. In addition, passive and active components such as resistors, inductors, capacitors, and the like can be integrated into the circuit board for additional functionality. Thus, such systems, known as low temperature cofired ceramic-metal support substrates, or LTCC-M, have been demonstrated as a means of highly integrating multiple devices and circuits in a single package. The system can be tailored to be suitable for silicon based devices, indium phosphide based devices and gallium arsenide based devices, for example by appropriately selecting the glass of the metal and green tape for the support substrate. .

The ceramic layers of the LTCC-M structure must match the coefficient of thermal expansion of the metal support substrate. Glass ceramic compositions are known to match the thermal expansion properties of various metals or metal matrix composites. Such compositions are described, for example, in US Pat. No. 5,625,808 to Tommy et al .; US Pat. No. 6,017,642 to Kumar et al .; US Patent No. 5,256,469 to Cherukuri et al .; Azaro et al., US Pat. No. 5,565,262. United States Patent No. 5,581,876 to Prophu et al. Discloses a laminated glass composition for attaching a ceramic layer to a metal support substrate. Such composition patents are incorporated herein by reference.

While conventional LTCC and LTCC-M substrates enable good temperature control and heat dissipation appropriate for most conventional circuit devices, they do not provide sufficient power consumption for all forms of high power devices such as high power resistance. Can't. For example, the substrate does not allow printing of syntactic high power resistances on the substrate. Rather, the substrate requires the use of surface mounted chip power resistors, which are very costly and complex to manufacture. Accordingly, it would be desirable to provide a method and structure for improved temperature control of multilayer LTCC and LTCC-M substrates.

1 is a flow chart of the steps of a method of providing a multilayer ceramic circuit board device with improved temperature control.

2 is a cross-sectional view of an exemplary device formed by the process of FIG. 1.

3 is a plan view of an advantageous form of the device of FIG. 1.

Multilayer ceramic circuit boards include a top layer of electrically insulated ceramic having a core and an outer surface of a high conductivity material such as metal. According to the present invention, a circuit board for accommodating a high power device includes at least one thermal via through a ceramic that thermally couples the heat dissipating layer and the heat dissipating layer to the core on or near the outer surface. Is provided. The via and diverging layer comprise an electrically insulated thermally conductive material. The final structure provides high power device rapid heat dissipation formed or mounted on or near the divergent layer.

The advantages, nature and various additional features of the present invention will become more apparent from the description of exemplary embodiments to be described in conjunction with the accompanying drawings.

It is to be understood that the drawings are intended to illustrate the concept of the invention and are not drawn to scale.

1 is a block diagram of the steps involved in providing a multilayer ceramic circuit board device with improved temperature control. The first step, shown as block A, is to provide a non-sintered multilayer ceramic circuit board having an electrically conductive core layer and an outer surface and comprising an electrically insulating ceramic layer over the core layer. Unsintered circuit boards may be LTCC or LTCC-M formed using green tape technology. This can be formed by applying a glass ceramic material densified at about 800-950 ° C. to a core green ceramic tape made of glass. The core may be a metal such as Kovar, copper, or molybdenum-copper.

The next step, shown as block B, is to form one or more thermal vias extending from the outer surface to the core through the ceramic layer. Via holes are typically formed by punching holes in green ceramic tape, which are filled by screen printing with screen printable ink to form a highly thermally conductive and electrically insulating material. The term thermally conductive material refers herein to materials such as aluminum nitride (AlN) having thermal conductivity in excess of 40 Watt / m ° K. The ink may comprise a powder of a thermally conductive material such as diamond, aluminum nitride (AlN), beryllium oxide (BeO), or silicon carbide (SiC), or fiber / whisker made of SiC or carbon. . It may also include glass-forming powders such as glass or PbO and / or Bi ₂ O ₃ or other low temperature molten oxides that are densified in the 800-950 ° C. range. The blend of powder is chosen to match the coefficient of thermal expansion (TCE) and plastic shrinkage of the multilayer ceramic. Advantageous ink mixtures include high conductivity materials in the 30-70 volume ratio and the remaining glass and low temperature molten oxide.

As an alternative to glassy glass materials, it is possible to use crystallization materials which are first densified by viscous flow and then crystallized in the firing step. The use of crystallized glass for via inks has the additional advantage of further improving conductivity, since crystalline ceramics generally have greater conductivity than glassy ceramics.

The third step (block C) is to form a heat dissipation layer on the surface that is thermally coupled with the filled thermal vias. This step can be accomplished by screen printing a thin layer of electrically insulating highly thermally conductive ink on the surface. The ink for the heat dissipating layer is composed of the same or similar materials as the materials used to fill the vias, but has the advantage of being low in viscosity.

The next step shown in block D is to form or mount the high power device thermally coupled with the diverging layer. As used herein, the term high power component is considered to be a component such as a power resistor, or a power semiconductor having power consumption of 20W or more. For example, after printing any necessary conductive ink connection layer, the high power resistor can screen print resistive ink between the connection layers and over or adjacent the emission layer. The next structure is densified and heat treated according to known techniques.

2 is a schematic cross-sectional view of an exemplary device made according to the method of FIG. 1. The multilayer ceramic board apparatus 20 includes a metal core support board 21 supporting an upper ceramic layer 22 having an outer surface 23. The heat dissipation layer 24 is located on or near the surface 23, and the plurality of filled vias 25 extend from the surface 23 to the metal core 21 through the ceramic layer 22. Via 25 is thermally coupled to heat dissipating layer 24 on surface 23 by physical contact. High power component 26, such as a resistor, is thermally coupled to the diverging layer 24. The high power device 26 may extend between the metal leads 27A and 27B.

3 is a plan view of a preferred form of the device of FIG. The high power resistor 26 may extend between the leads 27A, 27B adjacent to the diverging layer 24.

The use of crystallized glass in the thermal via composition adds the advantage of further strengthening the thermal conductivity of the forming vias, since crystalline ceramics are amorphous (glassy) with higher conductivity. The same or similar composition as those used in the via inks can be used to make screen printable glaze inks that are provided as a thin layer on the surface of the green tape, having the same inorganic composition but lower in viscosity than the via inks, so that the x, y plane Thermal vias (shown in FIGS. 1 and 2) can be connected at and further enhance heat dissipation / loss just under the hot device.

Suitable glass compositions for thermal vias have the same or similar composition as the glass materials used to form the LTCC green tape, Zn-Mg-borosilicate, Zn-Mg-Al-borosilicate, Mg-Al-borosilicate, Pb- Zn-Al-silicates, Ca-Al-borosilicates and Pb-Al-silicates (disclosed in patents 5,625,808 and 6,017,642 for LTCF co-sintering on metal support substrates such as coba and copper-molybdenum-copper) Can be. In LTCC-M systems, the use of thermal vias has the additional advantage that they can be directly connected to an integral high conductivity metal core that further aids heat loss (compared to LTCC alone).

In various cases, the heat generating surface of a power component such as a power resistor may not have a heat exchange surface that is directly connected to the heat sink. For power components, a number of electrically conductive vias used for heat exchange short the resistors. Thus, the dielectric properties of the vias are important in most fields with regard to the heat flow from the deposited or film-integrated component to the conductive core heat sink.

The present invention will be more clearly understood with reference to the following specific examples.

Example

For example, thermally conductive vias can be made from 50 vol% diamond powders (SiC whiskers, AlN powders, carbon fibers, etc.) that make up the inorganic portion, or SJK-5 with a 4-8 micron particle size. Commercially available from Micron Products) and 50% glass powder (KU-8 glass for the Cu-Moly-Cu system; HEG-12 glass for the Kovar system), which can be screen-printable homogeneous It is mixed into a 3-roll mill to form a mixture and combined with an organic medium. This ink may be used to fill the via holes punched in the LTCC tape layer by screen printing through a metal stencil. Many such filled via tape layers are stacked or laminated to form a laminate, and the vias are stacked together to provide a direct thermal path from the top of the stack to the metal core to attach the laminate to. Inks having the same inorganic composition or lower solids content can be used to print pads on top tape layers that connect vias to each other and act as heat dissipating agents on the top surface.

Class composition:

Composition (w%) ingredient KU-8 glass HEG-12 glass MgO Al ₂ O ₃ 20.0 10.0 CaO 26.0 SiO ₂ 50.0 38.0 B ₂ O ₃ P ₂ O ₅ 1.50 PbO 42.0 ZnO 10.0 ZrO ₂ 2.50

The invention provides a heat dissipation for a power component comprising providing a non-sintered layer ceramic circuit board comprising an electrically conductive core layer and an electrically insulating ceramic layer overlying the core layer and having an outer surface. It can be seen that it includes a method of manufacturing a multilayer ceramic circuit board to strengthen the. At least one thermal via is formed extending from the outer surface to the core layer through the ceramic layer; When formed on the surface, the heat dissipating layer is thermally coupled with the thermal vias. The power component is formed or mounted thermally coupled to the dissipation layer such that heat from the power component passes through the via and core layers via the dissipation layer.

Non-sintered circuit boards may include LTCC or LTCC-M ceramic boards. And, the core may comprise coba, copper or molybdenum. Thermal vias may be formed by filling the holes with ink to form holes in the ceramic layer and to form a thermally conductive, electrically insulating material. The heat dissipating layer can be formed by providing an ink layer on the surface that is electrically insulating and thermally conductive.

The present invention also provides a metal core support board; A low temperature cofired ceramic-metal (LTCC-M) integrated package comprising a ceramic layer disposed on the metal core support board, wherein the ceramic layer is disposed on an outer surface and an outer surface of the ceramic layer. Has a diverging layer. One or more thermally conductive vias thermally bond the metal core support board and heat dissipation layer. The via controls the temperature of the power component disposed on or near the heat dissipation layer. The power component may be a resistor. The resistor can be formed by printing a resistive ink between connecting layers over or adjacent to the diverging layer.

The power component may be a resistor or a power semiconductor. The core may comprise coba, copper or molybdenum. Thermally conductive vias include sintered printable inks. The printable ink may include a material selected from the group consisting of diamond, aluminum nitride, beryllium oxide, and silicon carbide. The ceramic layer may be at least one ceramic circuit board comprising a plurality of ceramic circuit boards, electrical components, and conductive traces.

It will be appreciated that the disclosed embodiments represent only some of the many specific embodiments possible, and represent applications of the present invention. Many modifications may be made by those skilled in the art within the scope of the invention.

Claims (15)

A method of making a multilayer ceramic circuit board having improved heat dissipation performance for a power device, Providing an unsintered multilayer ceramic circuit board comprising an electrically conductive corecmd and an electrically insulating ceramic layer located on the core and having an outer surface; Forming one or more thermal vias extending from the outer surface through the ceramic layer to the core layer; Forming a heat dissipation layer on the surface thermally coupled with the thermal vias; And Forming or mounting said power device thermally coupled to said dissipation layer, wherein heat from said power device is transferred to said vias and said core layer through said dissipation layer. Way. The method of claim 1, wherein the non-sintered circuit board comprises an LTCC or LTCC-M ceramic substrate. The method of claim 1, wherein the core comprises Kovar, copper, or molybdenum. The method of claim 1, wherein the thermal vias are formed by forming holes in the ceramic substrate and filling the holes with ink to form a thermally conductive and electrically insulating material. The method of claim 1, wherein the heat dissipation layer is formed by providing a layer of an electrically insulating and thermally conductive ink on the surface. The method of claim 1, wherein the power device is a resistor. The method of claim 1, wherein the resistor is formed by printing a resistive ink on top of the diverging layer or between adjacent connection layers. Low temperature cofired ceramic-metal (LTCC-M) integrated package, A metal core support substrate; A ceramic layer disposed on the metal core support substrate and having an outer surface; A heat dissipating layer of thermally conductive material disposed on the outer surface of the ceramic layer; One or more thermally conductive vias thermally coupling the heat dissipating layer and the metal core support substrate; Vias for controlling the heat of the power device; And And a power device disposed on said heat dissipating layer, said power element having a conductive lead for connection to a circuit. 9. The low temperature cofired ceramic-metal integrated package of claim 8, wherein the power device is a resistor. 10. The low temperature cofired ceramic-metal integrated package of claim 8, wherein the power device is a power semiconductor. 9. The low temperature cofired ceramic-metal integrated package of claim 8, wherein the core is Kovar, copper or molybdenum. 9. The low temperature cofired ceramic-metal integrated package of claim 8, wherein the thermally conductive vias comprise a sintered printable ink. 13. The low temperature co-fired ceramic-metal integrated package of claim 12, wherein the printable ink comprises a material selected from the group consisting of diamond, aluminum nitride, beryllium oxide, and silicon carbide. The low temperature co-fired ceramic-metal integrated package of claim 8, wherein the ceramic layer comprises a plurality of ceramic circuit boards, at least one of the ceramic substrates comprising an electrical element and a conductive trace. 15. The device of claim 14, wherein the power device is disposed on the heat dissipation layer located on the ceramic circuit boards, wherein the heat dissipation layer is thermally connected to the metal core support substrate by the thermal vias. Low temperature cofired ceramic-metal integrated package.