JP5165859B2 - Composite board - Google Patents

Description

  The present invention relates to a composite substrate formed by laminating a plurality of substrates or electrical elements having different thermal expansion coefficients.

  In recent years, in the field of electrical products such as personal computers and digital home appliances, miniaturization, high functionality, and high added value of products have been increasing. Accordingly, composite substrates formed by bonding substrates of different materials or electrical elements of different materials have been put into practical use. However, since such composite substrates have different thermal expansion coefficients, stress is concentrated on the interface between different materials, and delamination, warpage, cracks, and the like are likely to occur.

  Thus, a structure in which an intermediate layer made of a synthetic resin is sandwiched between different material layers and laminated and integrated by hot pressing has been proposed (for example, see Patent Document 1).

However, as a synthetic resin constituting the intermediate layer, for example, when a thermosetting resin is used alone or when a thermoplastic resin is used alone, a via-hole conductor for electrical conduction formed in the intermediate layer or a heat-dissipating material is used. It is difficult to achieve both the shape and position accuracy retention of thermal vias, the warpage of substrates and electrical elements, and the ability to follow pattern irregularities. There is a problem in that adhesion failure or the like due to lack of unevenness is easily caused.
JP-A-9-55336

  The present invention has been made in view of the above problems, and the object thereof is that there is no delamination, poor adhesion, cracks, etc. between the substrate and the resin layer as the intermediate layer, and the resin layer as the intermediate layer. It is an object of the present invention to provide a composite substrate having excellent reliability with little dimensional deviation in the shape and positional accuracy of via-hole conductors and thermal vias formed on the substrate.

The composite substrate of the present invention includes a multilayer resin layer comprising a first resin layer containing a thermoplastic resin and a second resin layer containing a thermosetting resin provided on both sides of the first resin layer, and the multilayer A heat generating element provided on one main surface of the resin layer, and a substrate having a thermal expansion coefficient different from that of the heat generating element and provided on the other main surface of the multilayer resin layer. The layer includes a via-hole conductor that penetrates in the thickness direction that electrically connects the substrate and the heating element, and a thermal via that penetrates in the thickness direction that transfers heat of the heating element to the substrate. Yes, and the thickness of the second resin layer of the multilayer resin layer is 1 / 40-1 / 5 of the thickness of the first resin layer, 50 ° C. ~ the layer plane direction of the multilayer resin layer The thermal expansion coefficient at 150 ° C. is 3 to 25 × 10 ⁻⁶ / ° C. as a whole , and the thermal expansion in the thickness direction The tension coefficient is not less than the thermal expansion coefficient of at least one of the via-hole conductor and the thermal via .

In the case of the above configuration, the multilayer resin layer serves to bond the heating element and the substrate , and the multilayer resin layer has a poor fluidity but a core including a thermoplastic resin that can maintain a via shape and positional accuracy. And a coating layer containing a thermosetting resin that has good fluidity and can follow pattern irregularities and warpage of the joint, provided on both surfaces of the first resin layer. It consists of a second resin layer.

Therefore, the resin layer for bonding directly to the substrate or heating element, since the resin layer containing a flowability and adhesion good thermosetting resin is a coating layer, the unevenness of the circuit pattern of the board or the heating elements, the warp On the other hand, excellent followability can be exhibited, and delamination, adhesion failure, and the like can be suppressed. Furthermore, since the core layer of the multilayer resin layer is a resin layer containing a thermoplastic resin, a desired via shape and positional accuracy can be maintained when a via hole conductor for electrical conduction or a thermal via for heat dissipation is formed.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, although embodiment of this invention is described below based on drawing, those drawings are provided for illustration and this invention is not limited to those drawings. FIG. 1 is a cross-sectional view schematically showing a composite substrate according to the first embodiment of the present invention.

  As shown in FIG. 1, the composite substrate 1 according to the first embodiment includes a ceramic substrate such as an LTCC (Low Temperature Co-fired Ceramic) substrate 2 as a first substrate, and a second substrate. For example, a ceramic substrate such as an alumina substrate 3 having a thermal expansion coefficient different from that of the LTCC substrate 2 and a multilayer resin layer 4 interposed between the ceramic substrates of different materials are provided.

  The LTCC substrate 2 and the alumina substrate 3 each have a via hole conductor (not shown) as an internal wiring, and a circuit pattern 5 is formed on the surface so as to be electrically connected to the via hole conductor. These circuit patterns 5 are electrically connected to via-hole conductors 6 that penetrate the multilayer resin layer 4 in the thickness direction.

  The multilayer resin layer 4 is a resin adhesive layer that bonds the LTCC substrate 2 and the alumina substrate 3 together. The multilayer resin layer 4 includes a core layer having a thickness of 50 to 100 μm as a first resin layer, and a second resin layer that is a coat layer provided on at least one side of the core layer, in this embodiment, both sides. It has. The thickness of the coat layer 8 is 1/40 to 1/5, preferably 5 to 10 μm, of the thickness of the core layer 7. By making the second resin layer that is the coat layer 8 within the above range with respect to the thickness of the first resin layer that is the core layer 7, the influence of the thermoplastic resin that is the core layer 7 becomes dominant, and the dimensions Stability is ensured and the via shape can be maintained.

The core layer 7 as the first resin layer only needs to contain a thermoplastic resin, and the volumetric shrinkage (dimensional change) of the multilayer resin layer 4 is suppressed and the desired shape and positional accuracy of the via-hole conductor 6 are maintained. From the point which can be performed, the thermoplastic resin composition which mix | blended and adjusted, for example, polyetheretherketone resin, polyetherimide resin, and an inorganic filler is preferable. As a blending example, for example, the blending amount of the inorganic filler is 5 to 65 parts by weight with respect to 100 parts by weight of the resin composed of 70 to 20% by weight of polyetheretherketone resin and 30 to 80% by weight of polyetherimide resin. It is preferable. The core layer 7 configured as described above can provide good electrical conduction when sandwiched between substrates and heated and pressed to be integrated. The core layer 7 has a thermal expansion coefficient of −10 to 30 × 10 ⁻⁶ / ° C. in the layer plane direction (XY direction) at 50 ° C. to 150 ° C., and the thickness direction (Z direction). The thermal expansion coefficient is preferably equal to or higher than the thermal expansion coefficient of the via-hole conductor 6 formed in the multilayer resin layer 4. By setting the thermal expansion coefficient within such a range, when the composite substrate 1 formed by joining the ceramic substrates 2 and 3 of different materials of the present embodiment is manufactured, the multilayer resin layer 4 and the ceramic substrates 2 and 3 are formed. The stress concentrated on the interface can be relaxed. Moreover, the stress concentrated on the interface between the core layer 7 and the coat layer 8 in the multilayer resin layer 4 can be relaxed.

The coating layer 8 as the second resin layer is provided on both surfaces of the core layer 7 in this embodiment, and is excellent for the unevenness of the circuit pattern 5 formed on the surface of the ceramic substrate 2 and 3 as an adherend. In addition, it is possible to suppress delamination, adhesion failure, and the like. The coating layer 8 only needs to contain a thermosetting resin, exhibit high heat resistance, and have excellent flowability and adhesiveness. For example, polyimide resin, modified epoxy resin, BCB resin, PPE resin, Cyanate resins and the like are preferable. The coat layer 8 thus configured has a coefficient of thermal expansion of 10 to 60 × 10 ⁻⁶ / ° C. at 50 ° C. to 150 ° C. in the layer plane direction (XY direction) and the thickness direction (Z direction). Preferably there is. By setting the thermal expansion coefficient in such a range, when ceramic substrates having different thermal expansion coefficients are joined together, stress concentrated on the interface between the multilayer resin layer 4 and the ceramic substrates 2 and 3 is alleviated. The stress concentrated on the interface between the core layer 7 and the coat layer 8 in the resin layer 4 can be relaxed. In addition, since the thermal expansion coefficient of the thermosetting resin alone as described above is large, a method of reducing the thermal expansion by incorporating a filler is generally used. In this case, an increase in the filler content causes a decrease in the flowability of the resin, but a good pattern followability can be obtained without impairing the fluidity as long as the thermal expansion coefficient is within the above range.

The thermal expansion coefficient of the multilayer resin layer 4 composed of the core layer 7 that is the first resin layer and the coat layer 8 that is the second resin layer is the layer plane direction as a whole including the coat layer 8 and the core layer 7. The thermal expansion coefficient at 50 ° C. to 150 ° C. is 3 to 25 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient in the thickness direction is preferably equal to or greater than the thermal expansion coefficient of the via-hole conductor 6. By setting the thermal expansion coefficient within such a range, stresses concentrated at the interface between the multilayer resin layer 4 and the ceramic substrates 2 and 3 can be alleviated when the ceramic substrates 2 and 3 of different materials are joined to each other. it can.

  As a method for producing such a multilayer resin layer 4, for example, a film-like coat layer 8 made of polyimide resin or the like is provided on both surfaces of a film-like core layer 7 obtained by an extrusion casting method or the like. Examples thereof include a method of heating and pressing, a method of applying a varnish-like resin, and the like.

In addition, although the LTCC board | substrate 2 was used as a 1st board | substrate and the alumina board | substrate 3 was used as a 2nd board | substrate, it demonstrated, The material which comprises these board | substrates can be changed suitably. That is, in the present embodiment, the difference between the absolute values of the thermal expansion coefficients at 25 ° C. to 300 ° C. between the first substrate and the second substrate is more preferably within 10 × 10 ⁻⁶ / ° C. Examples of the constituent material include known ceramic materials such as silicon nitride, yttrium oxide, aluminum nitride, and silicon carbide, and a single material or a composite material containing two or more materials may be used. Further, the number of different types of ceramic substrates is not limited, and may be three or more.

  In addition to the ceramic substrate, the first substrate and the second substrate include a resin substrate (for example, an FPC substrate, an epoxy buildup substrate), an insulating substrate such as a glass substrate (quartz glass substrate, etc.), a metal substrate ( An aluminum-based substrate, a copper-based substrate, a single metal, or the like), a silicon substrate, or an electric element (for example, a passive element such as an inductor element or a capacitor element or an active element such as a semiconductor element) can also be applied.

  The composite substrate 1 of the present embodiment described above is manufactured, for example, as follows.

First, the molded and fired alumina substrate 3 (thickness 1.0 mm, 20 mm square, thermal expansion coefficient 6.8 × 10 ⁻⁶ / ° C. at 25 ° C. to 300 ° C.) and LTCC substrate 2 (thickness 1.0 mm, A thermal expansion coefficient of 5.9 × 10 ⁻⁶ / ° C. at 20 mm square and 25 ° C. to 300 ° C. is prepared. In these substrates 2 and 3, via hole conductors are formed inside, and a conductive paste containing, for example, Ag, W, Cu powder or the like is formed as a circuit pattern 5 on the surface thereof by pattern printing.

  Next, via holes are formed in the multilayer resin layer 4 (thickness 50 μm) by, for example, laser processing such as a carbon dioxide laser, punching processing or drill processing, and a conductive paste is screen printed, press-fitted, dispenser, etc. The via-hole conductor 6 for electrical conduction is formed by filling. The conductive paste is obtained by adding a liquid resin, a plasticizer, a curing agent, or the like to Ag, Cu, Sn powder or the like, and is preferably a solventless system.

  Subsequently, the multilayer resin layer 4 is sandwiched between the alumina substrate 3 and the LTCC substrate 2 and laminated and integrated by heating and pressurizing with a vacuum heating press machine, for example, at 275 ° C., 5 MPa for 30 minutes.

  As described above, according to the present embodiment, the ceramic substrates 2 and 3 having different thermal expansion coefficients are joined using the multilayer resin layer 4 in which the coat layer 8 made of a thermosetting resin is provided on both surfaces of the core layer 7. By doing so, the desired via shape and positional accuracy formed in the multilayer resin layer 4 can be maintained and good interlayer conduction can be obtained, and the unevenness of the circuit pattern 5 in which the coat layer 8 is formed on the surfaces of the ceramic substrates 2 and 3 Therefore, it is possible to provide the composite substrate 1 having excellent reliability without delamination, adhesion failure, cracks, etc. between the substrates 2 and 3 and the multilayer resin layer 4. In addition, the multilayer resin layer 4 is sandwiched between the ceramic substrates 2 and 3 that are pre-molded, fired, and patterned, and then heat-pressed to enable bonding at a relatively low temperature. Stress concentration at the interface between different materials due to the difference can be reduced.

  Next, a composite substrate according to a second embodiment will be described with reference to FIG. FIG. 2 is a cross-sectional view schematically showing a composite substrate according to the second embodiment. The composite substrate 21 of this embodiment is different from the first embodiment described above in that the coating layer 8 of the resin adhesive 4 is provided on one side of the core material 7. In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and the description is simplified or abbreviate | omitted.

  As shown in FIG. 2, in the composite substrate 21 of the second embodiment, the coat layer 8 of the multilayer resin layer 4 is provided on one side of the core layer 7. The coat layer 8 may be omitted when the circuit pattern 5 formed on the ceramic substrates 2 and 3 that are to be bonded to the multilayer resin layer 4 has little unevenness and is almost flat.

  Therefore, according to the present embodiment, the first substrate is formed by bonding the ceramic substrates 2 and 3 of different materials using the multilayer resin layer 4 in which the core layer 7 is provided with the coat layer 8 made of a thermosetting resin. Similar to the embodiment, it is possible to provide a composite substrate 21 that can obtain good interlayer conduction and can prevent delamination, warpage, and cracks and has excellent reliability. Further, by using the multilayer resin layer 4 having the coat layer 8 on one side of the core layer 7, the bonding surface of the multilayer resin layer 4 can be selected depending on the unevenness of the circuit pattern 5 formed on the surfaces of the ceramic substrates 2 and 3. Can be selected.

  Next, a composite substrate according to a third embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view schematically showing a composite substrate according to the third embodiment. The composite substrate 31 of this embodiment is different from the first embodiment described above in that a flexible print (FPC) substrate 32 is laminated and bonded in addition to the ceramic substrates 2 and 3 of different materials. In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and the description is simplified or abbreviate | omitted.

  As shown in FIG. 3, in the composite substrate 31 of the third embodiment, the multilayer resin layer 4 is sandwiched between the LTCC substrate 2, the FPC substrate 32, and the alumina substrate 3, and these are heated and pressed to be laminated and integrated. Is. In the present embodiment, the multilayer resin layer 4 is obtained by providing the coat layer 8 on both surfaces of the core layer 7. The FPC board 32 has a via-hole conductor (not shown) inside, and a circuit pattern 5 electrically connected to the via-hole conductor is drawn out to the surface of the FPC board 32. This circuit pattern 5 is electrically connected to the via-hole conductor 6 of the multilayer resin layer 4 provided on both surfaces of the FPC board 32.

  Therefore, according to the present embodiment, the ceramic substrates 2 and 3 of different materials and the FPC substrate 32 are bonded using the multilayer resin layer 4 in which the coat layer 8 made of thermosetting resin is provided on both surfaces of the core layer 7. Thus, as in the above-described embodiment, delamination, warpage, and cracks can be prevented, and the composite substrate 31 having excellent reliability can be provided. In addition, since bonding at a relatively low temperature is possible, the types of substrates that can be bonded are increased, and the degree of freedom in selecting an object to be bonded can be increased. Although the ceramic substrates 2 and 3 of different materials are used, in this embodiment in which the FPC substrate 32 is sandwiched between them, ceramic substrates made of the same kind of material can be used.

(Other embodiments)
The embodiments of the present invention are not limited to the above-described embodiments, and can be expanded and modified. The expanded and modified embodiments are also included in the technical scope of the present invention.

  In the above-described embodiment, the structure in which two or three substrates made of different materials are bonded has been described. However, the number of stacked substrates is not limited to this, and may be four or more.

Moreover, in the said embodiment, although the resin film comprised from polyetheretherketone resin, polyetherimide resin, and an inorganic filler was used as the core layer 7 of the multilayer resin layer 4, it is not limited to this. For example, when bonding and joining ceramic substrates of different materials, the core layer 7 is a material containing a thermoplastic resin, and preferably has a thermal expansion coefficient at 50 ° C. to 150 ° C. in the layer plane direction of the core layer 7. -10 to 30 × 10 ⁻⁶ / ° C. and a resin material and filler that have a thermal expansion coefficient in the thickness direction that is equal to or greater than the thermal expansion coefficient of the via-hole conductor 6. Moreover, as a thermoplastic resin, a thermoplastic polyimide, a liquid crystal polymer, etc. are mentioned other than polyetheretherketone resin and polyetherimide resin, for example.

  Moreover, in the said embodiment, although the LTCC board | substrate 2 and the alumina board | substrate 3 were used as a ceramic board | substrate used as a to-be-adhered thing, the dielectric material ceramic board | substrate which has a high dielectric constant is also applicable besides this. Examples of the dielectric ceramic substrate include barium titanate, strontium titanate, calcium titanate, lead titanate, or a mixture thereof.

  In addition to the substrate, for example, a passive element such as an inductor element or a capacitor element or an active element such as a semiconductor element can be applied as an electrical element to the adherend. Here, FIG. 4 shows a composite substrate in which the inductor element 42 and the capacitor element 43 are joined via the multilayer resin layer 4. The composite substrate 41 shown in FIG. 4 is obtained by, for example, pre-molding and firing an inductor element 42 and a capacitor element 43, which are hot-pressed with the multilayer resin layer 4 interposed therebetween, and laminated and integrated.

  In addition to the via hole conductor 6 for electrical continuity, a thermal via for heat dissipation can be formed in the multilayer resin layer 4 according to the type and application of the object to be bonded, and can be used in combination with the via hole conductor 6. it can. Here, FIG. 5 shows an example of a composite substrate in which a thermal via 53 for radiating heat generated from a heating element 52 such as a semiconductor element is formed in the multilayer resin layer 4. In the composite substrate 51, a heating element 52 such as a semiconductor element is provided on the upper surface of the thermal via 53 forming portion of the multilayer resin layer 4. The heat generated from the heating element 52 is transferred to the metal substrate 54 provided on the back surface of the multilayer resin layer 4 via the thermal via 53.

  In the above embodiment, the ceramic substrates 2 and 3 having the circuit pattern 5 formed on the surface thereof and the FPC substrate 32 are used as the adherend, and the resin adhesive having the via-hole conductor 6 formed as the multilayer resin layer 4 is used. However, the present invention is not limited to this. For example, a multi-layer resin layer 4 having no via-hole conductor 6 can be used to bond a substrate made of a different material having no circuit inside or on the surface.

Sectional drawing which shows typically the structure of the composite substrate which concerns on one Embodiment of this invention. Sectional drawing which shows typically the structure of the composite substrate which concerns on another embodiment of this invention. Sectional drawing which shows typically the structure of the composite substrate which concerns on another embodiment of this invention. Sectional drawing which shows typically the structure of the composite substrate which concerns on another embodiment of this invention. Sectional drawing which shows typically the structure of the composite substrate which concerns on another embodiment of this invention.

Explanation of symbols

  1, 21, 31, 41, 51... Composite substrate, 2... LTCC substrate, 3... Alumina substrate, 4 ... Multilayer resin layer, 5 ... Circuit pattern, 6 ... Via-hole conductor, 7 ... Core layer, 8 ... ... FPC board, 52 ... heat generating element, 53 ... thermal via, 54 ... metal board.

Claims (4)

A multilayer resin layer comprising a first resin layer containing a thermoplastic resin and a second resin layer containing a thermosetting resin provided on both sides of the first resin layer;
A heating element provided on one main surface of the multilayer resin layer;
A thermal expansion coefficient different from that of the heating element, and a substrate provided on the other main surface of the multilayer resin layer,
The multilayer resin layer includes a via-hole conductor that penetrates in the thickness direction that electrically connects the substrate and the heating element, and a thermal that penetrates in the thickness direction that conducts heat from the heating element to the substrate. possess a via,
The thickness of the second resin layer of the multilayer resin layer is 1/40 to 1/5 of the thickness of the first resin layer,
The thermal expansion coefficient at 50 ° C. to 150 ° C. in the layer plane direction of the multilayer resin layer is 3 to 25 × 10 ⁻⁶ / ° C. as a whole , and the thermal expansion coefficient in the thickness direction is the via-hole conductor or the A composite substrate having a thermal expansion coefficient equal to or greater than at least one of thermal vias .   The composite substrate according to claim 1, wherein the heat generating element is a semiconductor element. The thermal expansion coefficient at 50 ° C. to 150 ° C. in the layer plane direction of the first resin layer of the multilayer resin layer is −10 to 30 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient in the thickness direction is composite substrate according to claim 1 or 2, characterized in that said one of the via-hole conductors or the thermal via at least one of the thermal expansion coefficient higher. 2. The thermal expansion coefficient at 50 ° C. to 150 ° C. in the layer plane direction and thickness direction of the second resin layer of the multilayer resin layer is 10 to 60 × 10 ⁻⁶ / ° C. 4. The composite substrate according to any one of items 1 to 3 .

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