JP2006165353A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board, configured with a first resin insulation layer 4 reinforced by a sheet-like fiber base material, and to provide a metallic layer 3 integrated on both sides of the layer 4 by bearing the mount of a heat generating component such as a power element 1 in mind, wherein at least the metal layer on one side has the functions of electrical wiring, and cracks are hardly caused to solder 2 for connecting the mounting component. <P>SOLUTION: The total thickness of the metal layer 3 located on both the sides of the first resin insulating layer 4 is selected to be larger than the thickness of the first resin insulation layer 4. Then the end edges of both the metal layers 3 are located inwardly from the circumferential edge of the first resin insulating layer 4. Further, a second resin insulating layer 5 with reinforcing fibers filled therein the thickness of which is equal to or more than the thickness of the metal layers is attached to the first resin insulating layer 4, in a way of being in contact with the entire circumference of the metal layers 3 on both the sides. The thermal expansion rate of both the first resin insulating layer 4 and the second resin insulating layer 5 is selected smaller than that of the metal layers 3, each located on both the sides of the first resin insulating layer 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wiring board having high connection reliability even when a heat generating component is mounted.

  A wiring board mounted on an electronic device is required to have a technology for fine wiring and high-density mounting in accordance with a reduction in the thickness and size of the electronic device, and a technology for high heat dissipation corresponding to heat generation is also required. In particular, in electronic circuits such as automobiles that use a large current for various controls and operations, heat generation due to the resistance of the conductive circuit and heat generation from the power element are very large, and the heat dissipation characteristics of the wiring board may be high. It has become essential.

  As a countermeasure, prepare a laminated board in which a thick metal layer (copper plate or copper foil) is integrated with an insulating layer holding a thermosetting resin on a highly heat-dissipating ceramic substrate or sheet-like fiber base material. There is a circuit processed wiring board (for example, description in paragraph 0002 of Patent Document 1).

  In a wiring board in which a thick metal layer is integrated with an insulating layer holding a thermosetting resin on a sheet-like fiber base, mounting a heat-generating component such as a power element on the wiring board by soldering will cause thermal expansion / contraction of the metal layer. Stress is applied to the solder portion, and cracks are likely to occur in the solder portion.

JP 2003-198103 A

  The problem to be solved by the present invention is composed of a first resin insulating layer reinforced with a sheet-like fiber base material and a metal layer integrated on both sides thereof in consideration of mounting a heat generating component such as a power element. In the wiring board in which the metal layer on at least one side has a function of electric wiring, it is difficult to cause a crack in the solder portion connecting the mounted components.

  In order to achieve the above object, a wiring board according to the present invention (Claim 1) is composed of a first resin insulating layer reinforced with a sheet-like fiber base and a metal layer integrated on both sides thereof, and at least one side. In the configuration in which the metal layer has a function of electrical wiring, the total thickness of the metal layers on both surfaces of the first resin insulation layer is set to be greater than the thickness of the first resin insulation layer. And the edge of the metal layer of both surfaces of the 1st resin insulation layer is located inside the periphery of the 1st resin insulation layer. Furthermore, the first resin insulation layer is provided with a reinforcing fiber-filled second resin insulation layer that is in contact with the entire circumference of the metal layer edges on both sides and has a thickness equal to or greater than the metal layer thickness. The second resin insulating layer is characterized in that the coefficient of thermal expansion is smaller than that of the metal layers disposed on both surfaces of the first resin insulating layer.

  In another wiring board according to the present invention (Claim 2), in the above configuration, the second resin insulating layer added to the first resin insulating layer has the entire circumference of the metal layer edge on both surfaces of the first resin insulating layer. The thickness of the metal layer exceeds the thickness of the metal layer, and a part of the metal layer surface is covered from the periphery.

  In the first or second aspect, preferably, the metal layer having a function of electric wiring is a copper layer having a thickness of 0.7 mm or more.

  When a heat-generating component such as a power element is mounted on a metal layer having a function of electrical wiring, the thermal expansion coefficient of the power element is about 5 ppm / ° C. On the other hand, the coefficient of thermal expansion (α) of the metal layer directly under the power element is about 17 to 30 ppm / ° C. If the heat cycle of the power element is repeated and the heat generation is stopped, stress is concentrated on the solder part that joins the two due to the difference in the coefficient of thermal expansion between them, and the solder part is cracked and connected. Reliability decreases.

However, in the wiring board according to the present invention (Claims 1 and 2), the thermal expansion coefficient of the first resin insulating layer and the second resin insulating layer is smaller than the thermal expansion coefficient of the metal layer, and the metal layer has its edge. The entire circumference is regulated by being in contact with a second resin insulation layer equal to or greater than the thickness of the metal layer. Thereby, the thermal expansion in the plane direction of the metal layer is suppressed. In addition, since the first resin insulation layer is thinner than the total thickness of the metal layers on both sides, the first resin insulation layer is less likely to inhibit thermal conduction, and the metal layers on both sides through the first resin insulation layer Thermal conductivity is ensured, and the temperature rise of the metal layer itself is suppressed. In this way, the expansion due to the temperature rise of the metal layer is suppressed, and the stress applied to the solder portion is reduced.
By setting the thickness of the metal layer to be thick (Claim 3), the heat dissipation effect is increased.

  The specific form for carrying out the invention according to claim 1 is preferably, for example, a configuration as shown in FIG. Metal layers (for example, copper layers) 3 are integrated on both surfaces of the first resin insulation layer 4 reinforced with the sheet-like reinforcing fiber base, and at least one metal layer has a function of electrical wiring. The heat generating element 1 is mounted on the metal layer having the function of electric wiring by solder 2 in a later step. The total thickness of the metal layer 3 integrated on both surfaces of the first resin insulation layer 4 is set to be greater than the thickness of the first resin insulation layer 4. Further, the end edges of these metal layers 3 are located inside the periphery of the first resin insulation layer 4. The first resin insulation layer 4 is provided with a reinforcing fiber-filled second resin insulation layer 5 that is in contact with the entire circumference of the edges of the metal layers 3 on both sides and has a thickness equal to or greater than the thickness of the metal layer 3. The thermal expansion coefficient of both the first resin insulating layer 4 and the second resin insulating layer 5 is set to be smaller than the thermal expansion coefficient of the metal layer 3.

In the configuration as described above, first, metal layers are arranged on both sides of a prepreg layer in which a thermosetting resin is held on a sheet-like fiber base material, and are integrated by heating and pressing. The prepreg layer becomes the first resin insulating layer 4 by the molding. Then, the metal layer is processed so that the edge of the metal layer 3 is located inside the periphery of the first resin insulating layer 4 to obtain a plate-like body with a double-sided metal layer. This processing includes processing so that the metal layer has a function of electric wiring. In addition, it is good also as a plate-shaped body with a double-sided metal layer by arrange | positioning the metal layer previously processed into the predetermined shape on both surfaces of the said prepreg layer, and integrating by heat press molding.
Next, a prepreg layer is stacked on both sides of the plate-like body with the double-sided metal layer, and is integrated by heating and pressing to form the second resin insulating layer 5. The second resin insulating layer 5 on the metal layer 3 is removed by polishing or counterboring to expose the metal layer 3. The edge of the metal layer 3 is polished or spotted so that the entire circumference is in contact with the second resin insulating layer 5. In this way, the second resin insulation layer 5 is added to the first resin insulation layer 4. If the second resin insulation layer 5 is not removed up to the edge of the metal layer 3 in the polishing or spotting process, and the periphery of the metal layer 3 is partially covered by the second resin insulation layer 5, the process shown in FIG. The configuration shown in (b) (claim 2) is obtained.
If the prepreg layer from which the region facing the metal layer 3 has been removed in advance is overlapped on the plate with double-sided metal layer and integrated by heat and pressure molding, the polishing or counterboring process may be omitted or simplified. it can.

  In the above, since the thickness of the first resin insulation layer 4 is thinner than the total thickness of the metal layers 3 on both sides thereof, by pressing the metal layer 3 into the first resin insulation layer 4, the periphery of the edge of the metal layer 3 can be obtained. Further, the resin insulating layer cannot be in contact with the thickness more than that. Adding the second resin insulation layer 5 to the first resin insulation layer 4 is an essential matter.

The sheet-like fiber base material constituting the prepreg is a woven fabric or a nonwoven fabric made of glass fiber or organic fiber. In order to reduce the thermal expansion coefficient of the resin insulating layer, a sheet-like fiber base material made of aramid fiber or alumina fiber is suitable. In Claim 3, Preferably, the first resin insulating layer has a thermal conductivity of 4 W / m · K or more. The thermosetting resin for impregnating the sheet-like fiber base material to form the resin insulating layer is, for example, as follows when the thermal conductivity of the resin insulating layer is 4 W / m · K or more. Adopt resin composition.
That is, an epoxy resin composition containing an inorganic filler and containing an epoxy resin monomer having a molecular structure represented by (Formula 1) is employed. The inorganic filler has a thermal conductivity of 20 W / m · K or more, and is present in the insulating layer in an amount of 10 to 100 parts by volume with respect to 100 parts by volume of the resin solid content.

  The epoxy resin monomers having the molecular structure represented by the above (formula 1) are all epoxy compounds having a biphenyl skeleton or a biphenyl derivative skeleton and having two or more epoxy groups in one molecule. In order to advance the curing reaction of the epoxy resin monomer, a curing agent is blended. Examples of the curing agent include amine compounds and derivatives thereof, acid anhydrides, imidazoles and derivatives thereof, phenols or compounds and polymers thereof, and the like. Moreover, in order to accelerate | stimulate reaction of an epoxy resin monomer and a hardening | curing agent, a hardening accelerator can be used. Examples of the curing accelerator include triphenylphosphine, imidazole and derivatives thereof, tertiary amine compounds and derivatives thereof, and the like.

The inorganic filler with a thermal conductivity of 20 W / m · K or more blended in the epoxy resin composition blended with the curing agent or curing accelerator is a metal oxide, hydroxide, inorganic ceramic, or other filler. For example, inorganic powder fillers such as boron nitride, aluminum nitride, silicon nitride, silicon carbide, titanium nitride, zinc oxide, tungsten carbide, alumina, magnesium oxide, fibrous fillers such as synthetic fibers and ceramic fibers, colorants, etc. is there. Two or more of these inorganic fillers may be used in combination.
An inorganic filler is mix | blended so that it may become the quantity of 10-100 volume parts with respect to 100 volume parts of resin solid content. The lower limit values of the thermal conductivity and the blending amount of the inorganic filler are necessary when the thermal conductivity of the resin insulating layer is 4 W / m · K or more. Moreover, when there are few inorganic fillers mix | blended with an epoxy resin composition, it will become difficult to disperse | distribute an inorganic filler uniformly in an epoxy resin composition. In this respect as well as ensuring thermal conductivity, it is important to define the lower limit value of the inorganic filler content. On the other hand, when the blending amount of the inorganic filler is increased, the viscosity of the epoxy resin composition is increased and the handling becomes difficult. Therefore, the upper limit value of the blending amount of the inorganic filler is defined from this viewpoint.

  A thermal conductivity of the inorganic filler of 30 W / m · K or more is preferable because the thermal conductivity of the resin insulating layer can be further increased. In addition, the inorganic filler may have any shape such as powder (bulk, sphere), short fiber, long fiber, etc., but when a flat plate is selected, the inorganic filler itself with high thermal conductivity is resin. It exists in the state which accumulated in the inside, and since the heat conductivity of the thickness direction of a resin insulating layer can be made still higher, it is preferable. In addition to the above epoxy resin composition, a flame retardant, a diluent, a plasticizer, a coupling agent, and the like can be blended as necessary.

The resin insulation layer is formed by preparing a prepreg in which the epoxy resin composition is diluted with a solvent as necessary to prepare a varnish, impregnating the varnish into a sheet-like fiber base material, and drying by heating to a semi-cured state. And these are heat-press-molded and it is set as a resin insulating layer. In the heat and pressure molding, metal layers are arranged on both surfaces of the prepreg layer, and these are integrated by heat and pressure molding. The metal layer may be either electrolytic metal or rolled metal.
When the varnish is prepared by diluting the epoxy resin composition in a solvent, the blending and use of the solvent does not affect the thermal conductivity of the cured epoxy resin.

  Examples of the present invention will be described below, and the present invention will be described in detail. In the following examples and comparative examples, “part” means “part by mass”. Moreover, this invention is not limited to a present Example, unless it deviates from the summary.

Example 1
As an epoxy resin monomer component, prepare 100 parts of an epoxy resin monomer having a biphenyl skeleton (Japan Epoxy Resin “YL6121H”, epoxy equivalent 175), and dissolve it at 100 ° C. in 100 parts of methyl isobutyl ketone (Wako Pure Chemical Industries, Ltd.). , Returned to room temperature. The “YL6121H” is an epoxy resin monomer in which R = —CH ₃ and n = 0.1 in the molecular structural formula (formula 1) described above and R = —H, n in the molecular structural formula (formula 1). = 0.1 An epoxy resin monomer containing an equimolar amount of an epoxy resin monomer of 0.1.
As a curing agent, 22 parts of 1,5-diaminonaphthalene (“1,5-DAN” manufactured by Wako Pure Chemical Industries, Ltd., amine equivalent 40) is prepared and dissolved in 100 parts of methyl isobutyl ketone (manufactured by Wako Pure Chemical Industries) at 100 ° C. And returned to room temperature.
The epoxy resin monomer solution and the curing agent solution are mixed and stirred to form a uniform varnish, and boron nitride (“GP” manufactured by Denki Kagaku Kogyo, average particle size: 8 μm, thermal conductivity 60 W / m K (particle shape: flat plate) 107 parts (corresponding to 50 parts by volume with respect to 100 parts by volume of resin solid content) were added and kneaded to prepare an epoxy resin varnish.
This epoxy resin varnish was impregnated into an aramid fiber nonwoven fabric having a thickness of 50 μm and dried by heating to obtain a prepreg. A 1.3 mm thick metal layer (copper layer) with a thermal expansion coefficient of 17 ppm / ° C. is layered on both sides of one prepreg, and is formed by heating and pressing for 90 minutes under the conditions of a temperature of 175 ° C. and a pressure of 4 MPa, A laminated board having a thickness of 2.7 mm in which a metal layer (copper layer) was integrated on both surfaces of the first resin insulating layer was obtained. And the metal layer (copper layer) was processed into the predetermined shape, and it was set as the plate-like body with a double-sided metal layer (copper layer).

  Next, the epoxy resin varnish was impregnated into a 120 μm thick aramid fiber nonwoven fabric and dried by heating to obtain a prepreg. 10 sheets of this prepreg are placed on both sides of the plate with the double-sided metal layer (copper layer), sandwiched between release films, and heated and pressure-molded for 90 minutes under conditions of a temperature of 175 ° C. and a pressure of 4 MPa. The layers were integrated. The release film is peeled off, the second resin insulating layer is polished and removed until the metal layer (copper layer) having a predetermined shape is exposed, and the second resin insulating layer added to the first resin insulating layer is the metal layer. A wiring board having the same height as the (copper layer) was obtained. This corresponds to the configuration shown in FIG. The thermal expansion coefficient of the first and second resin insulation layers is 12 ppm / ° C.

The results of measuring the thermal conductivity, warpage amount and solder connection reliability of the wiring board obtained in Example 1 are shown together in Table 1 together with the used copper layer thickness. The measurement is based on the method shown below.
Thermal conductivity: A plate-like sample having a diameter of 50 mm was cut out from the wiring board, and the heat conduction in the thickness direction including the copper layers on both sides was measured by a heat flow meter method (based on JIS-A1412).
Warpage amount: A cooling / heating cycle test was performed in the range of 105 ° C. to −40 ° C., and the amount of lift relative to the plane after 1000 cycles was measured as the amount of warpage.
Cooling / heating cycle: A power element (ceramic chip) was soldered, and a cooling / heating cycle test was conducted in the range of 105 ° C. to −40 ° C., and the presence or absence of occurrence of solder cracks after 1000 cycles was examined.

Example 2
A wiring board was obtained in the same manner as in Example 1 except that the metal layer (copper layer) thickness of Example 1 was 1.4 mm on the upper side and 1.4 mm on the lower side.

Example 3
A wiring board was obtained in the same manner as in Example 1 except that the metal layer (copper layer) thickness of Example 1 was 0.7 mm on the upper side and 0.7 mm on the lower side.

Example 4
A wiring board was obtained in the same manner as in Example 1 except that the metal layer (copper layer) thickness of Example 1 was 1.3 mm on the upper side and 0.018 mm on the lower side.

Example 5
The epoxy resin varnish of Example 1 was impregnated into an aramid fiber nonwoven fabric having a thickness of 50 μm and dried by heating to obtain a prepreg. A copper foil having a thickness of 1.3 mm was stacked on both sides of one prepreg and integrated by heating and pressing for 90 minutes under the conditions of a temperature of 175 ° C. and a pressure of 4 MPa to obtain a laminated plate having a thickness of 2.7 mm. And the metal layer (copper layer) was processed into the predetermined shape, and it was set as the plate-like body with a double-sided metal layer (copper layer).
Next, the epoxy resin varnish was impregnated into a 120 μm thick aramid fiber nonwoven fabric and dried by heating to obtain a prepreg. 10 sheets of this prepreg are placed on both sides of the plate with the double-sided metal layer (copper layer), sandwiched between release films, and heated and pressure-molded for 90 minutes under the conditions of a temperature of 175 ° C. and a pressure of 4 MPa. The layers were integrated. The release film is peeled off, the second resin insulation layer is removed by spotting until the copper layer of a predetermined shape is exposed, and the second resin insulation layer added to the first resin insulation layer is a metal layer (copper layer). ) Was obtained. This corresponds to the configuration shown in FIG.

Example 6
A wiring board was obtained in the same manner as in Example 1 except that the metal layer (copper layer) thickness of Example 1 was 0.6 mm on the upper side and 0.6 mm on the lower side.

Comparative Example 1
The epoxy resin varnish of Example 1 was impregnated into an aramid fiber nonwoven fabric having a thickness of 50 μm and dried by heating to obtain a prepreg. A copper foil having a thickness of 1.3 mm was stacked on both sides of one prepreg and integrated by heating and pressing for 90 minutes under the conditions of a temperature of 175 ° C. and a pressure of 4 MPa to obtain a laminated plate having a thickness of 2.7 mm. And the metal layer (copper layer) was processed into the predetermined shape, and it was set as the wiring board with a double-sided metal layer (copper layer). It is the structure shown in FIG.

Comparative Example 2
A wiring board was obtained in the same manner as in Comparative Example 1 except that the metal layer (copper layer) thickness of Comparative Example 1 was 1.0 mm on the upper side and 0.012 mm on the lower side.

Comparative Example 3
The epoxy resin varnish of Example 1 was impregnated into a 50 μm thick glass fiber nonwoven fabric and dried by heating to obtain a prepreg. A 1.3 mm thick metal layer (copper layer) with a thermal expansion coefficient of 17 ppm / ° C. is layered on both sides of one prepreg, and is formed by heating and pressing for 90 minutes under the conditions of a temperature of 175 ° C. and a pressure of 4 MPa, A laminated board having a thickness of 2.7 mm in which a metal layer (copper layer) was integrated on both surfaces of the first resin insulating layer was obtained. And the metal layer (copper layer) was processed into the predetermined shape, and it was set as the plate-like body with a double-sided metal layer (copper layer).

  Next, the epoxy resin varnish was impregnated into a 0.6 mm thick glass fiber nonwoven fabric and dried by heating to obtain a prepreg. Two prepregs are placed on both sides of the plate with the double-sided metal layer (copper layer), sandwiched between release films, and heated and pressure-molded for 90 minutes under the conditions of a temperature of 175 ° C. and a pressure of 4 MPa. The layers were integrated. The release film is peeled off, the second resin insulating layer is polished and removed until the metal layer (copper layer) having a predetermined shape is exposed, and the second resin insulating layer added to the first resin insulating layer is the metal layer. A wiring board having the same height as the (copper layer) was obtained. This corresponds to the configuration shown in FIG. 1A, but the thermal expansion coefficient of the second resin insulation layer is 18 ppm / ° C., which is larger than the thermal expansion coefficient of the metal layer (copper layer). The thermal expansion coefficient of the first resin insulation layer is 15 ppm / ° C.

  About the wiring boards of Examples 2-6 and Comparative Examples 1-3, the characteristic was measured similarly to Example 1, and the result was shown in Table 1 and Table 2.

As shown in the above table, in Comparative Examples 1 and 2, there is nothing that regulates the periphery of the edge of the metal layer, so the thermal expansion of the metal layer cannot be suppressed, the warping of the wiring board increases, and the solder portion Cracks are also likely to occur. In Comparative Example 3, although the second resin insulation layer is added, since the thermal expansion coefficient is larger than the thermal expansion coefficient of the metal layer, the generation of the warp of the wiring board and the crack of the solder portion is not suppressed.
In the embodiment according to the present invention, it can be understood that warpage of the wiring board and occurrence of cracks in the solder portion are suppressed. When the thickness of the copper layer is 0.7 mm or more, the occurrence of cracks in the solder portion can be suppressed to a lower level (contrast of Examples 1 to 3 and Example 6).

It is a wiring board sectional view of an embodiment concerning the present invention. It is conventional wiring board sectional drawing.

Explanation of symbols

1 is power element 2 is solder 3 is metal layer 4 is first resin insulation layer 5 is second resin insulation layer

Claims (3)

In the wiring board composed of a first resin insulating layer reinforced with a sheet-like fiber base material and a metal layer integrated on both sides thereof, at least one metal layer having a function of electrical wiring,
The total thickness of the metal layers on both sides is set to be greater than the thickness of the first resin insulation layer,
In both metal layers, the edge is located inside the periphery of the first resin insulation layer,
The first resin insulation layer is provided with a reinforcing fiber-filled second resin insulation layer that is in contact with the entire circumference of the metal layer edges on both sides and has a thickness equal to or greater than the metal layer thickness. A wiring board characterized in that the thermal expansion coefficient of both of the resin insulation layers is smaller than the thermal expansion coefficient of the metal layers disposed on both surfaces of the first resin insulation layer. In the wiring board composed of the first resin insulating layer and the metal layer integrated on both surfaces thereof, and at least one metal layer has the function of electrical wiring,
The total thickness of the metal layers on both sides is set to be greater than the thickness of the first resin insulation layer,
In both metal layers, the edge is located inside the periphery of the first resin insulation layer,
A reinforcing fiber-filled second resin insulation layer that is in contact with the entire circumference of the metal layer edges on both sides and exceeds the metal layer thickness is added to the first resin insulation layer so as to cover part of the metal layer surface from the periphery. The wiring board characterized in that the thermal expansion coefficient of both the first resin insulating layer and the second resin insulating layer is smaller than the thermal expansion coefficient of the metal layers disposed on both surfaces of the first resin insulating layer.   The wiring board according to claim 1 or 2, wherein the metal layer having a function of electric wiring is made of a copper layer and has a thickness of 0.7 mm or more.

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