JPH0685414A - Printed wiring board for mounting semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a printed wiring board suitable for the wiring board used for the surface mounting with which a semiconductor device can be mounted in the state of high density. CONSTITUTION:The printed wiring board consists of an iron-nickel alloy plate on which copper is clad on both surfaces, and the printed wiring board is formed by laminating metal foil and an insulating layer, consisting of heat-proof thermoplastic resin having Young's modules (ASTMD-882) of 200 to 800kg/mm<2>, at least on one side of a metal plate having the linear expansion coefficient (ASTMD-696) of 6X10<-6>mm/mm deg.C or lower. This is the printed wiring board used for mounting of a semiconductor device having the thickness of an insulating layer of 20 to 200mum, the linear expansion coefficient of the entire laminated board of 2X10<-6> to 8X10<-6>mm/mm deg.C. As a result, cracks and the like are hardly generated on the connection part even when a hot-cold cycle is added, and a layer type semiconductor device can be surface-mounted in the state of high density. As a result, this printed wiring board has a high utilizational efficiency for the printed wiring board and the like used for motorcar control device of wide range of working temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board suitable for a surface mounting wiring board capable of mounting large-sized semiconductor elements at high density.

[0002]

2. Description of the Related Art Printed wiring boards are supplied to various electronic devices for the purpose of forming circuits and mounting semiconductor elements. In recent years, the development of so-called surface mount wiring boards, in which lead-free chip type semiconductor elements are directly soldered to predetermined circuit positions on the printed wiring board for high-density mounting and the two are joined at the solder part Has been.

However, when a cold temperature cycle is applied to a printed wiring board on which the above-mentioned semiconductor element is surface-mounted, cracks occur at the soldered connection portion between the semiconductor element and the wiring board, leading to defective conduction and the element. There is a problem that it is easily peeled off from the wiring board, and the problem is likely to occur particularly in applications having a wide operating temperature such as a printed wiring board for a control device of an automobile. As a countermeasure against such cracks, it has been considered to make the thermal expansion coefficient of the wiring board as close as possible to that of the semiconductor element. The effect of preventing the occurrence of cracks was small. In particular, as a semiconductor element to be mounted becomes larger (about 5 to 10 mm square) with higher functionality, heat generation of the semiconductor element itself increases and cracks tend to occur.

[0004]

DISCLOSURE OF THE INVENTION The present invention has solved the above problems and has found a printed wiring board on which a large-sized semiconductor element can be mounted. The gist of the invention is to coat copper on both sides. Made of an iron-nickel alloy plate with a linear expansion coefficient (ASTM D-696) of 6 × 10 ^-6 mm / mm
The linear expansion coefficient is 3 on at least one side of the metal plate whose temperature is ℃ or less.
× 10 ⁻⁵ to 8 × 10 ⁻⁵ mm / mm ° C. and Young's modulus (ASTMD-882) of 200 to 800 Kg / mm ²
And an insulating layer made of a heat-resistant thermoplastic resin in the range of 10 and a metal foil are laminated, and the thickness of the insulating layer is 20 to 200 μm.
And the linear expansion coefficient of the whole laminated plate is 2 × 10 ⁻⁶
It exists in the printed wiring board for mounting a semiconductor element in the range of up to 8 × 10 ⁻⁶ mm / mm ° C.

The metal plate used in the substrate of the present invention has a coefficient of linear expansion (ASTM D-696) of 6 × 10 ^-6 mm / mm ° C. or less. Specifically, it is an iron-nickel alloy (hereinafter referred to as “Fe- Ni alloy ”) having a copper layer metallurgically coated on its surface is used. The linear expansion coefficient of Fe-Ni alloy is
It depends on the content ratio of the metal component, and in order to satisfy the linear expansion coefficient of the present invention, the Ni content is preferably 35 to 45% by weight. Further, the above alloy coated with a copper layer has an advantage that the coefficient of linear expansion is slightly increased, but the heat dissipation is improved and the copper layer can be used as a power source layer or a ground layer.

As the above-mentioned metal plate, a plate provided with a plurality of through holes can be used if necessary. Next, one side or both sides of the metal plate is coated with an insulating layer. As the heat resistant thermoplastic resin used for this insulating layer, the linear expansion coefficient (ASTMD
-696) is 3 × 10 ⁻⁵ to 8 × 10 ⁻⁵ mm / mm ° C.,
And Young's modulus (ASTMD-882) is 200-800
It is necessary to use those satisfying the range of Kg / mm ² .

It is considered that this insulating layer plays a role of absorbing shear stress and the like due to the difference in linear expansion coefficient between the component and the substrate during the cooling / heating temperature cycle.

Specific resins used in the resin layer include polyphenylene sulfide, polyether ether ketone, polyether sulfone, polyphenylene oxide, etc., which satisfy the above characteristics. Copper foil is usually used as the metal foil provided on the insulating layer.

Next, the materials having the above-mentioned constitutions are laminated and integrated by hot pressing or the like. The hot pressing conditions vary depending on the type of heat-resistant thermoplastic resin used, etc., but the pressing temperature is not less than the flow start temperature of the resin to be used, the pressing pressure is in the range of 5 to 100 Kg / cm ² , and the depressurizing condition is It is preferable to do so because voids can be prevented from occurring. The obtained laminated board is sent to the subsequent printed wiring board manufacturing process, and is subjected to usual processing such as pattern printing on a metal foil, etching, washing with water, and formation of through holes to obtain a final printed wiring board.

[0010]

EXAMPLES Example A printed wiring board having the following contents was obtained. Metal plate: Fe-Ni alloy plate (Ni content 36% by weight) is coated with copper layers on both sides (thickness ratio is copper: Fe-Ni alloy plate:
Copper) = 1: 8: 1 and coefficient of linear expansion 3 × 10 ⁻⁶ (mm / mm
C.) Plate thickness is 800 μm.

Insulating layer: polyether ether ketone (coefficient of linear expansion 5 × 10 ⁻⁵ mm / mm ° C., Young's modulus 460 kg /
mm ² ) The layer thickness is 100 μm.

After placing the insulating layer and the copper foil (18 μm thick) on both sides of the metal plate, they were heated and pressed to be laminated and integrated.
The linear expansion coefficient of the entire laminate is 3.5 × 10 ⁻⁶ (mm / mm
C). When a "cooling / heating cycle" test was conducted using the obtained laminate, there was no problem for 4200 cycles or more.

Here, in the cooling / heating cycle test, a semiconductor element (10 mm square) was solder-bonded by a reflow method to a printed wiring board composed of the above-mentioned laminated plate by using a solder bump, and the temperature was -65 ° C.
By repeating the cooling / heating cycle of up to 125 ° C., the electrical resistance at that portion was measured, the occurrence of cracks at the joint was detected, and the number of cycles until cracks were generated was measured.

[0014]

As described above, according to the printed wiring board of the present invention, cracks and the like are unlikely to occur at the connection portion even when a thermal cycle is applied, and large semiconductor elements can be surface-mounted at high density. Therefore, it is highly applicable to printed wiring boards for control devices of automobiles having a wide operating temperature.

Claims (1)

[Claims] 1. An iron-nickel alloy plate having copper coated on both sides, having a linear expansion coefficient (ASTMD-696) of 6 ×.
The linear expansion coefficient is 3 × 10 ⁻⁵ to 8 × 10 ⁻⁵ mm / mm ° C. on at least one surface of the metal plate having a temperature of 10 ⁻⁶ mm / mm ° C. or less.
And Young's modulus (ASTMD-882) is 200 to 8
The insulating layer and the metal foil made of a heat-resistant thermoplastic resin in the range of 00 Kg / mm ² are laminated, and the thickness of the insulating layer is in the range of 20 to 200 μm and the linear expansion coefficient of the entire laminated plate is 2 × 10. ^A printed wiring board for mounting a semiconductor element in the range of ^-6 to 8 x 10 ^-6 mm / mm ° C.