JP2913886B2 - Printed wiring board - Google Patents

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 used for mounting electric parts, electronic parts and the like.

[0002]

2. Description of the Related Art Printed wiring boards are widely used as mounting boards for components incorporated in electrical equipment, electronic equipment, communication equipment, and computers. These devices are small,
Weight reduction has been achieved by mounting components on printed wiring boards with high density. As one of such high-density mounting, a method of surface mounting components on a printed wiring board has been adopted.

However, between the coefficient of thermal expansion of an electric component, an electronic component, and the like, and the coefficient of thermal expansion of a printed wiring board, for example, 3 to 5 ppm / ° C. for a semiconductor chip and 1 for a printed wiring board.
There is an order of magnitude difference, such as 2-20ppm / ° C, and the problems such as the soldered parts coming off the printed wiring board and the parts being damaged due to environmental changes in actual use and the heat generated by the parts themselves. Had.

[0004]

SUMMARY OF THE INVENTION The present invention relieves the stress caused by the difference in the coefficient of thermal expansion between a printed wiring board and a surface-mounted component, and reduces the stress on the mounted printed wiring board due to loss of soldering or damage to the component. An object of the present invention is to provide a printed wiring board suitable for surface mounting that can reduce the failure rate.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has a thickness of 5 mm on a substrate surface.
A printed wiring board comprising a sea-island structure resin layer having a silicone resin island in the sea of a thermosetting binder resin of 0 μm or more.

Hereinafter, the present invention will be described in detail. As the resin forming the thermosetting binder resin layer of the present invention, an epoxy resin, a polyimide resin, an unsaturated polyester resin, a phenol resin, or the like alone, a modified product, a mixture, or the like is used, and the resin is particularly limited. Not something. The resin layer of the thermosetting binder resin needs to be formed to have a thickness of 50 μm or more. If the thickness is too large, the strength as a printed wiring board is reduced.

As the silicone resin dispersed as an island in the sea of a thermosetting binder resin, both ends are amine, epoxy, piperidine, carboxylic acid, etc. in order to enhance the compatibility with the binder resin forming the sea. A resin having a functional group that reacts with a thermosetting binder resin such as an acid or a hydroxyl group, a method of forming a polar structure by fluorination, or the like can be used. This compatibility greatly affects the particle size of the silicone resin dispersed as islands in the sea of the thermosetting binder resin, and particles having a diameter of 0.01 to 10 μm are preferably dispersed. If the compatibility is poor, the diameter of the particles becomes 10 μm or more, and cracks easily occur in the resin layer, which is not preferable. The compatibility is too good and the particle diameter is 0.
If it is less than 01 μm, the effect of the sea-island structure is lost and the effect of stress relaxation is reduced to half by the effect of only the thermosetting binder resin.

This resin layer can be formed by the following method. However, it is not limited to these methods. As in the related art, a predetermined number of prepregs are stacked, and a copper foil formed by applying the above-described resin layer to a mat surface of the copper foil is stacked on one or both surfaces thereof. As in the related art, a predetermined number of prepregs are stacked, a film made of the resin layer described above is stacked on one or both surfaces thereof, and a normal copper foil is further stacked thereon.
As in the prior art, a predetermined number of prepregs are stacked, and the resin layer of the prepreg coated with the resin layer shown above on one side or both sides is stacked outside, and further, a copper foil is stacked thereon and stacked. There is a way.

[0009]

By forming a sea-island structure having islands of a flexible dispersed phase in the sea of a thermosetting binder resin cross-linked and cured three-dimensionally, the sea of the thermosetting binder resin by heat is formed. Since the change is absorbed by the islands of the dispersed phase, the change of the entire resin layer can be reduced. Therefore, in a component soldered to a printed wiring board having this resin layer, the stress generated in the soldered portion is reduced or reduced by the resin layer due to an environmental change in actual use or heat generation of the component itself. This eliminates problems such as detachment from the printed wiring board and damage to components.

[0010]

The present invention will be described below with reference to specific examples and comparative examples. In addition, this invention is not limited to a following example.

EXAMPLE 1 A resin layer composed of an epoxy resin as a thermosetting binder resin and α, ω-bisaminopropyldimethylsiloxane represented by the following structural formula as a dispersed phase constituting an island is formed on a matte surface of a copper foil to a thickness of 70 μm. And dried to prepare a copper foil with a resin layer. This copper foil was laminated and formed on both sides of eight glass cloth base epoxy resin prepregs, and the thickness was 1.
A 6 mm double-sided copper-clad glass cloth-based epoxy resin laminate was obtained.

The structural formula of α, ω-bisaminopropyldimethylsiloxane is shown below. Example 2 A 1.6 mm thick double-sided copper-clad glass cloth-based epoxy resin was prepared in the same manner as in Example 1 except that the resin layer of Example 1 was applied and dried at a thickness of 120 μm to prepare a copper foil with a resin layer. A laminate was obtained.

Example 3 A 100 μm-thick film of a resin layer composed of an epoxy resin as a thermosetting binder resin and α, ω-bisaminopropyldimethylsiloxane as a dispersed phase constituting an island was prepared, and eight sheets of glass were formed. This film was laminated on the outside of the cloth-based epoxy resin prepreg, and a copper foil was further laminated on the outside of the prepreg, and laminated to form a 1.6 mm-thick double-sided copper-clad glass cloth-based epoxy resin laminate.

Example 4 A double-sided copper-clad glass cloth-based epoxy resin laminate having a thickness of 1.6 mm was prepared in the same manner as in Example 1 except that the disperse phase of Example 1 was changed to the following siloxane oligomer modified with an epoxy terminal resin. I got a board.

The structural formula of the terminal epoxy resin-modified siloxane oligomer is shown below. In addition, Ep represents an epoxy group. Example 5 The same procedure as in Example 1 was repeated except that the thermosetting binder resin in Example 1 was replaced with a polyimide resin, and the glass cloth base epoxy resin prepreg was replaced with a glass cloth base polyimide resin prepreg. A 6 mm double-sided copper-clad glass cloth-based polyimide resin laminate was obtained.

Comparative Example 1 An ordinary copper foil was laminated and formed on both sides of eight glass cloth base epoxy resin prepregs to obtain a 1.6 mm thick double-sided copper clad glass cloth base epoxy resin laminate. .

Comparative Example 2 An ordinary copper foil was laminated and formed on both sides of eight glass cloth base polyimide resin prepregs to obtain a 1.6 mm thick double-sided copper-clad glass cloth base polyimide resin laminate. .

On a printed wiring board on which a predetermined circuit was formed on the copper-clad laminate obtained above, 100 silicon chip components were surface-mounted by soldering. For soldering, after printing and applying cream solder on the circuit of the printed wiring board,
The silicon chip component was temporarily placed thereon, and the solder paste was heated and reflowed with a far-infrared heater to be connected and integrated.
This mounted product was subjected to the condition C (minus 65 ° C., 30 minutes-25 ° C., 15 minutes-125) specified in the MIL test method 102A.
(30 ° C., 30 minutes−25 ° C., 15 minutes), and the number of detached portions due to cracks in the solder joints after completion was measured. The results are shown in Table 1.

[0019]

According to the printed wiring board of the present invention, the stress caused by the difference in the coefficient of thermal expansion between the printed wiring board and the component to be surface-mounted can be relaxed, and the printed wiring which has been mounted, such as a loss of soldering or damage to the component. The failure rate of the board can be reduced.

[0020]

[Table 1]

Claims (1)

(57) [Claims] 1. A printed wiring board comprising a resin layer having a sea-island structure of a thermosetting binder resin sea and a silicone resin island having a thickness of 50 μm or more formed on a substrate surface.