JPH06209146A - Printed-wiring board - Google Patents

Abstract

PURPOSE:To provide a printed-wiring board, which is reduced or is made to dissolve a warpage or a twist at a level that no problem is caused in practical use and is suitable for a circuit to mounting meet needs lightening, reduction in a thickness and reduction in size and the like. CONSTITUTION:A printed-wiring board consisting of a composite board, which is made using a glass cloth as its base material and is impregnated with a resin, is characterized by that the glass cloth, which is positioned on at least the outside of the board, is provided in such a way that roughly the diagonal directions of meshes 1a of the cloth creep along the cut surface of the external shape of the board to constitute the printed-wiring board. That is, the printed- wiring board is one making a method of constituting the board into a constitution, wherein the diagonal directions of the meshes 1a, which are formed by the warps 1b and wefts 1c of the cloth, and the cut (an external shape processing) surface of the board are made to roughly coincide with each other, the point.

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,
In particular, the present invention relates to a thin printed wiring board that uses glass cloth as a base material and prevents warpage and twisting.

[0002]

2. Description of the Related Art As is well known, so-called printed wiring boards have been widely put to practical use in circuit configurations of electronic devices, electric machines and the like. Then, while multilayer wiring (multilayer wiring board) is attempted for the purpose of downsizing the circuit configuration, glass cloth is used as a base material in consideration of mechanical strength increase, heat resistance, etc. Impregnated composite board type printed wiring boards are also put to practical use.

By the way, a composite board type printed wiring board in which a resin is impregnated using the glass cloth as a base material is usually manufactured and constructed as follows. That is, glass cloth forming a square or rectangular mesh (texture) is impregnated with the required resin, for example, epoxy resin.
Conductor foil such as copper foil is laminated on the prepreg surface that is adhered, heated and pressed to integrate, and the conductor foil is selectively etched to form the required circuit pattern. Or by stacking the circuit-patterned circuit element plates in multiple layers via prepregs and heating and pressing to integrate them. In any of the manufacturing and construction of the printed wiring board, as shown schematically in FIG. 4, for example, the weave of the glass cloth that forms the base material, in other words, the plain weave glass cloth that forms the rectangular or rectangular mesh 1a. The outer shape is processed along the warp 1b direction and the weft 1c direction (in parallel). In other words, in printed wiring board products, the glass cloth forming the base material has a warp 1b direction and a weft 1c.
The directions are orthogonal to the outer shape cutting surface (end surface).

[0004]

However, in the case of the conventional printed wiring board having the above structure, the following disadvantages are recognized. That is, by using the glass cloth as the base material, it is possible to improve the dimensional stability of the wiring board, but when the thickness of the printed wiring board is about 0.6 mm or less, there is a problem that warpage or twisting easily occurs. is there. In more detail, when the printed wiring board using the glass cloth as a base material is thinned to have a thickness of, for example, about 0.6 mm or less in response to, for example, lightening, thinning and shortening of electronic devices, warping or twisting occurs. Occurs, for example, it becomes impossible to print the cream solder, or it becomes impossible to recognize the pattern by the mounting operation / work by the mounting machine.

The cause of the warp and twist of the printed wiring board is, firstly, that the glass cloth forming the base material is bent (mesh deformation), that is, the weft 1c is bent with respect to the warp 1b. It is considered that the glass cloth has an oblique directionality, which causes warpage and twist of the printed wiring board product. Secondly, one of the warp yarns 1b and the weft yarns 1c forming the glass cloth forming the base material.
Because one strand is twisted, twist the warp 1b,
It is considered that this is because the force to return both the weft 1c acts. This can be easily understood from the phenomenon that the plain glass cloth is twisted when it is vertically supported. That is,
Corresponding to the first factor, even if a glass cloth without mesh bending is prepared, the warp 1b is formed by forming the glass cloth.
Since it is indispensable to twist each of the wefts 1c, it is difficult to eliminate warpage and twist of the printed wiring board, and effective means and measures have not been established.

The present inventor has conducted intensive studies in response to the above circumstances, and as a result, in a thin printed wiring board made of a resin-impregnated composite plate using glass cloth as a base material, the glass cloth forming the base material is used. As shown schematically in, for example, FIG. 1, when the diagonal direction of the mesh 1a of the glass cloth is arranged so as to substantially coincide with the cut surface (end surface) by the outer shape processing, the thickness is about 0.6 mm. It has been found that the phenomenon of warpage and twist can be greatly reduced or eliminated even under the following conditions.

The present invention has been made on the basis of such knowledge, and the warp and the twist are reduced or eliminated to a level that does not cause a problem in practical use, and the printed wiring suitable for the construction of the mounting circuit along with the miniaturization of the light, thin and short circuit. For the purpose of providing boards.

[0008]

The printed wiring board of the present invention is a printed wiring board made of a resin-impregnated composite board using a glass cloth as a base material, and at least the glass cloth located at the outer side is almost the same as the mesh. It is characterized in that it is arranged in a diagonal direction along the contour cutting plane.

In the present invention, for all the glass cloths forming the base material, the diagonal direction of the mesh does not need to be arranged substantially along the contour cutting surface, and is located at least at the outermost side (front and back surfaces). The glass cloth only needs to satisfy the above conditions. That is, in a configuration in which a plurality of glass cloth layers are arranged, the glass cloth layers arranged on the outer side (front and back surfaces) are more effective in reducing and eliminating the warp and twist than the glass cloth layers arranged on the inner side. This is because there is a tendency to have a large effect.

The mesh of the glass cloth may be square or rectangular, but is more preferably rectangular, and the diagonal direction of the mesh with respect to the outer shape cutting plane need not be exactly the same, for example ± 15. There is virtually no problem even if there is a deviation.

On the other hand, as the resin with which the glass cloth forming the base material is impregnated, any resin such as thermosetting resin such as epoxy resin or polyimide resin, or thermoplastic resin such as polyphenylene sulfide resin can be used. Good.

[0012]

As described above, although the reason is not always clear, according to the present invention, the glass cloth forming the base material is arranged such that the diagonal direction of the mesh of the glass cloth substantially coincides with the cut surface by the outer shape processing. Due to the configuration,
Even if the thickness is less than about 0.6 mm, the occurrence of warpage and twist is greatly reduced or eliminated. Therefore, solder solder printing for mounting electronic components,
Alternatively, the pattern recognition on the mounting machine can be performed easily and accurately.

[0013]

Embodiments of the present invention will be described below with reference to FIGS.

Example 1 A plain weave glass cloth having a thickness of 0.06 mm (60 lengths / 25 mm, 40 width)
(25 mm) (25 mm) is placed and laminated with a 25 μm thick polyphenylene sulfide resin film on both sides of a glass cloth piece cut in the warp and weft directions.
By heating and pressurizing at 20 ℃ / cm ² at ℃, polyphenylene sulfide resin impregnated base plate was obtained. Then, 5 sheets of the polyphenylene sulfide resin-impregnated base plate were laminated with the directions of the warp and the weft of the glass cloth being aligned, respectively, and copper foils were arranged and laminated on both sides thereof.
Heat and pressurize at 20 ℃ / cm ² to obtain a copper-clad laminate, and photo-etch the copper foils on both sides to form the required circuit pattern. The thickness of 0.36mm, 250 × 330mm A chamfered wiring board was manufactured.

From the above-prepared multi-chamfered wiring board, a printed wiring board of 50 × 80 mm (comparative example) is obtained by cutting (outline processing) in line with the direction of the warp and weft of the glass cloth, while It was cut (outer shape processing) so as to substantially coincide with the diagonal direction of the mesh formed by the warp and weft of the cloth, and a 50 × 80 mm printed wiring board (Example) was obtained. The following table shows the results of measuring the warpage rate% and the twist rate for each of the 30 printed wiring boards manufactured in this manner.

[0016] Here, as shown in a side view in FIG. 2, the warpage rate is determined by arranging the printed wiring board 3 so that it has the maximum convexity with respect to the constant plate 2 and measuring the maximum distance 4 from the constant plate 1. It is shown by the ratio between the value and the length of the printed wiring board 3. On the other hand, as shown in a perspective view in FIG. 3, the twist rate is such that one corner on one side of the printed wiring board 3 is fixed and the diagonal corner on the other side is separated (lifted) from the constant plate 2. The distance 4'is measured and shown as a ratio of the measured value to the length of the printed wiring board 3.

As can be seen from the table, in the case of the printed wiring board according to the present invention, the warping and twisting phenomena are greatly reduced and improved as compared with the comparative example. It was possible to print solder with high precision and to perform pattern recognition with high precision in the mounting process by the mounting machine.

Example 2 A plain weave glass cloth having a thickness of 0.06 mm (60 lengths / 25 mm, 40 widths)
First, a prepreg was prepared by impregnating and adhering an epoxy resin to a glass cloth piece obtained by cutting the warp and the weft in the respective directions (25 mm). Then, a prepreg piece is obtained by cutting the prepreg so that the diagonal direction of the mesh formed by the warp and the weft of the glass cloth as a base material and the longitudinal direction of the cut piece are substantially aligned with each other. After placing and stacking foil circuit patterns,
Heating and pressurization was performed at 170 ° C and 30 kg / cm ² to obtain a prepreg piece with a circuit pattern. Then, four prepreg pieces with this circuit pattern were superposed with the directions of the warp and the weft of the glass cloth being matched, and 170 ° C,
Heating and pressurizing at 30 kg / cm ² , and further, cutting and external shape processing with the diagonal direction of the mesh formed by the warp and weft of the glass cloth and the longitudinal direction of the cut piece approximately matched, and a thickness of 0.4 mm Manufactured a printed wiring board for a memory card.

The warp rate and the twist rate of each of the 30 printed wiring boards manufactured as described above were measured in the same manner as in Example 1. The warp rate was 0 to 0.5% and the twist rate was 0 to 0.4. %, Which was suitable for mounting chip parts and the like.

It should be noted that the present invention is not limited to the above-exemplified structure, and modifications can be made without departing from the gist of the present invention.

[0021]

As is apparent from the above description and examples, the printed wiring board according to the present invention has a warp or a warp that causes a practical problem even when the printed wiring board has a thin structure of, for example, 0.6 mm or less. Almost no twisting phenomenon is observed, and it is possible to print and adhere to a predetermined position with high accuracy, such as cream solder. In other words, in the conventional printed wiring board that has a thin structure of about 0.6 mm or less, there are problems such as the difficulty of highly accurate printing and deposition of cream solder and the difficulty of pattern recognition in the mounting machine. Provided is a printed wiring board which is completely eliminated or reduced. Therefore, it can be said that the present invention greatly contributes to the configuration of the mounted circuit that is required to be light, thin, short, and small.

[Brief description of drawings]

FIG. 1 is a plan view partly schematically showing an arrangement mode of glass cloth in a printed wiring board according to the present invention.

FIG. 2 is a side view schematically showing an aspect of measuring a warp rate of a printed wiring board.

FIG. 3 is a perspective view schematically showing a mode of measuring a twist rate of a printed wiring board.

FIG. 4 is a plan view schematically showing a partial arrangement of glass cloth in a conventional printed wiring board.

[Explanation of symbols]

1a ... glass cloth mesh 1b ... glass cloth warp 1c ... glass cloth weft 2 ... regular plate 3 ... printed wiring board 4, 4 '... maximum distance from printed board 1 to printed wiring board

Claims (1)

[Claims] 1. A printed wiring board comprising a resin-impregnated composite board using glass cloth as a base material, wherein the glass cloth located at least on the outside is arranged along the outline cut surface in a substantially diagonal direction of the mesh. A printed wiring board characterized by comprising: