JP2001284491A - Plastic board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic board that is prevented from deforming, i.e., warping, etc., by reducing a density difference of metal wirings between the front and the resin sides. SOLUTION: The plastic board 10 has a wiring pattern 20 on the front plane 11 of the board and round patterns 40 on the rear plane 12 of the board, which are used for mounting. The rear plane 12 of the base plate 10 is provided with dummy patterns 50 that has a metal wiring density equivalent to the metal wiring density difference between wiring on the front plane 11 and that on the rear plane 12, and the plastic board 10 is prevented from deforming caused by the density difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic substrate provided with a wiring pattern and a plated lead on a front surface and a land pattern on a back surface for mounting on a board.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 2A and 2B, a plastic substrate used for a small electronic device uses a plastic ball grid array (PBGA) and is disposed on the surface 110 side of the plastic substrate 100. The wiring pattern 200 is disposed, and a plated lead 300 for plating the wiring pattern 200 is provided from the through hole 210 provided at the end of the wiring pattern 200 to the periphery of the surface 110. On the back surface 120 side of the plastic substrate 100, a land pattern 400 to be mounted on the board is arranged so as to be connected to the through hole 210. The plating process for the land pattern 400 is performed by sharing the plating lead 300 provided on the front surface 110 of the plastic substrate 100 and connected to the wiring pattern 200, and connecting the wiring pattern 200 on the front surface 110 and the land pattern 400 on the back surface 120. Through plating.

[0003]

However, in the above-mentioned conventional method, the wiring pattern 200 on the front surface 110 and the land pattern 400 on the back surface 120 are almost balanced in metal wiring density.
Since 00 is arranged, the metal wiring density on the front surface 110 side becomes higher than the rear surface 120 side by the plating lead wire 300. Therefore, the surface 11 of the plastic substrate 100
There is a problem that a metal wiring density difference occurs between the 0 side and the back surface 120 side, and the peripheral end of the plastic substrate 100 warps and deforms due to a difference in thermal expansion between the metal and the resin (plastic), thereby lowering the yield. there were. The present invention has been made in view of such circumstances, and has as its object to provide a plastic substrate that reduces a difference in metal wiring density between a front surface side and a rear surface side and prevents deformation such as warpage.

[0004]

According to the present invention, there is provided a plastic substrate provided with a wiring pattern on a surface thereof.
A plastic substrate provided with a land pattern for mounting on a board on a back surface, and a dummy pattern having a metal wiring density corresponding to a metal wiring density difference between a front surface side wiring and a back side wiring on a back surface of the plastic substrate, This prevents deformation of the plastic substrate caused by a difference in metal wiring density. With such a configuration, the difference in the metal wiring density between the front side and the back side of the plastic substrate is reduced by the dummy pattern, so that the difference in thermal expansion between the front side and the back side is reduced, and deformation such as warpage of the plastic substrate is reduced. This can be prevented. In the plastic substrate according to the present invention, the dummy pattern provided on the back surface of the plastic substrate may be provided at a position corresponding to the plated lead of the wiring pattern provided on the front surface. Conventionally, the position of the back side corresponding to the plating lead wire on the front side was blank, so the difference in metal wiring density between the front side and the back side was large,
In this case, since the dummy pattern having the same metal wiring density as the plating lead wire is provided at a position corresponding to the plating lead wire, the dummy pattern compensates for the metal wiring density difference between the front side and the back side of the plastic substrate. This makes it possible to effectively reduce the difference in thermal expansion between the front side and the back side of the plastic substrate.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. Here, FIGS. 1 (A) and 1 (B)
FIG. 2 is a partially enlarged front view of a front surface and a back surface of a plastic substrate according to one embodiment of the present invention.

As shown in FIGS. 1A and 1B, a plastic substrate 10 according to an embodiment of the present invention is made of, for example, epoxy resin, and has a wiring pattern 20 formed on a surface 11 thereof by a precision printed wiring technique. In order to apply a plating process to the wiring pattern 20, a plating lead 30 extending from the through hole 21 provided at the end of the wiring pattern 20 to the periphery of the plastic substrate 10 is provided. A land pattern 40 for mounting on a board of an electronic device is provided on the back surface 12 of the plastic substrate 10, and is electrically connected to the wiring pattern 20 on the front surface 11 by a through hole 21. Also,
The peripheral portion of the back surface 12 of the plastic substrate 10 has
1, a dummy pattern 50 having a metal wiring density substantially equivalent to the metal wiring density of the plating lead wire 30 is provided at a position corresponding to the plating lead wire 30, and the dummy pattern 50 is in contact with the land pattern 40 and the through hole 21. It is arranged not to be.

With such a configuration, the difference in metal wiring density between the wiring on the front surface 11 and the wiring on the back surface 12 caused by the plated lead 30 can be compensated for by the dummy pattern 50. Therefore, the metal wiring densities on the front surface 11 side and the back surface 12 side are balanced, the difference in thermal expansion between the front surface 11 side and the back surface 12 side of the plastic substrate 10 is reduced, and deformation such as warpage of the plastic substrate 10 is prevented. In addition,
A dummy pattern 50 is formed on the back surface 12 of the plastic substrate 10.
10 samples each with and without
For 000 pieces, the warpage failure rate at the substrate end was examined. The warpage after the temperature cycle test is 0.05 / 25.4mm
The MIL883D standard that passed the following was adopted. As a result, the defect rate in the case where the dummy pattern 50 is provided is 0.
Although it was less than 01%, the defect rate when the dummy pattern 50 was not provided was 0.1 to 1.0%. From this result, by providing the dummy pattern 50 on the back surface 12 of the plastic substrate 10, the plastic substrate 10
It was confirmed that the effect of reducing the warpage was sufficient.

[0008]

According to the first and second aspects of the present invention, since the dummy pattern is provided on the back surface of the plastic substrate, the difference in the metal wiring density between the front side and the back side of the plastic substrate is reduced by the dummy pattern. Deformation such as warpage is prevented. In particular,
In the plastic substrate according to the second aspect, the dummy pattern provided on the back surface of the plastic substrate is provided at a position corresponding to the plating lead line of the wiring pattern provided on the front surface. Compared to the case where there is no dummy pattern at the corresponding back side position, the difference in metal wiring density between the front side and the back side is smaller, and the difference in thermal expansion between the front side and the back side of the plastic substrate can be effectively reduced. It becomes possible.

[Brief description of the drawings]

FIGS. 1A and 1B are partially enlarged front views of a front surface and a back surface of a plastic substrate according to an embodiment of the present invention, respectively.

FIGS. 2A and 2B are partially enlarged front views of a front surface and a back surface of a conventional plastic substrate, respectively.

[Explanation of symbols]

10: plastic substrate, 11: front surface, 12: back surface, 2
0: wiring pattern, 21: through hole, 30: plating lead wire, 40: land pattern, 50: dummy pattern

Claims (2)

[Claims] 1. A plastic substrate provided with a wiring pattern on a front surface and a land pattern on a back surface for mounting on a board, wherein a metal wiring density difference between a front surface wiring and a back surface wiring on the back surface of the plastic substrate. A plastic pattern provided with a dummy pattern having a metal wiring density corresponding to the above, and preventing deformation of the plastic substrate caused by the metal wiring density difference. 2. The plastic substrate according to claim 1, wherein the dummy pattern provided on the back surface is provided at a position corresponding to a plated lead of a wiring pattern provided on the front surface.