Effective Measures to Reduce The Cost of Printed Circuit Board Manufacturing (2)

4.The influence of the ratio of the line width to the gap width of the conductor pattern on the cost.

If the width of the conductive pattern in the printed circuit board is represented by L, and the width of the gap between the conductive patterns is represented by S, then LIS represents the ratio of the width of the conductive strip to the width of the gap. As this ratio decreases, the production yield of printed circuit boards will decrease sharply, and the cost will also increase. This phenomenon is more obvious when the circuit density is relatively high. Therefore, the value of LIS must not be reduced arbitrarily.

5.The impact of the diameter of the through hole on the cost.

In the case of drilling a printed circuit board with a drill, when the hole diameter is lower than a certain value, the drilling depth of the drill will be shortened sharply. That is to say, the same hole is punched. When drilling a hole with a small diameter, the drill needs to be withdrawn for heat dissipation many times, which will reduce the production efficiency and increase the cost. Therefore, do not arbitrarily reduce the diameter of the through-holes; but also reduce the number of through-holes as much as possible.

6. Fill the through hole with silver paste.

For the through holes of double-sided printed circuit boards, instead of copper plating to achieve the connection of the two-sided circuits, the method of filling the through holes with silver paste can also reduce the cost of double-sided printed circuit boards. This method is generally used for common phenolic resin paperboard with double-sided copper coating. In this method, the surface of common phenolic resin paperboard coated with copper on both sides is first cleaned, and then a resist pattern is printed on both sides by screen printing. After etching, a conductor pattern is formed. The holes are filled with silver paste. In order for the silver paste to be in good contact with the conductor patterns on both sides, the silver paste should have a through hole, and the diameter of the silver paste pattern in the bulged part is larger than the diameter of the through hole. In order to block the migration of silver ions, a cover layer was applied by screen printing on the surface of the protruding part of the silver paste. Then, the solder mask pattern and the isolation pattern are screen printed on both sides, and the screw holes for fixing the printed circuit board are punched or drilled, and the shape is processed. Finally, through the inspection, the double-sided printed circuit board with the through holes filled with silver paste is completed.

Generally speaking, such double-sided printed wiring boards with through-holes filled with silver paste are not suitable for high-reliability circuits due to the base material. In addition, since there are a large number of non-conductive materials in the silver paste besides the conductive substances, the conductivity of the silver paste is not as good as that of the copper foil, and we should also pay attention.