Analysis and solutions of 5 problems in FPC board production!

1. Bubble

between the lines of the FPC printed board or the side of a single line, there will be bubbles after development. The main reason: the bubbles between two or more lines are mainly due to the narrow line spacing and the high line, which makes the solder resist cannot be printed on the substrate during screen printing, resulting in the existence of air or moisture between the solder resist and the substrate. When the gas is heated and expands during curing and exposure, the single line is mainly caused by the line being too high. When the scraper is in contact with the line, the line is too high, and the angle between the scraper and the line increases, so that the solder resist cannot be printed to the root of the line. There is gas between the side of the root of the line and the solder mask layer, and bubbles are generated after heating. The solutions are: when screen printing, visually check whether the screen printing material is completely printed on the substrate and the side wall of the line, and strictly control the current during electroplating

2. Solder mask in the hole

The reason for this is that the paper was not printed in time during screen printing in the soft board factory, resulting in too much residual ink accumulated on the screen, and the residual ink was printed into the hole under the pressure of the scraper. The solution is to print the paper in time, and screen mesh. If the number is too low, it will also cause solder resistance in the holes. Use a high-mesh screen for plate making. If the viscosity of the printing material is too low, use a printing material with a high viscosity. The angle of the squeegee screen printing is large, and the squeegee screen printing angle is appropriately adjusted. , the blade edge of the scraper becomes round, and the blade edge of the scraper is sharpened

3. Jump printing is also called flying white

Mainly due to the excessive electroplating current and the thick coating, the graphic lines are too high. When the printed board of the flexible circuit board is screen printed, because the squeegee knife and the screen printing frame are screen printed at a certain angle, the lines on both sides of the line are too high. If it is high, no ink will be placed: another reason for skipping printing is that there is a gap in the squeegee blade, and no ink can be placed in the gap, causing skipping printing. The main solutions are to control the electroplating current and check whether the scraper blade has a gap.

4. Oxidation

There are signs of blackening on the copper foil lines under the solder mask layer of the FPC printed board. The reasons are that the water is not dried after wiping the board, and the surface of the printed board is splashed with liquid or touched by hand before printing the solder mask. The method is to visually check whether the copper foil on both sides of the printed board is oxidized during screen printing.

5. The graphics have pinholes

The reason is that there is dirt on the photographic plate, so that the part of the printed plate that should see light during the exposure process does not see light, resulting in pinholes in the pattern. The solution is to check the cleanliness of the photographic plate frequently during the exposure process.

Any FPC request, email to [email protected]