How to Test PCB Soldermask?
Soldermask is widely used on printed circuit boards. After soldermask process sometimes you need to inspect whether there is any problem of solder resist. This article will introduce how to test PCB soldermask.
Soldermask Test
1. Solder quality test: direct visual inspections and then with 1.5 to 10 times magnifier.
2. Adhesion (tape test): According to IPC-TM-650 / TM2.4.28.1 Standard, testing peel strength by 3M tape.
3. Hardness Test: According to IPC-SM-840C 3.5.1 / TM 2.4.27.2 Standard, draw an inch long line on a board after the baking with a pencil hardness (JIS standard) and using about one Newton force at an angle of 45 ℃. Use an eraser to remove the toner and check whether there are scratches. It is ok when the copper are not exposed.
4. Acid and alkali resistance test: according to IPC-SM-840C 3.6.1.1 standard, take two 6PNL silver test panels of each dipped into 10% HCl, 10% H2SO4, 10% NaOH solution for 30 mins. Then take another two 6PNL OSP panels immersed in 10% HCl, 10% H2SO4, 10% NaOH solution for 60mins. Then inspect whether the surface blistering, peeling, discoloration and other situations occur.
5. Solvent resistance: according to IPC-SM-840C 3.6.1.1 standard, clean coating surface, then inspect whether the surface blistering, peeling, discoloration and other situations occur.
6. High temperature resistance
1）Welding: according to IPC-SM-840C 3.7 standard
2）Soldering resistance：according to IPC-SM-840C 3.7.2 standard
3）Solder heat resistance
4）Tin drift test: Temperature: 260 ℃, time 10S, the test three times
7．Soldermask ink thickness: take silver and OSP board to do a number of sections, measure the ink thickness at different locations.
8．Undercu: To measure whether the deepness of undercut is within 1.2mil.
9．Thermal shock resistance：According to IPC-SM-840C 3.9.3/TM2.6.7.1 standard, H degree, 65~125°C，100times cycling，inspect whether the surface blistering, peeling, discoloration.
10. Solder Dam Test
Design 2mil, 3mil, 4mil, 5mil solder dam on the negative film (according to the various process capabilities). After development, baking, FQC, check whether it is off.
