PCB Technical - How to prevent the high frequency circuit board solder mask from falling off

Usually we will see a green film on the surface of the double-layer high-frequency circuit board. In fact, this is a double-layer high frequency circuit board solder mask ink. It is printed on the double-layer high frequency circuit board to prevent soldering, so it is also called solder mask ink. However, when processing high-frequency circuit boards, you will encounter such problems from time to time. One of the most common problems is the drop of solder mask on double-layer high-frequency circuit boards. Then, what causes the ink on the high-frequency circuit board/Rogers circuit board to fall and how to prevent this, then how to prevent the solder mask from losing the oil, the editor of Shenzhen Mingchengxin Circuit will introduce in detail below.

Prevent the solder mask from dropping oil

1. Regularly maintain the pretreatment machine and check whether the pretreatment brush roller and absorbent sponge are worn or not;

2. During the production of high-frequency circuit boards/Rogers circuit boards, when employees stir the solder mask, they must enter the ground to add oil and water in accordance with the requirements of the process specifications, and the foreman will review and supervise them;

3. Before you need to bake the solder mask, please confirm the setting temperature and time of the bake board, and then bake after the parameters are set. The foreman is responsible for the complete record of the parameters, and the QA will check it;

4. When preprocessing the high-frequency circuit board/Rogers circuit board, it is necessary to perform a solder mask treatment to first confirm whether the production parameters (speed, drying section temperature) of the pretreatment are consistent with the process requirements, and the parameters are Production before adjustment to 0K;

5. When the solder mask process enters the ground for solder mask printing, the first board must be measured with a solder mask thickness meter, and the machine must be adjusted according to its thickness. After meeting the requirements of the ERP directive, the thickness of the solder mask can be produced;

6. For the circuit boards that have been pre-processed in the standard solder mask process, the solder mask printing must be completed within 2 hours, and the high-frequency circuit boards that have not been printed for more than 2 hours must be reprocessed before printing. (The pre-processed high-frequency circuit boards are time-recorded by the solder mask process).

Reasons for the peeling off of the solder mask on the high frequency circuit board/Rogers circuit board

1. The high-frequency circuit board/Rogers circuit board solder mask ink is too thin. After the gold is deposited, the solder mask will fall off due to the corrosion of the gold solution on the solder mask;

2. After the solder mask is printed, the baking time and temperature are insufficient, resulting in the solder mask not being completely cured. After the high temperature impact of the client's furnace, the solder mask will bubble;

3. When stirring the solder mask, add too much boiling oil and water. When spraying tin or passing through a furnace, the ink between the vias will evaporate and expand, causing the solder mask to fall and blisters;

4. After the solder mask has been pre-treated, if it is placed in the solder mask room for too long, it will cause a single point of oxidation on the copper surface, resulting in poor adhesion between the solder mask and the double-layer circuit board surface, and solder mask will appear after baking. Blistering

5. The pre-treatment of solder mask is not effective in processing high-frequency circuit boards. There is a single point of oxidation on the copper surface, resulting in poor bonding between the solder mask and the board surface, and solder mask blistering after baking (high-frequency circuit board/Rogers Insufficient drying of the circuit board causes moisture in the via holes, which leads to oxidation of the copper surface at the edge of the hole, which makes the bonding force between the solder mask and the copper surface poor, and causes solder mask to occur after baking or when passing through the furnace. Bubble).