hole metallization process
What we are talking about here is a method that is close to the normal production process of the factory, but the production process is relatively simple, the equipment is extremely cheap, and it is easier to complete the operation under amateur conditions. Zhengzhou East Electronic Institution specially design and manufacture of the "east DM - 2120 type hole metallization case", the small cabinets, built-in hole metallization required for all chemicals, household utensils, phosphorus copper electrode, plating power supply (5 v, 20 a current adjustable), can do no more than 200 * 200 mm hole metallization process of multilayer rigid PCB, concrete operation process is as follows:
1, drilling: after complete heat transfer printing plate, drilling welding pad according to the design requirements, and drilling hole should be aligned with the center of the welding pad.
2. Prepreg: pour the prepreg solution into the tray and put it into the circuit board. Prepreg for 30 seconds to 1 minute.Its main function is to ensure that the hole wall is uniformly infiltrated and charge adjustment, and at the same time to prevent harmful impurities on the circuit board into the KH-22- L activation fluid, prepretreatment is mainly to protect the expensive activation fluid.
3. activation: take out multilayer rigid PCB directly and into the activation fluid after activation, the activation temperature should be controlled between 20 ℃, 40 ℃ with 5 to 7 minutes.If the room temperature is too low, the activated liquid should be heated. When activated, the circuit board should be slightly shaken to make the liquid flow through the circuit board evenly, so that each part of the circuit board can provide sufficient and effective catalytic activity core for subsequent electroless copper plating.
4. accelerate: put circuit boards in accelerating fluid, accelerate the reduction of 2-3 minutes, accelerate the liquid temperature should be controlled in 20 ℃-35 ℃,and slightly shake the board in the accelerator fluid.
5. Copper precipitation: put the circuit board into the copper precipitation solution, and add quantitative formaldehyde into the copper precipitation solution before copper precipitation. After the copper precipitation liquid begins to produce chemical reaction, put the circuit board into the copper precipitation liquid, the copper precipitation reaction should be carried out for 10-15 minutes. When sinking copper, keep shaking the board so that chemical copper can be evenly sunk in each place of the circuit board.
6. Electroplating: remove the oxidation layer of the circuit board with dilute sulfuric acid, and put the negative electrode into the electroplating box provided by dongming DM2120 for electroplating. Before electroplating, the electroplating power supply provided by dongming DM2120 shall be adjusted to the required current, and the electroplating current shall be calculated as 3A current per square decimeter. During electroplating, the electric machine in the electroplating box drives the driving mechanism to slightly shake the board. The pcb (phosphor copper plate) is placed in the white polyester cloth bag at both ends of the electroplating tank. During electroplating, the base plate is connected to the positive pole of the electroplating power supply and the printed board is connected to the negative pole of the power supply.The circuit board shall move back and forth between the copper plating solution and the distance from both sides of the substrate shall be controlled above 15cm. Copper plating time should be generally controlled in about 30 minutes, if you need to thicken the copper plating layer, the plating time can be appropriately extended.
7. Secondary transfer: after electroplating, align each welding pad of the top and bottom layers of the multilayer rigid PCB diagram with the corresponding through hole carefully, and then fix it with adhesive tape. Remove the transfer paper after the completion of the transfer, if there are graphics defects can be repaired with a marker pen.
8. Corrosion: before corrosion, use special T-1 coating to cover all metallized holes tightly, so as to prevent them from being corroded away. After coating can be sent to DM2110A corrosion machine to do corrosion. After etching, wash the T-1 coating on the through hole with T-2 solvent.In this way, a complete double-sided printed circuit board is successfully produced, and the quality of the process can fully meet the experiment requirements.