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★ Clean hole treatment: The graphite and carbon black in the PCBA black holeization solution are negatively charged, and repel the negative charge on the resin surface of the hole wall after drilling, and cannot be electrostatically adsorbed, which directly affects the adsorption effect of graphite carbon black. By adjusting the positive charge of the regulator, the negative charge on the resin surface can be neutralized and even the pore wall resin can be given a positive charge to facilitate the adsorption of graphite and carbon black.
★ Water cleaning: clean the excess residual liquid in the hole and on the surface.
★ PCBA black hole treatment: through physical adsorption, a uniform and fine conductive layer of graphite carbon black is adsorbed on the surface of the hole wall substrate.
★ Water cleaning: clean the excess residual liquid in the hole and on the surface.
★ Drying: In order to remove the moisture in the adsorption layer, short-time high-temperature and long-term low-temperature treatment can be used to improve the adhesion between the graphite carbon black and the surface of the pore wall substrate.
★ Micro-etching treatment: Firstly, it is treated with alkali metal boron salt solution to make the graphite and carbon black layer appear micro-swelling, forming microporous channels. This is because in the process of PCBA black holeization, graphite carbon black is not only adsorbed on the hole wall, but also adsorbed on the inner copper ring and the surface copper layer of the substrate. In order to ensure a good combination of electroplated copper and base copper, The graphite carbon black on the copper must be removed. For this reason, only the graphite and carbon black layers generate microporous channels that can be removed by the etching solution. Because the etching solution etches to the copper layer through the microporous channels generated by the graphite and carbon black layer, and the copper surface is microetched by about 1-2μm, the graphite carbon black on the copper is removed because there is no foothold. The graphite and carbon black on the non-conductor substrate of the hole wall remain in the original state, providing a good conductive layer for direct electroplating.
★ Inspection: Use inspection mirror or stereo microscope to check whether the coating on the inner surface of the hole is complete and even.
★ Electroplated copper: charged into the tank, and used impulse current to ensure that the conductive plating is completely covered.
3.6 Matters needing attention
(1) The black hole solution tank is equipped with a circulating stirring device. When using a horizontal production line, it is best to use an ultrasonic method, or a water jet spray method.
(2) Drying by dipping method can use oven or drying tunnel, the temperature is 80~85 degree Celsius, and the time is 2~3 minutes. The horizontal type should be equipped with hot and cold air drying section. If the processed special material is not resistant to high temperature, it should be dried at 60~65 degree Celsius for 8~10 minutes; if black hole liquid is used to make FR-4 or PTFE and CEM-3 boards with a thickness of more than 1.0mm, The drying temperature should be set at 95 degree Celsius for 2 minutes.
(3)PCBA black hole liquid should be tested for solidity and PH value on a regular basis. Under normal conditions of use, the fixed line points will not decrease. If the fixed line points decrease, use Miele's MN-701B for adjustment. When the pH value of the black hole liquid is lower than 9.5, the activity of the solution is correspondingly reduced, and it must be adjusted in place with reagent ammonia.
