Maybe we will wonder, the substrate of the circuit board only has copper foil on both sides, and the insulating layer in the middle, so they do not need to conduct between the two sides of the circuit board or multi-layer lines? How can the two sides of the wire be connected so that the current flows smoothly?
Maybe we will wonder, the substrate of the circuit board only has copper foil on both sides, and the insulating layer in the middle, so they do not need to conduct between the two sides of the circuit board or multi-layer lines? How can the two sides of the wire be connected so that the current flows smoothly?
See the circuit board manufacturers for you to analyze this magic process - copper (PTH).
Copper precipitation is short for Eletcroless Plating Copper, also called Plated Through hole, short for PTH, is an autocatalytic REDOX reaction. The PTH process is performed after drilling of two or more layers.
Role of PTH: a thin layer of chemical copper is deposited chemically on a non-conductive hole wall substrate that has been drilled to serve as a base for subsequent copper plating.
PTH process decomposition: alkaline oil removal → two or three stage counter-current rinse → coarsening (micro-erosion)→ two stage counter-current rinse → preleaching → activation → two stage counter-current rinse → degelling → two stage counter-current rinse → copper precipitation → two stage counter-current rinse → leaching acid
PTH detailed process explanation:
1. Alkaline oil removal: remove surface oil, fingerprints, oxide, dust in the hole; The hole wall is adjusted from negative charge to positive charge to facilitate the adsorption of colloidal palladium in the following process. After oil removal, cleaning should be carried out in strict accordance with the guidelines, and copper backlight test should be used for detection.
2. Micro corrosion: remove the oxide on the surface of the plate, coarser the surface of the plate, to ensure that there is a good binding force between the subsequent copper deposition layer and the base material bottom copper; The new copper surface has strong activity and can adsorb colloidal palladium well.
3. Preleaching: mainly to protect the palladium tank from the pollution of the pre-treatment tank liquid, prolong the service life of the palladium tank, the main components except palladium chloride and palladium tank composition, can effectively wet the hole wall, facilitate the subsequent activation liquid into the hole in time for effective activation;
4. Activation: after pre-treatment alkaline oil removal polarity adjustment, the positively charged hole wall can effectively absorb enough colloidal palladium particles with negative charge, in order to ensure the uniformity, continuity and density of subsequent copper precipitation; Therefore, deoiling and activation are very important to the quality of subsequent copper precipitation. Control points: set time; Standard stannous and chloride ion concentrations; Specific gravity, acidity and temperature are also important and should be strictly controlled according to the work instructions.
5. Degumming: remove the stannous ions surrounding colloidal palladium particles, expose the palladium nucleus in colloidal particles, and start the chemical precipitation reaction with direct and effective catalysis. Experience shows that it is a better choice to use fluoroborate as degumming agent.
6. Copper precipitation: through the activation of palladium nucleus to induce the chemical copper precipitation autocatalytic reaction, the new chemical copper and the reaction by-products can be used as reaction catalyst to catalyze the reaction, so that the copper precipitation reaction continues. After this process, a layer of chemical copper can be deposited on the surface or hole wall. During the process, the tank liquid should keep normal air agitation to convert more soluble divalent copper.
Sink copper process quality is directly related to the quality of the production of circuit boards, is via impassability, open the main source of short-circuit unhealthy working procedure, and it is not convenient for visual inspection, after the process can only through the destructive experiment of probabilistic screening, not for a single for effective analysis and monitoring, so once the problems must be batch problem, even if the test can't complete to eliminate, The final products cause great quality hidden trouble and can only be scrapped in batches, so it is necessary to operate strictly in accordance with the parameters of the operation instructions.
