Immersion copper is the abbreviation of electroless copper plating, also known as plated through hole, abbreviated as PTH, which refers to depositing a thin layer of chemical copper by chemical method on the non-conductive hole wall substrate that has been drilled, as the following Electroplated copper substrate. So, what are the processes of the PCB circuit board sinking copper process? Let's take a look with the editor:
一. Decomposition of PTH process:
Alkaline degreasing→two or three countercurrent rinsing→coarsening (micro-etching)→secondary countercurrent rinsing→presoaking→activation→secondary countercurrent rinsing→degumming→secondary countercurrent rinsing→copper sinking→secondary countercurrent rinsing→ pickling.
二. PTH detailed process explanation:
1. Alkaline degreasing: remove oil, fingerprints, oxides, and dust on the surface of the board; adjust the hole wall from negative charge to positive charge, which is convenient for the adsorption of colloidal palladium in the subsequent process; after degreasing, strictly follow the guidelines Clean and detect with copper sinking backlight test.
2. Micro-etching: remove oxides on the surface of the board, roughen the surface of the board, and ensure good bonding between the subsequent copper deposition layer and the bottom copper of the substrate.
3. Pre-soaking: It is mainly to protect the palladium tank from the pollution of the pre-treatment tank liquid, prolong the service life of the palladium tank, and facilitate the subsequent activation solution to enter the hole in time for sufficient and effective activation.
4. Activation: after pre-treatment alkaline degreasing polarity adjustment, the positively charged pore wall can effectively absorb enough negatively charged colloidal palladium particles to ensure the uniformity, continuity and density of subsequent copper deposition.
5. Degelation: remove the stannous ions surrounded by the colloidal palladium particles, so that the palladium nuclei in the colloidal particles are exposed, so as to directly and effectively catalyze and start the electroless copper precipitation reaction.
6. Copper deposition: The activation of the palladium nucleus induces the self-catalytic reaction of electroless copper deposition. Both the new chemical copper and the reaction by-product hydrogen can be used as reaction catalysts to catalyze the reaction, so that the copper deposition reaction continues continuously. During the process, the bath should be kept under normal air stirring to convert more soluble divalent copper.
The quality star of the copper sinking process is directly related to the quality of the production circuit board, and it is the main source of the poor opening and short circuit of the via hole. Therefore, once a problem occurs, it must be a batch problem, which will eventually cause a great quality hidden danger to the product. Only batch Scrap, so operate in strict accordance with the parameters of the work instructions.
