Copper board production process
Copper is an abbreviation for Eletcroless Plating Copper, also known as Plated Through Hole (PTH), which is an autocatalytic redox reaction. After two or more layers are drilled, the PTH process is performed.
The role of PTH: A thin layer of chemical copper is chemically deposited on a drilled, non-conductive cell wall substrate to serve as a substrate for later copper plating.
PTH process decomposition: alkaline degreasing → 2nd or 3rd countercurrent rinsing → roughening (microerosion) → 2nd countercurrent rinsing → prepreg → activation → 2nd countercurrent rinsing → debonding → 2nd countercurrent rinsing → copper sink → 2 Countercurrent rinsing → pickling
PTH detailed process commentary:
- Alkaline degreasing:
Removal of oil on the board surface, fingerprints, oxides, dust in the holes; make the wall of the hole positively charged by negative charge to facilitate the adsorption of colloidal palladium in the subsequent process; cleaning after degreasing must be conducted in strict accordance with the guidelines, using copper back-lighting test Conduct the test.
- Micro-etching:
Removing oxides on the surface of the board to roughen the surface of the board to ensure good adhesion between the subsequent copper sinking layer and the bottom copper of the substrate. The new copper surface has a very strong activity and can well adsorb colloidal palladium.
- Pre-dip:
The main purpose is to protect the palladium tank from contamination of the pre-treatment bath and prolong the service life of the palladium bath. The main components except for palladium chloride are the same as those of the palladium bath, which can effectively wet the pore walls and facilitate the subsequent activation of the activation solution into the pores. Sufficiently effective activation;
- Activation:
After the pre-treatment alkaline degreasing polarity adjustment, positively charged pore walls can effectively adsorb colloidal palladium particles that are sufficiently negatively charged to ensure the average, continuity, and compactness of subsequent copper sinks; thus degreasing and Activation is critical to the quality of subsequent copper sinks. Control points: time specified; standard stannous ion and chloride ion concentration; specific gravity, acidity, and temperature are also important and must be strictly controlled by work instructions.
- Solution:
Removal of colloidal tin ions from the colloidal particles on the outside of the colloidal palladium particles exposes the palladium nuclei in the colloidal particles to directly and effectively initiate the chemical copper deposition reaction. Experience has shown that using fluoboric acid as a debonding agent is a better choice.
- Copper sink:
The activation of the palladium core induces the autocatalytic reaction of the copper deposit, and the newly generated chemical copper and the reaction by-product hydrogen can all be used as the reaction catalyst to catalyze the reaction so that the copper deposition reaction continues. After processing by this step, a layer of chemical copper can be deposited on the surface of the plate or hole. During the process, the bath must be kept under normal air agitation to transform more soluble cupric.
The quality of the copper sinking process is directly related to the quality of the production circuit board. It is the main source process for the failure of the via and the short circuit. It is inconvenient for the visual inspection, and the latter process can only be conducted through a destructive experiment to perform the probabilistic screening. For a single PCB board for effective analysis and monitoring, so once the problem is bound to be a batch problem, even if the test can not be completed to eliminate, the final product causes great quality hidden dangers, can only be scrapped, so it is necessary to operate in strict accordance with the parameters of the job instructions .
Grace Zheng
Email: sales06@andwinpcb.com