Boards per Panel Arithmetic before Anyone Argues Unit Price
Calculate usable circuits per master production panel and subtract outer border clearances before negotiating bare board unit prices with fabricators.
Chemical Spray Etching
Subtractive Process
Controlled removal of unprotected copper occurs through the pressurized application of acidic or alkaline solutions. Modern chemical spray etching utilizes high pressure nozzles to deliver a constant flow of etchant to the exposed metal on a panel. This method ensures that fresh chemistry reaches the surface while spent byproduct is cleared away.
Pattern Definition
Precision nozzles arranged in a conveyorized chamber provide uniform coverage across the entire width of the production panel. Adjusting the spray pressure and the conveyor speed allows for fine control over the etch factor and trace width. Fine lines require a high etch factor to maintain vertical sidewalls and prevent undercutting of the photoresist.
Regeneration Cycle
Chemical balance within the etching system is maintained by automated dosing units that monitor ORP and density. Spent liquor is continuously drawn off and replaced with fresh etchant or regenerator to keep the etch rate constant. Variations in copper concentration or pH level can lead to uneven metal removal and electrical shorts.
The process stops being effective when the solution reaches a saturation point where the chemistry can no longer hold dissolved copper. Proper filtration removes particulates that might clog the spray headers or damage the pump seals.