An acid copper tank holds a whole panel load. If the bath drifts out of range and nobody notices, every panel in it can come out with thin copper in the barrels. The fault may hide until a microsection or bare-board electrical test, by which time the lot has moved through outer-layer imaging. The PCB manufacturers page ranks this first for bare-board plants, and most of its roots are people roots.
On the wet line, it looks like this
- A scheduled titration is missed on nights because the lab technician is covering the etcher as well.
- Brightener or copper sulphate is topped up by feel instead of from the analysis result.
- Rectifier current is raised for a rush lot and never set back.
- An operator new to the conveyorised etcher misses a speed change, and fine tracks come out undercut.
- A shift hands over without mentioning that a tank was dosed an hour earlier.
- The electroless copper line runs past its bath life because the replacement date sat in one engineer's notebook.
Each slip is small. Each can become voids, thin barrels, overetched tracks or blistering. Panels move on quickly, so the defect usually surfaces at the next stage, on somebody else's shift.
What a scrapped panel lot costs
First, the laminate, chemistry, drilling and imaging hours already spent on panels that are now scrap. Then the restart from inner layers, which wrecks the ship date. Quick-turn prototype buyers rarely forgive a missed date. The quieter cost falls on people. If the scrap review ends with blame pinned on one operator, the next operator who sees a strange pH or conductivity reading will say nothing.
Why baths keep drifting
Three causes repeat across fabrication plants. Bath knowledge sits with one or two process engineers, and nights run without them. Operators move from helper to running a tank alone with no recorded check, so nobody knows who can interpret a Hull cell panel or a titration figure. And wet lines often run long shifts with few breaks, while analysis and dosing are exactly the steps a tired person skips.
Where bath knowledge hides
- Acid copper: when to add brightener and leveller from the analysis, when carbon treatment is due, and how many ampere-hours a dummy plating run needs after it.
- Desmear and electroless lines: permanganate strength, palladium activator life, and the micro-etch rate that keeps adhesion without thinning inner-layer copper.
- Etching: specific gravity and chloride readings for the ammoniacal or cupric etchant, regeneration timing and conveyor speed per copper weight.
- Stripping: dry-film and tin strip loading, and the signs a tank is spent before tracks show residue.
- Rectifiers and anodes: current density per panel area, anode bag condition and when a soft anode needs replacing.
Each item is a judgement the engineer makes several times a week. Few of them are written in one place. Fewer still can be made by the night operator, who is the person standing at the tank when the reading turns.
Five routines for the plating and etching lines
- 1
Write a sign-off ladder for each wet line
Rungs from watching additions, to dosing under supervision, to running the tank alone, to reading an analysis and deciding a correction. A senior signs each rung after watching it done.
- 2
Put the bath file on paper
Tank limits, replenishment rules, anode and filter care, known defect causes such as voids or undercut, and what to do at three in the morning. The engineer writes it, and a second person proves it by running the tank from it.
- 3
Protect analysis and dosing in the shift plan
Titration and dosing times are fixed, with a named person, and cannot be dropped to cover another line.
- 4
Hand over each tank in writing
A short log per tank: last analysis, additions since, rectifier or conveyor changes, anything odd. The incoming operator signs it.
- 5
Review scrap for the condition first
Ask what allowed the slip, such as a missed break, an unsigned cover operator or a missing instruction, before asking who made it.
The ladder doubles as a training record and a roster tool. A shift planner can see who may run the plating tank alone tonight. The learning and development page for PCB makers covers building one. Shift length and breaks for continuous wet lines sit under attendance and shift patterns for PCB plants.
Checks for this week
- Who can run each plating and etching tank alone on every shift.
- The last scrapped lot on a wet line, and who was on shift when its load went in.
- How many engineers or technicians can state the acid copper limits without looking.
- Whether last week's night titrations happened at their scheduled times.
Face shields and titrations on one sheet
The tired operator who skips a titration may also skip the face shield and the apron. Treat protective gear checks and bath checks as one shift-start routine on the same sheet, with eye-wash and spill-kit checks beside them. Health and safety for PCB plants sets out that routine, and the wider electronics page compares wet-line risk with SMT and test floors.
