The shop is swamped and orders are pouring in. There just isn’t any time to clean the equipment or scrub a tank — right? WRONG — a critical mistake made by some PCB manufacturers is to wait until a process is out of control rather than perform regular preventive maintenance (PM) procedures throughout their operations.
This can result in sudden breakdowns, work stoppages and the need for rework, all of which results in loss of money, time and energy. Planning and managing downtime through routine PM procedures is a much smarter and more effective approach to ensuring high yields and on-time shipments.
PM should be addressed in all aspects of the manufacturing process. The first and most critical area of concern is imaging. Problems here can result in shorts and open circuits that may not be detected until the end of processing. A lot of wasted time, labor and chemistries along with the expense of rework, make mistakes in this area very costly.
In addition to the stringent environmental controls required in the imaging area, RBP recommends using high quality, anti-static film cleaner applied with a lint-free cloth to the film. The cleaner should be dispensed from a container whose properties are not attacked by the cleaner itself. Nylon is typically a good choice. We do not recommend a polyethylene based container, as the plastic can dissolve into the cleaner and cause hazing problems. Reuse of containers can cause buildup of the antistatic agent which can also result in hazing.
In the developing process, it is imperative that the equipment be properly maintained following manufacturers’ recommendations. It is especially important to check and periodically replace worn nozzles.
They reduce the spray pattern area and produce an irregular flow. This can leave areas with less solution impingement and cause uneven developing or stripping of panels. Stainless steel nozzles generally perform
much better than plastic.
It is also critical to clean equipment to prevent residue build-up. The use of proprietary developing chemicals with cleaning agents can help to combat carbonate and polymer residues. A dirty developer results in greater chemical usage, poor developing quality, erratic or reduced developing speed and the need for excessive rinsing to fully clean panels.
Bleed and Feed Systems must also be properly calibrated and continually monitored for residue buildup. A dirty system will not release the correct amount of replenishing solution at the right time, reducing the developing speed and effectiveness. It can also cause chemical imbalances such as too much carbonate or antifoam in the solution. These can build up quickly and create the need for additional cleaning. The possibility of an antifoam problem can be reduced by using a highly concentrated, high purity product that will not build up as quickly.
PM in the Resist Stripping Process should be handled much the same as with developing. Equipment needs careful cleaning, monitoring and maintenance.
The critical issue here is to ensure a good match between the stripper and the resist. This results in optimum loading capacity, strip time and particle size. Matching the particle size created by a particular stripper/ resist combination with the capability of the filtering system reduces the potential for clogged nozzles and incomplete
In the Tin/Lead Stripping Process a buildup of tin/lead residues can contribute to overheating, premature depletion of the stripping solution and excessive chemical consumption. This results in incomplete stripping and lead salt residues being deposited on panels. Again, PM is a necessary aspect of ensuring efficient processing.
It is apparent that many aspects of the PCB manufacturing process can benefit from a carefully planned PM program. Along with this, RBP also offers several other tips that can help prevent problems:
Following a few guidelines and committing to a PM program can lead to higher yields, less rework and more cost-effective operations. Contact RBP direct for assistance in setting up a preventive maintenance program that will work for you.