The strategy of company for establishing and maintaining long-term working relationships is through creating and monitoring mutual performance expect ions and measurements. Performance metrics, constructive feedback, as well as prompt corrective action by the supplier and by customer are fundamental to achieving continuous process improvement.
Last article I mentioned that my company applied the metal dome without dimple as keypad contact solution just like the cell phone but we met keypad press insensitive issue. Now we had solved the problem by adding the dimple back to the metal dome and still reach 1,000,000 times of finger press cycle lifetime.
We did some failure analysis and found the keypad insensitive defect was caused by two major issues. One is the foreign contamination, include dust and fiber, that I mentioned at last article. Another one is the oxidation show on the immersion gold finished on the ENIG board pads.
We found the oxidation particles look like the chemical of “P” exuded from base material of PCB. The “P” is one of the major element for the ENIG fabrication process. So we only can control less “P” but can’t remove it from the board.
Polymer Thick Film (PTF) flexible circuits are manufactured by screen-printing conductive ink onto flexible substrates such as PET (Polyethylene terephthalate). It can be single layer or multi-layers circuit by further screen-printing dielectric materials as insulating layer and applying through-hole technologies.
The PTF uses silkscreen to print the silver and carbon combination conductive inks on PET substitute to reach low cost purpose as compare with FPC. Unfortunately, the screen-printing has some ability limits. Especially for small trace width and small space.
Applying a pressure and contacting on the soldering target is necessary to melt the solder and insure that components stay in place during cooling.
The electronic industry grows quickly. Each vendor takes responsible to his own component only to make it good and low cost. Take a flashlight manufacturer as example. There are bulb, wires, switch, spring, and plastic or metal housing make up the flashlight. The manufacturer buys all the sub-components from each supplier and assembles them together to fabricate the flashlight then sell to end-user.
All the sub-components are delivery by air, ocean, or truck to destination. It is important to prevent the delivery parts without damage during transferring. Most of the packaging uses corrugated paper carton and cardboard to hold inside components and prevent it from damage by falling or throwing down by porter or carrier.
Many FPCB designer are not familiar with the manufacturer and bring lot of quality issue after mass production. Here I summary some of the design notices for the flex cable (FPCB) manufacturing ability to prevent future quality fail.
