How can I make a Flat Flex Cable (FFC) Zero Insertion Force (ZIF) connector resistant to environmental contamination?
I have a microwave over my stove. Every few months, the keypad begins to malfunction and register key presses without human interference. Naturally, it's one of the buttons that will start the microwave. After a while, the keypad will become non-responsive. The keypad in this unit is a sealed membrane unit with a single FFC. Nothing in the keypad requires active electronics, and the number of contacts and buttons) strongly suggests a standard sampled keypad switch matrix.
I'm pretty sure a row line adjacent to a column line is getting a low enough resistance to register as a button press. Removing the FFC from the ZIF connector and re-inserting it will fix the problem for about a day. Cleaning the FFC and flushing the ZIF connector with isopropyl alchohol will fix the problem for a few months. Considering that the electronics compartment isn't well sealed, I believe steam and other cooking byproducts are making their way into the ZIF connector and causing measurable leakage between pins.
The FFC termination is single-sided with a pitch of about 1.25mm/50 mil. The microwave is a Samsung, but I don't think that's relevant to the solution.
How can I improve the environmental resistance of a FFC connection? Looking at the connector, it seems like there is an unsealed path on both the top and bottom of the connector. My priorities (in order) are:
- Don't buy a new microwave - the old one works*
- Make the fix permanent so I'm not constantly disassembling the microwave
- Don't make the connection permanent (e.g. soldering the FFC to the board)