Recommended connector for touchscreen cable?
Hello HNS,
The FPC for the touch screen must be soldered to your PCB. We are currently discussing adding a stiffener to our FPC to allow it to plug into a ZIF connector. Currently it is too thin.
We haven't been asked to measure the resistance of the touch screen before, however we have samples readily available from our distributor, Mouser Electronics for you to evaluate. They currently have 41 pcs in stock.
Regards,
Trevor
But soldering the FPC is a clear "no go". Unfortunately, it makes it impossible to use it, since we can't do any field-service and replace a broken one (people have a tendency to break the display glass), if the broken module has to be unsoldered and another one soldered.
The resistance is important to gauge the sensitivity, speed and precision depending on the touch screen controller chip and how the A/D system works. When there is no data sheet or specification for the touch screen, I wonder a little how quality control can be done in production without knowing its key parameters.
Hi HNS,
Please contact me offline about using the FPC with a stiffener. We aren't there yet, but should be shortly.
No problem for me to ask about the resistance of the touch screen, as I mentioned we just haven't been asked before so it is not something we publish as a norm/standard.
The terminal resistance of the touch screen is Rx-x: 100-1000 ohm, Ry-y: 100-1000 ohm (measuring at the FPC pin).
Thanks for the info about the resistance! I think the value is fine. It is needed for the TSC2007 controller to detect the pressure.
Regarding a touch screen zif connector, I wonder if a Molex 52271-0469 could fit.
How is mounting to a PCB intended? I guess that the module is glued to a (copper) side of the PCB by removing the protection from the adhesive strips. The display ffc will be bent behind the display. But I wonder if there is enough room on the PCB for the zif connector on the display side. Or should there be a hole in the PCB so that the ffc is connected on the opposite side of the PCB?
Since the touch screen FPC doesn't have a stiffener, I don't believe any ZIF connector will work, including he Molex part. I didn't see the thickness dimension on the Molex spec for the recommended FPC, did you? I puled the spec from Digi-Key's website. We've done some trial fitting with other suppliers and the stiffener is needed to have the clamp of the ZIF connector hold down the FPC.
Generally the mounting of the module is accomplished by making a holder in your front housing/case that accepts the TFT and double sided adhesive (usually 3M or similar) on the back of the TFT to your PCB. The mounting of the ZIF connector for the TFT depends on your board layout and where you have the most available room. From the feedback I've heard, most ZIF connectors are going on the opposite side the TFT and the FPC is being folded over. You' are correct this can be done with a hole or cut out in the board. I've also talked with other customers where they put a notch at the edge of the board for the FPC to fold over. I seem to recall that PCB houses charge a little more for either the hole or notch, so please explore that with your PCB supplier.
