Capacitive Touch Panel Fine Tune Procedures & Tips
Tuning capacitive touch panels (CTP) can be tricky sometimes because CTP needs tiny capacitance differences for its operation. Most customers will like CTP to be sensitive which the user can get good touch experience without punching on the touch with frustration. But when a CTP is sensitive to the touch, it will also sensitive to the surrounding noises or interferences. We had an experience that our engineers tested a CTP very well in factory but the customer complained that he could produce a lot of wrong operations or even couldn’t make it work. After several conference calls and trials, the possible root causes are:
1) Dirty power supplies. The customer used wall outlet plugging adapters which produced noises and dirty (unstable) voltage. After changing to more stable power supply, the performance improved; Please see the link for how CTP Performance affected by Power Supply:
2) The customer engineers tested the CTP on a stainless-steel table. For some reason, the table generated some level capacitance which interfered with the performance. After gaping the CTP and table for several mm, the performance was good.
In order to make CTP tuning procedure more smoothly, we recommend the following procedures and tips.
- We will send you the CTP samples already tuned well from factory.
- Please try to use stable power supply and try to avoid any unexpected capacitive or electro-magnetic or even ESD interferes.
- If the interference sources come from main board which can’t be avoided. We can design in a shielding ITO layer at the backside of CTP. We can also design a mesh or solid copper coating on FPC (flex) or even put a EMI shielding tape on FPC. But it will be great to design FPC as short as possible to avoid any unexpected headache.
- If the interference comes from human body, it will be better to design spacing between the housing/bezels and CTP. For our experience, if using glass as spacing, at least 10mm, if using plastic, it is better to be bigger than 10/3=3.5mm; if using air gap, it will better to be bigger than 10/7=1.5mm gap. If stronger interference sources, it will be better bigger gaps or even using a shielding layer (tapes). The shielding tapes are normally made of meshed metal wires.
- If the above measures taken and you still find the touch performance not satisfying, you can send the whole device to our factory to have fine tuning. Our engineers will either tune in house or send your device to CTP controller vendor to do the tuning. Our CTP vendor normally uses robots to do the tuning. Most of the devices can be tuned well in this way.
- If your device is too big to send to our factory to tune. We might have to invite our CTP controller vendor to visit you or your contract manufacturer to do the tuning. Some vendors might charge for the service depending on the complexity and the quantity.
- We highly recommend that you finalize all the designs including the housing before sending the device to our factory to do the fine tuning as the process can be time consuming (2-3 weeks) and expensive. If you have any changes (sometimes seems slight), the fine-tuning work might have to carry out again.
- We don’t recommend to put an extra protection film or glass (like a lot of people do on iPhone) in front of CTP. Our CTP has 7H surface already. In that case, we have to tune it again.
With the above procedures, we believe that you will get a very well performed touch. Wish your products achieving great success in the market. We are proud to be part of it