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ESD Testing

Has anyone done ESD tests on a device containing the INT035TFT-TS panel?
I'm seeing an issue where a 4 kV discharge to a mounting screw near the top left corner of the panel causes the display backlight to turn off. It does turn back on when power is cycled, but the brightness of the backlight is permanently reduced.
There is no direct electrical connection from the mounting screw to the TFT, but the distances are small enough for the charge to spike through. The closest contacts are the GND pin, and the metal chassis around the display panel.
Any ideas what would be the most sensitive component on board and how to protect it?

Replies

Guest's picture
Guest
June 5, 2013

I have no ESD test experience concering INT035TFT but I have 2KV,4KV,8KV ESD test experiences for my medical products. The cause of the malfunction by ESD test is hi-frequency,such as from 10MHz to 100GHz, radiation of ESD arc,and is not Grand-signal level fluctuations.

>Any ideas what would be the most sensitive component on board and how to protect it?
The most sensitive component is MCU. In your system there is 2 MCU,namely one is your MCU on your board and the other is MCU called ATMEL in INT035TFT. In your case it seems tha Atmel cause malfunction by ESD as the fact that "It does turn back on when power is cycled, but the brightness of the backlight is permanently reduced". I think you designed watch dog timer in your MCU software and so when your MCU cause malfunction by ESD, watch dog timer works and your MCU is reset. If in this timing, ATMEL and SSD1963 of INT035TFT operate correctly, your all system recoveres correctly after your MCU software re-operate. But in your system the brightness of the backlight is permanently reduced.

There are some ways to up proof stress. In your case I recommend below to INT035TFT board and your MCU board including peripheral wires and parts.

1. To cover Ateml and SSD1963 INT035TFT board by conductive thin sheet
http://www.ztj.co.jp/en/products_e/emi/em_masking_tape.html
2. To add celamic capacitor or increase celamic capacitor between +3.3V and 1.2V and GND pins of Atmel and SSD1963 and your own MCU as close as possible on INT035TFT board and your MCU board.
3. To add ferrite core in in your interface wire lines from your PCB board to peripherals such as power source(+3.3V,+5V,AC 100V and AC 200v and signal line such as switch or relay or Power semiconductors.
http://www.kitagawa-ind.com/product_en/sp/detail/274
http://www.kitagawa-ind.com/product/ferrite.html

And you should not connect reset signal to Reset pin of INT035TFT.