LCD Displays

[Totalsolutions]

Hi,
I'm hope I am not alone in asking this is and I have never seen explained before.

Can anyone tell me how the connections around the LCD "glass" connects to the PCB ?

That's the question.

Reason for asking, I have 12 yr old car stereo and the LCD display fades and vanishes. It can come back in warmer / dryer weather in the UK! I have tried to "repair", re-aligning the conductive strips but to no avail. I have two other radio units now with the same "blank" display.

I also managed to over spray (when cleaning a machine at work today) a display LCD. Some cleaner got into the display cover, and after stripping down and drying, got it going, but there were the little black conductive strips of material connecting the "glass" to the gold plated PCB lands.  Do these needs replacing due to shrinkage or can they be reused, apply a little conductive paste ? ? ?

How to check any connections are good, hampered, due to no access to the actual glass connections as they are invisible too ? ?
What voltage do they use ? ?

Thanks for the replies. 

Paul

[ovnr]

Most LCDs are connected to the PCB using "zebra strips", which are elastomer strips that only conduct in the Z (up/down) direction.

These may occassionally go bad, and need replacing. Getting replacement strips is... difficult at best, and I'd be very surprised if you actually found a working replacement. The strips themselves have varying thicknesses, pitches, and other properties, and are not generally interchangeable.

You should not use any conductive grease on them - clean the display and PCB contact surfaces with a good cleaner (isopropyl alcohol, etc) which doesn't leave any residues, and reassemble.

[sleemanj]

The rubbery strips are called zebra strips, if you look closely (you might have to look very closely depending on the density, or might be plainly obvious) you'll see that the black line on each side is actually alternating black and white (usually), black is conductor, and white insulator, so it conducts vertically, but not horizontally.

Contacts on the glass press against one edge of the strip, the signals and power conduct through to the other side of the strip, and thus to the PCB. 

See also:
http://www.fujipoly.com/usa/design-guidelines/89.html

[amyk]

What voltage do they use ? ?

Usually between 1 ~ 30 volts AC; exact values depend on the crystal material, segment size, etc.