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Hello Adam,
Ole Joe here, with a possible fix for your display which is missing segments but as you state, will work with a bit of pressure applied to the display. First the majority of the displays used in the Frontier watch modules were manufactured by Monsanto. The actual LEDS internal to the display are mounted on a small ceramic stick and wire bonded to pads located on the backside for external connection. As can be seen the display is covered with a transparent plastic lens. Since the display mounts directly to the substrate, there is no way to solder the contact pads on the back of the display to the appropriate pads on the substrate, other than using a reflow solder technique. Unfortunately, at the time in the early '70's, Monsanto recommend that the display not be reflowed soldered but be mounted to the substrate using a silver bearing epoxy compound, which Frontier did. You say in your post that the substrate in your module is cracked and is not ceramic. If this is fact, then the module you have was NOT produced by Frontier. All LED watch modules made by Frontier used Alumina Ceramic substrates. While I was an employee of Frontier, one of our representatives who was based in Hong Kong sent us several phony watch modules with the components mounted on standard epoxy glass circuit boards. The culprits copied the circuit track layouts from our ceramic substrate so that they could produce them for virtually nothing compared to what ceramic cost. We reverse engineered the module and discovered that they actually did have true Frontier chips installed. Further investigation revealed that the chips had been obtained out the backdoor of our manufacturing facility in the Philippines. The manufacturing facility in the Philippines would obtain the tested and known good watch chips from us in Calif., would mount the chips onto our ceramic substrates, wire bond the chips to the traces, cover with silicon compound and ship them back to us for final assembly, test and mounting into the plastic carrier rings. We expected a certain amount of loss each month due to ceramic breakage, bad wire bonds etc. The facility in the Philippines would report the loss each month and it was inline with what was predicted. They would return the bad parts to us. After a few months the cost to return the defective items to us was expensive, so the Philippine manufacture was told not to bother to return the failed items to us just report the number of failed items. Turns out the loss was virtually nothing to begin with from day one and they were selling known good chips to those in Hong Kong. They covered their tracks well until our representative happened to see a cheap watch in a Hong Kong shop which operated exactly like our product and purchased several for our evaluation. Looking back, it was easy to understand how this caper was executed as we had anywhere from 1 - 1.5 million modules in the pipeline at any given time for several years. Money was flowing into Frontier's bank account like water running downhill. With respect to your problem, I have remounted displays encountering problems like yours with good luck using silver bearing epoxy which I purchased years ago. I just did a search on Amazon and found it at this link;
https://www.amazon.com/Silver-Conductiv ... 1_2?sr=8-2I have removed displays from ceramic substrates using the blade of an Xacto knife placed under the edge of the display and gently applied pressure upward. If you try this, be very careful applying the upward pressure as it is easy to break the display substrate. Also be aware of the black silicon coating covering the chips and wire bonds just below the display. I found that once the display was off the substrate, most of the adhesive used for mounting was left adhering to the substrate rather than the display contacts. Don't remove the old adhesive off the substrate or the display contacts, as the adhesive left on both parts sort of acts as a guide for aligning the display to the correct position once you've applied the new adhesive. I've attached a picture of the Monsanto display from an old data sheet that I dug up. It shows the contact arrangement on the back of the display. Hope this helps.
Ole Joe
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