Hello all!
For my mechanical engineering study I want to etch a strain gauge in the Wheatstone bridge configuration in a copper layer of an PCB. The goal is to measure the strain occurring in an PCB even during the press process! We can measure with X-ray before and after, but we want to measure DURING the press process.
I am wondering if anyone has any experience or information about how to do this. I’ve looked around on the internet and asked some teachers but I did not find anything useful except electrical schematics of the Wheatstone bridge configuration (which is wildly available).
I’d love to etch these gauges in both the copper layers of FR4 32 mil 18”x12” material with 17,5 or 35 micrometer copper layer thickness on both sides. Two of such layers are subsequently glued together using 2-3 thin layers of 3mil 1080 prepreg in a press with a temperature time cycle predetermined by the manufacturer which is something roughly like this:
Temperature will go to from 100 to about 200 Celsius in 30 minutes. Hold the temperature at 200 Celsius there for 1 hour. Cool down in a cool press with press plate temperature of 60 Celsius.
How to measure the output of the strain gauges is also not clear yet since there are no inputs for such measurement equipment inside the press. I think it’s not impossible to get measurement equipment that can work at ~200 Celsius (which is vacuum anyways so probably less) inside the press chamber. There are also 6 thermocouple inputs in the press to the outside control station. Maybe I can use those and do some fancy tricks with the output to transform them to the required strains.
I want to do this experiment so I can measure strains in the PCB’s during process in the press. Any help is appreciated.
Greetings,
Julian
reply »