Performa 475 pcb red glue ...

franklyn

Well-known member
I need help and tips. The SMD components on the performa 475 board are fixed and glued with some red glue. I want to replace components but that doesn't work even with hot air.

How can I remove the red glue from components?
 

killvore

Well-known member
I just did my LC475 last week which has the same "red glue" situation. This was my first logic board recap, and it was successful! Note that the logic board was in good shape with no obvious leakage so ymmv. Here is how I approached it:

1. instead of hot air, I twisted the capacitors off using a pair of sharp nose cutting pliers. The sharp end meant it didn't bump the other components while I twisted it, and gave me a good grip on the capacitor I was taking off. I twisted slowly and gently while applying downward pressure - you will hear a small crack when the glue breaks its hold. I only had one out of... 11? that had an issue with exposed traces, and I don't know if that is from the glue tearing off or not.
2. once the cap is off - in addition to two capacitor legs and solder left on the pads you also have a lump of hard red glue. I carefully scraped off as much as I was comfortable with using an 18mm blade which is not an ideal shape! Scalpel would be better but I don't have one. I made sure to not tear into the solder mask.
3. I then added flux (I have ROL0) and used my soldering iron and solder wick to clean everything off, including the glue! For me just scrubbing it off worked pretty well - see pictures.
4. washed off with IPA.
5. For the one where the trace was exposed, I painted over with clear coat nail varnish protector since I don't have solder mask! The varnish I am using is the expensive stuff that is based on cellulose acetate (you can check the ingredients if you decide to buy some). The cheaper stuff is nitrocellulose which you probably don't want on your board! I have tested the clear coat on some scrap PCBs and have found that it both insulates well (no beeps) and responds safely to heat (no smoke/fumes, just melts at 200°C+). I just wish I had some actual nail varnish based on cellulose acetate, it would make it a lot easier to see where I have painted!

Here's the pad where there is solder mask missing, before I cleaned it up.

IMG_6700.jpeg

Here is what a typical pad looks like after cleanup - you can see the blackened blob remains of the glue where I have removed it with the soldering iron and wick:
IMG_6783.jpeg
 

franklyn

Well-known member
I want to desolder two resistors. I applied flux and removed the solder from the pads on both sides of the resistor using a desoldering wick and then tried to remove the resistor using hot air at 400 degrees and tweezers, but that didn't work. I thought the red glue would soften, but that wasn't the case. I don't want to tear the resistor off the mainboard with force to prevent the pads from tearing off.
 

franklyn

Well-known member
... it worked with a lot of solder and the soldering iron. I use the overclock software already but I want it fix in hardware.
 
Top