I’m having trouble getting the solder paste to wet my glass PCBs. I am using SAC305 solder.
Funny that it works fine on FR-4 but with glass it just balls up.
Maybe it is because glass conducts heat better?
Any suggestions on how I can improve this process?
This is the profile I use. It works fine with FR-4:
Glass PCBs can be made by gluing copper on them. The copper then bonds to solder. If heat conduction were the factor, then copper would have a hard time bonding (which is not the case).
If you are soldering to copper, glass vs FR4 has no bearing to begin with. Soldering is a very localized process. If you can tin your iron, you can get around heat related issues by carrying the solder with your iron. If you can't tin the iron, your iron is not hot enough for your solder.
You simply need to clean the copper surface. Soldering does poorly when your metal surface is oxidized. Flux bonds to the oxygen, effectively burning it off. You can also mechanically remove the oxide layer, but must promptly apply solder as pure metal exposed to atmosphere will form some (sometimes small) amount of metal oxide simply because entropy does not favor purity.
