TIL a ton of folks are using the wrong flux for SMD rework and it's causing cold joints.

3 comments

3 Comments

You're right about the wrong flux causing cold joints. I learned that the hard way trying to fix a graphics card. I was using a general purpose paste flux and couldn't figure out why my solder wouldn't flow right under the microscope. Switched to a no-clean liquid flux made for fine pitch work and it was like night and day. The difference in how the solder wets the pad is huge. That wrong paste just left a crusty mess that insulated the joint.

piper7791mo ago

Yeah, that crusty mess is the worst. I had the same thing happen when I was trying to rework an old motherboard, @sage_green. I was using some cheap flux pen from a general kit and it just wouldn't clean up. Switched to a proper no-clean for SMD stuff and suddenly the solder actually moved where I wanted it to. It's crazy how much the right flux matters for getting that shiny, smooth joint. That bad paste basically acts like glue and ruins everything.

amy_anderson1mo ago

Remember when everyone used to just grab whatever rosin core solder they had lying around... it's wild how much the hobby has changed. My first kit had this awful paste that would just turn into a black rock if you looked at it wrong. Makes you appreciate the good stuff now, even if it costs a bit more.