Got roasted for using too much flux on a motherboard repair

I was fixing a laptop board last month in my home shop and a guy from a local repair meetup watched me work. He flat out told me I was using WAY too much flux and it would cause corrosion down the line. I always thought more flux meant better joints, but he showed me how the residue traps moisture under components. Now I use a tiny syringe with a 22 gauge needle and apply just a dot per joint. Has anyone else dealt with flux residue causing issues months after a repair?

3 comments

3 Comments

xena12d agoMost Upvoted

You said "he showed me how the residue traps moisture," what did he actually do to prove it?

miam751d agoTop Commenter

Tell @xena1 that flux residue only causes issues if you leave it on there half-assed. Clean the board right and you're fine.

jana_fox5012h ago

Started cleaning boards with 99% isopropyl and a stiff brush first, then hit them with deionized water rinse and compressed air to dry. Never had a moisture issue doing it that way, even on boards left sitting for weeks. That extra drying step makes all the difference, takes maybe 30 seconds more but saves you headaches later. People skip the drying part and that's where the trouble starts, not the flux itself.