Chosen Solution

Hey all So i’ve recently started messing around with microsoldering. I’ve mostly been practicing on dead or iCloud devices. I’m having a few big issues.

  1. Is there any good way to easily remove under-fill? 2 My solder just sticks to the board in a big clump. Not to it’s respective pads, just in a big ball. I can wick it away but it just happens again when I try and reball / clean the pads. I’m using plenty of flux so I don’t see that as being the problem but then again I know absolutely nothing about this. And finally does the orientation of FPC connectors matter? I don’t think it would but like I said I know nothing. Any and all help would be appreciated. Even if it has nothing to do with these specific questions anything is helpful. At this point I break everything I touch hahaha. Thank you all :)

Here are a few observations… Underfill is the bane of micro-soldering iDevices. Everyone develops their own method so you’ll have to experiment but consider that most underfill softens up at about 125-150C. That is lower than the melting point of leaded solder (and also non-lead solder) so the trick is to get the are of the board to that temperature without going over the melting point of the solder. That way you can scrape away the visible underfill before removing the IC. For the cleanup underneath the IC, the same temperature guidelines apply. Look at videos from multiple techs online to see a good variety of techniques (and tools) and experiment. You’ll note some folks use hot air, others use a pre-heater or combine the two.If your solder is just clumping to the board, that means the board isn’t at the right temperature…it needs to be hotter. This is kind of like freezing rain (but sorta different ;-), the water freezes immediately on a cold surface. This will usually happen on pads or areas under an IC that are a large ground plane. They require more heat than little-bitty pads that are essentially connected to nothing more than a tiny trace or via.FPC are not orientation sensitive. It’s good that you are experimenting with iCloud boards. Try various temperatures and nozzles (for hot air) and tips for your soldering iron. In the end, it’s all about heat transfer. Once you get the area under work at the proper temperature (and no more), you’re technique will improve dramatically. The flip side is to avoid getting too much heat otherwise you will cause lots of collateral damage.