PICS! I need some help with one hole....

[rudeguy]

There is one hole on one board that I work on that always give me trouble. These are through-hole solders with a tab instead of a post. All the other ones I do are fine but this one hole always ends up trashed.

Here are some pics of the board and the problem hole. The purple arrow points to the other hole on the board that always turns out fine.





I use the same method on both: lots of flux. Chisel tip heated to 350C. Solder wick all the solder that I can from both sides, then pull the tabs out. Every time the one hole is fine while the other is trashed. I have to resort to picking out the old solder with a pick if I can't blow it out with hot air.

What am I doing wrong?

[capkid]

Re: PICS! I need some help with one hole....

Is there a heat sink nearby on the other side of the board?

[redwire]

Re: PICS! I need some help with one hole....

You are heating three things - the top pad, the bottom pad, and the lug... With one hot tip.
Once you use solder wick, there is little heat transfer from lug to pad due to the lack of solder. You apply heat to the top lug+pad, but the bottom pad stays cool and gets ripped up. I think this is what's going on.
I use either two soldering irons (one on top, other on bottom) or one iron but leave fresh solder ( not wicking it all off) and pull the lug out when hot.

[domas]

Re: PICS! I need some help with one hole....

Agree. I wouldn't use wick here. I mean, as funny as it sounds, more fresh solder with some flux is what helps you. Yes I know the amount of heat you transfer to the board is enormous (huge amount of solder + the heating time), but that is the way I would go. Make sure solder melts on both sides before you try to pull the component

[rudeguy]

Re: PICS! I need some help with one hole....

You are heating three things - the top pad, the bottom pad, and the lug... With one hot tip.
Once you use solder wick, there is little heat transfer from lug to pad due to the lack of solder. You apply heat to the top lug+pad, but the bottom pad stays cool and gets ripped up. I think this is what's going on.
I use either two soldering irons (one on top, other on bottom) or one iron but leave fresh solder ( not wicking it all off) and pull the lug out when hot.

Thanks!

That makes perfect sense. I even resorted to Chip Quik alloy to try to keep the solder wet but it wasn't enough.

I do have an IR preheat station, I'll give that a try on the next one I do. Leave the old solder in, heat it up to 350, and remove the old tab. I don't have enough hands to use 2 irons at once....how do you guys do that stuff?

[rudeguy]

Re: PICS! I need some help with one hole....

Did another today, same thing.

The old solder just won't melt through the hole. So I finally got mad and left it on the IR preheat station for 30 minutes set to 350C. I felt like I was baking cookies.

But the solder finally melted through. Now to put the thing back together and make sure I didn't melt anything I wasn't supposed to.

[goontron]

Re: PICS! I need some help with one hole....

^ replace any electrolytics, they went and off gassed more than likely....

[rudeguy]

Re: PICS! I need some help with one hole....

^ replace any electrolytics, they went and off gassed more than likely....

worked like a champ!

I thought for sure some of the plastic would warp.