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Topic: Soldering Hell (Read 2 times) previous topic - next topic

vasquo


Since we're on the subject of the best soldering techniques, I am getting my hand into fine pitched ICs.  I have a few 2560s that I am trying to solder.  I have a syringe with solder paste and I used my hot air station.  The problem I am having is that no matter what I do, I keep getting solder bridges across the pins.  I use very little paste and still get bridges.  I use so little solder that it barely solders the pin, but I still get bridges.  I have tried not using extra flux and using a ton of it.  Using more paste, still get the same result.  It seems like the solder just isn't reflowing very well.  I have also tried different temps.

Solder paste is from Kester and is 63/37


Are you laying the solder paste across the pins? or individually on each pin?
I just lay a very *very* thin bead across all the pins, and on the outer edge.
(I'm using lead free solder paste.) 

Don't have your hot air blowing too hard... because that can push molten solder to places you don't want to (forming a bridge).

Still with this technique, 2 pins out of 16 may form a bridge (SSOP-16)... then just use some flux and wick to fix it.

codlink



Are you laying the solder paste across the pins? or individually on each pin?
I just lay a very *very* thin bead across all the pins, and on the outer edge.
(I'm using lead free solder paste.) 

Don't have your hot air blowing too hard... because that can push molten solder to places you don't want to (forming a bridge).

Still with this technique, 2 pins out of 16 may form a bridge (SSOP-16)... then just use some flux and wick to fix it.


I am laying across all the pins.  The tutorials I've watched use that method.  The velocity of the air was low. 


This is usual with manual soldering. People just take some solder wick, and wick away
the bridges.


It's funny you say that.  I have tried to use wick to remove the extra solder, but I can't get it suck up into the wick.  The bridges are on the board crossing the pads. 

I will just have to keep practicing.
//LiNK

oric_dan

Quote
It's funny you say that.  I have tried to use wick to remove the extra solder, but I can't get it suck up into the wick.  The bridges are on the board crossing the pads. 


I don't do a lot of really fine-pitch smt myself. But someone else mentioned that you
might try taking some flux or solder and flow it onto the wick first. It does tend to be
difficult to get the heat transferred enough to get the surface-tension working through
a dry wick, even on non-smt parts.

codlink

I have used flux on the wick, but never thought about tinning it.  I will try that.
//LiNK

kg4wsv

Quote
The bridges are on the board crossing the pads. 


Do your boards have soldermask?

This stuff isn't just for looks, it's actually more "solder-phobic" than bare substrate. When I made my own boards I found they'd bridge quite badly as compared to boards with soldermask.

-j

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