EEVblog Electronics Community Forum

EEVblog => EEVblog Specific => Topic started by: n6nz on March 07, 2012, 12:09:47 am

Title: #163 solder paste
Post by: n6nz on March 07, 2012, 12:09:47 am
Hi,

A gang of us have been working on a homebrew solder paste dispenser, using my friend's CNC mill (Mikini 1610L) and a manual paste dispenser (that I bought used on E-Bay), plus some mechanical & electronics & software hackery.

Here's a short video from our first day of testing:
www.youtube.com/watch?v=Yg8YRLRvTS0 (https://www.youtube.com/watch?v=Yg8YRLRvTS0#)

It isn't working well yet for fine pitch TQFP pads, but was doing sort of OK for 0603 and SOIC pads.

Your commercial unit in blog #163 is really interesting to watch.  We have some questions:
1) What is the granule size on the solder that you are using, or is there some specific solder that they recommend?
2) What is the needle size?
3) How small of a dot size can you get?
4) It looks like the board is on a spring loaded holder and the needle contacts and deflects the board.  Is that right?  When is the paste dispensed -- before, during, or after, or <something complicated> the needle contacting the board?

Thanks! Great blog!

-dave

Title: Re: #163 solder paste
Post by: Psi on March 07, 2012, 12:27:48 am
yeah, it seems the amount of paste is too much. need smaller needle and/or less pressure.
Title: Re: #163 solder paste
Post by: n6nz on March 07, 2012, 12:35:41 am
The video was shot when we were still tuning a lot of things.  We were able to get less paste.  We tried a smaller needle, but couldn't get good solder flow, so I'm wondering if we had too large of granulate?  Pressure was set to about the max of the unit's spec.

The biggest issue was getting consistent results.  It's hard to tune when things aren't consistent.  As you can see from the video, the PCB was clamped in a milling vise, so we didn't want to crash the needle into the board.  The commercial unit in Vlog #163 looks like it has a spring loaded board holder and the needle deflect the board.  I'm wondering if we need to knock out a spring loaded jig.