SparkFun Forums

[baluba]

I am slowly venturing into hotplating or reflowing my own boards. Just curious, how do you guys keep e.g. 0402 components in place on your board prior to reflow? Seems to me that applying small drops of glue beneath such components would take lots of time, and it would be easy to forget some components.

Is there some kind of spray, i.e. flux, that can be applied to the board before components are placed, and which would keep the components stuck to the board?

Or is the solderpaste enough to keep components in place? If so, how long can solderpaste be in dry air before the board needs to go in the oven?

[NleahciM]

If I'm soldering with an iron, I'll first put a drop of solder on one of the pads. Then, with some curved tip tweezers I'll heat up that pad and put the discrete in place, and let the solder cool. Then I just finish off the other pad.

With solder paste - I just put a drop on each pad and then place the component with some straight tweezers. I use a hot air station instead of an oven or hotplate, so it has more direct air on it and the components still hold on just fine. I've never experimented with how long you can leave the paste on for - but I expect you can go a couple hours at least... I mean it's just flux and little balls of solder after all.

[geekything]

Surface tension should just keep things in place...obviously don't juggle the board(s) while on the way to the hotplate, though.

-marc

[FESCSteve]

Like the others mention - the parts will stay in place in the paste as long as you don't jiggle things around. If you have a good reflow profile and design, the parts will self align also during reflow because of the wetting forces.

If you have a bad design and improper reflow profile, chip components may try and 'drawbridge' or 'tombstone' on you where one end will begin to wet before the other and draw it to one pad, away from the other.

As for solder paste in open air (we call this print life) it really depends on teh environmental conditions of heat and humidity and what environment the paste is designet for. Many pasts are custom formulated for the humidity of the manufacturing environmnet. Some are for humid, costal areas, others are for dryer conditions. Assuming that you are under 60-70% humidity, and above 25-30%, and the paste has been properly stored (not left open) I would think that you could get 3-4 hours at least. In a good environment you could extend that to 6 hours even.

I guess there is really no one answer. If you don't have an controlled environment, then you'll have to go with a couple of hours and then just experiment to see how long you can extend it.

Good luck and let us know how it goes.

Steve

[baluba]

ok, thanks guys.

While I am on it... Any idea if it would be possible to solder something ultra-coool like this in a homemade oven or on a hotplate? I know i know, I will read the datasheet, eventually...

http://www.telit.co.it/modulef.asp?famI ... 20Embedded

erik