SMD Guide

[Techx]

I've been researching SMDs and how to solder them properlly. I found this site which has some good info and illustrations, just felt like sharing.

http://www.smdin.com/guideindex.html

edit: I have been considering the Hakko 936 since many of you guys recommend that iron, only problem is they run too hot for smd work it seems, can anyone confirm this or be able to give some advice. I'm assuming at this point I would have to buy an additional low power iron just for smd work. :/

 

[plot]

Hakko 936 was a variable iron... meaning... you can turn it down, can't you? Maybe it won't go low enough... not sure.


And thanks for teh guide, i recently got some SMD components dropped on me and am not sure what to do with them.

 

[Techx]

i know its variable, but if you look at that the temp that the smd guide recommends for smd soldering, as opposed to the lowest temp that the 936 goes to, it seems too hot for this type of application

 

[groggory]

Originally posted by Techx
i know its variable, but if you look at that the temp that the smd guide recommends for smd soldering, as opposed to the lowest temp that the 936 goes to, it seems too hot for this type of application

The guide calls for an 18W iron. I don't know what that translates to in temps, but my variable Weller WES50 goes down to 350 deg F. I don't even know any solder that'll melt at 350.

 

[plot]

Originally posted by groggory
The guide calls for an 18W iron. I don't know what that translates to in temps, but my variable Weller WES50 goes down to 350 deg F. I don't even know any solder that'll melt at 350.

hrm. goto national.com and get the datasheets for the part and see what temperature they can sustain (it's on there, for soldering purposes)

 

[gee]

I do quite a lot of SMT stuff at work... we've got a rework station but it's normally being used for assembly line type work (company's too cheap to buy a table top reflow oven and stencilling tools) so I use my Hakko 936 ESD for most of my work.

The temperature is fine - it depends on what you do, but for most things you want the temperature to be in the 300C range which is at about 10 o'clock on the Hakko. For soldering large (1210, 2225) ceramic caps you'll want to use a lower temperature for a longer time so that you don't thermally shock and possibly crack the part.

If you're seriously getting into SMT stuff, you'll want to pick up a syringe of flux and use fluxless solder... especially if you're working with small (eg, SOT-323) surface mount parts. Soldering one of these things while trying to hold solder in one hand and the iron in the other hand seldom ever works - usually you end up pushing the part around the board with one or the other. It's easier to put some flux on the pads, put a dab of solder on the tip of the iron, hold the part in place with tweezers or something with one hand, and solder with the other hand.

The only thing that's tricky is soldering TSSOP, PQFP and other 25 mil pin spacing packages... if you get a solder ball between two pins of one of these bastards, you'll drive yourself crazy trying to free it and you'll probably end up having to remove/resolder the chip. To do these parts, I took a large bevelled tip (Hakko 900M-T-4C) and milled a cavity in the tip with a Dremel to create a mini-wave tip, and I "wave solder" the parts in place.

That web site is interesting to look at, but it really doesn't describe a whole lot...

If anyone has any SMT questions, just ask away.

 

[Acceptable_Risk]

One thing that I've found helps immensely for SMT work is a flux pen and a fine gauge flux-less solder. The pen is basically a highlighter with a thin liquid flux. You just paint some over a the traces and set your part down. It's usually just sticky enough to keep the part from sliding around. Then touch your iron to the trace and feed a little solder into the joint. The flux should pull it right in. Once you get one leg attached, the rest are easy. The trick is to apply heat to the trace and not the component.

 

[Techx]

Originally posted by Acceptable_Risk
One thing that I've found helps immensely for SMT work is a flux pen and a fine gauge flux-less solder. The pen is basically a highlighter with a thin liquid flux. You just paint some over a the traces and set your part down. It's usually just sticky enough to keep the part from sliding around. Then touch your iron to the trace and feed a little solder into the joint. The flux should pull it right in. Once you get one leg attached, the rest are easy. The trick is to apply heat to the trace and not the component.

sounds good, but where do i find this stuff online?! I have no clue where

thx