The AM Forum

The first thing you learn when trying to deal with surface mount is that you need a good microscope.
The second thing you learn is you need 3 hands. 1 for the soldering iron, 2 one to hold the part, and 3 one to feed solder. A girl who worked for me once taught me a cool way to save one hand. Just break off a small hunk of solder and place it on the joint you want to solder first. This frees up the hands to hold the part and apply heat.

I've taken to tinning one or 2 leads (IC) and a pad or 2....

then just hold in place and heat...

so-far ... so-so good     :-)

My senior design project in college was a varactorless VCO using SMD components - back in 1985 they were pretty new and nobody (including my adviser who was an engineer at EF Johnson) really knew the best way to mount 'em.  I used a drop of superglue to hold 'em down then soldered 'em in place.  Worked very well, just don't use too much glue!

One thing's fer sure, my eyes were a hell of a lot better back then - didn't need a magnifier at all.  Good luck with that now  ;D

Hell!!...... with these 50+ year old eyes I need magnifying reading glasses (cheaters) a large magnifying light, and a 3rd magnifying glass just to see that stuff. That doesnt leave enough free apendages to hold the slobber, iron and part!!

at almost 57 I love my microscope. yes SMT is easier till you get down to the tiny parts. The hunk of solder in the joint is far faster than any other method I have tried. Tinning can damage a part if you are not careful.

I haven't tried assembling SMT, but a solution to the 3rd soldering hand problem I have developed over the years is to take about a 3-inch length of solder, wrap enough to hold it into position round the tip of the index finger of the hand I use to hold the part, bend the rest of the piece of solder to the appropriate position, and feed the solder to the joint by contorting the finger, while I use the other hand to hold the iron.

Frank,

The reflow technique  has worked best for me. You need to buy a small tin of flux. Firstly, over tin the pads... quickly, so as not to damage them. I use 20 mil core solder. Then, after cooling, a bit, apply some flux with small paintbrush or toothpick to pads to reflow. Position part on pads in flux and then touch with iron tip. For IC's do opposite corners first to align and hold part in place for rest of pads. When done, wash excess flux with 90% Isopropal Alchohol, and dry. BY using the flux, you eliminate need to pretin part leads. 

ras

Excellent demo video  here:

http://www.youtube.com/watch?v=3NN7UGWYmBY

and

http://www.curiousinventor.com/guides

rob,
Sounds like you need to train Max. fc

Jewelers use a tool called a "third hand" which is a large tweezer that works backwards, i.e. it closes when released.  I have 3 or 4 of these and it took only one SMD cap to realize that this is the perfect tool.

I bent the tips down a bit to provide some extra clearance.  The device is placed on the board, the "third hand" is reached over the device which is wiggled into position and released then one end is tacked.  It is then removed and the other side soldered.

I did all the caps on a SoftRock 40/80 in less than 30 mins in spite of the fact that I had never done this before in my life.  It worked just as well on all the SM IC's.

If you need a source, riogrande.com and they are called cross lock tweezers and range from $4.50 to about $50.  Mine are all the $4.50 type.

I have a nice collection of microscopes but find a $3 pair of 3 or 4 diopter reading glasses far more convenient and save the scope for final inspection.

js

Just remember to wear a grounding strap while working with this stuff. ESD can poke its head up months or even years later, which will leave you scratching your 'bohunkous'.

when I used to be all that it was. That's how I made my money. reworking and repairing SMT computer boards for these guys. 5 years. When my left hand went bye bye, so did I.  But I can still work on ol junk!

www.datalux.com (http://www.datalux.com)

click on the company information link to get a FLV video showing the stereoscopic binoc Scorpion viewers we used. They dude with the grey hair peering into it is sitting in 'my' chair. Such as it was.

http://www.paceworldwide.com/index.asp#
 (http://www.paceworldwide.com/index.asp#)

I went here to school as well as worked for them for 3 years back in the 80's. pinpoint hot air is how to handle smt stuff. But it's real expensive.

For repair, when removing IC's which can be a daunting task, I have used dental tools to separate the leads form the solder pads. This works OK but excessive heat to the joint can increase the risk of pulling the solder pad. 

A better technique I found is to thread a length of magnet wire under the leads of the IC and anchor one end to a solder pad away from the IC on the board.  Then heat the leads of the IC with the soldering iron using a square tip and at the same time apply tension to the loose end of the magnet wire. The tension will lift the leads in short order sparing the solder pads.  Solder won't stick to the wire because of the enamel coating. No need for solder wick until the IC is off the board.

If you know the IC is bad I just snip all the pins near the body and remove them one at a time. This also works great for through hole.
Bob, I do your trick with a scalpel but wire is a good idea.

I like the "snip the leads of the IC" technique as well but sometimes I find the leads so close to the board and if the snips are not sharp enough one can damage the board.  When you repair consumer electronics the manufacturers use the cheapest materials.  Getting the IC off the board with minimal heat is necessary otherwise the traces lift. I like to minimize the mechanical forces when dealing with this stuff.

I'm finding working on this stuff more difficult.  I don't know about you guys but seeing this stuff is a strain on the eyes even with magnifiers.  I actually had to buy a pair of reading glasses a couple of weeks ago for some of the work I'm doing on the 813 rig.  At 48, age is catching up to me.  Yikes!

I like the Weller Ultralight heat gun with a small tip and a pair of tweezers to remove and reflow SMT parts like SOIC's and SOT23's. You use a circular motion around the pads and the parts flip right off clean.

You use the smallest baffle adapter with the tiny hole in front.

Don't tarry cause you can lift pads or burn the board - don't worry about the semiconductors - they are OK with the heat.

Mike WU2D

Mike ask Mark about Long Tall Sally....she taught me how to repair boards so I could get a solder cert....a long time ago.

Frank said:
I used to do this when I was doing 2M in the Navy. Most of our 'flat packs' were spot welded to the runs on the circuit board. I have a nice Pace station at home. I just needed a vaccuum pump to complete it, (I got one courtesy of our sample pumps here at work). Personally, I liked working with the American Beauty resistive tweezer for spot work. They prevented you from overheating the pad and the leg of the chip. But that was damn near 20 years ago.

Anybody need a good vacuum pump for their station I have a few new ones left..cheap

Frank:

I have been repairing SMT boards for years. I got a sample chip in about a month ago from maxim. I was thinking they were the original size and I could tack solder leads to it. It was so small I thought the plastic case it came in was empty until I took my glasses of and looked closely. If I sneezed, they would be gone. About 1/4 the size of the end of my pinky finger.

Dan

 Here is good SMD soldering info

http://www.sparkfun.com/commerce/present.php?p=SMD-HowTo-1

(Sparkfun ROCKS!)

I have one of their cheap hot air rework stations, works well.

Rich