quixotron

Hello, I was wondering if anyone has experience and thus suggestions for good soldering techniques of those tiny, 603 and 805 surface mount caps, resistors and inductors?

What I used to do, is place the part on the solder pads, heat the pad and then apply solder. however, I found that solder leaks underneath the part, and either lifts the part perpendicular to the board or lifts it parallel, with a small air gap in between. I only have two hands, so i have to pick between the iron, tweezers and the solder.

I have been experimenting by applying the part on the pad, apply pressure to the tweezers and heat the pad so that the tiny solder on the pad locks the part in place. I then apply the solder, to get a nice, uniform flow on the pads. with no air gaps and a straight connection w/o shorts and mess.

I tin the solder iron point and i use non-lead, water soluable solder with flux. So far I have been getting good, solid solders with it. before, I was monkeying around with the part trying to correct its position and burning the board or my fingers. I also use solder wick, but I found out those plungers suck solder much better, but is a bit messy with solder shavings coming out.

The only complaint I have is that this procedure takes an extra step to implement. I can sometimes pull a tech to the side to do the job for me, but I'd like to get to learn how to do it effectively by myself.

Any tips?

RadioRon

Well, I think you are on the right track there. Here's what I do. First of all, I still use leaded solder, not lead free. Of course, this is just for engineering prototypes. Leaded solder flows so much better than lead free that I will keep using it for engineering work as long as is convenient. I do mostly 0603 and 0402 size parts these days. For chip resistors and caps, I will tin one pad with an iron and some fine solder, then tack the part by melting the solder again and pushing the part down into it using tweezers. A steady hand is important, and best done using a microscope. Once the one side is tacked down, I solder the other terminal with a very quick dab of solder. Don't hold the iron on the part for more than a moment or the other end of the part may reflow and the part will move. You get the hang of this quickly. Unfortunately, it requires your part holding hand to switch between solder and then tweezers and then solder while the other hand holds the iron.

Where I used to work, it was quite common for some of the guys to tin both pads with an iron and then switch to a fine tip hot air pencil to melt the solder and preheat the part at the same time while holding and pressing the part on the tinned pads with tweezers. This does a nice clean job and is fairly quick. I just found it a bit awkward to switch from iron to hot air pencil. Once you get good with a hot air pencil, rework of chip parts is an absolute breeze. Two seconds of hot air, lift the part. To put another back on the pads, just hold it above the pads, two seconds of hot air and push the part down and let go. Its pretty easy.

If you have any difficulties with getting the solder to flow easily, don't be afraid to grab a flux pen and touch some flux onto both pads before soldering. This helps a lot.

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RadioRon

bananasiong

I always tin on the pads before anything. Then put the part on place, compress with my nail and just heat up the joint of the solder and the part. All these are done nicely.
But when doing with QFN, it always take me long time. Liquid flux is really important.

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Superman returns..

whiz115

hi quixotron check this out

http://www.curiousinventor.com/guide..._Soldering/101

Darth Bagel

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

Rougly my method for soldering discrete SMD components.

mneary

I tin one pad like RadioRon does, and if I have more than one part to do I do this for several parts. After tinning one pad for each part, I install them and solder that end. Then I turn the board around to solder the other leads instead of swapping hands for the iron.

speakerguy79

I tack one end down, either with the little tin that is already on the pcb, or I add a little solder of my own. I then solder the other pad, then come back and do a proper solder on the first. You'll need extra flux since you burn off what's in the solder before you tack the part down.

http://www.youtube.com/watch?v=qs7rSM731gk

Boncuk

Hi quixotron,

I read an article in a German electronics magazine about WAVE SOLDERING SMD-components. I haven't tried it yet since I could find the proper soldering tip for my soldering station.

The principle is easy to understand and logical from my point of view.

This is how it works: the soldering tip has to have a small dimple to get the shape of a miniature pan. This dimple is filled with tin. Place the component on the board without any glue or some other device to fix it into position. Use lots of flux and distribute evenly where you want to solder.

Slowly strike the tip along all pins of the device. Capillar force will bring the tin only there where there is metal and additionally the flux takes care of equal usage of tin. (provision: solder stop masc)

That way you are able just to use the two hands given, one fixing the component and the other one to solder.

Regards

Hans

speakerguy79

I know Pace and some other iron manufacturers have wave tips available. You have to use extra flux because it burns off when it sticks to the cup of the tip, but I had a coworker that loved using it on 0805s and smaller.

quixotron

Cool. Thanks guys, BTW whats a solder mask? I have been hearing about that. I don't know what it is.

dknguyen

It's that (usually) green coating that covers the PCB traces and protects them from the atmosphere and from solder. It opens up on pads and such where solder should be.

quixotron

AHHH...yeah some of the guys in PPA testing were talking about that on some antenna I was working on, I know we are supposed to cover the trace with some dielectric for protection against oxidation and stuff.

Thanks.