Working with SMT components

If you're going to use a regular iron, some wick could be handy.

Bye. Jasen

I apply solder paste to a PCB with a dispenser, carefully place my parts with some tweezers and then chuck it all in a mini oven for 4 mins and that's it.... Have been doing it for years and have built 100's of PCB's usually with 0603 parts with no problems. Works well with any IC => SOIC, anything smaller, in my opinion, is best done with a Pace iron and a wave tip.

Regards

Adrian

First, Get yourself a nice pair of curved tweezers, especially if you are planning on doing the work by hand with a soldering iron. This way, you can lay the butt end of the tweezers on the table, hold them like a pencil, and press down on the device with the point. This allows you to avoid holding the device from the sides, which will result in the part being lifted off the board.

Second, there are a couple of techniques you can practice that will make it easier. The first, and one I use most often, is to first flux the board (yes, get yourself a flux pen at least), place the part and while holding it in place with the curved tweezes, tack one side of a chip component or several pins of an IC. The other method is to place a small pad or ball of solder on one of the pads, flux and place the component, and reflow the solder bump with your iron.

Third, get yourself a good viewer. What you are able to get will depend on your budget, and they are not cheap, but being able to see clearly see what you are doing can make a real difference.

Fourth, if you can get a Pace iron and wave tip, do so. With mine I have put 200+ pin fine pitched flat packs on a board with no trouble what so ever. The wave tip is also very handy for removing solder bridges and a lot safer than solder wick which can easilly apply too much heat to the board.

Fifth, especially if you are using a wave tip, get yourself some good flux, like an RA or RMA which will make the reflow process much easier due to the higher level of metal wetting.

Lastly, and VERY IMPORTANT, unless you use an oven with a no clean flux you MUST clean the board with a chemically compatible solvent. Also remember, no clean fluxes are NOT no clean in hand processing. No clean fluxes spread and flow more than any other and unless the flux gets heated sufficiently, it remains an active acid on the board.

Try:

(see surface mount soldering)

I have tried the toaster deal with a solder stencil from the place recommended by Sparkfun. Worked well and looked like a production board.

Thanks guys. Maybe its not so difficult with the right tools ;)

Jon

The instructor of the SMT rework class I took made the statement that surface mount soldering is easier than thru hole. Based on my experience with both, I tend to agree with him.

The right tools, though, certainly do help.

One more thing I'm curious about is the temperature rating of the components. I was looking at a component that said its max operational temperature is about 80 oC and its storage temp is up to 125 oC. It gives a reflow profile which has a max temp of 230 oC for 15 seconds while the preheating is about 150 oC.

Wouldn't the relow process destory the component? I'm assuming not because but I don't understand why. Do components that have a significantly lower operating temperature are able to withstand the relow process quite easily because of the "short" time they are at this temperature?

Thanks, Jon

That's pretty much it. Hence, the 15 second max in the specs - it's very important to not keep the part that hot for more than the minimum time needed to reflow.