My reflow solder project (pics)

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I uploaded photos of my first reflow solder project here:
https://www.avrfreaks.net/index.p...

I've since finished assembling my second project, which was substantially harder. The real buggers were the two QFN 0.5mm pitch ICs on there. Everything else was easy by comparison. The good news is that I've made 5 of them and 4 actually work! The first attempt didn't work because I didn't align those QFN ICs carefully enough, and I should be able to fix it.

Attachment(s): 

-Brad

Last Edited: Wed. Apr 2, 2008 - 08:55 PM
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A few more photos:

Attachment(s): 

-Brad

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Very nice assembly Brad. And a creepy small device on the tip of your finger. Or thumb ;)

Nard

A GIF is worth a thousend words   They are called Rosa, Sylvia, Tessa and Tina, You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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Nice job! And... what is it?

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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Male I guess ..

A GIF is worth a thousend words   They are called Rosa, Sylvia, Tessa and Tina, You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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It looks to be a USB to some form of RF transceiver thingy.

Pleas tell us what it is that you have created!

And also, how you went about re-flowing the components to the PCB...

Nice job!

You can avoid reality, for a while.  But you can't avoid the consequences of reality! - C.W. Livingston

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Thanks for the comments. That was the least creepy thumb picture I had ;)

The device is basically a USB radio, although its full purpose is still "hush hush" since its part of a larger entertainment idea that is under development.

My reflow process was basically the Sparkfun skillet approach (I used a griddle). The stencil was a low budget plastic one mentioned in a Sparkfun tutorial. I tried both lead-free and leaded noclean solder paste from stencilsunlimited. The leaded paste was easier to work with.

I also used a heat gun on the top while heating with the griddle from below and an IR temp gun to keep track of the heating progress. One mistake I made in the test project was overheating the boards a bit. The issue was a poorly calibrated heat gun, which I've since measured manually.

The biggest improvement from my first attempt resulted from creating a simple frame to put the pcb in while applying the solder paste. I just asked the board house (pcbcart) for some scrap of the same thickness and then cut a hole in it. That kept things in place better while applying the paste, and kept the putty knife level.

Other tools include very fine jeweler's tweezers, an OptiVisor, and a fairly steady hand.

-Brad

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May I ask what pcb software you use?

I may have to give smt a go. If I could do a TQFP-44/64 (.8mm pitch), I would be happy. Maybe I could go the combo route- TQFP for the avr and major ic's to save space, and 'normal parts' for most everything else (so I don't have to deal with tiny parts). Cook up the 'big' smd parts, solder the normal parts. Or something.

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curtvm wrote:
May I ask what pcb software you use?
Eagle 4. Initially the light version, then I upgraded to the standard without auto-routing. I tried auto-routing once, but ended up doing it all by hand. One thing I really liked about Eagle was the active newsgroup, and of course the price is reasonable.

curtvm wrote:
I may have to give smt a go. If I could do a TQFP-44/64 (.8mm pitch), I would be happy. Maybe I could go the combo route- TQFP for the avr and major ic's to save space, and 'normal parts' for most everything else (so I don't have to deal with tiny parts). Cook up the 'big' smd parts, solder the normal parts. Or something.

Well as far as difficulty goes, you have it backwards. The small resistors and caps are really not that hard, even with 0402 parts. 0603 is a snap. Surface tension tends to pull things into place and prevent bridging. I've now placed close to 150 small passives and I don't think a single one was bad after reflow. The ICs are the hard part because they don't move much, the pins are very close together, and there isn't much solder under each pin. So positioning the ICs correctly is important and somewhat difficult. I started placing those first because if I dropped them way off position I'd start over. Usually I can drop them fairly close and then nudge them into alignment. But with QFN 0.5mm parts it takes a 10x loop to even see if they are aligned.

0.8mm pitch would be somewhat easier, but probably still harder than the passives.

-Brad

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I could write up a smt tutorial if there is interest. Most of the info is already out there, but somewhat spread around. A big part of the tutorial would be what tools are needed.

-Brad

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I suppose its like anything else, you just have to start trying things until you figure out what works best.