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Basic Electronics » SMD reflow

December 11, 2011
by esoderberg
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There are a few SMD components I've been wanting to use, so I thought I'd start trying to learn how to re-flow solder with a simple project(ie your basic Nerdkit but with SMD components and LCD pin-out built in). The the PCB design was done with Eagle, it was fabricated by BatchPCB (this PCB is available there for $6, design name: nksmd), and the re-flow solder was done in a frying pan on a hot plate (total cost in fab and components is about $15.00). The re-flow was relatively simple (Sparkfun has a very helpful tutorial), but I did have shorts on the 328 pins that required going back over with solder wick to clean up. All in all the SMD/re-flow was not as painful as I thought it might be starting out, but perhaps I won't think so after moving to more complicated circuits.
The end product here is a compact Arduino nano like form factor but with a known good Nerdkit circuit with LCD pinout that lets me move to de-bugging software without worrying about loose wires or other hardware issues.

Eric

Alt Text

December 11, 2011
by BobaMosfet
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esoderberg-

Congratulations, and beautiful work. It is a big step forward for anyone truly serious in this to get to PCB fabrication- and particularly SMD. I've done a lot of through-hole PCB design and creation (2-layer boards, silkscreen etc), but have yet to take the step to SMD (although I'm going to have to for some things).

So, again, beautiful job, much respect- really nice job.

BM

December 11, 2011
by treymd
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Nicely done! Boba, how do you silkscreen? Laser printer method?

December 11, 2011
by Rick_S
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Looks real good Eric, One question though, why didn't you go with a SMD Voltage Regulator? I've been tossing the idea of doing this around too only instead of using the 328, I was thinking more of the 32u4 with built in USB support. I've only done thru hole boards and wondered how the electric fry pan reflow would work out. I've seen the tutorial you referenced before. I bet it was neat to watch the magic happen BigGrin

Rick

December 11, 2011
by SpaceGhost
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Hey Eric, beautiful work - Very professional looking!

December 11, 2011
by esoderberg
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Rick,

I guess I could have gone with an SMD voltage regulator, but the only ones I saw with the same basic specs as the standard TO-220 7805 had a larger footprint on the PCB(although of course a much lower profile). If I find the right part I might update on future builds.

Eric

December 11, 2011
by Ralphxyz
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BatchPCB is kinda a stupid site. Or I am once again totally missing how to use a site.

There is no description of what the boards do or listing of the components the board is designed for.

I'd like to see what this board does.

This is another of Eric's creations but I can not find any description of what it is for.

Also you pay the advertise price and shipping but then there is a "handling" charge I was going to order three of eric's boards but the "handling" charge kinda put me off, or at least gave me second thoughts.

Ralph

December 12, 2011
by esoderberg
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Ralph,

The problem you point out is really with me, not the PCB site; I just haven't provided very much info for most of the boards I've put on the market there because almost all of them are very specific to my own projects and I wouldn't really expect much interest in them. The nksmd PCB should be a little more genericaly usefull and I should really provide better documentation on the site. I'll post the schematic and parts list later if you want it. As for the handling cost, it is a little steep if you only want one or two PCBs, so it definetly helps to bundle your orders.

Eric

December 12, 2011
by BobaMosfet
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treymd-

I actually have equipment for silkscreening, so I use that.

BM

December 12, 2011
by Ralphxyz
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Eric what is the project?

You have (relatively speaking) a steep price on it $25.43 so it looks like you must have put some work into it.

A schematic for the nksmd would be great. One of these days I am actually going to learn Eagle or other PCB program and learn how to etch my own pcbs but until then I really appreciate the effort you and others have put forth.

It wasn't just your boards but most that I checked did not have a component list or even a general discription.

I think you deserve a return on your work so I would take the time to make it more saleable.

Ralph

December 12, 2011
by dgikuljot
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Hahah @ esoderberg

The frying fan works, but a hot air rework station isn't that expensive and alot more effective and precise.
I bought Xtronic 4040 for about $125 and it is a hot air station and a soldering station.

I did do a video review of it a while back in case you are interested.

Video Review Part 1

Theres a link to the station in the video desciption Good luck!!!

December 13, 2011
by Ralphxyz
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Not to change the subject but hey dgikuljot, I have the Aoyue int 968 Hot Air Rework Station which I think I paid $135.00 for.

Could you do more videos on doing SMD soldering using a hot air rework station versus the frying pan (back on subject).

Actually Eric I'd like to see a video of you using the frying pan.

I have on my list of projects to do a reflow oven (modified toaster oven) thanks to Rick's and Noter's help with using Triacs.

Ralph

December 13, 2011
by esoderberg
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Ralph,

I added direct links on the nksmd PCB description at BatchPCB, one to the schematic and another to a picture of the board on Eagle. Also included is a BOM for the basic Nerdkit setup with part numbers from Digikey. It should be a lot more user friendly at this point. As for a video of the reflow, I'll give it a try and post if it turns out OK, although from my limited experience there is not much to learn from watching the reflow - that part is easy (as long as you monitor the temp carefully); the hard part is applying the solder paste in the right amounts and only where you want it.

Eric

December 14, 2011
by Ralphxyz
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Eric are you using a stencil?

Otherwise a video of getting the solder paste where you want it would be greatly appreciated.

Thanks for the updates at BatchPCB I would really like to get some of your nksmd PCBs.

Ralph

December 14, 2011
by esoderberg
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Ralph,

I didn't use a stencil for the PCB above. I used a syringe and magnifying glass to apply, which doesn't leave much in the way of extra hands to film. The 603 caps, resistors, and crystal were easy. The TQFP 328 chip was another story. Having done two runs I made mistakes on both ends of the spectrum: first time I used too little paste and it got me no shorts but a few pins were not connected; the second run I used more paste and had 4-5 shorts between pins (only some of which were readily visible). It took going over each side of the quad with solder wick to fix it up. Going forward I'll lean towards too much vice too little paste as the clean up was not too hard for the shorts compared to going back and hand soldering pins that did not get enough solder from the reflow.

I'll be putting together a board with a much larger number of components and an MPU-6000 gyro/accel combo chip with a QFN package that looks like it will be much harder to fix mistakes with the initial reflow; for that one I'm planning on using a stencil.

Eric

December 27, 2011
by boxvic
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I'm not a big fan of reflow unless using hot air- and even then I'd rather use my iron unless its entirely impossible (J-leg chips are a pain in the you know what to do with an iron). 90% of my job involves soldering/re-soldering SMD components- you'd be surprised how sensitive a DSP chip is to cold solders, and how often a wave machine creates them.

I think a lot of people are scared to solder SMD components with an iron; but if you stick with using SMD you will eventually have to work on individual components. I can assure you it isn't as bad as some people believe. Once you do it enough you'll be able to drag solder gull wing chips in your sleep (I mean that literally... don't ask lol).

Also, not to sound like a jerk or anything but I highly advise against using wick on anything more sensitive than can a resistor or cap. If you have solder bridges on chip pins then use flux and brush them away with your iron. If they are being difficult then just keep adding flux. You can never use too much flux, but with wick you can easily use too much heat.

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