Will it work :) (first SMD goofball project)

Read the SMD soldering tutorials on

and you won't be so intimidated by SMD stuff. And after doing your first board, you'll think "I shouldn't have waited so long to do this."

steve

Funny you mention the sparkfun site. I found it on you tube, and watching him blob solder all over one side of that chip made me cringe, then he pulled out the de-solder ribbon and I was like "Oh.... neat trick.." :)

I was also surprised just how relatively inexpensive this board turned out to be. All said done, one board fully populated is going to run about $25.00. I'll need 4 of them for the proto-type, and another 16 to finish the project if all goes well. The question is am I gutsy enough to order all 20 up front and hope and pray, or just get 4 and see if it works....

--
Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 15KW generator project)

"Anything that can happen, will happen" -Stephen Pollock from:
"Particle Physics for Non-Physicists: A Tour of the Microcosmos"

" Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent. "

I developed my own way of soldering SMT parts, especially 0603 size components:

1. Use tinned fine point tip on low wattage iron to solder one lead/end of the part onto its pad - even if not well.
2. More properly solder the other end or remaining leads.
3. Solder properly the first connection.

As for getting a really small part such as an 0603 into place to begin with:

1. Have a good fingernail on your index or middle finger on your non-iron-holding hand.

1. Dip the fingernail edge into rubber cement.

2. Have the part handy on a convenient surface. Land the tip of your rubber-cemented-finger (not the nail) near the part, with your rubber-cemented fingernail tip over the part.

Using the landed fingertip as a pivot, lower your rubber-cemented fingernail onto the part so that the part sticks onto your fingernail.

1. Similarly land your fingertip in an appropriate location close to where the part has to go (typically requiring fingertip to land on the board - ground yourself and board supply rails and the soldering iron if static-sensitive parts are involved).

Using a fingertip pivoting method as above, lower the part into place.

1. Once the part is located well, tack one lead/end onto the PCB with a tinned iron as above. Proceed from that point as above.

- Don Klipstein ( snipped-for-privacy@misty.com)

coating site)

15KW generator project)

James;

I took a brief look at your design. Your board has a lot more parts than your schematic. Your board's main problem is that vias are both too close to other vias an also too close to traces. The software let me place two pads that overlapped each other. This is BAD. And if there is a menu or command to verify that the board conforms to ExpressPCB's design rules, I didn't see it. So while the CAD software is relatively easy to use, it will allow you to make mistakes and won't tell you about them! I don't know if you can send your board files to ExpressPCB and have them check it.

I'd suggest using a different CAD program. EAGLE wouldn't be a bad choice (tho it's a bit quirky), but the problem is that your 1.25" x

12" PCB is too big for the cheap/free version which is limited to a max size of 4" x 3.2".

Perhaps someone else has some words of wisdom...

-Dave Pollum

(snip)

I put just a *tiny* bit of solder on one pad - even just dragging the tinned tip of your iron is usually enough. Then I place the part with a pair of tweezers, and lightly press straight down on it with the tips of the tweezers to lightly hold it in place. Heat the pad that you tinned, remove your iron, and bam - it's tacked down, and perfectly placed. Then you can do the other pads as you wish.

steve

Thanks Dave,

I was / am worried about the via size and placement. I looked at a bunch of OEM boards I had laying around and they seem to use similar setups. (**funny how after doing this one excercise, it interests me to see how others have done it!! **).

Also, the ExpressPCB program does a little checking when you run the "Layout / Comput board cost" process. It yelled at me the first few times complaining exactly about via placement...

BTW, is there a good write up somewhere on "How they do it" ? I'm guessing they cut and drill a non plated board, then copper plate the whole board, apply resist, then etch? I'm curious how they manufacture the plated thru vias...

James

--
Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 15KW generator project)

"Anything that can happen, will happen" -Stephen Pollock from:
"Particle Physics for Non-Physicists: A Tour of the Microcosmos"

" Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent. "

I make about 20 SMD PCB's/year in my kitchen.. But if you want just a few boards then using a PCB fab house will be my recommendation.

D from BC

One more bit of advice: Don't worry about packing those SMD devices tightly. The first SMD board I did was a board with a 555, 4017, darlington transistors, and associated caps/resistors to sequence strings of LEDs on a model rocket. When I laid it out, I did it as densely as I thought I could solder... then nudged them a little closer. Then I thought "Ah... this board really has to be small. I'll nudge them a little closer." Then I did that about three more times.

In the end, along with hookups for the LED strings and all, it ended up being about 1 square inch. And when you look at the thing, it looks

*sparse*. Assembly was no problem, I could have gone tighter still and been just fine. I stopped where I was because the board had to be large enough to put an SMT coin-cell holder on the other side. :-)

steve

When I build SMD boards I always pluck a hair from my head and use it as a spacer.

MY DIY SMD PCB's are sooooo high density that I made a DIY manual pick and place vacuum machine. Tweezers took too much space. D from BC

Late at night, by candle light, snipped-for-privacy@manx.misty.com (Don Klipstein) penned this immortal opus:

I usually use a toothpick to nudge it into place and hold down. I'll try rubber cement on the tip, seems like a neat idea.

For lifting I have a piece of aquarium tubing with a filed-off syringe needle on one end. Place the needle over the part and suck on the other end of the tube.

- YD.

--
Remove HAT if replying by mail.

Dave,

I carefully read the specifiation from the company, and you are correct, my via placement was indeed to close to each other and other traces. What a bummer.

However, I've since re-done the layout a 2nd time and I think I got it under control this time. Thanks for the heads up!

James

-- Take Care, James Lerch

(My telescope construction,testing, and coating site) (My 15KW generator project)

"Anything that can happen, will happen" -Stephen Pollock from: "Particle Physics for Non-Physicists: A Tour of the Microcosmos"

" Press on: nothing in the world can take the place of perseverance. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. "