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Prototyping Surface Mount

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Possibly a stupid question but how do you prototype suface mount PCBs? I will mostly be using Surface Mount LEDs and standard components for most other things so I don't need anything too crazy but I would prefer to prototype with actual surface mount LEDs instead of simply prototyping something as simple as this with actual LEDs and then bumping up resistors on the final assembly. Reason being, I need a small battery powered test bed which I can use on the move for testing various components for translucency and its important that I use the LEDs which I will be using in the final gadget to make things easier for myself.
 

alec_t

Well-Known Member
Most Helpful Member
Depending on the size of the LEDs, couldn't you just solder them to strip-board tracks?
 

MrAl

Well-Known Member
Most Helpful Member
Hi,

You might also want to look up the "Dead Bug" technique.

Here you basically turn the chip upside down and glue it to a piece of blank one sided PC board, with the copper side DOWN (so you glue to the non copper side). The copper acts as a ground plane but if you dont need this you can use any kind of board.
You then carefully solder wires to the IC leads that will be sticking up, and run the wires to wherever they go.
You do have to be extra careful to get the lead pinouts correct as the chip will be upside down which is an unusual orientation when trying to figure out what pin is pin 1, pin 14, etc. Best to mark pin 1 on the BOTTOM of the ic chip BEFORE gluing it down.
 
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Joe G

Member
I've held them with tiny allegator clips w/ wires attached for breadboreds, its a real pain when you've got 6 leads on a tiny chip, but does work w/o soldering it, I've also make
special pcb's from scraps with pins that I clamp them onto,
 

CraigHB

New Member
I do all my stuff with SMD. You can either do your own reflow or, with the right tools, hand solder components.

Doing your own reflow is sort of an art and I haven't mastered it. I hand solder everything so I can give you some pointers on that. I've done a bunch of projects with using 0603 (1608) parts and chips with .5mm pin pitches.

For multi-pin chips, I use a flux pen on the PCB pads. The flux comes out of the pen liquid but then hardens to a sticky paste in a few minutes which works perfect for holding the chips in place for soldering.

For really small parts like resistors and LEDs, I just melt a little solder blob on one PCB pad then tack the part down while manipulating it with a pair of beading tweezers. Once an end is tacked down, I can do the other end without holding it then finish the first end.

De-soldering braid is a must for fixing botch-ups and sopping up overflow.

With these very small parts, it's important to keep the tip on the iron squeaky clean. Re-tin and wipe the tip with a damp sponge frequently. If the tip gets any crud stuck to it, hit it with fine steel wool and re-tin.

An iron with an adjustable temp is critical, preferably digital. If the iron is too hot or too cold, soldering joints that small becomes next to impossible. Too hot and the solder can start getting sticky and fouled on you, too cold and it doesn't flow.

Here's what you need to do small SMD parts by hand;

* A PCB (obviously). I make my own for simple stuff and pay to get them manufactured for complex stuff.
* A flux pen. I use a Kester #186 activated rosin pen.
* Some beading tweezers or other fine tweezers
* .015" wire solder. I use 63/37 tin/lead with a mildly activated rosin core, Kester Part# 24-6337-9703.
* A temperature controlled soldering pencil with a .015" tip
* A stereo magnifier like the kind jewelers and watchmakers use, at least 10x
* De-soldering braid, #1, #2, & #3.
* 99% Isopropyl Alcohol for cleaning off flux residue (if using standard rosin flux)
* Small plastic container and flux brush for cleaning off flux residue.
* Canned air to blow off the alcohol after cleaning
 
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