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SMT Soldering: It's Easier Than You Think (comic) [pdf] (siliconfarmers.com)
18 points by gnosis on May 19, 2012 | hide | past | favorite | 15 comments


This video shows how easy it is: http://store.curiousinventor.com/guides/Surface_Mount_Solder...

Through-hole: Fit part through holes, grab iron, tack solder, put iron back, flip board, grab cutter, cut leads, put cutters back, solder joints, flip board back.

SMD: Grab tweezers, pick up part, place, tack solder, adjust fit, solder.

Through-hole sucks. SMD is a bitch with the wrong methods and tools, but very pleasant with decent tweezers, liquid flux, good desoldering braid, Chip-Quik super-low-melting-point desoldering solder, and a reasonable tip on the iron. No expensive stuff needed. But the right methods are, which are easily learned.

SMD has better electrical properties - less noise pickup and lower inductance, which is necessary for high frequency work.

Certain chip packages are tricky to solder in SMD, like BGAs I believe. Possible though. And probably easy with the right tools and technique - capillary action tends to align everything anyway if you can get heat into the solder.

Very small SMDis not pleasant ... 0805 is a breeze, 0603 is fine, 0402 can be a bit tense sometimes. Smaller than that is unpleasant ...

You can do SMD soldering!


I can't tell if you are forcing your point or not, but I have to correct. You're doing through hole wrong: that way will take forever to do a board.

Stuff the board with the smallest height components. Place a compliant material on top of the board (e.g., firm foam rubber). Flip board over and solder all components. Put iron down. Cut leads. Flip board over and repeat for next highest components.

This minimizes the number of tool swaps and handling and is very fast.

That said: I much prefer SMT soldering and I don't even use an iron anymore, even for just one board: manually dispense paste on all the pads. Place all components at once. Put in toaster oven. Bake (I manually adjust the profile while watching the clock). Remove perfectly soldered boards. But yeah, I won't do anything smaller than 0805 or 0.5mm pitch QFP just yet :-)


Hahha, forcing a point yes, but also just being a little thick and not 'getting' the foam-pad method. THANK YOU.

In real life, doing many through-hole components at once, I have tack soldered them top-side - when possible, e.g. resistors, not possible for radial caps.


In production environments you buy special frames for that method.

You can also get "cropping plates" and "cropping machines". A cropping plate is a sheet of steel with holes drilled for all through-hole component leads. You place a few PCBs on it, then stuff all components. You then place the plate on the cropping machine, which has "drop down pins" to hold the components in place and sliding blades under the plate which scrape / cut the leads off. You then take the PCBs off the plate and put them through a wave solder machine.

One potential problem with tacking topside (and this is more theoretical than real) - sometimes the through hole plating is cracked. On a multilayer PCB this may mean that you don't have proper connection between all layers. If you only solder from the bottom of the board you can see if the solder has correctly flowed. Some high-spec jobs will forbid soldering on the topside. (Aerospace, etc.)


To give some context, All of this stuff is actually easy to build: 41Hz Amp32, energy-efficient 2x25W hifi amp, sounds amazing, 17 grams, fits in a matchbox with room to spare: http://shop.41hz.com/shop/item.asp?itemid=38 41Hz Amp4, similar but higher power and sounds ridicullusly good - looks like a hard SMD build maybe, but absolutely isn't: http://shop.41hz.com/shop/item.asp?itemid=6 41Hz PS4, tiny switching voltage regulator - modern 780x/LM317 replace ent that is 90% power efficient and can handle a ~90V in/out differential: http://shop.41hz.com/shop/item.asp?itemid=317&catid= GrubDAC, pretty small and nice usb powered audio out: http://diyforums.org/GrubDAC/GrubDACoverview.php

None of them are really feasible through-hole; Similar is possible but noticeably bigger and less performant.

(Not affiliated with any vendors listed above, no commercial interest, just like the stuff.)


The editing of the jumble up above was precluded by the HN anti-procrastination feature kicking in. Here it is - along with my apologies - in a more presentable form:

41Hz Amp32, energy-efficient 2x25W hifi amp, sounds amazing, 17 grams, fits in a matchbox with room to spare: http://shop.41hz.com/shop/item.asp?itemid=38

41Hz Amp4, similar but higher power and sounds ridiculously good - looks like a hard SMD build maybe, but absolutely isn't: http://shop.41hz.com/shop/item.asp?itemid=6

41Hz PS4, tiny switching voltage regulator - modern 780x/LM317 replacement that is ~90% power efficient and can handle a ~90V in/out tension differential: http://shop.41hz.com/shop/item.asp?itemid=317&catid=

GrubDAC, pretty small and nice usb powered audio output: http://diyforums.org/GrubDAC/GrubDACoverview.php


"Through-hole: Fit part through holes, grab iron, tack solder, put iron back, flip board, grab cutter, cut leads, put cutters back, solder joints, flip board back.

SMD: Grab tweezers, pick up part, place, tack solder, adjust fit, solder."

You didn't even mention flux! Flux is very important in all hand-soldering. Without it, you are going to have a very hard time.


Yeah, you're right. A simple two-joint part like that can be done without additional flux, just using what's in the solder - but the example would have been less poetic, more accurate, and most importantly more educational if it had had a fluxing step.


In Japan, even run-of-the-mill home-improvement DIY stores have SMD soldering supplies :) Good solder, very nice soldering irons labelled "For SMD Use", even high-quality liquid flux in 50-100ml bottles with a needle tip.


From experience, its definitely not easy (even with a hot air station).

Bring back though the hole components - much more hackable.


Really? I'm much happier placing SMT parts than through hole. Granted BGAs are an issue, but everything else is honestly easier.


0402s and below kill me. I did a bit of time doing rework in the 90s and controlling solder on such a microscopic scale is an absolute bastard. its ok placing it first time but if you screw up, life is pain. Never tried a BGA and never want to. They're pick'n'place territory if you ask me.


I couldn't imagine doing 0402 by hand. For people who don't know, 0402 is 1.0 mm x 0.5 mm (0.039 in × 0.020 in).

Using an oven to solder is nice because it's mostly self-correcting. The melting solder pulls itself to the shape of the pads and also pulls the components into correct placement. (With a bit of luck).

Hand soldering SMD components wasn't ever one of my skills. (And my through hole soldering was, if I say so myself, pretty good.)


I have to agree. The day I need to do an 0402 is the day I seriously start looking for a used P&P machine.


You may want to try using solder paste and either a hot plate or a toaster oven.




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