Hello everyone!

Today I've been thinking about and researching how to get SMT parts somehow stuck onto a PCB. In particular, I found out about stencils, solder paste, and ovens.

I did a little playing in KiCad just now to see if I could reduce my own DIP-only board into mainly PLCC and SOIC parts, with maybe the ROM in a ZIF socket. It seems I can *greatly* reduce the size of the board by using SMT parts. I use JLCPCB and they also have a stencil creating service. Add a toaster/oven and presto, you (seem to) have greatly reduce size, cost, and effort. It seems almost too easy.

Over the past months I've been a DIP-only kind of guy, thinking that I couldn't possibly solder SMT parts by hand. And I probably still couldn't, but this seems like a viable option.

I have read here a few posts where some of y'all have techniques to hand-soldering these sorts of things. Raking, wicking, dipping, dripping, etc (whatever you'd want to call it). I... don't know if that's what I'm going for here but I'm all ears What experiences do y'all have with SMT in general, and maybe even this solder paste / toaster method? Is it as easy as it seems? Got any horror stories?

Just exploring and want to see what the experts think about it. Thank you everyone!

Chad

Don't be shy, is my advice.

There's no need to jump into the deep end; you could begin with the SMT packages with .050" pin spacing. You get a substantial space saving, and they're really not that much harder to solder than .100" devices.

Later, as you get more confident with your soldering skills, the even higher density devices won't seem so daunting.

-- Jeff

_________________
In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

1, 2, 3, 4 of SMT soldering in order of importance:
1. A good microscope
2. Fine tip solder
3. fine solder
4. liquid flux

2, and 4 are easy to find, 3 is hard to find, and 1 is expensive. Very few people believe in 1, but it is a game changer. There is a good reason why high-rel assembly shops have high quality microscope on every assembler's bench. If you have a good 10X stereo inspection microscope, you'll wonder what's all these chatters about SMT soldering being difficult.

My bet is you'll spend a few frustrating years doing SMT without a good stereo inspection microscope and eventually got one and then kick yourself for putting it off.
Bill

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

As others have said, I would just go for it. SOIC devices (0.05" spacing - half the DIP spacing) are not hard to solder. The first "proper" SMT device I soldered was a FT240 USB chip, which has a 0.65mm pin spacing (a quarter of DIP). That was quite daunting at first, but it gets less daunting once you've done it once and more so once you've done a few.
I didn't use a microscope, but I did use a pair of these:

https://www.jmldirect.com/mighty-sight- ... lights-new

After soldering, I inspected all the pins carefully with a x10 handheld magnifier. Then I did a continuity check to each IC pin and a check for shorts to neighbouring pins. Some rework was required, but eventually it was all good. You will almost certainly get a few solder bridges, but they are easily removed using solder wick. I wouldn't use a solder sucker though - the sucker can kick back and bend the tiny pins on the SMT chip, which will cause you a major headache.

For practice and to allow you to do prototyping with SMT devices, I'd suggest getting some of these boards:
https://www.ebay.co.uk/itm/272079767591
https://www.ebay.co.uk/itm/394519627239
https://www.amazon.co.uk/gp/product/B08P5J5KVZ

The other problem is, a solder sucker tool accumulates tiny flakes of solder inside. And what you DON'T want is for some of that debris to exit the tool and end up on your circuit board, where the tiny particles could end up wedged unseen between IC pins, or in some other unfortunate place.

(I do occasionally use sucker, but I make an effort to keep it below the PCB, not above.)

-- Jeff

_________________
In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

Yep, people are generally not convinced about the merits of inspection microscope. I, on the other hand, have two stereo microscopes.

SMT library for hand soldering is different than SMT for machine soldering. Hand soldering needs longer pads where soldering tip can heat the pad instead of heating the SMT pins directly. Longer pads also allow you to inspect "toe" and "heel" where SMT pin joins with SMT pad. I have a page showing the difference between machine soldering pads and hand soldering pads.
https://www.retrobrewcomputers.org/doku ... tsoldering
Bill

Good responses, thank you for the insight. I could definitely use a microscope, or some type of magnification. When I'm soldering and trying to look at things, I sometimes have to look below or above my glasses and get REEEAAALLLYYY close with my nose to molten solder and a blazen hot iron. The SOIC and PLCC parts were definitely on my list to try first, anything more than that is downright scary.

BUT, I guess I started this to learn more about stencils, solder paste, and toaster ovens. I have seen (as Garth pointed out) a lot of discussion from y'all already about SMT stuff. I am more interested in not having to do a fantastically terrible job by hand Any body use an oven before?

Thank you all!

Chad

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

I was sure it would be impossible to hand-solder SMD parts for me. I remember when I received my first PCB fotr the 74HCT6526, I just started laughing when I saw the PCB. "It's so tiny!!"

And sure, first try was a mess. Second and third were no better.

I found out, you need good tools. A good, clean, in good shape solder tip. Good quality solder. Good flux. Lead-free solder is a pain to handle. For me, it doesn't flow properly without tons of flux, and was using a top quality solder. Average leaded solder gave me much better results.

Eventually, i moved on to solder paste and hot air gun. Works like a dream. SSOP parts (1.27mm - 50 mils) I can do with no visual aid. (In my 40's, but I'm lucky to still have goot sight, after having surgery 4 years ago). Last year i did my first TSSOP (0.65 mm - 25 mils). It took a good amount of flux, but again, solder paste plus heat gun worked like a charm. Only a couple of bridges. Still, at this pitch, I needed some magnification.

I really think with steady hands, good sight(or proper visual aid) and good tools, SSOP is within the reach of many people. It's worth giving it a try. I, fore sure, surprised myself here!

I got a fairly cheap video microscope thing with a built-in screen, and it works pretty well - I used it to do SMT soldering with a practice kit, and it was quite effective especially for smaller components.



Regarding footprint libraries, I recently wanted to lay out an SMT version of something I'd already made with through hole components, but found that Kicad 6 doesn't seem to have standard footprints for SMT components. I thought there would be some standard footprints based on pin pitch, package width, etc. Are they actually not standard sizes, do you have to download the individual footprints for all the ICs you're planning to use? Or make your own footprints?

I haven't tried Kicad, yet. I'm still using a 25-year old schematic/layout tool and have created many non-standard footprints.
Bill

Garth, I found that topic created by BDD:

viewtopic.php?f=4&t=3509

I see he gooped it on thick, and his conclusion was to try a stencil next time but didn't get around to trying it. One thing that was confusing to me was BDD mentioned the solder that was already 'printed' onto the board, but then he used solder paste as well. Are BOTH needed? I had thought it was only the solder paste that was needed. I also found it interesting that so much turned into so little (relatively). It's like it nearly vanished, minus the few bridges that resulted.



Heat gun! That's a good idea too!



I see KiCad has some of the SOIC parts, and the PLCC's also. It doesn't have a SOIC-20 though, oddly. I am definitely not opposed to making my own footprints, I see that I have to do that more regularly than not for my various components. I think nearly every connector I have is custom, my oscillators and polarized caps are custom, and anything else besides the DIP sockets, resistors, and bypass caps is custom.

Anyways, I think the conclusion I'm seeing is that I will just have to try it out for myself sometime and see what I think. And *when* it fails, try again, and then again

Chad

If your boards are single sided and smaller parts (eg. no big chonky inductors or connectors), the skillet method works really well. It has much better visibility than the toaster oven method so you can easily see when your board is done. For small boards, I have a hot plate at work that is used specifically for this purpose (I also have access to an industrial 6-zone reflow oven there as well, but will often just hot-plate smaller boards when making prototypes).

I do recommend using a stencil and no-clean solderpaste. I use a laser cutter at work to cut stencils out of mylar, but I've also milled them out of brass shim stock from McMaster using a V-bit and you can also just order them from oshstencils for pretty cheap if you are in the US (the shipping is more than the stencil if out of the US). Anywhere in the 3-mil to 5-mil (1mil = 1 thousandth of an inch) range for thickness is a good place to start.

One note about solderpaste - it's just like heat sink grease... if you get some on your hands and wipe them on your pants, you will just have it on your hands AND on your pants.

Some other folks mentioned a stereo microscope, and I will add my vote for that as well. I liked the ones at work so much that I bought my own for home. I usually add a Barlow lens, which is an add-on objective lens that screws in on the bottom of the scope. A 0.5X Barlow lens will cut the magnification in half, but it also doubles the focal length. That gives a lot more room for a soldering iron and hands, and it's removable if you need the magnification back.

I've also used video microscopes and those work reasonably well, but the stereo vision makes it much easier to see things in 3D. I also solder through-hole components under my microscope and do SMT component placement with tweezers under it as well.

I prefer the "Zoom" style of stereo microscopes, but they are more expensive. My home unit is an AmScope brand with widefield eyepieces and a 0.5X Barlow lens and I paid around $400 for it. It's a big investment, but it was worth it for me and I use it for non-electronics things too.