I want to try the soldering paste method, and notice that the paste comes in different temperature ranges. I wonder what you all would use for transistors that are approx. 2.9 mm x 1.4 mm? And if you have any other tips or suggestions as to what equipment you use, that would be appreciated also.
Here's a pic of one on a penny:
Here's a pic of one on a penny:
If you want to use paste then this will be of little use, but as you ask for other tips and suggestions:
https://www.diyaudio.com/community/...ow-to-do-it-without-specialised-tools.127924/
https://www.diyaudio.com/community/...ow-to-do-it-without-specialised-tools.127924/
Check the datasheet, some manufacturers provide the soldering information.
It would be helpful if you posted the transistor type.
It would be helpful if you posted the transistor type.
The short version is that it usually doesn't really matter, especially with small devices. The lower-temp stuff is easier to make sure it all reflows, and will allow you to assemble a board with some larger components that would otherwise resent higher temps... but the low-temp stuff is often not lead-free, which may or may not be relevant to you.
For a board with a few passives and semiconductors only, no really large items like power inductors, you can use pretty much any grade of solder, up to the lead-free high-temp stuff. Datasheets for each component will give a suggested temp profile, and a max temp. Obviously you need to stay below the max temp for every component present, and you want to obey they pre-soak times for larger components so as to avoid thermal stress.
Boards that get very hot in use should not be assembled with low-temp solder, for obvious reasons.
For a board with a few passives and semiconductors only, no really large items like power inductors, you can use pretty much any grade of solder, up to the lead-free high-temp stuff. Datasheets for each component will give a suggested temp profile, and a max temp. Obviously you need to stay below the max temp for every component present, and you want to obey they pre-soak times for larger components so as to avoid thermal stress.
Boards that get very hot in use should not be assembled with low-temp solder, for obvious reasons.
Duh! I didn't even think of that. I've only had a couple sips of coffee. It's this transistor:
https://www.mouser.com/ProductDetail/onsemi/MVMBF0201NLT1G?qs=3PKVEWFFm2/F4Y4GJLifjg==&mgh=1&gclid=CjwKCAiAiKuOBhBQEiwAId_sK9qvYVQo3em7f3x6GtLf-otiGvxbrlUaKXz70RzSuYJllQvcVIyMwhoC9QMQAvD_BwE
And I have the datasheet. Thank you.
okay its only a sot-23, don't bother with solder paste, unless you have to solder a couple of hundred.
Solder paste is too fiddly for soldering a couple of sot-23 transistors, just use small diameter solder, around 3mm will do and a fine tip soldering iron, it will take a few seconds to solder.
Solder paste is too fiddly for soldering a couple of sot-23 transistors, just use small diameter solder, around 3mm will do and a fine tip soldering iron, it will take a few seconds to solder.
I will be doing several hundred. (Possibly, several hundred per month.) I was thinking that the paste option would allow me to do more of a production line type assembly technique. But also, I'd like to try the paste/hot-air style just for the sake of learning it. I am micro-min and SMD formally trained. But the training was oriented more towards single component repair/replacement, rather than production line.
okay, that make sense. Have you considered looking at getting the boards loaded by a contract electronics company ?
The reason I say this, when you are reaching this quantity the assembly house is the only way to go to achieve consistent quality. They also have the proper pick and place machines and reflow ovens. Then consider how are you going to do all this by hand and more-so as you are new to smd soldering.
It may seem like fun for the first 10 boards, then you'll realise it's not worth all the effort and headache. The reason smd came about was to fully automate the assembly and soldering processes. A couple of hundred boards is a days work for an assembly house, you are looking at weeks of work doing it by yourself.
The reason I say this, when you are reaching this quantity the assembly house is the only way to go to achieve consistent quality. They also have the proper pick and place machines and reflow ovens. Then consider how are you going to do all this by hand and more-so as you are new to smd soldering.
It may seem like fun for the first 10 boards, then you'll realise it's not worth all the effort and headache. The reason smd came about was to fully automate the assembly and soldering processes. A couple of hundred boards is a days work for an assembly house, you are looking at weeks of work doing it by yourself.
I agree. But it's not my company. I'm the one who's being contracted out to, so to speak. It's a very small business. (I'm not at liberty to say who, at this time.) And, It's a great opportunity for a retired electronics tech, such as myself. I can do it. But I do want to be as efficient, and cost effective, as possible.
After this job, you likely won't want to do any large scale smt work again. SMT wasn't designed or intended
to be done manually.
Yup. I understand. Primarily, I do guitar, and some vintage audio, repair and mods. One of the things I learned from my luthier friend, was to build jigs any time you needed to do repetitive tasks. I'm working on one right now to place, and hold, these things in position while I solder them in. Looks good on paper. 😉
The first thing you should buy is reverse tweezers. It grips the part until you squeeze it to release.
Also small diameter solder, and some flux in a dispenser. You'll use a lot of flux.
And a magnifying glass, a good one.
https://www.techni-tool.com/product...Rl9hak_2nUTeWpX3CowHNt_LLNPW0jiRoCbGgQAvD_BwE
Yup. I have all of those, except my flux is paste. Looking at "liquid" flux on Amazon as we speak. 😉
Go to JLC, get your boards fabbed and parts assembled for you.
It's inexpensive and fast to get this done.
It's inexpensive and fast to get this done.
Adam: Not my company. Not my decision. And, it would put me out of a job. 😉
Rayma: Got it.
For smt hand work, tinning all the pads first (even if they are already tin or gold plated), works much better.
Once tinned, use flux and braid to remove most of the solder, leaving only a very thin layer on each pad.
Then soldering will be much easier and more reliable. Don't worry about making a mess, when finished just
wash off all the water-soluble flux. A small stiff brush will help.
https://www.digikey.com/en/products...cDaIDoBcAEBlAsgEQCwGYAMeAKgGICMeAtAHIYgC6AvkA
I would consider outsourcing that. It shouldn't cost much to have a few transistors mounted to a board, especially if you have a panel of boards and only a few unique parts. I found a local company to do my assembly for me. Never looked back. Hand-assembly simply doesn't scale.
If you really, really, really want to solder them yourself, I suggest having a solder paste stencil made. OSH Stencils is your friend in need. Then set up a jig that allows you to align the board and the stencil. OSH Stencils sell some L-shaped polycarbonate bits for that. For prototyping I tape the L bits to the table and then tape the stencil to the L once I have it aligned with the PCB. That makes it easy to just flip the stencil out of the way when you're done smearing the solder paste. I've done several boards that way. Reflow either in an oven or with a hot air tool.
Tom
I really, really, really MUST do it myself. But that's a good idea too. I've watched some YT vid's of that process. I'm going to try several different techniques until I find what work's best for me. But I appreciate all the ideas and feedback I've gotten so far.
Thanks all;
Artie