Homemade printing and soldering for small components.. the best way

Question

Which is the best way to solder small components such as SOIC or QFP44 packaged components to a PCB without using adapters?

And how can I manage to print PCBs with small track distances and widths for those type of packages?

Answer 1

Drag-soldering works very well for me. Tack down two opposite corners ensuring that the chip is correctly positioned, apply plenty of jelly flux, put a small blob of solder on a medium tip and drag it along each row of leads. Remove any solder bridges with desoldering braid. I use a mini-hoof cartridge with my Metcal system which is specifically designed for drag-soldering.

I often make my own PCBs at home using the photo-etch process; the UV exposure unit cost me about £20 to make, and I print the transparencies on my HP inkjet printer. I don't have any problems with fine-pitch devices, and can go down to 8/8 mil track/spacing. I normally use 10/10 or 12/12 mil, though.

Answer 2

I'd go buy a hot air rework station, like the one reviewed here: http://www.youtube.com/watch?v=vva2t21sOAs

The rework station is an absolute must-have if you plan on doing anything with SMD and you can do a lot of assembly using one.

An IR oven is nice to have if you plan on producing several PCBs, but you can't do rework with one.

Unless you are in a hurry, then forget all about making PCBs yourself, order some from China in stead, it's much higher quality than what you can do yourself and it's really cheap these days.

See this page for a description of what you can expect and a link to the webshop: https://github.com/dren-dk/HAL900/wiki/Quirks-of-PCB-manufacturing-at-ITead

Answer 3

SOIC packages can be soldered with out the need of any special soldering equipment. http://murlidharshenoy.wordpress.com/2009/10/17/diwali-project-led-luminaire/

For finer pitch packages try the Hot plate technique.This blog has good instructions on how to solder Finer pitch packages

http://kennethfinnegan.blogspot.com/2010/12/soldering-goodfet-31.html

Answer 4

For the soldering of those type of components you either want a Hot Air Rework station (a small hot-air blower that gently blows air at hundreds of degrees C) or, ideally, a reflow oven.

You can make your own Reflow oven from a small Toaster oven, and something to control the temperature. There are many sites on the net where people have documented their attempts.

As for the production of the boards - I wouldn't recommend trying to make your own.

I assume you mean with the toner-transfer method...

Having tried myself and had poor results I wouldn't recommend even bothering to try it.

Firstly, getting the heat just right so the toner transfers well without it blurring and blending with the neighbouring tracks is almost impossible at those distances. Also, you need a very good high resolution laser printer in order to get the detail levels.

Secondly, you really really really require a solder resist mask, which you won't get when you make it yourself. Without that you'll just end up with a homogeneous blob of solder instead of a nicely soldered line of pins.

For TT board production I rarely go below 20/20 (20 mil track width and 20 mil track spacing), and never below 15/15. Even then I sometimes get problems.

Of course, you could always invest in the equipment to do Photo Resist etching - but that's not cheap and only worth it if you're going to do quite a few boards.

Personally I like to use a service called "Go Naked" from Spirit Circuits here in the UK. They will create a professional prototype board for you free of charge, but with no solder mask or ident layers - just the tinned copper tracks. It's pretty good for testing things or making a one-off to try out an idea. It can be a bit of a pain not having the solder mask layer though, and I tend to paint the critical areas with liquid latex (under the name of Multi-Core Solder Resist Mask - price about £10 per 250ml bottle) to make soldering easier.