[sdiy] Digital delay memory

Fri Apr 29 20:46:06 CEST 2016

I started SMT probably 20 years ago as well (with a 208-pin PQFP - soldered
with a 3mm diameter tip; no idea how I was able to do it with that!). I
don't miss through-hole at all - SMT saves a lot of drilling...

I eventually learnt drag-soldering (maybe 5 years ago) - a little bit
harder with home-made boards, but not impossible.

Smallest I've done happily is 0402, but I did try some 0201 work on an
iPhone. That didn't work as expected - although a solder blob was good
enough to make the circuit work. I've also pulled components quite easily
with an SMT rework hot air soldering pencil (only one of the many
components I've pulled didn't work the second time).

The biggest chip I've done is a 240-pin PQFP (Xilinx Spartan 3E), and
hooked SDRAM and also SRAM onto that. Both memories worked fine - and that
was all DIY.

So to me, DIY is 10mil track (with 10mil clearance), and 0.5mm pin spacing
(I have done 0.4mm, but that's really at the limit of my lithography).
Smallest hole size is 0.6mm, but prefer 0.8mm. But because I don't have an
accurate drill (it's just a pillar drill), the pads need to be a little bit
larger than I would like (I can just about get a 16mil track in between
0.1" spaced pins).

At the beginning of this year, I was able to switch from a software
development role in my company to a hardware development role, running the
hardware development team in the UK.

This meant I had a budget to buy a load of gear (it's a new team, and we've
never had hardware capability in our office before), so I've been able to
get all the stuff I always wanted at home, but couldn't afford - and also
use the components I wanted to use but couldn't because soldering them
would've been a huge pain (mainly QFN).

So I've got a stencil holding/alignment machine, reflow oven, PCB
preheater, proper fume extractor, magnifying glasses and will shortly have
a manual pick-and-place machine. I've also got a much better logic analyser
and 4-channel oscilloscope, and a room with antistatic flooring and desk.

It also meant I was forced to switch from Eagle to Altium, since Altium is
used in the US office.

And I don't really make PCBs at home any more now. I still do for test
boards, but being able to do 6mil tracks (and smaller) and multi-layer
boards is fantastic. And stencils really makes life easy.

I used the reflow oven for the first time this week, and it was probably
99% successful - one component hadn't been aligned properly, and I'd
smudged the solder paste while putting it down (which is why I want the
pick-and-place machine - I do have a vacuum component holder, but it's
still fiddly when it's a 0.5mm QFN package). This meant it had a couple of
shorts. And, for some reason the solder on one aluminium capacitor's leg
didn't melt. I've upped the temperature from 235 to 245 (it's lead-free),
and increased the initial heating time by 30 seconds to see what happens
the next time.

Currently I'm just doing 0603s on the board, but the next one will be
0402s. I don't think I need to go down smaller than that just yet...

What I don't like is that I need to fill in a hot-works form every time I
want to do some soldering. But as I was asked to come up with the form,
I've made it easy but not too onerous.

I am contemplating my next home project - which may use BGA - since I can
use the gear at work to solder it. Could that still be considered DIY? I
suppose it could be - but you need to fork out a lot of cash to be able to
DIY.

Maybe that could be the topic of another thread - what is DIY? What can be
expected of people?

On Fri, 29 Apr 2016 at 17:18 Jay Schwichtenberg <jays at aracnet.com> wrote:

> I was dragged into SMT about 20 years ago. I thought it was going to be
> really hard. Right now I don't think so. I don't like going below 0805s and
> things like SOT363 packages aren't easy.
>
> For me what really matters is having the right tools for the job. Decent
> temp controlled soldering iron, small diameter solder, solder flux, good
> light and a magnifier. You will also have to change you working technique
> to
> do SMT. So I think that a big issue is getting the tools (which can cost
> money, a lot are on a budget) and just not learning how to do something
> new.
>
> I have 3 Mutable boards that I will be doing sometime this year in a
> toaster
> reflow oven. So that is an option. If I can get the reflow oven working
> I've
> been thinking about actually doing some work with BGA packages too. Some
> have been pretty successful at it.
>
> And BTW I'm 63 so the hands and eyes are as good as they use to be but I
> can
> still get it done.
>
> Jay S.
>
> -----Original Message-----
> From: Synth-diy [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of
> Gordonjcp
> Sent: Friday, April 29, 2016 3:48 AM
> To: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Digital delay memory
>
> ***
>
> Surely SMD would be easier for the DIYer than through-hole?  I can only do
> through-hole stuff at work because I don't have the tools to deal with it
> in
> my workshop at home.  I guess I should really get a bigger nozzle for my
> welding torch.
>
> --
> Gordonjcp MM0YEQ
>
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