Homebrew PCBs

----- Original Message ----- 
From: "Matthew Smith" <matt@...>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Monday, March 24, 2008 10:11 PM
Subject: [Homebrew_PCBs] New Member


>
> Transparencies are contact printed with the above onto Kinsten
> pre-sensitised board and developed using sodium metasilicate.  (I gave
> up with caustic soda - often as not it would remove ALL the etch-resist,
> exposed or not.)

I don't have any problems with NaOH, you just need the right concentration 
(about 12 g/litre). You do have a lot more latitude with sodium 
metasilicate, though.

>
> Holes are something I hate; I have been trying to use carbide drills in
> a cheap-and-nasty, full-sized drill press.  All I will say is that it is
> very expensive in drills.  Last week, I took delivery of a Dremel and
> press - hopefully this process should get a bit easier for me.  (I still
> prefer larger SMDs though - anything that saves drilling is worth it!)
>
> Issue that I will be needing to address:
>
> * I'm still a little shaky when it comes to double-side boards; I have
> yet to perfect a method of aligning top and bottom films in a way that
> suits a) my UV exposure box and b) my shaky hands.  If I can get away
> with single-sided and a few jumpers, I generally will.

I just use jumpers.

>
> * Tinning boards.  Tinning solution is just too expensive for what I am
> doing.  Hand-tinning with solder doesn't seem to suit smaller components.

I don't bother, I remove the resist by rubbing with kitchen paper moistened 
with IPA, and it leaves a small amount of resist on the board which stops 
them oxidising. I don't have any soldering problems, although it would be a 
bit easier with tinned boards.

>
> * Making vias.
>
> * Mounting SMDs with central pads (in addition to the side pads).
> Haven't actually tried this yet, will probably just run a big pad end-to
> end of the device, poking out either end, and put the iron on one of the
> ends.
>
> * Mounting SMDs with lots of small pins.  At the moment, I'm just trying
> to avoid them altogether.  I've read about the toaster oven technique -
> still sounds pretty tricky to me.

I don't have any problems with that, using drag-soldering with plenty of gel 
flux.

Leon
--
Leon Heller
Amateur radio call-sign  G1HSM
Yaesu FT-817ND transceiver
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller