On 24/03/2011 02:12, Vitaliy wrote:
> Oli Glaser wrote:
>> I remember having a hard time finding them in the first place - just
>> looked quickly now for a US source but no luck.
>> We get them from Mega:
>> https://www.megauk.com/through_hole_rivets.php
>> The brand is Favorit, they are meant to be used with a special punch but
>> we didn't get one, as they work well anyway for our purposes.
>> I got some ideas from this page (very good in general for PCB making)
>> Look under the Through-Plating header - some of the links may still work
>> (I remember a couple being out of production though)
>> http://www.electricstuff.co.uk/pcbs.html
> Interesting. So how do you get the rivets in -- just push them in with th=
e
> tip of a tweezer?
>
>

Yep, pretty easy as long as the hole is drilled right. They give you a=20
drill size (0.2mm larger IIRC) for each corresponding rivet e.g. 0.4mm=20
rivet hole size needs 0.6mm drill bit, 0.6mm rivet needs 0.8mm bit and=20
so on.

>> We use a UV light box (4 x 15W tubes, timer etc, bought on eBay, very
>> good quality and cheaper than RS/Mega offerings. If anyone wants to know
>> exactly which one let me know and I'll check)
>> I imagine for hobby purposes the price will be more of a factor and some
>> savings could be made, probably as you say about half the price of a
>> board house for materials.
>> However there is a free 2-layer service available here (UK, Spirit
>> Circuits) although I think it is directed more at companies (they ask
>> for company details, though it does not specifically mention that they
>> will not deal with hobbyists)
> What is the advantage of using UV over presensitized PCBs sensitive to
> regular light?
>
>

I'm not sure, never used sunlight. I imagine the timing is more=20
repeatable (3-4mins for our UV box) as the strength is consistent, so=20
maybe there is less risk of over/under exposure. Possibly the focus of=20
sunlight is better given it's a direct point far away, though as long as=20
the mask is flat (no space underneath for "sideways" light to get in)=20
then this shouldn't matter much - the more expensive UV boxes have=20
vacuums to hold the mask flat.
How long does it take to expose your boards using sunlight?
Might try making an additional (identical) board in sunlight next time I=20
use the tank, see which comes out better.

>> I use Ferric Chloride - have you had better results with Ammonium
>> Sulphate?
> We like Ammonium Sulphate because it's clear. FeCl is dirty, it stains
> everything it comes in contact with and you can't see the board in the ta=
nk
> as well.
>
>

Sound like good reasons, may have to get some and try it out. Be useful=20
to have clearer fluid (you can put a teaspoon of salt in FeCl to make it=20
clearer, but it's still pretty dark) and if it doesn't stain as badly=20
that's a bonus.


>> I do use Sodium Metasilicate rather than Sodium Hydroxide for developing
>> as it's far easier to use (not as sensitive to timing, temperature etc)
>> I made a small etch tank using nichrome wire for the heater driven by
>> PWM/MOSFET with a PIC16F, and a DS18B20 with PID to control temperature.
>> Used a fishtank pump for the agitation also.
> Fancy! We use a glass tray and sodium hydroxide, because that's what the
> manufacturer of our PCBs (MG Chemicals) recommends. It works fast and
> definitely is time-sensitive (easy to overdevelop), but with practice it
> stops being an issue.
>
>
>> We could do with a proper drill press though (did have one but it was
>> old and broken, so we gave it away), that's probably the most time
>> consuming part currently, plus as you mention broken drill bits. I'm
>> thinking it's worth spending the money to get another half decent one,
>> as it will have plenty of other uses too. The Proxxon one looks nice and
>> a decent price - are you happy with it?
> We are happy with it. There are some minor things that could be better
> (e.g., a universal chuck) and we use it with a variable transformer for
> speed control, but it does the job very well, and has minimal vibration.
>
> Vitaliy
>


--=20
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