Homebrew PCBs

Hi all,

I appologize for the rather vague subject line, but I'm having a 
little trouble.

First off, want to say hi to the list, Although I have done some PCB 
etching and such, I still consider myself a very newbie.

Here is my problem - I'm looking to decide on a path to follow for 
doing my pcb's at home.  I really only expect to do single and dual 
layer boards.  

My problem is methodology.

I've done a little photo resist, some ink resist, etc., but I'm at a 
crossroads now.

I'm either going to follow the path of photoresist and etch, and buy 
or build a UV exposure box.  Or I am going to go the path of getting 
an inexpensive or homebuilt CNC router to cut out my PCB traces.

I've talked with one person that happens to be on the list and he 
prefers the etching methods.

But I really am looking for opinions - I don't want to start a war, 
which I know a post like this can do, so if you prefer to respond to 
me in private, that's fine.

My personal thoughts, the reason why I am fence hedging right now 
is...

Etching - chemicals hazardus with disposal rules, extra time taken 
to print transparency, expose the board, develop the board, then 
etch the board.  Not sure where to get a good supply of the 
photoresist and developer, negative or positive.  Been using pre-
sensitized boards, but would rather self-sensitize the boards as 
needed.

Routing - Seems quicker, generates a bit of a mess, can't do as 
dense traces which limits use of surface mount chips, or higher 
density TH chips.  More difficult to align for dual sided boards. 
significantly more expensive to enter into, but equipment could be 
used for other things.  Not sure where to find quality bits for 
routing PCB's (the angular tip ones)

The other thing I'm confused about is the solder mask (I think 
that's what it's called) - the green layer commonly found on 
production PCB's -is it possible to find this stuff and how 
difficult is it to apply?

I really hate to ask so many questions in one email, but I've been 
reading thru the files on this site, and the links provided in the 
links section, as well as the past several pages of posts, and I'm 
still unsure of where/how to proceed.

-Tony

> Routing - Seems quicker, generates a bit of a mess, can't do as 
> dense traces which limits use of surface mount chips, or higher 
> density TH chips.  More difficult to align for dual sided boards. 
> significantly more expensive to enter into, but equipment could be 
> used for other things.  Not sure where to find quality bits for 
> routing PCB's (the angular tip ones)

Don't forget the dust is copper and fiberglass.  unless you remove it 
as the source, it will chew up your machine.


As far as bits, go, Harbor Freight often has 10 bits for 10 bux or 50 
bits for 25 bux.  there are others around.  Most often, these are 
really high quality bits that are ground out of tolerance.




> 
> The other thing I'm confused about is the solder mask (I think 
> that's what it's called) - the green layer commonly found on 
> production PCB's -is it possible to find this stuff and how 
> difficult is it to apply?


I wonder how to get the stuff everywhere but on the pads !

This is a thread I'd like to see get discussed.

Dave

> 
> > 
> > The other thing I'm confused about is the solder mask (I think 
> > that's what it's called) - the green layer commonly found on 
> > production PCB's -is it possible to find this stuff and how 
> > difficult is it to apply?
> 
> 
> I wonder how to get the stuff everywhere but on the pads !
> 
> This is a thread I'd like to see get discussed.
> 

This is an interesting one - I have found only one solution so far, 
but I'm not sure how I feel about it yet.

There is a GC product called Red Insulating Varnish - this varnish 
can be thinned with another GC product (which I can't remember the 
name of off hand) - but from a vendor that I had purchased from in 
the past, they had said that it has been done where you make a print 
of the solder mask, and develop a printing screen for it, with the 
thinner, thin the varnish to a point where it can be used in the 
printing screen like a normal ink and viola (sp?) instant 
soldermask/insulation layer.

Keep in mind I have NOT tried this yet, but I do plan to at some 
point when I have my screen printer that I anticipate getting for 
christmas.  

Also, it's a red coloring, so it won't look normal ;)

-Tony

There's a Japanese site that I saw (didn't bookmark) that the guy 
just put some tiny stickers to mask off individual pads.  The solder 
mask was also a Japanese labled product and came in a spray can.  
Peeled the stickers off after the laquer setup.  It looked pretty 
good when he was done, but man that's pretty maticulous.

Found it!
http://www.interq.or.jp/japan/se-inoue/e_pwbm.htm

--- In Homebrew_PCBs@yahoogroups.com, "Dave Mucha"> > The other thing 
I'm confused about is the solder mask (I think 

> > that's what it's called) - the green layer commonly found on 
> > production PCB's -is it possible to find this stuff and how 
> > difficult is it to apply?
> 
> 
> I wonder how to get the stuff everywhere but on the pads !

--- In Homebrew_PCBs@yahoogroups.com, "kg4wfx" <tony@e...> wrote:
> > 
> > > 
> > > The other thing I'm confused about is the solder mask (I think 
> > > that's what it's called) - the green layer commonly found on 
> > > production PCB's -is it possible to find this stuff and how 
> > > difficult is it to apply?
> > 
> > 
> > I wonder how to get the stuff everywhere but on the pads !
> > 
> > This is a thread I'd like to see get discussed.
> > 
> 
> This is an interesting one - I have found only one solution so far, 
> but I'm not sure how I feel about it yet.
> 
> There is a GC product called Red Insulating Varnish - this varnish 
> can be thinned with another GC product (which I can't remember the 
> name of off hand) - but from a vendor that I had purchased from in 
> the past, they had said that it has been done where you make a 
print 
> of the solder mask, and develop a printing screen for it, with the 
> thinner, thin the varnish to a point where it can be used in the 
> printing screen like a normal ink and viola (sp?) instant 
> soldermask/insulation layer.
> 
> Keep in mind I have NOT tried this yet, but I do plan to at some 
> point when I have my screen printer that I anticipate getting for 
> christmas.  
> 
> Also, it's a red coloring, so it won't look normal ;)
> 
> -Tony


OK, There are work arounds, but what do the board houses do ?

I was thinking a little brush on the drill so if you maksed first, 
the brush could scrape the mask off, but then that would have to be 
before thru-holes are plated.....

I would think the mask it last ?

Dave

I use the positive method using MG Chemicals borads, etch with 
Ferric Chloride.  I like this best of any that I have tried.  Yes it 
is a lot of stuff to have set up, you really need a room or rooms 
just for this if you make PCB's very offen.  Make the Positive with 
Transparency film with a ink jet printer and using Ivex Winboard 
software.  

Ben