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Ok, copper etchants come in many different flavors. The ammonia alkaline are
type the most commonly used for tin or tin/lead metal resists (i.e. pattern
plating). The tin forms near perfect resistance (3 um thickness) to the
ammonia type etchants, especially the sulfate based. I recommend visiting
your local university library and getting hold of a book called "Coombs'
Printed Circuits Handbook". It has many of the basics of PCB fabrication that
can start you off.

Here is the alkaline ammonia sulfate etchant I use. It is suitable for room
temp operation; Note: the high alkalinity makes it not suitable for use with
photoresists.

CuSO4.5H20 - 150 to 190 g/l (optimum 175 g/l)
25%(wt) aqua ammonia - 70% (vol.)
98% sulfuric acid - 3.0% to 4.0% (vol.)

pH should be between 10 and 11, adjust with aqua ammonia additions.
Tank must be sealed virtually air tight when not in use. Otherwise NH3 will
evaporate over time and pH drops significantly. regeneration is done with
stainless steel anodes in stagnate solution at current density between 3 and
5 A/dm2. Etch times at 25???C using air bubble agitation is 20 to 25 minutes
for 35 um copper foil. Only one place in the world I know of markets this
type of etchant, and that is the German company Elo-Chem. You won't see it
documented in many places.



No one uses electroless tin unless they have to. The tin is plated on all the
tracks directly after copper plating. Electrolytic tin plating works much
faster, cheaper, safer, more reliable, lower maintenance and more predictable
than electroless tin. The bath I use is the acid stannous sulfate type (looks
like banana flavored milk drink). See your friendly plating supplier for
necessary brighteners and chemicals.




j_hallows wrote:

At 06:32 AM 7/03/2002 -0000, you wrote:

--- In Homebrew_PCBs@y..., Adam Seychell <adam_seychell@y...> wrote:

I'm afraid it doesn't work like that. Buying a secondhand plating

machine

ain't going to make you PCBs.

I didn't mean second hand. I have been looking at the Prototype
plating machines. Like QuickPLATE. But they all seem to use the
process of squeezing conductive ink into the hole manually. The INK
in itself is expensive.

BTW: In your process the board is completely coated then plated
correct? So the board must have a thinner layer of copper to work
with in the first place or the thickness would be uneven correct?

Lates.

--
John Hallows

By starting off with blank copper cladded board you mean ? then yes.
The process is called "pattern plate" which I think is the most common
method of making through hole boards, both double sided and multilayer. The
other widely used method is "panel plate". This requires better setup with
photoresist and it must "tent" the hole walls to stop etchant from removing
copper inside the holes.
The carbon black though hole method is not suitable for making large
surfaces conductive. The holes are of relatively short dimension so the
contacts made to the carbon (i.e. at the hole ends where it meets up with
copper foil) can propagate copper through the hole wall during the first 1
to 2 minutes of the copper electroplating process.


Here is a good link describing the steps on manufacturing a multilayer
board (pattern plating).




some more PCB info can be had at;

First you should worry about how your going to etch.

You read my mine this was my next question.

If you decide on
pattern plate then you have choice of tin or tin/lead metal resist.

If you

choose tin then you must use alkaline ammonia etch. If you choose

tin/lead

then can use sulfuric/peroxide, ammonium persulfate etch, or

ammonia etch.

Is this the same stuff called Liquid Tin by MG Chemicals and a
similar prodouct by Datak? Or would these get disolved by the etching
solution?

However, I would be wary on having toxic lead plating solutions

laying

around. For the ammonia etch it can be chloride or sulfate based. If
chloride based then you have major waste problems because the

copper cannot

be recovered easily (at least what I know) and you will need to

treat then

dump your solution ($$$).

This is like ferric chloride?

If you use sulfate based alkaline ammonia then

the etchant can be electrolytically regenerated although the

etching rate

is much slower than chloride.

PCB fabrication may look simple on a flow chart but when it comes to
actually making it work its a whole different story.

Please excuse my ignorance. I have a lot zeal and a lot to learn.

--- In Homebrew_PCBs@y..., Adam Seychell <adam_seychell@y...> wrote:

I'm afraid it doesn't work like that. Buying a secondhand plating

machine

ain't going to make you PCBs.

I didn't mean second hand. I have been looking at the Prototype
plating machines. Like QuickPLATE. But they all seem to use the
process of squeezing conductive ink into the hole manually. The INK
in itself is expensive.

BTW: In your process the board is completely coated then plated
correct? So the board must have a thinner layer of copper to work
with in the first place or the thickness would be uneven correct?

Lates.

--
John Hallows

At 04:11 AM 6/03/2002 -0000, you wrote:

--- In Homebrew_PCBs@y..., Adam Seychell <adam_seychell@y...> wrote:

The cost is not the problem since the carbon dispersion should be

available

free from one of the large colorant producers. The dye is similarly
available. I got 20 kg of dispersion paste for $130 AU. This is

enough to

make about 1000 liters of solution. I've used about 100 grams so

far. The

cost will be in building or setting up your chemical tanks. Plating

copper is

easy but trying to plate uniform smooth copper on to your PCB takes

a lot

more effort. I would say the carbon black process is simple

relative to

copper plating. In other words, if you can get successful copper

plating then

I'm sure the carbon black process will be easy for you. The success

rate for

plating holes is just about perfect, but it has taken me a long

time to get

at this stage. The guide I described is a good start. The only

concern I have

is that a different carbon black dispersion concentrate may give

different

results.


Adam

I had a nice long reply to the group, (covering two posts). But it
seems yahoo decided to screw up my message. But the gist was
the cost of producing prototypes at home or sending away. I am not
too concern at plating since I am thinking of buying a prototype
plating machine. I more worried about making the holes conductive.
Your prodeduce looks appealing.

Lates.

First you should worry about how your going to etch. If you decide on
pattern plate then you have choice of tin or tin/lead metal resist. If you
choose tin then you must use alkaline ammonia etch. If you choose tin/lead
then can use sulfuric/peroxide, ammonium persulfate etch, or ammonia etch.
However, I would be wary on having toxic lead plating solutions laying
around. For the ammonia etch it can be chloride or sulfate based. If
chloride based then you have major waste problems because the copper cannot
be recovered easily (at least what I know) and you will need to treat then
dump your solution ($$$). If you use sulfate based alkaline ammonia then
the etchant can be electrolytically regenerated although the etching rate
is much slower than chloride.

PCB fabrication may look simple on a flow chart but when it comes to
actually making it work its a whole different story.

Adam

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I've been interested the subject of plated through holes for a long
time, however the cost of making 2 sided PCB's is so low it is not worth
the effort to start the mess with chemicals and plating tanks, not least
getting rid of old chemicals can become a problem.

Example: Two boards of Two Sided board with through plated holes, LPI
mask and silk screen, any size upto 64 square inches. $33.00 (thirty
three US dollars) per board total cost $66.00 no tooling charges, there
are a few limitation on drill sizes the smallest is 20 mil. Plus
freight... Five days turnaround.
Hans Wedemeyer

j_hallows wrote:

I had a nice long reply to the group, (covering two posts). But it
seems yahoo decided to screw up my message. But the gist was
the cost of producing prototypes at home or sending away. I am not
too concern at plating since I am thinking of buying a prototype
plating machine. I more worried about making the holes conductive.
Your prodeduce looks appealing.

Lates.





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I'm afraid it doesn't work like that. Buying a secondhand plating machine
ain't going to make you PCBs. There is long list of processing tanks
required along with an good understanding of the process. If ALL you are
trying to do is save money then your idea of making PTH at home is not
logical. Bath compositions are given to you by the vendors of the plating
additives and chemicals. You can also find much information in books. There
is no need for you to re-invent the wheel.

--- In Homebrew_PCBs@y..., "caveteursus" <j.walton@a...> wrote:

If I had a design with hundreds of boards, or multilayer boards, or
even tens of through-holes on 4 or 5 boards, I think that I could
find better uses of my time than etching them "homebrew" style.
Homebrew is great for PROTO's and One-off's, where you would like
something in a couple of hours, but the personal economics quickly
get swamped.

I have to admit I tradionally prototype using wirewrap method. I find
this faster with debugging. But since everyone is moving to highspeed
devices with more compact densities, (like PGA), I have no choice but
figure a way to easily make multilayer, (or doubly sided) boards at
home. The cost of sending away for boards to be made is a little
costly for me.

You are right about the economics part.

I was considering saving all my pennies and buying a commerical
prototype PCB plating machine. They are around the $1000.00 mark,
(the cost of sending out 20 boards to be made). I can always make my
money back by making prototypes for others at half the cost but this
isn't the main reason. But the main problem is making the holes
conductive in the first place which Adam address. This method seems
the easiest but major draw back is the experimenting with chemicals
to get the right ratio.

This is my first plan. My second plan would be to register in a local
community college PCB manufacturing course and use thier equipment.
$200.00 for the course and 50 prototypes made. ;) Cheaper I think.

--- In Homebrew_PCBs@y..., Adam Seychell <adam_seychell@y...> wrote:

The cost is not the problem since the carbon dispersion should be

available

free from one of the large colorant producers. The dye is similarly
available. I got 20 kg of dispersion paste for $130 AU. This is

enough to

make about 1000 liters of solution. I've used about 100 grams so

far. The

cost will be in building or setting up your chemical tanks. Plating

copper is

easy but trying to plate uniform smooth copper on to your PCB takes

a lot

more effort. I would say the carbon black process is simple

relative to

copper plating. In other words, if you can get successful copper

plating then

I'm sure the carbon black process will be easy for you. The success

rate for

plating holes is just about perfect, but it has taken me a long

time to get

at this stage. The guide I described is a good start. The only

concern I have

is that a different carbon black dispersion concentrate may give

different

results.


Adam

I had a nice long reply to the group, (covering two posts). But it
seems yahoo decided to screw up my message. But the gist was
the cost of producing prototypes at home or sending away. I am not
too concern at plating since I am thinking of buying a prototype
plating machine. I more worried about making the holes conductive.
Your prodeduce looks appealing.

Lates.

At 12:05 PM 4/03/2002 EST, you wrote:

In a message dated 04-Mar-02 08:15:05 Central Standard Time,
j.walton@... writes:

Homebrew is great for PROTO's and One-off's, where you would like
something in a couple of hours, but the personal economics quickly
get swamped.

Exactly! The only things that would make PTH at home "worth it" would be

any

one or combination of the following:

1. The personal "need" to prove "I can DO that!";
2. A lack of a professional PC-house within 50 miles, that will do PTH

for

you, essentially "while you wait";
3. A need to make PTH boards for a top-secret national-defence project that
must be completed TONIGHT;

Yes, it simply not worth doing PTH for a hobby. That's why I am selling the
boards I make.
Admittedly up until now they have all been single sided requests.

If I had a design with hundreds of boards, or multilayer boards, or
even tens of through-holes on 4 or 5 boards, I think that I could
find better uses of my time than etching them "homebrew" style.
Homebrew is great for PROTO's and One-off's, where you would like
something in a couple of hours, but the personal economics quickly
get swamped.

In a message dated 04-Mar-02 08:15:05 Central Standard Time,
j.walton@... writes:

Homebrew is great for PROTO's and One-off's, where you would like
something in a couple of hours, but the personal economics quickly
get swamped.

Exactly! The only things that would make PTH at home "worth it" would be any
one or combination of the following:

1. The personal "need" to prove "I can DO that!";
2. A lack of a professional PC-house within 50 miles, that will do PTH for
you, essentially "while you wait";
3. A need to make PTH boards for a top-secret national-defence project that
must be completed TONIGHT;

The cost is not the problem since the carbon dispersion should be available
free from one of the large colorant producers. The dye is similarly
available. I got 20 kg of dispersion paste for $130 AU. This is enough to
make about 1000 liters of solution. I've used about 100 grams so far. The
cost will be in building or setting up your chemical tanks. Plating copper is
easy but trying to plate uniform smooth copper on to your PCB takes a lot
more effort. I would say the carbon black process is simple relative to
copper plating. In other words, if you can get successful copper plating then
I'm sure the carbon black process will be easy for you. The success rate for
plating holes is just about perfect, but it has taken me a long time to get
at this stage. The guide I described is a good start. The only concern I have
is that a different carbon black dispersion concentrate may give different
results.


Adam

j_hallows wrote:

At 02:10 PM 3/2/02 -0500, David Saum wrote:

I need to draw some schematics
of my circuits, but I do not have
any software.

I think very highly of CADINT. They now have a free version which is good for up to 250 pins. In fact, you are using the paid for version with a license good for 250 pins. That license is free.

You can download the most current version from both www.cadint.com and www.cadint.se . You will have to fill out a little form to get it but they don't spam you or sell your email address. Be sure to also download the manual and tutorial - these are not included in the main download.

If you decide you like the package enough to upgrade to the pay version, they have several options available. The high end is fairly pricey but I feel it is serious bang for the buck. Note that the only thing that changes when you upgrade is the license file and passwords. You still keep the same program you were using with the free license.

In a nutshell:
250 pins - downloaded: free
250 pins - shipped on CD: $10
non-commercial - 500 pins: $90
Other variants are available.

dwayne



Dwayne Reid <dwayner@...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax

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--- In Homebrew_PCBs@y..., "caveteursus" <j.walton@a...> wrote:

Why not use Circuit Works conductive epoxy?

I think this product is just for reworking/repairing traces. Also
imagine if I had a board with 10000 holes. Do you think I want to
spend me time coating each hole.

--
John Hallows

This sounds good. I assume that this is just for hole activation and
standard electroplating is done next to build up the holes. What is
the success rate at home? And estimated costs? I don't want to dive
into something that would be so hard to replicate. Thanks for the
Info Adam.


--- In Homebrew_PCBs@y..., Adam Seychell <adam_seychell@y...> wrote:

The BLACKHOLE processes is fast, cheaper and safer to run than

conventional

electroless copper. This is expected since its aim is to replace the
electroless copper line in the PCB fabrication plant. The low

toxicity is the

reason I choose to develop a carbon black processes myself at home.

However

the chemistry of BLACKHOLE is a trade secret and your not going to

replicate

the same results at home. BLACKHOLE SP is the latest process from

MacDermid

and performs many times better than the process explained below. Of

course

the hobbyist doesn't need the reliability of a multimillion dollar

plant

producing a hundreds of panels a day. Its taken me about 6 months

of fiddling

around with carbon black dispersions, conditioning solutions and

circuit

board material to get a working process suitable for home use.

Basically my

process can be written down as follows;

1) drill PCB
2) clean copper surface with week solution of detergent/NaOH and

600 emery

paper.
3) rinse well with tap water
4) immerse in a "hole wall conditioner" 1 min
5) rinse well with with tap water
6) immerse in "carbon dispersion" 1 min
7) sponge off excess dispersion with sponge, so all holes are fully

empty.

8) hot air dry
9) repeat steps 4 to 8
10) immerse in "activator" for 1 minute
11) rinse well with with tap water
12) microetch in a conventional non-chloride etching solution
13) spray rinse with with tap water to remove all traces of carbon

on copper

surface.
14) air dry (optional)


Bath compositions/conditions;

hole wall conditioner:
5 to 10 g/l gelatine
0.04 to 0.06 g/l CuSO4.5H20 (as a biocide)
temperature between 26°C and 32°C
agitation: unnecessary


carbon dispersion:
2 to 4% (w/w) of non-ionic surfactant based
conductive carbon black dispersion paste*
6 to 10 g/l acetic acid
room temperature
agitation: unnecessary


activator:
1 g/l of dye D&C Green No.5 , C.I 61570.
room temperature
agitation: not known

non-chloride etchant:
100 to 200 g/l ammonium persulfate
or
1% hydrogen peroxide
10% sulfuric acid.
both baths may be used at room temperature.


* The carbon black dispersion paste is FLEXOBRITE BLACK 258/86

manufactured

by Degussa Coatings & Colorants.

You will have to phone around and get a 500g sample for aqueous

based

non-ionic surfactant conductive carbon black dispersion. Many of

the colorant

manufactures will have these. 500g will last you forever. There is

still a

whole range of information I left out, either because I haven't

worked it out

yet or I missed it. The D&C Green No5 is available from food, drug

& cosmetic

dye suppliers, either as a sample or in small volume (1 kg). Good

luck

Adam

No doubt it has a use for repairing things that need to be conductive.
I can't see squeezing epoxy into 500-1500 0.032" holes.
Another thing it would not allow through hole connections where
components like sockets need to be soldered in place. The chance of a
short due to smearing the epoxy during application makes me think it's
never going to be practical as a through hole connection.
hansw


caveteursus wrote:

Why not use Circuit Works conductive epoxy?


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Why not silver plate your PCB. It's easy to do with "CoolAmp".
CoolAmp silver plating powder is applied to a clean PCB with a damp
cloth pad. Simply dip the damp cloth pad into the powder and run onto to
the PCB, in about 30 seconds you will have a silver plated circuit
board, wash with water. I save the cloth pad in a plastic bas and for
small circuits, I find it still "plates" days later by simply wetting it
and not having to apply more CoolAmp powder. Soldering qualities are
improved also.
The plating is pure silver, this product is normally used to silver
plate very large circuit breaker switch contacts to reduce the contact
resistance. I originally ordered a 4 ounces and paid $70 for it. that
was 3 years ago and it's about half way used. I do a lot of prototype
PCB's in a year. $70 sounds expensive but compared to "Tin-It" that I
was using, CoolAmp is CHEAP.
This link shows my CNC stepper motor driver PCB plated with CoolAmp. The
plating does not turn black like silver does. This board is one of the
first I did three years ago, and last I looked at it (it's enclosed) it
was bright and shiny.

There are other examples at my site

Link to CoolAmp Description in the Thomas Register, and contact infor
for the manufacturer:-


For High Frequency applications I think CoolAmp will provide same
reduced surface resistance as normal silver plating does.

Hans W


caveteursus wrote:

I don't know if you want this around if you have kids, but MG
Chemicals makes "Liquid Tin" -- which plates in 5 minutes. The
contents are nasty -- fluoroboric acid and stannous fluoroborate.
Allied Electronics sells it, but not that they will ship all
chemicals separately and you pay a UPS surcharge for Hazmat. It's
expensive at $27 for 17 ounces.


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