Ed Okerson wrote:
>>There is nothing wrong with wet chemistry if handled properly. I've been
>>plating holes at home and nothing compares to real copper inside the
>>holes.
>
>
> So how exactly do you do this? What chemicals, equipment are needed?
>
> Ed
I happen to find chemistry fascinating, which I guess started since I
was introduced to the subject back in high school. Because it this I was
able to spent a ∗lot∗ of my time experimenting and learning about doing
PTH for the end goal of being able to fabrication PCBs at home. Having
spend the last 4 years or so fiddling with this I conclude PTH a time
consuming and tedious task, even with all the equipment laid out in
front of you. It is ∗not∗ possible to make a quick and simple PTH board
but rather requires lots of patients combined with enthusiasm to make it
work.
I've made probably a dozen PTH PCBs so far using my latest tank
equipment. About the quickest time I've made a PTH board is 4.5 hours,
counting from the time I begin drilling to the time I'm ready to solder
parts on, and no board yet has come out perfect. I prefer to make single
sided PCB whenever possible. When I've finally finished my setup I'm
hoping to get it down to 3 hours or less, otherwise PTH is just too
monotonous.
There are lots of steps, all of which have potential problems.
The processing tanks and the maintenance of the chemicals is important,
as well as a good understanding of how the process behaves.
These are most of steps and chemicals I use to make a PTH PCB. I'm still
refining the "Make holes conductive" step, as my current method needs
much improvement.
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1) Drill board
2) Cleaning
dishwashing detergent
60~80°C
5 minutes immersion
3) immersion rinse
4) Make holes conductive
high purity conductive carbon black aqueous dispersion
using a cationic type dispersion agent.
pH controlled to 9.0 with sodium bi-carbonate
room temp
5 minutes immersion
5) Absorb excess liquid with sponge.
6) Hot air dry
... repeat steps 4 to 6 ...
... repeat steps 4 to 6 again ...
7) Microstrip
Ammonium persulfate
room temp
5~10 minutes immersion
8) Spray Rinse
9) electroplate the holes
200g/L H2SO4
75g/L CuS04.5H20
Macdermid Macuspec copper plating additive
30~60ppm chloride
15~35 °C
120 minutes, bubble agitation
10) immersion rinse
11) laminate dry film photoresist
12) Expose
13) Develop
9g/L sodium carbonate
25~35 °C
2 minutes, paint brush agitation
14) immersion rinse
15) Etch
CuCl2+O2
room temp
5 minutes spray
16) immersion rinse
17) strip resist
50g/L NaOH
20~55 °C
10 minutes immersion
18) immersion rinse