Hi Adam
[snip]
> From what I imagine, you have all the tanks close to each
>other and you dip the boards in the appropriate order in
>each bath.
Yes, however the tanks are SEPERATED from each other by a ~1" sized
gap. That's needed cause the temperature of the baths must be
controlled individually. That's important here and I mention it to
give another indication why creating a tank and puting in walls is a
bad idea here.
>Obviously you must rinse between baths so that
>the subsequent baths do not become cross contaminated at any
> appreciable rate. I'm wondering how you do the rinsing. Do
>you have the tanks near a water tap, and simply lift the
>board from the process tank, wait 20 seconds to finish
>dripping, move to the running water tap, rinse, wait another
>20 seconds to drip, then proceed to the next process tank?
Ok, here we go:
bath #1 is a Cleaner Conditioner that must be run at 65-70 degrees
celsius (149 - 158 farenheit) the PCB must reside in this bath for 7
minutes. Thereafter there is a 1 minutes static rinse followed by 1
minute spray rinse .
bath #2 is a "Predip" - no heating requiered roomtemperature is ok.
The PCB must be in this bath for 1 minute. There is NO rinse made
after this bath cause the water would contaminate the following bath.
bath #3 is the "Palladium" bath also called "Activator". That's said
it's the bath which makes the holes conductive. Duration is 7 minutes,
temperature is also room temperature. There is a 1 minute static rinse
followed by 1 minute spray rinse after this and before the next bath.
bath #4 is the so called "Intensifier". The purpose is to make
palladium that happens to reside on the copper go away and to
intensify it in the holes. Duration is 4 minutes. The bath temperature
must be 45 degrees celsius ( 113 fahrenheit) There is also a 1 minute
static rinse followed by 1 minute spray rinse.
bath #5 is then finally the coper plating bath. This is ok at room
temperature. Duration is 24 minutes followed by a final 1 minute
static and 1 minute spray rinse.
I rinse the pcb's simply in a water tank, then go to the wall water
outlet? (don't know the propper english term) and rinse it there for
another minute. I use a kitchen timer watch to controll the durations
and take very much care to stay within these times and temperatures. I
never had a problem yet by doing so.
>I am thinking of building my own processing tanks, but
>wondering if its worth including the rinse tanks after each
>stage. Like you I have managed to weld 3 mm PVC plastic
>sheet (the gray stuff) and I bought a secondhand hot air
>welder for this job. I also built a plastic sheet bender
>using a hot element wire running a line in the middle of the
>piece of particle board. I found it impossible to get
>straight and neat right angle bends using only a hot air
>gun.
I did not used any aditional tools. If the gun is having a small pipe
header it's sufficient to simply move it up and down along the line
you want to bend it up until it stats to bend. Then take a 90 degree
angel that lies on a table or such and bend the plastic to 90 degrees
holding it down to the table and into the angle. Was really easy with
the "hobbyglass" I was using. I created a little piece of wood with
the size of the final width of the tanks (i.e. two of them. one for
the 5cm tanks and another one for the 10cm tank) that I used to keep
the distance of them equal. The remainig part is practizing :) I had
to create ~4 aditional tanks that were not ok.
>The best way to construct a series of small narrow
>tanks is to divide a big tank into small ones by welding
>dividers inside. In this way 10 or 15 separate baths could
>easily be built with the least amount of welding and materials.
No, that's a problem with heating and keeping temperatures apart. I
also can tell you that it's going to be very difficult to have those
tanks dens cause you will have big trouble reaching them as narrow as
they are.
>A two stage counterflow rinse stage would consist of two
>tanks next to each other, the first tank (the tank you first
>dip) has about 1" higher liquid level than the second tank.
>The wall between the two tanks has a open hole so the first
>tank pours into the second tank when its liquid level goes
>above this hole. The second tank has an effluent hole about
>1" below this level. If you are a bit interested in
>counterflow rinsing then check out;
>http://www.justoffbase-tools.co.uk/tools.asp?parent=1I2433P1056M0
>
>Theoretically a 20cm x 20cm PCB will need 100 mL of fresh
>water added each rinse cycle to keep the concentration of
>the second rinse tank 1/1000 of the process tank in a two
>stage counterflow rinse system.
>If 3 stage counterflow rinse is used the concentration of
>the final tank is reduced to 0.005% or 50 ppm. Ok its clear
>2 stage rinsing is more than enough for the job.
Intresting article Will look into this later (I'm a bit short of time
at the moment)
>In your setup, is it possible to empty individual baths ? I
>was thinking of welding small block of plastic to the tank
>bottom and then tap a 3/4" BSP thread into this block for
>screwing in a drum tap. Something like shown
>http://www.justoffbase-tools.co.uk/tools.asp?parent=1I2433P1056M0
I wanted to do something with such a drum tap but haven't found them
here. Since with my station the tanks simply are standing within the
grid takeing them out even if they are full is no problem. Once they
are out they can easily be emptied into normal plastic tanks. In
general this is definately a very good idea cause some of the fluids
tend to "vaporize" away if the tanks are not closed - which is hard to
achive. So, if you can empty the tanks whenever the station is not
needed this is definately the best solution. Aditionally you will find
that the stations remains a lot cleaner over time this way.
>My aim is to have then entire PCB processing equipment in
>the one area so I can make a board without having to run
>around over the place. By including rinse tanks I think it
>will make the job easier to control. Would you agree ?
Yes, I agree that having the rinse tanks close is a good idea. I don't
know though if you manage to have a good spray rinse situation without
too much hazzle though.
Markus