Think & Tinker, Ltd.
P.O. Box 1606, Palmer Lake, CO 80133
Tel: (719) 488-9640, Fax: (866) 453-8473
Sales: Sales@ThinkTink.com, Support: Support@ThinkTink.com
||Hull Cell Analysis
Tin/Lead Plating Baths
The Hull Cell
The brightener/leveler formulation
developed by Lea Ronal is a two part part additive system that
functions to smooth out and distribute the solder plated onto the
surface and in the holes of a PCB. At the current time there is
no simple test to directly analyze the additive or carrier levels
in the bath or to determine if they are in balance with the other
functional constituents. There is, however, a rather simple
technique to infer when the additive level needs attention and to
determine just how much material to add. This technique uses a
miniature plating cell commonly known as the Hull Cell.
Using the procedure described below, the cell is used to
test plate a series of sample boards to determine when the bath
needs adjustment, and, when used with the above analytical
techniques, to determine how much of to add. PC SolderOn
Carrier is normally maintained through routine replenishment of
PC SolderOn Additive which contains small quantities of Carrier.
Principle of Operation
The Hull Cell is intended to act as a
quick check on the health of the tin/lead plating bath. Using the
cell in conjunction with the chemical analyses it is possible to
qualitatively and quantitatively analyze all of the major
constituents of the bath.
When filled to the line marked on the side
of the cell, the volume of the test sample is 267 ml. If we
- V = volume of main plating tank (liters)
- H = amount of addition agent added to Hull Cell to produce acceptable test plate (milliliters)
- C = amount of addition agent needed by main tank (milliliters)
the multiplicative factor that relates
what you add to the Cell and what you will need to add to your
plating bath is given by:
- No. 267 Hull Cell
- Copper test plate
- Corrugated solder anode
- 5 cc syringe of SolderOn additive
- Read the manual that came with the Hull Cell carefully
before testing your bath! Or you can not read the
book, flounder around for half of the day, burn up $25
worth of test plates, and still not know what is going
on. READ IT!
- If this test is being conducted prior to using the bath
for the day, dummy plate a test board (i.e. plate a piece
of scrap copper for about 45 minutes). It is important
that the bath be adequately stirred up and filtered and
that the tin/lead level be adjusted by dummy plating
before using the Hull Cell.
- Fill the cell to the line marked on the side.
- Peel the thin plastic cover sheet off of the copper test
plate and face the mirror bright surface toward the
anode. This VERY smooth surface will act as the target
for solder plating and will vividly show any defects in
the plating process.
- Connect the corrugated anode to the positive (+) terminal of the
power supply and the test plate to the negative (-) terminal.
- If the power supply can source more than 2 Amps, adjust
it's output until it is sourcing 2 Amps.
- Plate the test panel for 10 minutes.
- Remove the panel from the bath, thoroughly rinse under
cool tap water, and carefully dry with a non-abrasive
- Examine the test plate carefully. A properly adjusted bath will yield a test plate that is a uniform gray-white matte across the entire panel.
- If the plate shows a dark band in the mid to high current density areas or bright banding in the mid regions, the additive level in your bath is probably too low, or the bath has become contaminated with organic leachings from dry film plating resist. (This assumes that you have conducted all of the previous chemical analysis tests and have adjusted the bath to be at the optimum point for each parameter)
the syringe filled with additive, add 10 ml to the sample
bath and run another test plate. This will be equivalent
to adding C mL to
the main bath and should be enough to compensate for any
additive consumption from regular use (assuming, of
course, that you have been somewhat diligent in
maintaining your chemistry). Examine the second
the high current "burn" and bright band have
disappeared and the test panel acceptable, your bath is
probably not contaminated and it is safe to add the
equivalent amount of additive to the main bath.
It is safe
to dump the contents of a Hull Cell back into the main
bath but MAKE SURE TO REMOVE THE CORRUGATED ANODE FROM
THE CELL PRIOR TO DECANTING THE LIQUID. IT IS A
CLASS "A" PAIN TO FISH AN ANODE OUT OF THE
BOTTOM OF THE PLATING TANK.
the test panel indicates that the plating solution could
use a bit more tuning, start with a new sample, add 10
ml additive (to bring the additive up to the level used
in step 11 and add an additional 2 ml to the cell.
Plate a new panel and examine it very carefully to
see if its appearance has improved. Continue in
this fashion until no further improvement is observed.
Total up the additions to the final test cell,
multiply by C, and add
the resulting quantity of PC SolderOn Additive to the
If the addition of additive in step 11 did
nothing to improve the panel, the bath is probably
contaminated and should be carbon treated prior to
- Once the plating bath is properly adjusted you may proceed. Remember to diligently record any and all additions
to your plating bath so that you can build a
"consumption database" to assist you in cost of
goods determination when estimating the operating costs
of your shop.
- Once the plating bath is properly adjusted you may
proceed with your board plating.
Proactive Additive Maintenance
The additive is constantly being consumed
by the plating operation at the rate of approximately 0.35
to 0.50 ML (cc) per Amp hour. Before plating each board,
use this relationship to determine the amount of additive to add
prior to using the bath. This will help insure that the bath is
always operating at an optimum level and should reduce the need
for large periodic additive adjustments. A small amount of
carrier is present in the additive so the proper carrier level in
the bath is accomplished by additive maintenance.
If you are plating a board with 100 sq.
in. of copper exposed (both sides including robber bars), and you
are plating up 260 micro-inches at 20 Amps per Square Foot (ASF). Total plating time will be 6.5 minutes and the plating
current will be 14 Amps (20 ASF x 100 sq.in. / 144 sq.in per sq.ft). This plating job will require about 1.5 Amp-hours
of current and consume about .65 ML of additive.
HANDLE WITH CARE
Always wear protective clothing, acid resistant gloves, and a full coverage face shield
when handling this or any other corrosive material.
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Copyright © 1994 - 2014 Think & Tinker, Ltd.
Updated 2/13/2014 7:36:58 AM