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PREVIOUS NEXTAcid-Copper Electroplating Module Model 1000 Manual
Chemical Analysis - Hull Cell I
The Hull Cell
The brightener/leveler/carrier formulation used in most acid copper plating systems is basically a two part organic additive system that functions to smooth out and brighten the copper plated onto the surface and in the holes of a PCB. At the current time there is no simple test to directly analyze the brightener or carrier level in the bath or to determine if it is in balance with the other functional constituents. There is, however, a rather simple technique to infer when the brightener 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. In 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 colorimetric analysis techniques, to determine how much of each component to add.
Principle of Operation
The Hull Cell is intended to act as a quick check on the health of the copper plating bath. Using the cell in conjunction with chemical analysis it is possible to qualitatively and quantitatively analyze all of the major constituents of the bath. Further, by making all additions to the cell before adding anything to the main bath, you can avoid making mistakes that might result in irreparable damage to the bulk of your electrolyte.
When filled to the line marked on the side of the cell, a "standard" Hull Cell contains 267 ml (or 267 cc if you prefer) of electrolyte. Any additions made to the cell during the following tests must be multiplied by:
Scaling factor A = [Volume of main bath (ml) / 267 ml]
(A11 gal = 156, A22 gal = 312)
to yield the volume of the particular additive that must be added to the main plating bath.