If the test strip legs are spread outward on the side that has been plated (plated side out and resist side in) the deposit stress is tensile in nature. If the test strip legs are spread inward on the side that has been plated, the deposit stress is compressive in nature. It is necessary to know the total units or increments spread between the plated test strip leg tips from both sides of the center line on the measuring block scale and the average deposit thickness in order to calculate the deposit stress. If the deposit thickness cannot be determined by actual measurement, it can be calculated as follows:
W
T = ────────── = cm
D (7.74 cm²)
T = deposit thickness in cm
W = deposit weight in grams,
D = Density of the plated material, g/cm³ (Table of Density Values for the D)
A = surface area in square centimeters. Since the plated surface area on a test strip is 7.74 square centimeters, the formula for nickel thickness can be shortened as follows:
Note: If using x-ray for thickness it would = T after the deposit thickness is known and the number of increments spread between the test strip leg tips has been determined, the deposit stress can be calculated thus:
S = UKM÷3T where: S = kg/cm²
U = number of increments spread (See Table B for conversion),
T = deposit thickness in cm,
K = the test strip calibration constant will be labeled on each lot of test strips,
M= the modulus of elasticity of the deposit ÷ by the modulus of elasticity of the substrate material (See Table A).
Test strip material recommended plating conditions for plating See table 2 page 8 of DSA Brochure
Note: If the test conditions cause the test strip leg tips to spread beyond 20 units, reduce the deposition time and the deposit thickness for the test to improve accuracy.
For PN: 1194 – Copper-Iron Alloy 0.00508 cm thick (deposit stress from 105 to 10194 kg/cm²)
DEPOSIT STRESS M value for nickel plating M = 1.715 The correction factor for the difference in the modulus of elasticity between the deposit and that of the substrate = EDeposit ÷ ESubstrate = 2110813 ÷ 1230797 = 1.715 kg/cm².
For PN: 270NI – Pure cold rolled Nickel 0.0011 inch thick (deposit stress from 14 to 4218 kg/cm²)
DEPOSIT STRESS M value for nickel plating M = 1.0000 The correction factor for the difference in the modulus of elasticity between the deposit and that of the substrate = E Deposit ÷ E Substrate = 2110813 ÷ 2110813 = 1.0000 kg/cm²
