Any deposited metallic coating can be tested for stress using the DSA Method

Note: Avoid storing Test Strips under UV lighting. This can over time crack the resist on the test strip causing it to break or peel during plating which will produce inaccurate results.

Nickel Sulfamate Bath Plating Conditions – See Brochure for select work process conditions. If the test stip legs do not spread after 2 min. you may need to plate the test strip slightly longer.

The deposit stress is compressive if the resist is on the outside of the Test Strip legs.

The deposit stress is tensile if the plating is on the outside of the Test Strip legs.

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 = ─────────────────── = Inches

D (7.74 cm²)( 2.54cm/inch)

T = deposit thickness in inches,

W = deposit weight in grams,

D = Density of the plated material, g/cm³ (see 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:

T = 0.0509 (W divided by D)

To determine the thickness of a nickel deposit that weighed .0349 grams, the calculation would be:

.0349

T = ───────── X .0509 = .000200 inch

8.88

**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:**

After plating a given test strip per the instructions given on page two, solve the equation

S = UKM ÷ 3T, where

U = Total number of increments spread between the test strip tips: example (2.4 + 3.1 = 5.5).

**NOTE:** The plating test should be continued until the test strip legs deflect from 2-20 units spread for the most accurate results. The required plating time can be determined experimentally by examining the degree of spread after each minute of plating. Metallic deposits should not exceed and average thickness of 150 microinches unless the deposit is soft such as tin. If the stress is near zero, a reading as low as 1 unit may result.

T = Deposit thickness in inches.

M = The correction factor for the difference in modulus of elasticity values between the deposit (in this case nickel) and substrate materials offered as follows:

PN: 1194 Copper Alloy Test Strips M = 1.7143

PN: 270NI Pure Nickel CR Test Strips M = 1.0000

* Note once you determine what the Modulus of Elasticity the deposit in PSI then divide that number with the Modulus of Elasticity of the Substrate material (PN: 1194 Copper Test Strips are 17,500,000 and the PN: 270NI Nickel Test Strip is 30,000,500) this will give you the M Value.

For the Copper alloy Test Strip Example: 55,000,000 ÷ 17,500,000 = 3.1428

*If your Modulus of Elasticity number is in GPA ÷ that number by 145 to get the PSI.

K = The calibration constant value provided by the manufacture (on Test Strip package).

S = The internal deposit stress in pounds per square inch.

Record the value of S for each.