B0 Introduction
B0.1 Conventional method

All methods given in this Appendix may be considered to be of sufficient accuracy provided that specimens conforming to the methods specified in this Appendix are used correctly. The conventional test method chosen should be the one that yields the most reliable results expected, taking into account factors such as coating thickness, part shape, part size, coating composition and substrate material.

Other methods that prove to be equivalent to or better than the test methods given in this appendix may also be used in individual cases.

ISO 2179-1986 “Common national standards for Electroplating coating thickness measurement

B0.2 Arbitration method

B0.2.1 General Requirements

In case of dispute, the arbitration method shall be selected according to the specific circumstances in B0.2.2~B0.2.6. When using the Coulomb method and the chemical regression method, the method given in Appendix A is also applied to determine the alloy composition, and the calculation formula given in B2.5 is used to obtain more accurate thickness values, although the thickness values calculated from the coating density may still be less than the true thickness values.

The local thickness of B0.2.2 is greater than 9µm

Microscopy as specified in B1.1 was used.

The local thickness of B0.2.3 is less than 9µm

If the surface of the coating is smooth enough that the electrolyte does not leak out from the electrolyzer probe, the Coulomb method specified in B1.2 is used for determination; Otherwise, the microscopic method specified in B1.1 was used for determination.

ISO 2179-1986 “Common national standards for Electroplating coating thickness measurement

Note: To measure the base layer by Coulomb method, the tin – copper alloy layer should be removed first. To remove the tin-lead alloy layer by Coulometric measurement, or to use the backoff method used to analyze the specimen in A2.

B0.2.4 Average thickness of tin-lead alloy coating on copper, nickel or steel

The chemical regression method specified in B2 was used.

B0.2.5 Average thickness of bottom coating or average thickness of tin-lead alloy coating on substrate or bottom coating other than copper, nickel and steel.

If the surface of the coating is smooth enough that the electrolyte does not leak out from the electrolysis probe, the Coulomb method specified in B1.2 is used; Otherwise, the microscopic section should pass through the center of the sample using the microscopy method specified in B1.1, and at least 5 equidistant measurements along the microscopic section are required.

ISO 2179-1986 “Common national standards for Electroplating coating thickness measurement

B0.2.6 Thickness of tin-lead alloy coating in through holes of printed circuit boards

Microscopy as specified in B11 was used. The microscopic section should be parallel to the axis of the hole and perpendicular to the surface on which the coating or substrate is to be measured (see GB/T “62).

B1 local thickness measurement

B1.1 Microscopy method

Use the method specified in GB/T6462, which includes the protective coating procedure, that is, use a copper protective coating with an electroplating thickness of not less than 10µm.

The accuracy tolerance of the proposed method is ±0.8µm, or ±5% of the thickness when the thickness is greater than 25µm.

B1.2 Coulomb method

The method specified in GB/T4955 was used. The proposed method generally has an accuracy within 10%.

ISO 2179-1986 “Common national standards for Electroplating coating thickness measurement

B1.3 β-ray backscattering method

The method specified in GB/T5931 is adopted, which requires the accuracy of the instrument and operation to make the measured value of the coating thickness accurate to less than 10% of its real value; The accuracy is determined by the mass per unit area of the coating, the atomic number of the substrate metal and the variation of the alloy composition.

B1.4 X-ray spectroscopy

The method specified in GB/T16921 is adopted, which requires the accuracy of the instrument and operation to make the measured value of the coating thickness accurate to less than 10% of its real value.

ISO 2179-1986 “Common national standards for Electroplating coating thickness measurement

Measurement of the average thickness of B2

B2.1 Principle

A suitable sample of known surface area (if the sample is small, several more can be taken), clean, weigh, remove the coating by chemical dissolution method, and weigh again.

This method is generally not suitable for small workpieces or coatings on certain metals (see D2.5 in Appendix D). If necessary, the average thickness measurement should be taken as the average thickness measurement value (see GB/T12334).

B2.2 Reagent

Only analytically pure reagents and distilled or deionized water were allowed during the analysis.

B2.2.1 Removal of coating on iron substrate and nickel substrate

20g antimony trioxide was dissolved in 1000mL cold concentrated hydrochloric acid (l)=1.18g/mL).

Note: The workpiece to be backed by this solution may not be suitable for re-tapping.

B2.2.2 Removal of coatings on copper and copper alloys

Add 50mL of 6%(mass ratio) hydrogen peroxide solution to 50mL of 40%(mass ratio) fluoroboronic acid solution to make the deplating solution. A new de-plating solution should be prepared before use.

B2.3 Sample

The total surface area of one or more specimens shall be sufficient to obtain a weight loss of not less than 0.lg, and the surface area shall be measurable to an accuracy higher than 2%. Use appropriate organic solvents or steam degreasing to remove all dirt from the sample.

B2.4 Steps

ISO 2179-1986 “Common national standards for Electroplating coating thickness measurement

B2.4.1 Coating on iron substrate and nickel substrate

The cleaned sample (B2.3) was weighed to an accuracy of 0.00lg and immersed in the de-plating solution (B2.2.1). After stopping the gas, keep it for 2min, take out the sample from the solution, effectively clean it with running water, brush off the dirt, dry it, and weigh it after cooling. The accuracy is 0.00lg.

B2.4.2 Coatings on copper and copper alloys

The cleaned sample (B2.3) was weighed, accurate to 0.001g, and immersed in the de-plating solution (B2.2.2), the coating was complete

Remove immediately after dissolution. Clean effectively with running water, dry, cool and weigh to an accuracy of 0.00lg.

B2.5 Result representation

B2.5.1 The average thickness of the coating with a nominal tin content of 60%(mass ratio), in µm, is calculated as follows: