Quality Inspection

1.Diameter: Measured with a micrometer of a 1/1000 mm precision.

2.Appearance: Inspected by means of seeing and touching.

3.Tensile strength and elongation:

Take a sample of 250mm long, and with a pulling machine pull the sample on both ends until broken. Calculate the tensile strength by dividing the breaking force (in Kg) by the original cross sectional area (in mm2) of the sample. Calculate elongation in mm by subtracting 250mm from the sum of inner lengths of the two broken segments, and elongation in percentage by dividing the difference by 250mm.


4.Thickness of coating:

Measure the thickness by means of X-ray. Alternatively, immerse a piece of sample in 40% (or above) HBF4 solution. As soon as the coating is stripped and the copper base is exposed, remove the sample from the solution. Thickness of coating is the difference of diameters before and after tin is stripped.

Thickness of coating = (pre-stripping diameter – post-stripping diameter)/2

5.Bending endurance:

Fix one end of the sample in a hole with 0.5mm of curvature on the edge of opening. Attach the specified weight to the other end. Conduct a test run by first bending the loaded 90o to the left, then 180o to the right, and finally back to the original position. Repeat the above test run until the sample is broken. The bending endurance is the number of test runs successfully conducted.


                        Round Wire Diameter                       Weight       

                        0.51 (include) mm under                   250 g                  Sequence:1→2→3→4     

                        0.51 - 0.9 (include) mm                     500 g                  Counting  :1→2→3→4    

                        0.90 mm over                                 1,000 g                                   count 1 time


6.Winding property:

Wind a sample around round wire of the same diameter as the sample. Then unwind the sample. Repeat the above steps 3 times. Inspect if any crack is resulted on the coating.

7.Tin-soldering property:

Immerse the sample into melted solder (tin 60%, lead 40%) of 235±5. Wait for the amount of time specified below, then remove the sample from the solder. Examine the percentage of immersed surface that remains coated by solder.

Diameter (mm)

Time (second)

< 0.8





Take a sample of bare copper wire of 1 meter long. Measure its weight with a scale and its resistance with a resistance meter. Calculate the conductivity of 20 accordingly.