Test 17: How to do solderability test of enamelled round wire

1 General
This test is applicable to enamelled round wire and bunched wire.
Solderability is expressed by the time of immersion of the specimen in a solder bath required to remove the coating and to coat the conductor with solder.

Safety warning: Chemical hazard – Lead has been recognized by regulatory agencies to be a hazardous substance. Primary routes of exposure are by inhalation and ingestion. The information contained in the Material safety data sheet (MSDS) for lead, tin, flux and alcohol must be adhered to while using, handling or disposing of these products. Adequate ventilation or forced exhausting of solder pot vapours and products of decomposition from various solderable insulations may be necessary to comply with environmental regulations.

Safety warning: Thermal hazard – Care shall be exercised in removing test specimens from the solder pot to avoid skin burns.

2  Equipment
The following equipment shall be used:
•  temperature controlled solder bath of sufficient volume to maintain a constant solder temperature when immersing the specimen at any temperature specified in the relevant standard. Solder composition shall be of a mass ratio of 60 parts tin to 40 parts lead or a lead-free solder in accordance with ISO 9453 or as agreed upon between ustomer and supplier; any dross which forms shall be removed from the surface of the solder before each test; the temperature shall be controllable with ±5 °C of the temperature specified in
the relevant standard.

NOTE 1  Copper corrosion is greater when using lead free solder when compared to a tin/lead composition.
•any specimen holder that holds the wire under test free for at least 20 mm between the points of support when immersed into the solder (See Figure 4). The material used for the specimen holder shall be such that the solder does not undergo any contamination and the
dimensions of the holder shall not lead to significant change of the bath temperature during immersion.
NOTE 2  Contamination of the solder due to oxidation or from copper can affect the results.

3  Procedure
The specimen shall be held vertically over the centre of the bath maintained at the temperature as specified in the relevant standard. The bottom end shall be lowered to (35 ± 5) mm below the surface of the bath. The position at which the specimen is immersed shall be within 1 0 mm of the point where the temperature is measured. After immersion for the time specified in the relevant specification sheet, the specimen shall be moved sideways in the bath before it is withdrawn from the solder.

The surface of the tinned wire shall be examined with a magnification of 6 to 1 0 times. In the case of wire up to and including 0,1 00 mm nominal conductor diameter, the examination shall be restricted to the centre (25 ± 2,5) mm free length section between the supports. In the case of wire over 0,1 00 mm nominal conductor diameter and bunched wires the examination shall be restricted to the lower 1 5 mm of the segment immersed in the pot.

Three specimens shall be tested. The condition of the surface of the wire shall be reported.