A lecture on Soldering
3. Solder wire with rosin cores
As is shown in the picture, solder flux is clad in the tubes inside the solder wire so uniformly that no matter which section is cut, the cross-section presented is always identical like a deep-fried burdock or a Kintaro-candy. It can be seen in the sketch and the picture that there are three flux tubes. Solder wires with one tube, two tubes or five tubes are now available, dependent on different producers, usages and thickness.
The thicknesses of solder wires are classified as per usages. Solder wires ranging from Φ0.1mm～Φ3.0mm are available at various manufacturers. The thinner ones are for fine work-pieces and thicker ones for large work-parts.
Recently, Φ0.3mm wires are mostly used for surface mounting activities. The smaller the diameter is, the more expensive the product is. Should thick solder wires be used, the fused tin tends to pile up at the worked spot in case the soldering operation proves to be a difficult one, though the thicker ones are often encouraged to be used due to the cost issue. So the wire diameter selection should be done in the light of various factors taken into consideration.