How to Solder Electronic Components

Repair Cables and Connectors in the Field to Keep the Show going

Jan 15, 2009

Basic soldering skills help musicians and road crew to make minor repairs on site to keep the show on the road.

Anybody who uses music equipment in the field should consider learning how to solder . Most of the problems that occur in gear that is moved about a lot can be traced to poor connections. Knowing how to resolder dodgy connections can make the difference between a minor panic and the loss of the whole show.

Soldering Iron

For soldering connectors and signal-carrying cables, a soldering iron of between 25 and 50 Watts is needed. The cheapest soldering irons are thermally balanced - the power matches heat loss to the air such that the soldering iron tip reches approximately the right temperature. This works well for soldering connectors and cables, but struggles where the joint includes large metal parts that conduct away the heat, lowering the tip temperature. Such an iron should be about 25-30W

More expensive temperature controlled irons power the element only until the tip reaches the right temperature, and thereafter power is applied to maintain that temperature. These are easier to work with as they hold their temperature more closely to the optimum.

Soldering Temperatures

The ideal soldering tip temperature depends on the type of solder that is being used and the type of iron. For the older type of tin-lead solder with a melting point of about 188 C (370F) the soldering iron temperature ranges between 330 to 350 C (630 to 660F). However, particularly in Europe with the ROHS regulations which forbid the use of tin/lead solder, tin/silver solders are used instead. These have a poorer performance than the older tin/lead types. These need a higher temperature of about 370C (~700F)

Solder

Only electronics type solder should be used, with internal flux cores. This has a sharper setting point, than plumbing type solder, which should never be used.

Cleanliness is the Key to Success

Both metallic sides of the joint should be clean - older parts may need cleaning with a fine abrasive or fibreglass pen. Grease and dirt make it impossible to get a good joint. The soldering iron tip should be clean too - the tip can be wiped on a damp sponge and then a small amount of solder applied (tinning). Abrasives should never be used on the soldering iron tip, as they will destroy the thine iron coating that stops tip erosion.

Heat Both Sides of the Joint

The soldering iron is not a device to carry molten solder to the work - the iron should be applied to heat both sides of the solder joint, and the solder is then brought to the joint and melted in place. This allows the flux in the solder to melt onto the joint and keep the parts clean. Shortly afterwards the temperature of the joint rises enough for the solder to melt onto both sides of the joint to form the metallic bridge which is the point of the exercise. The iron should be in contact with the joint for a maximum of about five seconds for small parts.

Prevent Movement while Setting

The joint must not move while the solder sets, so it must be kept steady for a few seconds after the iron has been removed.

Conclusion

Using these techniques mean that cables and connectors can be repaired on site; these are the source of many mobile sound equipment faults and can be fixed in the field.

References

The copyright of the article How to Solder Electronic Components in Electrical Engineering is owned by Richard Mudhar. Permission to republish How to Solder Electronic Components in print or online must be granted by the author in writing.