Soldering

Soldering is the process of joining metal conductors together by melting solder to adhere to both parts. It creates both an electrical and mechanical connection. Unlike welding, the base materials do not melt.

Safety Concerns

Heat: tin-lead solder melts at around 188℃ / 361℉ and a typical soldering iron temperature is around 370℃ / 700℉. So the primary risk is burning yourself, either directly on the tip, shaft of the heater, excess solder drips, or by conduction through the parts while holding components.

Lead: we use tin-lead solder, and lead has long term toxic effects.

Rosin: the rosin flux inside the solder vaporizes under heat to clean the surfaces; the fumes are an irritant.

Eye hazards, primarily from trimming component pins which frequently leads to flying metal fragments.

Physical Computing Lab Equipment

  1. Soldering iron stations along the west wall. Each iron has an power switch in the base, but also a timer at the wall socket in case you forget to turn it off.

  2. Each iron has both metal sponges and foam sponges for cleaning the tip.

  3. Water bottles for wetting the foam sponges.

  4. Tin-lead rosin-core solder. (Please remember to wash your hands after use, lead is toxic.)

  5. Various kinds of vise, third hand, etc., for work-holding.

  6. Filter fans, suggested for dissipating rosin fumes.

  7. Wire strippers and diagonal cutters in the red tool cabinet.

  8. Heat shrink tubing on the spools near the door.

  9. Hot air gun in the bottom drawer of the red tool cabinet (for shrinking heatshrink).

  10. Copper desoldering braid (in the leftmost cabinets).

  11. Solder suction desoldering tools.

Tutorials

Adafruit Industries: Collin’s Lab: Soldering

About five minutes, includes basic theory, use of iron, soldering resistors to PCB. Quirky presentation style.

SparkFun: How to Solder with David Stillman

About three minutes, basic use of iron and soldering pin headers to a PCB.

More Video

Wire to wire lap joint (41 seconds): https://www.youtube.com/watch?v=JO0xTassruU

Tips and Tricks

My essential soldering tips:

  1. Lead is poisonous: wash your hands afterwards.

  2. Turn on the fan to absorb the rosin fumes.

  3. Put a little water on the sponge.

  4. Melt a little solder on the tip to “tin” it.

  5. Use the sponge to clean off excess solder and flux from the tip.

  6. Soldering is all about heat, oxides, and surface tension: the rosin flux vaporizes in the heat and removes oxides so the solder can wet the metal; the melted solder wicks into the freshly cleaned gaps.

  7. Heat the joint with the iron; let the hot joint melt the solder. The solder is applied to the joint, not the tip.

  8. Look for a shiny, symmetrical meniscus of solder when you’re done.

Common Mistakes

  1. The most common mistake is to fail to heat the two conductors hot enough for the solder to stick properly. Either the rosin fails to remove surface oxides or the solder fails to melt. This is called a cold solder joint and can usually be detected by visual inspection, as the solder will look uneven or beaded, without the shiny meniscus of solder which flowed while hot.