ENGR 201: Solder/Desolder

Here is one of those skills that mostly we're supposed to learn by osmosis. That's not a great plan for learning stuff so let's be a little more organized here. Soldering, the process of creating electrical connections between objects using low melting point metals, is fundamental to the assembly of all circuits and even shows up around the household from time to time. The basic principles are simple and the skills and understanding develop fast. On the other hand many many people don't really understand how to make a good solder connection which leads to what are called cold joints which tend to lead to intermittent and totally frustrating circuit failures. Bad solder joints rountinely show up even in commercially fabricated objects.

Another motivation for assuring that you have these sorts of fabrication skills is that there is a large and interesting community of folks out there who are hardware hackers. These folks figure out novel ways to reuse or repurpose items from our consumer electronic society. In a real way that is what this sequence of labs is designed around. For reasons that may be evident to you having a temperature controlled fan could be handy. The same technology can be used to create photocontrolled motors or fans which would have other uses. We can get a perfectly reasonable power supply from any junked computer along with it's cooling fan. With a few purchased components we will endeavor to build a PWM motor controller. In the process you will need some of the skills from this lab.d

Purpose:

For the student to learn basic soldering and desoldering skills.

Procedure:

• The following is a list of basic soldering and desoldering videos that I found fairly quickly on youtube and other places. Watch at least two all the way through before moving on to the next step of this lab. Note, in your notebook, how you would search to find these videos if you were to want them at some future time.

  • Curious Inventor - good intro
  • Make Magazine - long but covers several techniques
  • Hack-a-Day -- verbal description but good
  • Bug Brain -- not bad but a little simplistic
  • Tory Lovers -- also simple but fun
  • If you find others let me know and I'll add them to this list

• Find a PC board in the pile that has regular solder connections and describe in your notebook what a good solder connection looks like. How do you expect a bad solder connection to look and can you find one? Sketch a good connection. How does a standard solder connection look different from a surface mount connection?
• There will be several soldering stations set up around the class and in the hood in the stockroom. In general we will use the hood to waft away fumes but if you wish to work at a lab bench today that will be OK. Find a PC board with a number of devices that are through soldered to the board. Begin by desoldering a couple of resistors and capacitors (at least 4 total), a transistor, and something with at least 4 pins. Because you will be resoldering them back into the board in the next step you are encouraged not to burn the snot out of the board as you desolder them!
• Solder a couple of two pin objects and at least one multiple pin object back into the board. Verify with me that you have created "good" solder joint and haven't scorched the device into a useless crisp!
• Have me check your notebook before you call it done. Be sure your notebook is consistent with the practices outlined in the previous lab link.