Tuesday, March 25, 2008

PCB (Part 5 Soldering)

Part 5 (Soldering)
And now, for the final chapter in PCB making, soldering. Though it may seem complicated, it is actually very easy. The best way to get a perfect joint is to practice, practice and more practice. You need a good soldering iron, solder remover (sucker), soldering lead, flux, “Helping hands”, soldering iron stand and metal clippers.
Remember, a higher wattage iron does not mean it get hotter faster. 20 to 30 watts is sufficient. A good iron to get is Hakko Presto or Dash. The soldering lead should be the fine 0.5mm type. Never scrape the tip of the iron. Wipe on damp natural sponge to clean it. Once you are done soldering, don’t force cool the iron, let it cool down naturally.

Any grease or oxidation will make it difficult for the solder to stick. If your PCB is unclean, the best way to clean it is to get some household veinger, pour in a container large enough to place your PCB in. Add half teaspoon of salt and stir it. Add half cup of water. Then place the PCB in this bath solution and stir/shake the container for about 1 minute or so... You should have a extremely shiny and a bit smelly copper. Rinse under running water. Dry and start soldering. This tip was given to me by 9M2CF, Uncle Chow.

It is entirely up to you to cut the component leads to size before or after you solder. I find it neater to do it before. Mount the component on the PCB. Touch the tip of the hot iron on both the component lead and the pad then touch the other side of the component lead and pad with soldering lead. Let it melt and flow around. Remove the lead and then the iron. Always clean the tip of the iron before and after soldering on a damp natural sponge..
That’s all there is to it. If you find that doesn’t work too well, dip the tip of the iron in flux for a microsecond, and then solder. Or melt a tiny bit of lead on the tip of the iron and solder the component lead.

I suggest that you practice on a vero board (strip board). Use discarded network or phone cable. Practice until your soldering is perfect. The whole process of soldering takes less than 2 seconds. You know you have a good solder joint when it is cone shape and shiny.
When soldering PCB ALWAYS solder the lower components first, example: jumpers (if any), resistors, diodes, transistors, capacitors, etc.
Check orientation of polarized components BEFORE you solder. ie diode, cap, transistor, IC.

Strip board and some network wires for soldering practice

Helping Hands are great for holding up project and a extra one can even be used to hold component in place while you solder.

Top two joints are example of bad soldering. Bottom two joints are ideal

This concludes my lessons on PCB making. Thank you for your support. As usual, should have any questions, leave me comments.

Things to remember:
  • When doing PCB layout, take into account for housing/casing.
  • Label and store toxic chemicals in high and dry places where children cannot reach.
  • Print in 600dpi or higher resolution.
  • Examine printout for shorts and open circuit.
  • Dispose of used developer in a safe manner.
  • Examine etched PCB for shorts and open circuit.
  • Always drill smaller holes first. For double sided PCB drill before you etch.
  • Mount low components first.
  • Soldering should not take more than 2 seconds per pad.

Additional stuff i left out... :)

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