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Building a Bee

A simple lab for an advanced project. Besides the oven and solder pen, this is all the equipment you will need.


Freescales MC13192, a nasty little thing.
Freescales MC13192, without doubt the trixiest component of this project. As you can see there are small strips of plastic dividing the bottom and side parts of the pads. There's certainly a perfectly good reason to why one would make them like that but so far we haven't figured it out. As a hobbyist with limited equipment you will have a better chance of success without those plastic edges so we'll remove them!

BTW, Those are paper fibers you see, not some hairy arm :)


We have not checked, but this is probably not recommended by freescale. Manhandling a  component this way doesn't look very nice but so far we've done it without mishaps. Find something sharp and remove the plastic by gently scraping the edge. Maybe a very fine grained file will do the job too...

This is what what you should get after the modding. The solder paste will now have a much bigger chance of fusing with the pads in our home lab.



Time for the solder paste. The components in this project have a rather fine pitch so we were not able to use a dispenser in the form of a standard hospital needle. Instead we just used the leg of a ordinary resistor to dip in the solder paste and smear it out on the pads. Maybe a more sophisticated and professional dispenser will work but that would be like cheating. Make sure to clean the PCB from grease and dirt with alcohol or some such before applying the paste.

When it comes to the MC13192 experience says that it is better with too much solder than too little. When using too much it will just be pressed out from underneath the chip without causing problem but too little will give you problems. Though problems that can be solved, as we will show you later on.


Alignment of the components are easy, except for the (surprise!) freescale chip. This is the only time we make use of a magnifying glass.


Cookie time. When you put it in the oven, make sure that there are free air underneath the PCB, that way the board will heat faster.

This is what will happen if you use too much solder. The fix is really easy! Just touch the solder beads with a clean solder iron tip and they will be gone in a blink.



Same thing with the AVR, just touch the pins with a clean tip and the solder bridges will melt away.



When using too little solder paste on the MC13192 it will be a bit harder to fix.

Make sure the metal of the track to the offending pin is clear of the coating. Put some solder paste on the track and the edge of the component. Put the clean tip of the solder pen on the track about 1-2 mm from the chip (not touching the paste mind you!). Wait for the paste to melt and fuse with the pin.


   
No software patents!