OLinuXino Open Source Hardware Linux computer was designed to be Do-It-Yourself friendly Linux computer, but the more powerful versions contains BGA ICs.
Many people are afraid to try to solder BGA ICs and think, that this is very complicated process and require lot of expensive tools.
Indeed if you do mass production you need expensive and precise machines to place and reflow the boards which cost a lot of money.
If you have to assembly and repair small quantity of boards though you can do it with low cost equipment as well.
Sure you may broke some ICs and boards until you learn how to do this properly, but this should not discourage you.
In this tutorial we will show you how A20-OLinuXino with burned processor is repaired using only few low cost tools:
- hot air desoldering tool
- soldering iron
- solder wick
- tacky flux
- isopropile alcohol
all above cost total less than EUR 200
Step 1 – hold the IC with twizzers and move the hot air handle above the IC trying to heat it equally
Step 2 – using solder wick remove the excessive solder on the BGA pads, not everything will be removed
Step 3 – apply flux and repeat step 3 until make pads completely even with no solder blobs
Step 4 – clean with isopropile alcohol
Step 5 – apply tacky flux
Step 6 – position the BGA chip on the pads (in our designs we place 4 small pads in the BGA corners so when you place the IC the corner of the ICs lay on these registration pads)
Step 7 – heat the BGA with the hot air to 250 C and keep it hot above 250 C for about 30 seconds.
Lead Free Solder melting point is 225 C, to solder the IC reliable it should be heated to 250 C and then hold at this temperature for 30 seconds.
You can do some experiments to learn when the IC is heated to this temperature and how long it takes to heat up by using damaged BGA chip – put thermocouple on bottom of it and place the IC on damaged board as you have to measure the temperature of the balls not on top of the IC then start heating and monitor the temperature, you will see after what time, when you move the hot air gun the temperature reach 250 C, note that the distance between the hot air gun and IC changes the temperature significant, also the complete IC should be heated and you have to move the hot air with circulating moves not to keep it at one spot only.
Once you do the measurements you will know what amount of time you have to heat the IC and at what distance and you can try with real chip.
When BGA balls melt down they “collapse” and the BGA sinks down a little bit, with the time you will get experience and will notice this collapse to be sure when the BGA balls are really soldered.
You can check your soldering results with magnifying glass looking at the BGA sides.
Here is the move which show above steps: