SMT soldering methods

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hahahehihoha
 
Posts: 37
Joined: Fri Jan 05, 2007 9:54 pm

SMT soldering methods

Post by hahahehihoha »

I have done basic soldering before including SMT but would like to learn more while assembling my WB. I am ready to go with all the parts.


Please tell me about your favourite SMT soldering methods!
Last edited by hahahehihoha on Fri Mar 09, 2007 2:33 am, edited 1 time in total.

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none_such
 
Posts: 76
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tips

Post by none_such »

You might want to check the specs on each IC as well as passives: they will tell you recommended temps and times for both leaded and lead-free solder(they are not the same).

Personally, I find using a heat sink while soldering a great benefit on occasion so you might want to find one. This could be a metal clothespin or something longer (like what you can buy at an electronics store for this purpose). I also don't like to use the "flood and suck" method for ICs although you can find some tutorials on the net for this. I have better and faster success applying a little solder paste to the IC landings and the IC pins, placing the IC carefully and clamping with a heat sink (use a good magnifier during this part), slowly heating the PCB with the iron and then briefly touching each pin on one side of the IC (around 260 C to 280 C iron) while touching each heated pin with fine, flux-core solder. The object here is to move the iron quickly on the side to be soldered and slow down after three or four passes NOT to actually melt the solder on any of the pins just yet. when you see that some flux is beginning to flow from the fine solder then the pins are ready to accept melted solder. To do this is tricky and you need to practice a bit because the time window is short. Linger the iron a bit longer on every other LANDING and melt a small amount of solder - don't worry if you bridge the pin next to the one you are working on with solder or if the pin you are working on doesn't have any solder on it. Next I get an exacto knife loaded with solder paste and touch all the pins in the area being soldered while moving the iron from the pins to the landings on the PCB ( that is, instead of moving the iron from pad to pad you place the iron parallel to the IC, touch as many pins as you can and move the iron onto the PCB repeatedly) you should see the solder instantly on the pins and the pads. If there is a bridge between the pins just continue this motion on this area with the iron and draw the iron a little further out onto the PCB. This will pull the extra solder onto the board and away from the IC. Allow the IC to cool down and repeat all steps if there was not enough solder melted prior to this step (with practice you will know how much is needed.) IF you still have solder bridges from too much solder (I never have had this problem) you can use a solder bulb or your solder de-braid possibly to remove this but I don't recommend this because I find you have to heat the IC far too much to get these methods to work (hence my very complicated method) A successful solder job leaves the IC finger-touch safe. I can finish one side of an IC this way in under two minutes.

After reading my SMT solder method I feel it won't be much help to people: the best way is to practice and come up with what is comfortable for you.
Cheers

hahahehihoha
 
Posts: 37
Joined: Fri Jan 05, 2007 9:54 pm

SMT news

Post by hahahehihoha »

So far I've smoked a battery protection circuit and the 3.3V 200mA rider. After ten hours of my first SMT soldering I am halfway with the WBRC1. Apparently I am better at this now than the engineer students in the lab I sneeked into. Did the ATmega88 the first day I tried surface mount soldering. Althought I was trembling at first because I haev only two of them and I am doing this project under a deadline which cannot have a re-order.

I devised my own compilation of various techniques: ie, tilting the board with paste liquid to make it go onto the pads from the pins while applying solder...I use not the finest tip but I make these thread drips off the tip which work very well...and so on.

hahahehihoha
 
Posts: 37
Joined: Fri Jan 05, 2007 9:54 pm

SMT soldering video

Post by hahahehihoha »

Some SMT soldering of my WB:
http://youtube.com/watch?v=B55JajzCcvE

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