63/37 tin lead would be easier to work with, but the solder quoted will be OK. It does have a 2.5% flux content.kokoon wrote:hello i have another question
what do you think about this one?i just bought solder that reads Sn60 Pb38 Cu2.
hmm i wonder if it's got any flux hidden in it... cause if it hasn't i don't like it.
it also says Fg.2,5%
You can test it by just melting it on a safe surface. If it balls up it has flux. if it does not form itself into a ball it is dry.
Make it easier on yourself and get some ROSIN FLUX.
I wouldn't worry too much about tin wiskers. Not that I deny that they are a true phenominon, but the industries general concern is not in assemblies of this scale (the x0xb0x), the concern is in micro circuits using chip-scale packages (way smaller and tighter than that 1 SMT USB microchip on the x0xb0x) with extreemly tight tolerences (space between solder connections). Tin wiskers have not been known to grow long enough to effect the spacing apparent in the x0xb0x's circuit board. Even if it did happen in a circuit of this nature (relatively high-power analog circuitry), it would probabblu just be voporized by the amout of current and voltage present.
Speaking of the smallest chip on this board. The surface-mount microprossesor. To solder this part is pretty easy if you have good eysight( or a visual aid of some sort ) and most importantly a steady hand (don't injest caffeen and get sleep befor attemping). Also, decent, clean, fully functional equipment is key. Test the tip of your iron. When you melt solder on it, does the solder spead over the entire tip or does it ball up and fall away. If it balls up and is repelled fron the tip, the iron tip is corroded and will not work. You can try to revive it by scraping the layer of corrosion off gently (the plating is delicate) while adding solder at the same time till the molten solder spreads cleaned surface of the tip.
To solder this component:
1) Put a fine layer of flux on all the pads on the PC board.
2) Add small amount of solder to the bottom right pad (assuming right handedness on this and all other steps)
3) With your left hand with a pair of tweezers, grip the compenet by the body and correctly orientate and position it on top of and in the middle of all the pads
4) Maintain position and with your right hand use the soldering iron and tap the 1 pre-tinned pad (the one with solder on it). It should melt and attach.
5) solder 1 pin on the opposit side of the component (or 2, no worries if it bridges at this point)
6) Check alignment of all leads (component legs).This is key. The better the alignment, the easier the soldering will be. A little drift is OK, but if the leads are more than 20% off the pads you will have to do a little adjusting by heating one of the 2 solder connections and re adjusting the component.
7) Now add flux agin to the part of the component leads that are on top of the pads.
8} Find a way (angle) in which your iron tip will touch 2 leads at the same time.
9) Very gently place (not push) your soldering iron on tips 2 leads, slowly add solder and at the same time start to drag your iron down accross (left to right) the row of leads. Look sharp and you will see the solder will follow the heat source (the iron tip) and if you dont add more solder than what will bridge only between 2 leads, the perfect amount of solder will be left behind on each lead as you drag past it with the little ball of molten solder on the tip of you iron.
10) if done correctly you will have only the last 2 leads end up bridged. Add a little flux to the bridge (this will work for any solder bridge you may come accross) clean all solder from the tip of your iron. Put the iron tip in the middle of the bridge and pull straigt away once the solder melts. It will always migrat to the heat source, so now the excess solder is now on your iron tip and no more bridge.
11) repeat for remaining 3 sides of the component.
12) Inspect your work and touch up any problems (opens and/or bridges). Use solder wick if more than 2 leads in a row are bridged. Add flux to your wick to make it work really well.
This method (drag soldering) will work on any multi-leaded component, even the Through-hole IC's and such.
Hope that made sense. I used to train personnell in this method. If this is your first try soldering, get the chip pre-installed, unless you can find something else to practice on at least a couple of times.
Cheers