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TQFP soldering troubles

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KL27x:

--- Quote ---I guess it all depends on the iron you're using and the way you hold it.
--- End quote ---
The chisel is a 90 degree perpendicular edge. So it doesn't matter how you hold it. It will only form a straight line that is 90 degrees away from where you plant your right hand by the time you orient this edge flat to the PCB. This is main reason why it's an ergomonic fail right out of the gate. Then to drag this edge across a row of pins, you have to move the entire iron sideways. This is ergonomic fail number two.

The 45 degree slant of a knife tip, boom, automatically makes it a million times better for almost anything SMD. There are other differences, though. The way Hakko makes them, anyway:
1. the knife is tinned-face-only. Only the faces of the edge bevels are tinnable. The rest is chrome plated.
On the chisel or screwdriver tip, the entire shaft end of the tip is iron. The knife tip is better at sucking bridges and controlling solder due to this.
2. The knife tip comes to a true edge. The chisel is kind blunted over. For QFN's, this lack of a sharp edge makes the chisel unable to solder a QFN until you get very small chisels that are basically a conical that thinks it is something special but it's not.


--- Quote ---Regarding "hoof" tips - I think they are more commonly called "bevel"? - I have one of them. I don't use it very often, but I'll give it a chance for QFPs and see how that goes.
--- End quote ---
Please refer to my notes about bevel tips. There is variance between manufacturers. Hakko's bevel tips are sublime, for instance. Some of the clones and the high quality Plato aftermarket spoon versions do not have the proper features of a "hakko" bevel tip, having cut angles that are too slanted and/or rounded edges. Sharp edges are very important for bridge sucking. The size is also critical. When solder beads, it reaches a certain size of ball before gravity collapses this shape. 4mm is too big; the bead will collapse and be uncontrollable when it gets too large, and when a little solder is on there, it won't want to spread across the entire face. Too small, and you have to reload too often. 2.5-3mm with a 45 degree cut face is ideal with lead solder, IME.  As you go smaller, it will work with slantier cuts angles.

jmelson:
First, you need good alignment between part and pads.  The narrower the pads are, the less likely to get bridges.  Are you using paste or wire solder?  With paste, lay a VERY thin strip down the center of each row of pads before placing the chip.  With wire, use the finest wire you can get.  I have some .010" (0.25mm) solder that works the best.  Clean the pads with braid before getting ready to place the part, then put a dab of solder on two corner pads.  Align the chip and solder those two pads.  You can reheat the pads and adjust the chip for most accurate alignment.  Then, just apply the LEAST possible amount of solder and do 2 - 3 pins before applying more solder.  In some cases, the amount of solder plated on the PC board is enough to make good joints, all you need to do is supply the flux.

Finally, if you don't have a stereo zoom microscope, you need this BADLY to do 0.5 mm lead pitch. 

Jon

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