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soldering 44 pin TQFP

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MrDEB

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am running out of pins in my design and looking at going with a TQFP (18LF26K40) or similar.
Presently hand soldering 28 pin SOIC package with no issues.
thinking of using solder paste and maybe a fry pan w/ brick or a fine soldering iron tip with solder.
do I really need a stencil??
 

Ian Rogers

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am running out of pins in my design and looking at going with a TQFP (18LF26K40) or similar.
I'm assuming you are going for a 18LF46K40.. As the 18LF26K40 is a 28 pin device..

Watch the video Jason Lopez uploaded... It shows these packages being soldered... He doesn't use stencils..
https://atomsoft.wordpress.com/?s=soldering

I know they are small parts, But I have seen the same technique on 44 pin devices..
 

jpanhalt

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The 0.8 mm pitch is considered "legacy" by today's standard at Microchip. It is not that hard to solder. However, it you are unsure, you might be interested in an adapter board like this: http://schmartboard.com/schmartboard-ez-qfp-32-80-pins-0-8mm-pitch-2-x-2-grid-202-0009-02/

Scan down and it describes what "easy solder" means -- basically slightly milled detents that help alignment and keep it that way while soldering. I have used a Schmartboard for smaller QFN and they work. However, for 0.8 mm I would just go to a factory made board and not spend the $10 for the Schmartboard. Steady hands help, and there are of course ways to reduce the effects of unintentional movement.

A homemade board might be a different story. With the photo method, that resolution is easy to obtain. Alignment is slightly more difficult, but once you get one pin down, then an opposing pin, it is pretty easy. I precoat my boards with a very thin coating of paste rosin flux.

John
 

JonSea

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Most Helpful Member
MrDEB, I suggest you check which parts are supported by Swordfish, before making a random selection. The -K22 series has had most of the issues solved. I'm not sure the ssme is true with t&e -K40 series.
 
I solder TQFP-44 parts (PIC 18F46K22) with pretty good success. You'll need a fine tip solder iron, flux, and a decent magnifying glass (unless your eyes are good enough).

1) Apply flux to the pads.
2) While the flux is still wet, place the part on the pads. You don't have to have it in the correct orientation yet. You are just putting flux on the leads.
3) Orient the part to the correct position.
4) Start in one corner and align the pins so they are centered on the pads in that corner, both X and Y.
5) Tack solder ONE leg only. There should be enough solder from the PCB tinning to not require adding any at this time.
6) Repeat the process on the diagonal corner.
7) Re-inspect the first corner and adjust if needed.
8) Start soldering the un-tacked side of the part. I'm right handed and found going from left to right minimizes solder shorts.
9) Solder all remaining pins.
10) Inspect for shorts. If some are found, apply more flux and use a fine solder wick. Press down on the pads (not into the pins). The solder on pin shorts will wick down to the pads as pad solder is removed.
11) Have patience!
 

MrDEB

Well-Known Member
Thanks Ian, that video I have seen similar. Also viewed a video where the chip is hand soldered using a soldering iron.
My issue is the shelf life of the solder paste that Atom was using. Have searched and most if not all have a limited shelf life.
Sparkfun has a video using a soldering iron with a chisel tip.
 

schmitt trigger

Well-Known Member
Spudboy; Indeed, patience is the greatest asset.

I would add to your list that the magnifying glass should have its own illumination, to avoid shadowing.

Eventually, if you routinely solder fine pitched SMT components, you will want to get an USB microscope. They are no longer expensive and are available on may web sites.
 
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