LQFP-48 kicking my ass

[Mbira]

Been trying my hand at SMD for some modular synth DIY.  Doing ok but just tried my hand at two of these bad boys http://www.mouser.com/Search/ProductDetail.aspx?R=STM32F103CBT6virtualkey51120000virtualkey511-STM32F103CBT6

Totally kicked my butt.  Even using these headword x3 magnifiers, I couldn't really even see the traces well enough and bent a bunch of pins.  Ordered a cheap stereo microscope to give her another go here in a few days.  What a pain!

 

[JohnRoberts]

smd is not for old farts...

With that many pins  putting solder paste on the PCB pads and reflowing with a hot air station should allow the surface tensions of the molten solder to self center the pins over the pads.

For that many pins a stencil would help but it can be done by hand with patience.

JR

 

[Andy Peters]

Been trying my hand at SMD for some modular synth DIY.  Doing ok but just tried my hand at two of these bad boys http://www.mouser.com/Search/ProductDetail.aspx?R=STM32F103CBT6virtualkey51120000virtualkey511-STM32F103CBT6

Totally kicked my butt.  Even using these headword x3 magnifiers, I couldn't really even see the traces well enough and bent a bunch of pins.  Ordered a cheap stereo microscope to give her another go here in a few days.  What a pain!

What soldering equipment are you using?

Two choices:

One is to use solder paste, preheat the board and then use hot air to do the final solder melt and set the part.

Two: you need a tip that's as thin as the pins, and a tool that doesn't let that tip get cold. Put a bit of solder onto just one pad, preferably a corner. Align the part onto the footprint. Heat up that pad so the solder melts, the pin settles down onto the pad, and the part stays in place. Then solder the pin on the opposite corner. Now flux is your friend. Put some on all the pins, then start to solder each of them. Don't worry if you get solder bridges, because you can clean them up with some solder wick.

 

[john12ax7]

The bevel tips sure look interesting

https://www.youtube.com/watch?v=5uiroWBkdFY

 

[Ethan]

Get some organic water soluable flux, a big tip, and sweep solder. I've heard others calling it "drag solder" but I like the sound of sweep better  ;D
Once you get the hang of it, 128-pin flat packs will be easier than dealing with big honkin' thru-hole components. The real trick is making sure you have lots and lots of flux, and just the right amount of solder being fed to the tip--so that just the right amount 'slips' onto each pin without bridging pins. If you get a bridge, more flux, and go back over it with the iron, and so on.
Pretty soon, you'll be annoyed about the once in a blue moon occasion where you have to turn the board over and clip the leads of the thru hole parts you used.

PS: There are "no-clean" alternatives but if you use organic flux, make sure you carefully wash and dry the boards before use. Organic flux is corrosive and will eat away at the metal on the board if left on there.

 

[JohnRoberts]

If you are going to try to hand solder use Andy's advice to tack solder two corner pins... Even if the first corner pin is not perfect, it will flex enough when you tack a second corner pin the whole part can be indexed properly over the pads. Then you can solder the rest of the pins that won't move.

JR

 

[mattamatta]

When I've done things like that by hand, I don't even try to solder individual pins.  I'd tack a corner or two like Andy and John say and sweep across all pins with solder, then sweep across with the wick.  The solder will form around the pins and pads itself as it wets, and the wick will pull up bridges.  May take some practicing to get it right, as that's really a trick of trying to get the right AMOUNT of solder in the right areas such that it will pull itself cleanly onto separate pins.

I have seen those kinds of things done with paste dispenser + hot air or reflow oven, but I think many DIYers would be amazed how much gets done with a hand iron.  I'd expect hot air to get used if they wanted to pull a part like that cleanly, (if not re-using, just clip the pins with fine clippers or an exacto blade, remove the IC body, and remove the pins one or a few at a time), but in places I've been, small SMT passives and most leaded things are just done with a hand iron or two  and a good microscope.  They mostly break out the hot air and solder pot for leadless parts like BGAs, DFN/QFN, etc.  And a seriously skilled technician, of course.

 

[Mbira]

well  after destroying two $6 chips and a circuit board, I got a $200 microscope off amazon.  It does 10x and 20x and HOLY COW it is awesome!  Using that made these chips a piece of cake!  Well maybe not yet a piece of cake, but now I can easily see what I'm doing and see if I am all lined up...funny thing is now I'm looking for SMD DIY stuff to do because it is indeed kind of fun!