W801

[Just4Fun]

I wrote my w801 journey here, if anyone is interested: https://dannyelectronics.wordpress.com/ ... mpression/

Thanks for sharing. Very interesting!

My W801 board is on the way together with a bunch of W806 MCUs (chip only). They have a "nice" QFN-56 package with a 0.35mm pitch...

[dannyf]

Very interesting!

Yeah, and challenging - trying to figure out how things work with terrible documentation is frustrating and fun at the same time.

The ADC chapter was written by an alien for sure . Seems like some undocumented features there, on top of some interesting hardware.

fun, and frustrating as well

[dannyf]

they are way above my soldering skills

might be possible to flip them upside down and use fine wires to connect them to a breadboard. aka deadbug style. I used it on some tqfp chips.

[ag123]

I've wanted to solder my own stm32 (board), never dared try it, maybe one day i should order some chips and plain boards and try that.
I've read that solder paste reflow (e.g. hot plate) is easier, but for now I've only got a soldering iron so i'd guess one day I'd try soldering a stm32 after all.

one of those things i've wanted is to put a high speed usb 2.0 ulpi with a stm32, but that i've not even got pass the 1st stage which is the stm32 itself.

[Just4Fun]

I've soldered some SMT boards but up to now never with a QFN, so this one can be a good occasion to try...

This is my last toy (with a STM32F030R8T6):



I use the hot air gun only for the smaller parts (resistors, resistor arrays, caps, diodes, leds...) and the regulator ICs (as they have big masses on the PCB).
Anyway if you have only "big" 0805 SMD parts it is possible to use the normal iron as well, you'll be just slower.

All the IC are soldered with a normal TS100 iron with a BC2 tip using the drag soldering technique because is very very quick (and safe).
The big TFQ-208 IC required the use of a C4 tip (it is the only tip that can solder it) using the drag soldering as well.
Of course you need a stereoscopic microscope.

When you solder a new board first time (I mean a new untested design) you have to plan the order in a different way as you have to proceed one functional block a time to simplify the HW debug. In this situation the drag soldering is your best friend as you can decide the order of the IC to assemble without limitations.

The "secret" with all these ICs is just letting the flux work. So just try it...

[ag123]

Thanks for the encouragement, thus far the finest dimensions i've touched is 1.27mm (1/20 "), even LQFP 0.5mm looked 'impossible' to me, that's about what the STM32s are.

[dannyf]

The "secret" with all these ICs is just letting the flux work.

I can attest to that.

But it is scary to solder anything finder than 0.8 pitch. I did a pic24 44pin deadbug style and it wasn't pretty to look at and uglier to use.

[dannyf]

coming to think of it, "deadbug style" is exactly how the die was hooked up to the pins.

[ag123]

i'd think 'deadbug' is 'quite impossible' for this fine, it would take pretty clean good solders and tip, flux placement i'd guess

this looked unusually easy, i'd need to try, i'd think there'd be failures
https://www.youtube.com/watch?v=wUyetZ5RtPs


oh for the die inside i once spoke casually to someone who understand some of those processes, accordingly, that wire is pure gold, which is why it can stretch and fused so 'easily' to the contacts. I'm not sure for these 'cheaper' chips, if gold is after all used, but i'd guess it would be some other substitutes that works but not gold. gold wired contacts are probably used in those 'high end' premium intel / amd processors etc as they probably can include the costs in it.

[Just4Fun]

...this looked unusually easy...

Exactly

Here a short video I did a few years ago showing the complete soldering process (using a TS100 iron + BC2 tip):

https://www.youtube.com/watch?v=JlKLheYB8z0



The only "difficulty" is to align the IC to the pads at the beginning and solder the first two pins to block it (before completing the soldering with the "dragging" technique).