SMT soldering tip's
DigitalBob
Posts: 1,513
This is the way I do my P2's, Q44 P1, and FT232's. 1. lay some flux down, 2. position your IC pin alignment,
3. tack two corner pins, 4. fill pin rows with solder, 5. suck out soldered pins with a Hakko FM204. Done. See photo's.
1536 x 2048 - 762K
1536 x 2048 - 738K
Comments
I'm glad that works for you.
But I would encourage you to spring for solder-masked boards. They're not going to be that much more expensive than what you're probably paying for bare-bones PCBs, and they will make solder bridging even less of an issue than what you could be experiencing. You've invested $$$ in a really nice desolder station. Might as well spend a little extra for quality PCBs.
These guys do good work for cheap:
https://easypcbusa.com
Order the tin/lead finish, not the silver. The latter is a little harder to solder to.
Also be sure to clean the flux off with isopropyl alcohol and a toothbrush when you're done.
-Phil
Thanks for the tip. I've replaced the FPC connectors on the Ipad before with the hotair rework, but I just like this method for the bare boards.
FWIW, I order boards with a HASL finish, solder mask, and a stainless stencil from JLCPCB.COM. These boards get vapor-phase reflowed at 200c with a homebrew setup using about 8 oz of Galden 200 in a modified Costco kitchen fryer. Not as cheap as a toaster oven, but my little converted deep fat fryer gets it done quickly and reliably. I have very few problems even with 0402 components with this setup. (Caveat: my eyes need a video microscope to place components after about the 08xx size or the board will be junk. Placement accuracy counts. I dont even pretend to be able to see small things unaided anymore, but if I can get the components firmly and accurately placed in the paste with the scope, then getting them soldered is really simple).
The only thing that I tack down before reflow is the P2, always on opposite and adjacent corners. It isnt that it really needs it, its just that in the early days I had process and placement issues. I found it to be a real hassle to unstick, remove, clean-up, and reflow a P2, even with a hot air pencil. That blasted 9 mm thermal backpad is really challenging to get hot enough to release without hurting it once its soldered.
On that same note, I think very highly of hot air pencils. Really useful once you get the hang of it, especially for tiny leads and even small leadless (clock chips!) components. I have both the X-Tronic and the Zeph. Both are wonderful, mostly interchangeable, and highly recommended especially when used with Chip-Quik leaded paste and tacky flux.
On the P2, I smear some solder paste on the backside of the ground plane, solder all pins into one clob, then clean it up with the desolder, after that I hotair reflow the underside to bond the ground plane to the back of the P2. For me the smallest I can handle are the 603's, forget about 402's, can't get them out of the cut-tape without losing them.
Gotta admit, one good ah-CHOO or a bump on the table sends those tiny boogers flying. Out of an abundance of caution I usually tape the feed-tapes to the desktop, but even that is dodgy.
I have not had much success with applying paste to the P2 directly. While I’ve only assembled about 20 boards total, ever, (please save my ego and pretend you are impressed! Lol) but my experience is that the vias underneath that 9x9 thermal pad draw all that paste out from under it and you dont get a good thermal bond. What vias? Good point! I am using a modified footprint originally created by Peter Jackaki that ses multiple vias to improve thermal conduction between layers.
BTW: @"Ken Gracey" I really wish Parallax would take a few minutes and publish a good, tested, vetted, annotated, Chip-approved, multi-layered P2 footprint and 3D outline for the P2 for all of the popular CAD packages. Like my beloved KICAD. Hint-hint. And pretty-please-hint-hint put it up on the propeller.parallax.com site as part of the official docs where it can be used by all of us instead of rolling our own variant. 😁
I'm with Phil. I order boards from PCBWay.com and always get a stencil with my order. I haven't tried P2s yet, but I have made boards with the P1 and the ESP32.
This is my P2 layout from a while back.
Wow! And all that without a solder mask! Mad skills! 👍
Thanks, It wasn’t as difficult as I thought.
Just came up with a cool trick for solder bridges in tight spaces like under/at the edge of a USB AB surface mount connector. Even my smallest braid was too big to get under the edge of the connector. Solution was take a strip of 30g wire wrap wire, bend in a couple to few loops, coat with no-clean flux and use it to remove stubborn solder bridge from adjacent pins. It was able to get into the back side of the connector where the braid could not reach.