Andrew ZonenbergJul 15, 2023

Reworked all the bridges on the ESD diodes that I found during initial visual inspection, and tidied up a few bulk caps.

Did continuity tests to sanity check on each power rail and nothing is shorted.

Gonna start populating the front side after the little one goes to sleep. Should go faster than the back since it's mostly large ICs not hundreds of 0402s.

Show threadAndrew ZonenbergJul 15, 2023
Starting front side assembly. Paste print looks a lot nicer.
Show threadAndrew ZonenbergJul 15, 2023

I usually begin top side assembly with large but flat components like BGAs so I don't risk knocking tiny stuff around while placing them. Then smaller passives and ICs, and tall capacitors and connectors last.

This FPGA is the single most expensive component I've ever put on a board. Shipping an entire tray for one chip might be slight overkill though...

Show threadAndrew ZonenbergJul 15, 2023
All the BGAs and most of the big QFNs done. Still tons of tiny components left, but nowhere near as many as the back had!
Show threadAndrew ZonenbergJul 15, 2023
Probably about half done. Time to take a stretch break.
Show threadAndrew ZonenbergJul 15, 2023
Getting closer. Mostly just power supply stuff left. The lab is getting to be a bit of a mess with component bins covering every bit of bench and floor space.
Show threadAndrew ZonenbergJul 15, 2023
But the board is starting to look pretty nice! Definitely less work than the back side.
Show threadAndrew ZonenbergJul 15, 2023
Here goes... Hope this works.
Show threadNukularJul 16, 2023
@azonenberg waitasec, you can just solder the IDC connectors for JTAG using paste in the oven? That's amazing 😍, it never even occurred to me that this was possible!
Show threadAndrew ZonenbergJul 16, 2023

@Nukular Pin in paste / thru hole reflow is a thing, yes.

You need suitable connectors (not all are able to get their plastic parts this hot) so check the datasheet carefully. For example the RJ45s I use on this board are almost certainly not reflowable, while the JTAG connectors are listed as reflowable in the datasheet.

It can also be tricky to get adequate solder volume. You can actually buy SMT chip component shaped "bricks" or "preforms" made of solder, on tape, that can be placed next to a thru hole component's lead to provide additional metal without adding more flux. I've been thinking of getting some.

Show threadNukular
@azonenberg I love pin in paste and actually used it for usb connectors a few times. I'm just blown away that it's possible for the IDC connectors, I always shy away from using them because they can be a total pain to hand solder if you have many of them and the SMD ones always feel like they're going to rip off way to easily.
Jul 16, 2023 at 2:32pmWeb
Show threadAndrew ZonenbergJul 16, 2023

@Nukular The specific one I'm using here is Molex 0878311420.

The entire Milli-Grid connector series is specified as reflowable and Molex even has some test data and profile guidance on page 12-13 of https://www.japanese.molex.com/content/dam/molex/molex-dot-com/products/automated/en-us/productspecificationpdf/877/87761/PS-87761-100-001.pdf.