Yes, we ordered the wrong package + first project update

A project log for Pluto watch R2

Refresh of the Pluto programmable digital watch from Lukas / carrotIndustries. Cheaply manufacturable in 2019.

raphal-casimirRaphaƫl Casimir 07/02/2019 at 10:110 Comments

We finally received everything. So we went at our local hackerspace, Electrolab, to solder the first prototype.

So we started to put solder paste on the PCB with a sharpened toothpick (0402 parts are a thing of beauty and a joy forever), following the really handy interactive HTML BOM.

We thought we would put the MSP430 MCU last since it is the largest part and it could interfere with the soldering of the other components.

First issue, probably a clearance problem. One of the two R2 pads was under the solder mask. We scraped it (yes with all the other passive components already placed of course, note for future self: never trust a quality control from a $2 PCB supplier). It seemed to take solder just fine.

Crossed in blue, the pad in question.

Second issue, after soldering every other component but U4 (damn small and not necessary for the first tests), we tried to place the MSP430FR6972. Or the MSP430FR6972IPM should I say.

Let's take a look at the datasheet shall we?

Always check your packages. Twice.

I ordered some samples from TI to get the first prototype running, with the correct VQFN package.

We had access to a professional computer-controlled reflow oven, devouring 16kW of power, but it was probably just a bit overkill for a single 24mm board. We were glad to be able solder everything with a hot air gun, soldering iron, and a lot of dexterity.

Using too much solder paste is a common problem, featured here.

See you in the next log, hopefully with a working prototype!