Since I don’t use the DHL shipping option for PCB, it takes quite a while before the boards roll in. Today came in the STM32/GD32F103 QFN32 breakout board. I was very excited (for weeks) and soldered all the components quickly on the board.
Uptill now I used 0603 sized resistors and capacitors but for this project I switched to 0402 to save a few mm on the board. I have soldered many challenging chip packages so I felt confident. The technique is the same as for bigger sized devices: flux the area generous, hold the device with tweezers, solder one pad with fresh soldered iron and move the device into the molten solder puddle, retract the soldering iron and watch the solder joint cool down. If the solder joint is solid solder the other side too. I suggest using a fine (curved) tweezer and lots of lighting on your workarea. If you are a bit older as I am using a loupe or magnifying glass. Still use flux as much as possible. Never expected but the micro USB connector gave me (several) headaches to get it soldered properly.
Several weeks I’ve built a virtual machine containing Ubuntu and a toolchain for ARM cortex microcontrollers. I used the new project wizard and chose the de-facto-microcontroller-hello-world-blink-a-LED-example in the IDE. The GD is comparable (compatible?) to STM32 so I chose the corresponding stm32 project. As expected the LED hooked up to port RA0 blinked happily at me, but probably the clock is wrong as the blinkrate wasn’t ok.
Not happy with some parts of the PCB (no indication LED(s), bad USB connector footprint, bad switch footprint, wrong placement of USB pull-up resistor, some minor silkscreen error) I’ve send in a revision B to the PCB house. Expect more 32 bit news from me.