3V7 to 5V Boost Regulator Prototype
The boards for the prototype boost supply arrived yesterday and the parts I needed arrived today. I could not wait and had to put this together. The BOM for this sample had suggested a couple of 0402 resistors. I deliberately left these to try them out. This was my first time with such a small size. I had decided on the out-set that I would not be soldering these by hand and ordered a stencil. I was just unsure how the polymide stencil would work the 0402 size, so I decided to use a stainless steel stencil - also for the first time. I was not disappointed! The application of the solder went on easy. Though it did look a little thick.
After the re-flow, I am very pleased with the result. Only one resistor, an 0805 went walkabouts on the board but that was easy to put back in place. There was no other movements and no bridging on the Boost regulator. This would have to be one of my best efforts.
I was also delighted to find that there were no problems in bringing the board up. It powered up nicely and the initial wave forms look OK. The sample shown below is a 3.7V 500mAh LiPo (I used my lab supply on the initial power up, just in case there were any issues).
This is not the end of the testing. When I get a bit more time, I will be brushing the dust off the Current Sink or Swim and putting both the regulator and the battery through some further tests - this should also test my memory in the use of the CSOS!
The end result is that I am very pleased with the stainless steel stencil and for the price, I will definitely consider them for future, but not all, projects. As for 0402. I don't know if I would be using them more often. In the end, they were not a problem but placement was a little cumbersome. Luckily for this board, I only had three to worry about.