For my current project I searched for a good boost power converter which is able to deliver continuous 400mA power for various sensors.
There are an endless number of good boost converters around, but not many can be hand soldered to a board. I would really like to see some like the TPS61092 with SOIC or similar packages. The biggest problem seems to be the heat transport, why most chips have to be mounted flat on the board.
Before using the chip in my project, I created a small test board. Using this board I can test various things. First I liked to test the performance under load. Next I tested if the chip can be hand soldered and finally I tested the final board layout I will use in my project.
Performance
The performance of this chip is really good, producing a very stable output. I designed everything for a load up to 2A with all suggested components from the specification. There will never be a higher load than 0.5A, so I probably could use a smaller coil for the final project.
Running under 0.5A load from 3.3V for over half an hour, the chip stays quite cold. Even in my case, where the chip bottom is not directly soldered to the board, it seems to be able to transfer the heat into the board. This is nicely visible in the thermal image of the board.
The Board
The board was produced by OSH Park in a good quality. If you like to experiment with this chip, you can order this board very cheap at OSH Park using the following link.
You can find the BOM for this board here. The resistor R2 and LED1 are optional, all other components are required for the power converter to work.
IC1 Texas Instruments TPS61092RSAR L1 Panasonic ETQ-P3M6R8KVP LED1 Bivar SM0805GCL R1 KOA Speer RK73H2ATTD3303F R2 KOA Speer RK73H2ATTDD4701F C1 Vishay VJ0805G106KXQTW1BC C2 Vishay VJ0805V104ZXJCW1BC C3 Vishay VJ0805V225MXJTW1BC C4 AVX TAJC107K010TNJ
I routed all pins of the board to the connectors, so you can also test the battery level detection of the chip if you like. The image below shows the schema for this very simple board:
The schema lacks the correct labels for the connectors, see the silkscreen on the bottom of the board to see the meanings of the connectors.
The board looks great, especially the silk screen is incredible precise. All these labels are only 1mm in height. There is just a small misalignment between the copper layer and the solder mask (<0.05mm).
Soldering
Hand soldering this chip is no pleasant experience, nevertheless it is feasible. I designed the board to make hand soldering possible, keeping the connections between the pin pads of the chip to the copper fills small. This allows the solder iron to heat up the pad fast enough to melt the solder quickly.
I did all the chip soldering under a microscope, using additional flux to make sure the solder quickly connected to the chip pads.
All other components are very simple to solder. The pads for the capacitor C4 are a little bit too small for hand soldering, you have to center this capacitor carefully.
If you have questions, miss some information or just have any feedback, feel free to add a comment below.
Have fun!
Doing reflow in a toaster oven or hot plate, or just getting a cheap hot air tool, is really not a big deal. But, if insistent on not using one of those, you can simply expose a small bit of the copper pad on the back side of the PCB so that it’s solderable. Add solder to saturate the vias and have a bit of excess on both sides, including a slight “bump” on component side, then flux it, place and hold the chip aligned and apply the iron to the backside to reflow the solder through the board. When the bump reflows fully, the chip will sit down on the board. Yes, it’s a little tricky, but it allows doing assembly or rework with no special tools. Of course, for removal you still may need hot air, but some removal alloy or careful use of a standard heat gun can help.
Hi John,
I use hot air for soldering a lot. It is indeed no big deal and especially for chips, I prefer hot air soldering over hand soldering.
For a current project, I just like to create it in a way, people can build it with a solder iron. This is the reason why I search for a solution which can be hand soldered.
You idea is very nice, I just recently found a design with a “large” hole under a similar chip, which is just filled with solder. I will have to try this with another test board.