Dead bug soldering SMD.

Dead bug soldering of surface mount components can be a pain, but in some cases it is absolutely necessary. Many components with be based on a standard footprint (SOIC-8 for example), however occasionally parts will have their own footprint that is impossible to buy a breakout board for.

I wanted to test a MEMS I2S microphone made by Analog Devices which had a very interesting footprint. The eight square pads had a 5 mil pitch, however there is the round ground pad around the microphone port that needs to be connected. In this case I opted to flip the chip over and superglue it down to a different breakout board I had. The two following pictures are how it turned out.

 

I first fluxed all the pads, then added solder to both the breakout board as well as the pads on the microphone. Because the round ground pad was adjacent to another ground pad I bridged the gap with solder. After cleaning my iron and applying more flux I positioned single stranded wire ( I had removed the insulation with wire strippers) with tweezers and applied heat. The final product looks a little messy close up due to excess flux. The white haze is from the superglue.

After all the connections were made the I2S interface worked like a charm. I will post a tutorial on using I2S with the LPC1769 a little later in the month.

TI’s TMP006

Today I received a sample order from Texas Instruments. Among several ICs for a school project I also sampled some of the TMP006  “Infrared Thermopile Sensors”. I don’t have a PCB to solder them to yet, so I decided to take some macro photos.

I apologize for the quality. The top light in my microscope burned out and so all the pictures are light from the side with a handheld flashlight while trying to hold my camera steady and focused through the eyepiece. After this buying a nice microscope with a built in digital camera seems like a good idea.

The title picture is the top of the chip. It has the part number (TMP006), the alignment mark in the lower left, and what is probably the lot trace code. The interesting part is when the chip is flipped over. This is a chip-scale BGA package, which is convenient in terms of the amount of space it takes up, but almost impossible to solder by hand. To give a sense of scale the spacing between the center of each metal ball is 0.5mm.

I would have liked to get some higher quality pictures, but that will have to wait until I have a better setup .