Not being one to duck out of a challenge, I bought a tape of 20kΩ resistors and began designing a test vehicle. The board consists of four identical arrays of footprints; each array contains eight paralleled resistors with a test point on each side. If you do the math this works out to 2.5kΩ across the entire array if all joints are good. Significantly higher or lower would mean one of them was an open or short.
The first problem (which I had anticipated ahead of time) was that my existing tweezers were simply too large to pick up a component of this size.
|01005 passive on 0.5mm TQFP footprint, seen next to my normal tweezers|
|The same component next to my new tweezers|
Paste application used the same tried-and-true method as my earlier 0201 test - squirting a tiny dab of paste onto a microscope slide and using a scalpel blade as a "putty knife". In the interests of time I only hooked up a single column.
To give a better idea of how small the components (and the entire board) is, I put an 8-pin SOIC on it.
|Solder paste applied to the second column with SOIC-8 for scale. The exposed copper rings around the probe pads are the result of an error in the solder mask pattern.|
|Beginning component placement. Note heavy variability in paste volume.|
|Darkfield image of placed components before reflow. Focal plane is just above the top of the solder mask.|
This was confirmed with an ohmmeter check - 2.50KΩ exactly. Looks like a complete success :)
|Board post-reflow. Note probe scrub marks on test pads.|
|Darkfield closeup of a single component. Slight misalignment is visible on the one at the top edge, but electrical test passes.|
|Assembled board seen next to an 14-pin PDIP for scale.|
It was a rather labor intensive process but the end result was a complete success. While I certainly am not about to go and use all 01005 components on my future boards, if it becomes necessary to stick something in a tight place it's good to know my process can handle it.