I found this a week ago and thought it was so good, I ordered the parts from Amazon and eBay and built it yesterday I made three changes. I added a reverse-biased diode across the solenoid to reduce current surges. I added a low-side N-channel MOSFET so that the footswitch only has a minimum current flowing through it. Lastly and most important I 3D printed a pen and used a male luer lock to 1/8" barb. I choose metal instead of the plastic one suggested below. Here is a picture together with my solder paste dispenser: https://tinyurl.com/SMDTools. Note I have a simple push button for now until I finish my microswitch foot pedal design. You only need the release for the larger components because the paste pulls off the smaller ones like 0603 resistors.

fantastic! thanks for taking the time to provide feedback on this! great improvements!

The link to the image should work for everyone now.

The outside diameter of the pen is 0.5" and is slightly expanded near the tip to prevent finger slippage. The internal shape is profiled to theluer lock + barb and the 1/8" ID silicone tube. The tube can be pulled off the barb or reinserted onto the barb. The pen is made in two halves and super-glued together.

@MikePinball - awesome work! glad this project was able to inspire you!

Or you could just drill a hole in the side of the pen and stick your finger over it to get vacuum. No valves or pedals required. An aquarium pump with the valve turned around works well as a vacuum source.

@eng - indeed there are many options for creating a vacuum pickup tool. i started this build with very specific requirements, one of which was to be able to place 0.4mm QFN and 0.5mm BGA packages. the "hole-in-the-side" design wasn't able to accurately place those parts. in "Part2 - Application Pen" video above, i discuss the design choices for the pen. this design might not fit the budget or requirements of everyone, but it did for me, so i decided to share it with the community...

Feel your pain brother ;-)  I sprung for a pick & place after decades of going blind doing proto runs under a microscope.

i too ended up purchasing a pick and place! 
https://www.robotdigg.me/product/222/RDG802A-pick-and-place-machine

Hey, I was looking at building this for myself and found a way that might make this build even cheaper. You could use the following which is a 1/8" barb to a male luer lock. You could than 3d print a pen w/ a hollow center to run the tube through and would cover the barb up so that it just exposes the luer lock and provides a customized grip.

https://goo.gl/K5b9iq

Hi, Dave.  Great tool, tutorial, and resource!  I'm in the midst of upgrading my tool chain from hand soldering to reflow, and I'm just about to start work modding a toaster oven for a ControLeo2.  A vacuum pick was next on the list, so I just ordered everything on your BOM and will put the boxes in the closet until I'm ready for them.  It's a shame that most of the cool Luer lock tips aren't available individually (I'm only seeing 25 packs and such).  If you have some extras you want to unload some, let me know.

hey! thanks for the feedback! i'll be doing some videos on solder paste dispenser and solder paste stencils soon! i use the luer lock tips with the solder paste dispenser and flux tubes as well, so i use them up pretty quickly. be sure to post a picture of your build and make sure you subscribe to the Dave's Dev Lab youtube channel!