Few months ago I was assembling several dozens of PCBs and I did it as usual using pick and place pen without vacuum pump and just creating vacuum with my mouth. This works well for several PCB with limited components but is tedious when confronted with 50 boards with 100+ components on each.
At that point I ordered vacuum pump off eBay and just plugged it in. I soon gave up on it as I had to use the hole on the PCB pen to release the vacuum with finger which moves the pen and when you have a load of 0603 and smaller components is not good. Also, the pump that I bought was running constantly and was getting hot.
I decided to make my own vacuum pump that would feature the foot switch and two solenoids to release the vacuum quickly from the system so that I can place components fast.
First part was to go and develop the circuit. My idea, apart of the foot switch, was to have the pump run on full voltage just the first few seconds until I pick up the component and then to reduce the pressure after that. I used LM317 for that combined with the 555 timer chip.
I developed the circuit in KiCad and etched it and put together at home.
GitHub repositories can be found on link https://github.com/tdarlic/smd_pen
Step 1: Developing a Circuit
Details of development of a circuit and a board can be seen in embedded video.
Requirements that I had for the circuit were following:
- Powered directly from the 200V
- Having a foot switch capable of actuating a circuit with a at least 4 meters of cable
- Powering a pump on full first few seconds until the component is picked up and after that reduce the voltage to keep the pump cool
- Use 2 solenoids to release the pressure as fast as possible to get precise placement
- PCB must be so small to fit inside a Hammond case i had lying around
- Air pipe connection must be simple and sturdy so it can withstand force when I plug in and plug out the air pipe
I came up with the circuit consisting of several parts:
- Power supply - I bought one off eBay 220VAC - 6VDC 1A and made a footprint for it in Kicad
- Solenoid drivers for 2 solenoid used
- 555 timer paired with LM317 to reduce the voltage after certain amount of time
- Relay and relay driver
I've made several mistakes in a first video which are corrected in a video #3 at 11:00. Namely, the relay I had was not 2PDT it was SPST so I had to change that part of a circuit. Also, I changed the way the relay driver NPN transistor is connected with the current limiting resistors. Here's the link to the exact part of video were I explain some of the corrections to the circuit in short.
Step 2: Etching and Preparing the PCB
In this step I am preparing the PCB. Video details following steps:
- Printing toner transfer
- Transferring to PCB
- Adding top silk screen
- Adding solder resist
- Finalizing dimensions
At the end I was not satisfied completely with the board but I completed it anyway. My UV lamp has given up on me after 10 years and my next project will be UV exposure device.
Check the full video here
Step 3: Soldering the PCB Together
At this step I solder everything together and test it. At 11:00 I show off the second developed board which came out much better that the first one and from that moment I used newly developed board for the rest of the instructable.
In order to have the air pipes firmly connected in the enclosure I used a 4mm copper piper which I soldered into shape and then soldered to PCB so that it is firmly fixed.
Step 4: Putting Everything Together
In this part I just complete the enclosure and put everything together. I make one final test before closing the case and after that I use the pump on some 1206 resistors.