DIY Manual Pick and Place SMD Vacuum Tweezers

I own a small engineering company that designs and manufactures Surface Mount Technology-based hardware reverse-engineering and fault-injection tools. I typically manufacture boards in lots of 10 at a time. I do have an automatic Pick-n-Place machine, however its setup and alignment can be time consuming. Thus, I occasionally resort to manual hand tweezers. This presents a different set of issues.

Manually grasping the edges of a hundred tiny 0603 and 0402 resistors and capacitors per board with tweezers can be difficult, stressful and time consuming. Shaky hands hyped up on an energy drink or just tired after a late night geek session make the placing even more difficult. Gripping at an off-angle may mean the part flies off the tweezers never to be found again.

The solution to this problem is a manual vacuum-pump powered SMD pick and place device. There are commercial devices on the market. However, the most functional devices are rather expensive. There are inexpensive, rechargeable handheld units but they are not much more functional than actual tweezers or barely function correctly at all.

I have seen a few designs on hackster.io which peaked my interest at constructing my own. I very much liked this design by hackster.io contributor leumasyerrp (https://hackaday.io/project/182987-manual-pick-and-place-smd-vacuum) but I really didn't want to make yet another printed circuit board to control the vacuum pump motor and electric pneumatic shutoff valve. In addition, the design lacked variable vacuum power.

I decided to use this overall design with a few more modern features. I would use an Arduino UNO R3 and MOSFET breakout boards to control the motor and shutoff valve to avoid fabricating another board. In addition to the existing potentiometer in the design to control shutoff delay, I added an additional potentiometer to control vacuum strength. This would end up being very useful because full speed on the vacuum motor made it very difficult to use when placing 0402 SMD parts.

Theory of Operation:

At power on, the manual SMD Pick and Place determines the position of the potentiometers. The potentiometers act as voltage dividers, thus their position is easily determined by reading the voltage using the Arduino's ADC channels. Until the user depresses the footswitch a first time to place a SMD part, the vacuum pump remains off - keeping the workspace quiet. The user depresses the footswitch, MOSFETs triggered by the Arduino turn on the vacuum pump and allow the vacuum to flow in order to grasp the SMD part. The vacuum pump speed (which determines the vacuum pressure) is under PWM MOSFET control based on the potentiometer setting.

The second potentiometer determines how long long the vacuum pump remains on after the footswitch is released. Currently the Arduino firmware sets the delay between zero and ten seconds before the vacuum pump is switched off via it's MOSFET.

Construction Notes:

• Always a good idea to test fit and test possible component layouts when possible. As you can see here, one of my initial layout ideas is considerably different than the final layout.

• During the fabrication of the front and rear panels of the device case, I first drew out the design on 0.1"-ruled graph paper to determine the size and location of the mounting holes for power switch, 120V power cord panel, potentiometer mounting holes, 1/4 inch mono phone plug socket, etc. I then cemented the graph paper layout to the front and rear panels with rubber cement. I then used a sheet metal nibbling tool and drill press to complete the fabrication.

• I 3D-printed mounts for the vacuum pump motor, electric pneumatic valve and Arduino mounts. When mounting the vacuum devices, I cut out pieces of gasket material to place between the metal case and the 3D-printed mounts to lessen vibrations and noise.

• Instead of mounting the MOSFET breakout boards, I just covered these with red heat shrink tubing and labeled them.

Design changes I would make now:

• The Weller tip (https://www.digikey.com/en/products/detail/apex-tool-group/T0052918499N/1801476) is rather expensive. Knowing what I know now, I would fabricate my own from a SMD solder paste dispenser syringe and connect the clear hose to it.
• In addition to the rear panel 1/4 inch foot switch connector, I will be adding a 1/4 inch mono plug to the front of the panel too. It is sometimes desirable to plug in the foot switch to the front end of device instead of rear.