SMT Caddy Model A

The SMT Caddy Model A is a benchtop manual pick-and-place system for surface-mount components. You guide a vacuum pick spindle by hand on a two-axis gantry. A digital microscope, a laser landing guide and motorized tape feeders handle the seeing and the feeding.

Specifications

Where it fits

The Model A places parts on a board that already has solder paste, normally stencil printed. After placement, the board goes into a reflow oven. Stencil printers and ovens for prototype volumes are widely available; see the FAQ for practical notes.

Frame, motion and ESD

Frame. Anodized aluminum extrusions, with composite panels of carbon fiber in conductive ESD resin as work surfaces. Molded parts in the ESD path are specified at 10⁵ to 10¹⁰ Ω/sq surface resistivity. That drains charge at a controlled rate rather than through a fast metal-to-metal discharge.

Linear ways. A two-axis gantry on custom ways with 12 ball bearings per axis. Recirculating linear bearings hesitate between rest and motion, which fights fine hand movements; retained ball bearings avoid that. Shafts are hardened and chrome plated and need no lubrication.

Cable management. Conductive-polymer cable tracks, grounded at the end, guide the cables and vacuum lines. The power cable is a continuous-flex flat cable with four redundant conductors per line.

Board holding. The platform is an ESD composite skin over galvanized steel. Magnetic locators set around the board in any shape hold it without screws or clamps.

Pick and place. The integrated vacuum pump sits in an isolated, suspended enclosure for low noise. The spindle has a light pneumatic suspension, and its lines run through the cable track, so nothing hangs off the spindle. A button releases the vacuum; small parts often release on their own into the paste.

Arm support. An articulated armrest with double ball bearings and light damping in the main joints steadies fine motion. The ESD elastomer pad on ESD foam grounds the operator through the linkage and the power cord's ground pin, so no wrist strap is needed. A counterweight balances the arm's load, and armrest and counterweight swap sides for left- or right-handed use.

Digital microscope

A 5 MP color camera on the Raspberry Pi gives live video at 30 fps. Three lenses (wide angle, standard and zoom) change on a magnetic mount and keep their focus setting. The software adds up to 3× digital zoom and pan. Dimmable LED lighting illuminates the work area. The microscope also serves for paste inspection before placement and joint inspection after reflow.

Laser guidance

A video microscope has no depth perception. An adjustable diode laser puts a small red dot at the stylus landing point, so you can line up in X and Y before the final descent, then finish on the microscope image.

Computer and display

A Raspberry Pi 3 (quad-core 1.2 GHz, 1 GB RAM) runs Raspberry Pi OS (formerly Raspbian) from a preloaded 16 GB microSD card. The 7 in multi-touch display runs at 800 × 480. Wi-Fi, Bluetooth, LAN and USB are built in.

Software

The system boots into the SMT Caddy application, so no Linux knowledge is needed. From its desktop:

• Documentation: opens the user documentation.
• Microscope: live video, the normal working view. Double-tap to exit.
• Settings: set and save the zoom and pan relative to the stylus tip.
• Browser: web access over Wi-Fi or LAN.
• Exit: returns to the Raspberry Pi OS desktop for other uses of the Pi.

Tape feeders

Two feeder banks each take up to 10 feeders on 8 mm tape; wider tapes take more room. Bank pitch is 4 mm, so modules pack densely at any width. Each Model A Tape Feeder Kit configures without tools for 8, 12 or 16 mm tape, and setup with new tape takes about a minute.

Feeders are motorized and triggered by pressing the feeder button with the stylus. The motor spools the cover tape onto a small bobbin, which peels it and advances the carrier tape. A module plugs into any bank position and makes its electrical contacts automatically.

Plastic tape winds onto the supplied reel (100 mm OD, 40 mm ID). Paper tape is too stiff to spool; load it as a cut strip. Odd or low-count parts go on the included components tray.

Included with every system

• 3 microscope lenses: wide angle, standard, zoom
• Laser pointer module
• 4 magnetic PCB locators
• 6 pick styli in different sizes
• 3 ESD suction cups for large or odd-shaped parts
• Odd components tray
• Mirror for viewing component pads in transfer
• Roll of 1/8 in Kapton tape for attaching the cover tape
• Sheet of feeder labels

The Starter package adds 10 Model A Tape Feeder Kits.

Operation notes

How many feeder kits should I have?

For a hobbyist or small business, 15 to 20. Most passives come on 8 mm tape, so keep most kits at 8 mm and a few wider. Both banks hold 20 feeders at once on 8 mm tape. For a job shop, more kits preloaded with common values cut setup time.

How much tape fits on a feeder reel?

Maximum length in meters = 6 ÷ tape thickness in mm. A 1.5 mm thick tape gives 4 m. Most prototype jobs need only a short strip.

Why don't the feeders take standard 7 in reels?

Full reels would need larger motors and sprocket drives, and a much larger machine for the same feeder count. Prototype and short-run jobs rarely use full reels.

How do I set the laser?

With the stylus lowered onto the board, aim the dot at a small, fixed offset from the tip so the beam clears the part. The dot then marks the landing point at any spindle height. Re-adjust when board thickness changes or if a stylus is bent. Replace bent styli; they also wobble when rotating parts.

Should I lubricate the shafts?

No. The ways use shielded, internally lubricated ball bearings. Keep the shafts clean and dry; particles cause bumpy motion.

Can I change between righty and lefty myself?

Yes, following the documentation. Ordering the right configuration is easier. A spare armrest mechanism makes changeover quick.

Which styli do I need?

The 6 included styli cover parts from 0402 up to ICs of about 15–20 mm, larger with a suction cup. Order the fine component stylus only for 0201 and smaller; replacement styli replace bent ones.

What placement rate is typical?

Once practiced, an operator typically places 250 to 500 parts per hour, depending on package types and sizes.

Replacement parts: see spare parts. Questions: email info@smtcaddy.com.