System Backbone

 

Structure:

The machine frame is constructed of anodized aluminum extrusions. Composite panels with carbon fibers embedded in conductive ESD resin, produce safe platforms for the electronics environment.

All molded plastic components in critical ESD paths are produced from a blend of compounds and fillers which offer high stiffness, while producing 10⁵ – 10¹⁰ Ω/sq. of surface resistivity for proper electrostatic discharge. Long glass fibers are embedded to achieve stiffness while an IDP resin (Inherently Dissipative Polymer) renders the blend conductive.

Various other components are fabricated from metal alloys. However, the SMD components will never find a direct, metallic path to ground, hence, eliminating the chance of ultra-fast electrostatic discharge which can damage the components.

Linear Ways:

Planar manipulation for the pick & place system is achieved through a 2-axis, gantry linear motion system. The ways are custom designed, utilizing 12 ball bearings per axis. Standard, recirculating ball, linear bearing systems inherently produce random hesitation when transitioning from rest to motion. This hesitation is detrimental for manual manipulation of axes, while attempting to produce very finite movements (as is necessary for placement of fine pitch SMT components). Motorized systems are not sensitive to this phenomenon since servo controls can easily overcome this behavior. Ball bearings virtually eliminate this problem through their inherent design with integrated ball retainers.

Hardened and chrome plated shafting facilitates long life and rust protection. The shafts do not require lubrication and should be kept clean and particle-free for smooth operation.

Cable Management:

Link chain cable tracks have been custom developed to smoothly and safely guide the cables and pneumatic lines. The track links are also produced from conductive polymers, grounded at the end, to eliminate exposure to electrostatic charge which may build up in cable insulation and soft silicone hoses.

Cable failure in flexing motion presents a tough challenge in moving apparatus with electrical wiring. The power cable is custom developed with molded ends, ferrite bead for noise reduction, and utilization of a continuous flex, flat cable for power management. Additionally, four redundant current paths for each power line further increases system reliability. The cable life is estimated at over 10 million flex cycles! A standard USB cable is deemed to fail after only a few thousand flexes of equal radius.

PCB Presentation:

The main platform is constructed of a thin, top layer of ESD compliant composite, laminated over a thicker, galvanized steel panel. Magnetic PCB locators can be arranged around the PCB, in virtually any shape, to securely affix the PCB for assembly. No screws or clamps are utilized for convenient and quick PCB setup. The PCB locator components are all ESD compliant, including the elastomeric pads, conducting any accumulated charge onto the platform.

Pick & Place:

Vacuum is used for component pick & place. An integrated vacuum pump is utilized. The pump is housed in an acoustically isolated enclosure and mounted via elastomeric suspension components to minimize audible noise and vibration. Pump operation is very quiet! The pump can be turned off during setup periods and inactivity.

The spindle provides for vertical and rotary motions. The spindle accepts a pick stylus of choice (various styli are provided for different component sizes). The spindle utilizes a pneumatic suspension, providing for a light and constant pneumatic spring force, and, producing a compact package by eliminating the need for a large stroke mechanical spring. The spindle pneumatic lines are ergonomically managed through the cable track, without dangling attachments to the spindle.

Once a component has been placed, the vacuum release button is depressed to release the component. Smaller components tend to eliminate the need for a button release as the surface tension of the solder paste overcomes the vacuum force.

Arm Support:

An articulated arm support mechanism with multiple rotary joints provides comfort and stability during operation. The links are quite rigid to support the weight of a human arm; all joints boast double ball bearings for smooth and rigid manipulation. A slight friction/damping in each primary joint is integrated to stabilize fine motions and render better placement results. A very compliant and cushioned rest pad is molded from ESD elastomer and supported by ESD foam, eliminating the need for an ESD wristband which can be quite inconvenient. The articulated linkage internally conducts the human body electrical charges into the ground. This linkage follows the arm through all ranges of motion necessary to operate the SMT Caddy. The ground path is automatically produced via the ground line in the power cable, for all standards with 3-prong power receptacles.

SMT Caddy is quite small and lightweight; as such, a counterweight has been incorporated opposite side of the armrest to balance and stabilize the platform under the weight of the human arm. The armrest and counterweight may swap sides for left-handed or right-handed operation.