20N Fast Response Flat Voice Coil Actuator for Wire Bonding Z Axis Loop Control

The VCAP0020-0068-00A drives the bonding head of a wire bonder, where the vertical axis has to descend, touch the pad with a few tens of grams of force and retract again in the time the bonder needs for one wire. Peak force is 20 N, continuous force at 25°C is 5.5 N, and the usable travel is 6.8 mm inside a body of only 39 × 50 × 21.5 mm. The moving coil is the only part that travels, so the axis has none of the reflected inertia, screw whip or belt stretch that slows a motor driven bond head, and touchdown force is set directly by coil current rather than inferred from a lost step.

Golden and copper wire bonding is a force and time problem before it is a position problem. The capillary must contact the pad softly enough to avoid cratering, press hard enough to form a reliable intermetallic layer, and release fast enough for the loop profile to stay repeatable at wire counts above twenty per second. A screw driven head has to overcome static friction before it moves and cannot modulate force below the friction threshold, which is why bonders compensate with complicated touchdown detection and mechanical dampers. The flat voice coil removes that threshold completely: the coil is supported only by the air gap, so a 0.2 N command produces 0.2 N of contact force with no dead band. Force rises and falls within a millisecond, which shortens the touchdown window, reduces pad damage on thin wafers and improves loop height consistency across a whole lead frame. The same signal that commands force also measures it, because coil current is proportional to load, so a broken wire, a missing pad or a worn capillary shows up as a change in the current trace and can be flagged inside the same bond cycle instead of at electrical test.

Gold and copper ball bonders, aluminium wedge bonders, ribbon and heavy wire bonders, die attach pick and place heads, flip chip thermocompression heads, and probe or test contactors that need a controlled touch force on a small pad.

Q: Can bonding force be programmed per wire?
A: Yes. Force follows current, so the bond recipe can change force between the ball bond and the stitch bond within the same wire, and between different pad sizes on the same device, without any mechanical adjustment.

Q: How is touchdown detected?
A: The drive monitors the current derivative. When the capillary meets the pad the coil stops accelerating and current rises sharply, which gives a touchdown signal within a fraction of a millisecond, fast enough for copper wire processes.

Q: Does the actuator generate particles in a cleanroom?
A: There is no sliding contact and no lubricant in the motion path, only a coil moving in an air gap. The magnet track is enclosed, so particle generation stays far below the limits of an ISO Class 5 bonder enclosure.

Q: What happens on a broken wire or a missing pad?
A: The current trace deviates from the taught profile. A window comparison in the bonder controller flags the deviation, and the head can be retracted immediately instead of continuing the cycle.

Q: Is a vertical mount with gravity load acceptable?
A: Yes on a bond head, because the axis is short and the return spring or counterbalance already exists. For long dwell times at power off, keep a light spring so the capillary does not rest on the device.

Supplied with high flex cable, mounting screws and a force calibration sheet. Capillary holders, bond head brackets and matched current loop drives can be quoted together.