TFT LCD display production process step 4 – FOB Bonding – Where Flex Meets Function

Purpose:

Flex-on-Board/Glass (FOB) bonding permanently interfaces the Flexible Printed Circuit (FPC) or Chip-on-Film (COF) driver with the ACF-treated TFT glass electrodes. It establishes thousands of highly reliable, low-resistance micro-interconnects responsible for routing high-speed differential signals and power from the motherboard to the TFT pixel driving matrices.

Process Characteristics & Equipment:

This critical bottleneck process utilizes High-Precision Automated FOB Pulse-Heat Thermo-Compression Bonding Engines (e.g., Ohashi or Shibaura style systems). The machines incorporate Dual-Upward/Downward Looking CCD Alignment Cameras using sub-pixel pattern matching algorithms. Post-bond deformation and particle distribution are measured via Automatic Particle Indentation Inspection Systems (AOI) and Laser Confocal Scanning Microscopes.

• Bonding Accuracy: Features an alignment accuracy of ±3 μm, operating at temperatures between 160°C and 210°C and bonding pressures of 20 to 40 MPa.

Factory Processing Time:

The complete sequence—including automatic pick-and-place, vision alignment verification, thermode tool descent, a 10 to 14-second dwell cycle under pressure, and fast forced-air cooling—takes 16 to 22 seconds per panel.

Continuous Improvement (Kaizen) & Vision:

Maxen is deploying an AI-Based Real-Time Vision Tracking Loop. By collecting pre- and post-bonding offsets, the software calculates thermal expansion drift in the thermode head and feeds automatic coordinate corrections back to the servo motors. This predictive correction loop has pushed our first-pass bonding yield rate to an industry-leading 99.7% and eliminated manual calibration downtime.