FOG (Film-on-Glass) Bonding Process for TFT LCD Modules
A bare TFT glass has no way to talk to the rest of the system until its driver IC is bonded to it — that is the FOG (film-on-glass) step. Using anisotropic conductive film, the IC and then the flexible circuit are bonded to the glass edge, wiring the panel to the world. This page covers the FOG sequence: ACF, IC bonding, FPC bonding, AOI particle inspection and final electrical test.
The FOG Sequence
| Step | What happens |
|---|---|
| Material loading | Glass, ACF and IC prepared for bonding |
| Plasma washing | Surface activated for adhesion |
| ACF attachment | Anisotropic conductive film applied to the bond area |
| IC bonding | Driver IC pressed onto the glass through the ACF |
| FPC bonding | Flexible circuit bonded to the same glass edge |
| AOI particle inspection | Conductive particles checked for placement and bridging |
| Electrical test | Full function and line-connection check |
Where Quality Is Won
The bond is the most failure-prone junction in the module. ACF particles must sit correctly — too few and a line opens, too many and two lines short. That is why automated optical inspection of the particles sits right after bonding, and why the electrical test gates everything before assembly.
Why a Buyer Should Care
Bond yield predicts field returns. When you qualify a module, ask about ACF inspection and bond electrical test rates — a supplier that cannot describe them is a risk.
Matching Standard Panels
Every standard module is FOG-bonded. These sizes are frequent subjects of bond qualification:
- RG-T043BPSA-01 — 4.3″ 480x272 IPS TFT LCD Module
- RG-T050BPSA-01 — 5.0″ 480x272 IPS TFT LCD Module
- RG-T070BAHA-02 — 7.0″ 1024x600 1000 cd/m² IPS TFT
Related Guides
- Manufacturing Process Overview — all five steps
- POL Lamination (POG) — the preceding step
- LCM Assembly — the following step
Frequently Asked Questions
What is FOG?
FOG is film-on-glass: the driver IC is bonded onto the LCD glass via anisotropic conductive film (ACF), and the flexible printed circuit is then bonded to the same glass edge. It is the step that electrically connects the panel to the outside world.
Why is ACF inspection critical?
ACF carries the electrical connection through microscopic conductive particles. Missing, misaligned or bridged particles cause open or short circuits — so automated optical inspection of particles is what protects bond yield and field reliability.
What does the final electrical test confirm?
That every line is connected and the panel drives correctly — no open pixel lines, no shorts. It is the gate before the cell moves to LCM assembly.
Talk to Our Engineers
Send your qualification questions to sales@odmlcd.com — we will reply with how FOG bond yield is controlled on your module.