Flip Chip Rework

Flip Chip rework is a rather new field becoming more and more important in order to save costs by recycling valuable materials. Typical flip chip applications can be found in TFT display technology which is used for LCD, plasma, e-ink, OLED or 3D technologies.

A high quality, large format TFT/LCD panel is a good example for economic flip chip rework of chip on glass (COG) in combination with rework of ACF-bonded flex foil on PCB or panel (chip on flex (COF)). Exploiting one panel to repair ten or more other defect panels is the last resort if there is no more access to virgin material (OEM), if virgin material is too expensive or in case of EOP (end of production). This is especially interesting for production or warranty & service centres, but also for R&D.

Uncovered TFT panel
View with process camera
Top view machine and TFT panel
Side view machine and TFT panel

What are the challenges?

Bare, sensitive components with high packaging density
Chip sizes with special LxW ratios (example: LxWxH=20,0 x 1,5 x 0,35 [mm])
High number of I/O (300 or more)
Chip pitch of 60 µm (line/gap=25/35[µm])
Handling large TFT panel sizes (32” or more)
Particular demands on machine, tooling / fixtures and process reliability
Every working step of the rework sequence requires a high degree of process stability and safety to reach a high rework yield

The Finetech Solution

Disconnect, Remove, Clean, Re-bond

Panel after chip removal
Driver chip after removal
Driver chip after cleaning

The whole rework sequence can be performed on a FINEPLACER^® system:

Disconnect

Remove driver chip or flex foil
Clean all parts from residual adhesives
Re-bond driver chip or flex foil

Flip Chip Rework: Chip on Glass (COG)

View on chip through transparent TFT glas carrier
Top view on re-bonded chip

Example for COG: panel and chip preparation for reassembly

Open the monitor cover
TFT panel load on clamping table
Chip alignment in reference to removal tool
Chip removal by IPM for simultaneous process run with defined parameters (temperature, force, vacuum) and table movement
Clean panel and chip separately
Apply ACF segment on TFT panel
Pick up the cleaned chip with the bonding tool
Chip alignment by using the fiducial marks, supported by tool fine rotation
Start automated bonding process
Close monitor cover and function test

Integrated Process Management (IPM)

Integrated Process Management (IPM)
Principle of process gas integration
Operating software for rework

The Integrated Process Management (IPM) is the center piece of a FINEPLACER^® system¹ - the place where it all comes together. IPM is more than just thermal management. It synchronizes the control of all process modules and their related parameters:

Controlled and precisely balanced interaction of top and bottom (pre-)heating and cooling
Control of temperature, time, force, power, energy, flow
Controlled process gas integration for reduced solder contamination, minimized surface tension effects and smooth spherical solder residues

IPM is very complex, yet easy to access. Via the GUI of the operating software, the user has perfect control of all required adjustments. Just drag 'n drop to define temperature ramps or activate process modules. All settings are represented in only one profile, making for a very intuitive work flow.

The operating software provides an ever-growing library of profiles for all kinds of processes. It also offers comprehensive data logging functions essential for statistical process control.

In combination with the system-to-system process transfer capability this is as easy as process development can get.

¹ _{FINEPLACER^® core offers co-ordinated top and bottom heating but does not support IPM}