ELFORM HEAT SEAL CONNECTOR BONDING PARAMETERS
A. Bonding Equipment.
Equipment must be capable of applying a constant pressure by mechanical or
pneumatic means. The heated bonding blade must be flat. Beryllium Copper
is the most suitable metal. Silicone Rubber, 0.30mm to 0.45mm thick should
be placed under the bonding blade during bonding. Sarcon
TR is recommended.
- The machine
set temperature can vary depending on the equipment and type and the substrate
being bonded. The set point of the machine
should be determined by measuring the internal temperature of the adhesive.
- The jig
which holds the substrate can be made of either metal or phenolic, but the
area directly below the bond area should not be thermally conductive.
B. Bonding Parameters.
Temperature defines when the thermoplastic adhesive has reached the
optimum flow temperature.
30 ~ 40 kg/cm2
5 ~ 7s above 140°C
140° ~ 160° C
Silicone Rubber Hardness
70 ~ 80
Silicone Rubber Thickness
0.30 ~ 0.45mm
Indium Tin Oxide traces on glass are most commonly used. Clean with an
applicator soaked in ethanol. If the LCD manufacturer used a silicon zebra strip
to functionally test the LCD there is a good possibility that a silicone
residue is on the glass. This condition may be recognized by checking if water
beads on the glass. Only a plasma etch can remove the silicone. Consult with
your LCD supplier. Some suppliers of elastomeric connectors also have a type of
compression connector that uses a flex circuit wrapped around a rubber
core. This type should be used for testing.
Au, Sn or Carbon ink are recommended. Any metal that has non-conductive oxidizing
properties is not recommended, e.g. Pb-Sn (unless Pb content is less than 10%).
Check area for foreign particles.
C. Notes on Bonding
co-planarity between substrate and the bonding blade with Fuji Low
Pressure grade Prescale Film.
- Avoid touching
the Heat Seal Connector (HSC) and substrate terminal area.
- If the PCB
or TAB electrodes are thicker than 40 microns, double check adhesive
transfer and bond strength.
bonding area on the substrate must be at least 15mm wide. A depth of at
least 2mm is recommended.
bonding blade must contact over the substrate away from the edge,
otherwise trace shearing may occur causing an electrical open.
operations on the LCD and PCB are typically done separately, unless two
independently driven bonding heads are used to assure one substrate does
not act as a spacer to the other.
bubbles can break out in the adhesive if the bonding temperature exceeds
185° C. The bond will be unstable if this happens.
- On all
types of HSCs, the bonding temperature should not be exceeded by more than
20° C. Otherwise adhesive will be squeezed away and the bond will be
- HSCs can
be tacked into place before final bonding by touching them with a
soldering iron set at 160°C.
- The bond
is permanent, but if the HSC is peeled off it will not damage the traces
on the glass or printed circuit board. The conductive ink and adhesive
residue may be removed by using acetone or MEK.
- Bonding quality
should be judged after bonding to glass and performing a vertical peel strength test. All of the adhesive
and 70% of conductive ink should be transferred to the glass.