3M anisotropic conductive film adhesive 7313 tech bulletin 用户手册

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Technical Bulletin

Thermode bonding, also referred to as hot-bar bonding, involves bringing a heated thermode into
controlled-pressure contact with the previously aligned circuits to be bonded. This type of bonding
is typical for bonding an interconnect circuit to a printed circuit board. Thermode bonders can
utilize a constant temperature thermode or a pulsed-heat thermode with micro-processor-controlled
variable temperature.

Figure 2 shows an example of a temperature profile measured during the process of bonding a flex
circuit to a printed circuit board using a constant-temperature thermode bonder. The bonding
pressure is applied immediately at the start of the bond cycle, an continues uniformly throughout the
bond cycle. The temperature rises quickly at first and then begins to level off. The temperature then
slowly continuse to increase. Care must be taken to ensure that the maximum temperature is below
the temperature at which the parts to be bonded could be damaged. The bond pressure is released
after the full five seconds bond time is reached. When pressure is released with the adhesive at the
peak temperature, the circuits may undergo slight separation before the adhesive cools below the
recrystallization temperature. This may affect the mechanical and electrical performance.

Cooling under pressure is recommended for maximum mechanical and electrical performance.
Generally, the mass of a constant heat type thermode is too large to feasibly allow for cooling under
pressure. A pulsed-heat bonder permits cooling under pressure.

A pulsed-heat type thermode with micro-processor-controlled variable temperature can be used to
ensure that the parts heat more rapidly, maintain a more constant maximum temperature, and
optionally are cooled under pressure. Figure 3 shows an example of a temperature profile measured
during the process of bonding a flex-circuit to a printed circuit board using a pulsed-heat-thermode
bonder. The pressure is released after the adhesive temperature has dropped to below 90°C.

These examples show comparatively how to use these different types of bonders for a typical
application. The graphs shown in Figures 2 and 3 depict actual data gathered using a thermocouple
set in the bond-line of a flex-circuit-to-board sample and a thermally conductive compliant rubber
layer was used (for uniform pressure distribution). Any change in the circuits is likely to affect the
temperature measured in the bond-line, therefore, it is necessary to test the actual parts you will use
to identify the adhesive bond-line temperature and adjust to the recommended level of 135-150°C.

Figure 2. Graph of bond-line temperature vs. time for a constant-temperature thermode type bonder. Temperatures
shown are measured in the adhesive bond-line using a higher thermode setpoint temperature.