Mini LED displays can now be manufactured industrially using revolutionary production processes. However, when transferring LEDs from a carrier to a substrate, the yield is never 100%. Even if the yield is a rate of 99.9999%, this means that one LED out of 1 million transferred LEDs will not work correctly. For a display with one million LEDs, this leads to a significant need for repairs of the expensive systems.
Mergenthaler has developed unique systems for repairing Mini LEDS displays.
Using a laser that exactly replicates the shape of the Mini LED, a defective or improperly seated Mini LED can be desoldered and also re-soldered.
To prevent burning during the critical process, the temperature is measured 10,000 times per second during the laser process with an infrared pyrometer coaxial to the laser beam and closed loop controlled. The user programs a temperature curve for desoldering or soldering. This is precisely maintained by the control system. Due to the local heat input, the neighboring components are not affected. No additional thermocouples need to be installed. Since the laser process is the fastest soldering process, oxidation is minimized and the quality of the soldering is improved In addition, the drift caused by thermal heating is extremely low due to the very local heat input.
If desired, the system can also be equipped with a nitrogen nozzle so that the soldering process can also take place under inert gas.
In addition to the pyrometer, the system also has a high-resolution video system. This video system visualizes the soldering process and can also be used to perform Active Alignment of the laser head over the defective Mini LED. The recorded soldering process can also be used to optimize the soldering parameters such as temperature, ramp and soldering time.
The laser profile is Top Hat and absolutely homogeneous over the area of the LED.