General description

・For components that are bonded at a high-temperature and high-pressure state after being precisely aligned, their bonding quality is assured by the positioning mechanism that absorbs the plate thickness variations of the bonded components.This positional adjustment requires a simple mechanism allowing height adjustment without having to modify the parallelism of the bonded components.This lecture introduces the simple height adjusting mechanism that is designed based on the concept of parallel springs.

Explanation

・LCD driver devices are precisely bonded using technologies such as the COG (Chip on Glass) bonding method. (Fig.1)
・Products assembled in the COG bonding method cannot be reprocessed because two components are bonded at a high-temperature and high-pressure state after their X-Y coordinates have been aligned.Therefore, both the positioning and compression bonding processes must be as accurate as possible.
・Because both of the two components bonded are usually made of hard and brittle materials like glass, the pressure variation caused by a difference in plate thickness must be minimized. For this reason, a height adjustment technique is frequently adopted for absorbing the plate thickness variations.
・To absorb the plate thickness variations, the positioning mechanism must have the following characteristics:
1.The mechanism should be compact and simple.
2.The adjustment range can be narrow, but the variations in parallelism should be small.
3.The mechanism should be free from backlashes and can be fine repeatability on accuracy.
・The plate thickness adjusting mechanism (Fig.2) uses the parallel springs shown in Fig.3. The characteristics are as follows:
a) The mechanism should be simple and built with fewer parts.
b) The height can be adjusted while maintaining the parallelism.
c) Gaps or backlashes should not occur.
・The parallel springs should be made of stainless steel (e.g. SUS304). The tensile strength is enhanced by heat treatment.
・One of the precautions for producing parallel springs is the cracks at groove corners resulting from stress concentration.This can be prevented by adopting a round shape to the groove corners of the thin plate with spring properties.