A substrate that serves as a foundation for display is essential to manufacture a display. ‘Mother Glass’ refers to a large piece of glass that lays the groundwork for display production. The mother glass is classified into different generations depending on their sizes.
Panels that constitute either OLEDs or LCDs are produced through several processes on top of a large block of mother glass. These panels that we are familiar with are not produced respectively, but once fabricated through manufacturing processes, and mother glasses are cut into smaller display sizes.
As such, mother glass, which serves as the bottom layer for a panel, comes in different generations depending on the size of mother glass. Each generation of mother glass is not classified based on the universal standard, but manufacturers usually define similarly sized mother glass as the same generation of mother glass. In other words, the size of respective generations of mother glass may differ slightly by manufacturers.
The latest mother glass generation is the largest, as the newer generations of mother glass are larger than older generations of mother glass.
To compare each generation: Gen 10.5 glass became approximately 100 times bigger than the first generation. The main reason for the increased size of display mother glass is to produce panels more efficiently. Large mother glass allows manufacturers to produce more panels at once or increase the production of larger-sized displays. It is more time-saving to produce a large volume of panels with a single block of mother glass than using several mother glasses since displays require multiple manufacturing steps.
However, just because the size of the mother glass becomes larger, it doesn’t guarantee improved production efficiency. It is critical to make full use of a single piece of mother glass when cutting panels. Unit Per Sheet (UPS), representing a unit of cutting efficiency, refers to the number of panels produced from one mother glass. It is necessary to choose which size of the panel will produce in a single block of mother glass to minimize the wasted portion of the mother glass. And that’s where Multi Model on a Glass (MMG) comes in. For example, in a Gen 8 fab, only three 65” panels can be made, and over a third of the glass is wasted, which the cutting efficiency is only 64%. However, if you make six 32” panels more along one side of the glass, the efficiency goes up to 90%.
This being said, considering the size of the final display is significant when deciding the size of mother glass because higher cutting efficiency benefits reduce production costs.