First, you must understand that OCA is a special glue, it is softer than solid but harder than liquid LOCA glue, when using LOCA glue to refurbish the LCD we never have air bubbles, this is because air bubbles are easily removed from the liquid, but air cannot easily pass through the colloid. Why there is return bubbles? Do you think that after putting the air bubbles in the autoclave for about 5 minutes, do you actually remove all the air bubbles? The answer is no, the real process of removing the bubbles is to squeeze the air out of the OCA after lamination, maybe you don't see any bubbles after the bubbles are removed, but the fact is that the bubbles have been separated by a lot of tiny bubbles that you can't see with your eyes, but once those tiny bubbles come together after a few minutes or hours, they become tiny bubbles that you can see.   How can this be avoided? 1, choose a good quality OCA, Mitsubishi is the most popular glue on the market today, it is very soft and has a good adhesion, there are 3 thicknesses on the market, 175um, 200um, 250um, to be honest the best is 250um a method for laminating and removing air bubbles because it has more space between the glass and the LCD to squeeze the air, but 250um costs more than 175um and 200um, so you can find most OCA glue on the market that is significantly thicker than 250um 200um, or even only 175um. so make sure you have the real 250um OCA, the only downside of 250um glue is that the refurbished LCD will be a little thicker than the original LCD, but most customers don't care.   2, keep the OCA in good condition, e.g. 20°C, no sunlight, humidity about 30% to 70%.   3, Temperature, I want to preheat the OCA glue at 50°C for about 2 minutes before laminating the glass onto the LCD, for the iPhone I use cold pressed framed glass, so I laminate the OCA onto the LCD to preheat the LCD for the Samsung, after putting the OCA on the glass I will preheat the bonded glass. 4, Thickness of paint. All glass is painted (e.g. black/white/blue/gray) and has a minimum of 3 coats of paint, quality white glass should be less than 35um and quality black glass should be less than 15um thick, so if you buy fake quality glass with thicker paint, there is a greater risk of bubbling. If most of the tiny bubbles reappear around the edges of the LCD or near the bottom and top edges, it could be a paint problem. 5, The most important condition of a laminator is vacuum, pure vacuum can make the lamination perfect and easy to remove bubbles. If you fully understand what I have said above, you will solve the bubble problem with ease.