Generally, iPhone 6 LCD assemblies and frames are held together by PUR glue, which has two types HMG (Hot Melt Glue) and CPG (Cold Press Glue). OEM factories use CPG to assemble the screen and frame, which requires 15 seconds cooling time, 2-3 hours protecting time (Protecting time: time to keep the mold to hold the glued parts). It needs higher cost, longer working time and better equipment to produce and handle. While the assembled flex or refurbished iPhone 6 screen replacements are glued with HMG which the cooling time is 10 seconds and the protecting time is only around 6 seconds. It costs less, doesn’t require a strict working environment, has a shorter working time and results in weaker stickiness.HMG quality also varies by Low, Middle and High grades due to the different prices. Most third-party manufacturers use mid-grade glue for Apple products, however, it is not sticky enough to meet the higher requirements as the iPhone 6’s frame is thinner and the screen is bigger than previous models.
For assembled flex and refurbished iPhone screen assemblies with frames, both the frame and the front glass are high copies, and the frame is custom-made according to the size of the original front glass. After the molds of these two parts have been made, third party factories will constantly use them which means once the frame separation problems had occurred, many of the parts have already been sold in the market previously and currently.
The sizes of the iPhone 4/4S, 5/5C/5S and 6 frames are as follows.
We can see that the edge of the iPhone’s frame has been getting progressively thinner and thinner, thus the bonding area of the screen and frame is getting smaller. As we mentioned before not only is the problem with the mid-grade glue, but also with the machinery as well as the process that is used for previous iPhone models are not applicable any longer.
As you can see, there’re black areas on the bottom of 5/5C/5S and 6 frames. OEM factories will apply adhesive on that area, while many third-party factories won’t apply any adhesive to those areas in order to cut costs, which results in the glass separating from the frame.
The quality of high copy frames and front glass are not as good as OEM ones, the surface areas of these two high copy parts may not be smooth enough to ensure sufficient contact for the adhesive. This is also a reason why the frame tends to fall off.
※ Extended Research: Why the assembled flex frames have a higher refurbish rate than the OEM ones?
The high copy frames used in assembled flex parts are not as strong as the OEM counterparts, and third-party factories have lengthened the height of the frame in order to increase the bonding area. The height of OEM iPhone 6 frames is 0.89 mm VS 1.18 mm for the high copy iPhone 6 frame.
The assembly work put into iPhone 6 screens and frames should be done in a dust-free room, but many third-party manufacturers are unable to meet this standard. Dust easily sticks to the glass unless these conditions are met, which will affect the quality of the glue.
Besides, there’s a varnish on the bottom of the iPhone 6 glass, if it is not sticky enough and coming off, the frame is guaranteed to come off as well.
▪ Use high grade HMG to assemble iPhone 6 LCD assemblies and frames
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