iPhone XS Max Touch Screen Failure repair

iPhone XS MaxTouch Screen Failure repair

Hello, everyone. Welcome to the Xunwei case sharing. First of all, I would like to thank Li Gong of Xunwei Technology Group for providing case materials.
Machine model: iPhone XS Max
Symptoms: Touch screen doesn’t work.
Maintenance process:
Today, let’s discuss a failure of iPhone XS Max touch screen. Of course, the case we are discussing is definitely not the problem of the screen itself. We mainly study the trend of touch-related circuits on the motherboard and the maintenance points that should be focused on during maintenance.
First, we open the drawing software and find the component labeling drawing of iPhone XS Max.

iPhone XS Max Touch Screen Failure repairFigure 1.
Attention, everyone. Here, we divide the motherboard of XS MAX into several blocks. Upper surface A, upper surface B, middle frame, lower layer, touch BTB connector small board.
The fault we are discussing today is Touch failure, so we choose to keep an eye on BTB connector small board. As the fault does not involve any other place, according to the principle of easy maintenance before difficult maintenance, we first measured the BTB connector bit that touched BTB connector.  According to diode value given by Boardview software, if diode value is abnormal,Prove that the line and the components connected to the line are abnormal.

iPhone XS Max Touch Screen Failure repair Figure 2.

iPhone XS Max is a double-layer motherboard design, and the lines and communication between the touch panel and the upper motherboard are bridged through the middle frame. Therefore, many times, because of Fall hard or water damage corrode, the connection between the upper layer and the middle frame will be disconnected with high probability.

iPhone XS Max Touch Screen Failure repair Figure 3.

Many novice friends here may have questions, so if Touch failure is the case, there is an abnormal line in the measurement. Follow the upper middle frame, touch the BTB connector small board with the middle frame, and the mainboard must be separated during maintenance. Should I separate the upper layer or touch the BTB connector small board separately.
Here, let’s make a metaphor. If the same water cup falls at the same height, is the big water cup easily damaged or the small water cup easily broken? Therefore, we usually directly separate the upper layer from the middle frame, because the area and volume of the upper main board are larger than that of the small board, and the volume and weight of the small board are basically negligible.

iPhone XS Max Touch Screen Failure repair Figure 4.

At this point, let’s sum up,iPhone XS Max Touch failure without any other faults. The high probability is due to the disadvantages of the dual-layer motherboard design, but the advantages of the dual-layer design are definitely redundant disadvantages. Due to the double-layer motherboard, physical conditions or water damage corrode may cause the motherboard to touch the working line pad break off Inveracious Soldering or water damage corrode.Therefore, the functional failure of screen Touch failure appears. In the future, we only need to measure and touch BTB connector diode value, and then we can sum up the clear maintenance direction and ideas by combining the causes of the failure.