I got a car board from a friend, and the main appearance is as follows. Car controllers usually use metal housings to shield strong interference, allowing the system to operate more stably.
Today, we will mainly dissect this board to see what functional parts it has.
Opening the lower part of the housing, the back of the board comes into view:
The resources are abundant. After some research, I marked the main core functional parts on the back of the board as follows: the surrounding edge has a golden ground cage design to lock in the interference on the board. Of course, we can also add a plane layer to reduce interference. For example, if some originally 4-layer boards fail RE testing, we can add two plane layers to make it a 6-layer board to reduce overall radiation from the board.
During the disassembly, I found a part with a heat sink on the back cover of the housing. Checking the corresponding chip position, it is a MIPI-CSI camera chip. By the way, let’s mention the MIPI protocol.MIPI (Mobile Industry Processor Interface) is an alliance established in 2003 by companies such as ARM, Nokia, ST, and TI, aimed at standardizing internal interfaces of mobile phones like camera, display, RF/baseband interfaces, etc., to reduce the complexity of phone design and increase design flexibility. The MIPI alliance has different Work Groups that define a series of internal interface standards for mobile phones, such as camera interface CSI, display interface DSI, RF interface DigRF, microphone/speaker interface SLIMbus, etc.The benefit of a unified interface standard is that mobile manufacturers can flexibly choose different chips and modules from the market according to their needs, making it quicker and easier to change designs and functions. The chips used in this PCBA are mainly MIPI-CSI for the camera part.
Because the camera acquisition involves image processing, this chip area generates a lot of heat. During the structural design, thermal grease was specially added for heat dissipation. Thermal grease seems to be expensive; I have seen a lot of it when disassembling laptops in the past. This heat dissipation area can sometimes be challenging to solder because it dissipates heat too quickly. However, we can choose to optimize the PCB surface process to better solder. Currently, Jialichuang offers free upgrades to a thicker 2U gold plating, which not only provides better electrical connections, anti-corrosion, and soldering performance but also helps maintain good signal transmission and impedance control.
Next is the front of the board, which is also luxurious, with the main chip MCIMX6D6AVT08AD, packaged in FCPBGA-624.
This is an ARM-A9 series MPU, with a maximum clock frequency of 852MHz, and it has a wealth of external peripheral interfaces: DDR, PCIe, IIC, SPI, UART, CAN, SAI, Ethernet, USB, ADC, etc., making it very suitable for expansion during later project development.
After reviewing the chip, I marked the key functional parts as follows:
Similarly, the CPU power consumption area also has a large amount of thermal grease.
This PCB includes 4 SDRAM chips, 4G module circuit, eMMC unit, RS232 circuit, CAN circuit, 4-channel camera circuit, high-precision clock circuit, PMIC circuit, storage circuit, etc.
Overall, this board has a certain complexity; it is estimated to have around 6-8 layers. Hardware engineers who design their own boards know that the fanout for 4 DDR SDRAM chips is still somewhat challenging, with various equal-length routing.
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