How to improve their maintenance capabilities of junior PCB repair personnel

First, the welding Hate is important, Flux, hot air, and soldering gun must be used. The resistor-capacitor components these days are all 0603/0402/0201 size, go get a broken motherboard, remove the components on it and solder them back, you will Know what you need to practice.

Next, go to the Tektronix website and grab their oscilloscope manual to read. Most of the masters use this stuff. Please register yourself on the website.

The first choice for electricity meter is Fluke, which is simple and easy to use, just take a look and get familiar with it, or you can go to Guanghua mall to play with the real machine for practical aspects.

There are many grades for repairing circuit boards, and junior repairers basically only work as welders. The instructions you received were probably "replace U37 BGA64 with new, R32 UNSTUFF, STUFF C330 0.1u". That means, replace the number U37 on the board (usually there will be a silkscreen icon to indicate the location of U37, just follow the picture to find it) and replace a BGA (basically soldering with a machine, which is a lot of knowledge, and will be described later), put R32 (resistor) is unsoldered (UNSTUFF means that the component is not used), and a 0.1u capacitor is soldered to the position of C330.

As long as the soldering iron and tools are familiar with the junior repairman, there is nothing to worry about. Soldering BGA is learning. BGA solder balls will melt just a little under a certain temperature, but they will not collapse. Unloading, removing tin, ball mounting, solder paste on stencil, positioning, and reflow are all knowledge. Usually made for older birds with a bit of experience. The machine soldering BGA must be at a constant temperature and timing, and be careful not to blow away the nearby components. It's very complicated, but usually the manufacturer of BGA components will provide the rework document file, just read it obediently. Google "ti bga rework instruction" can find a bunch of documents. (TI is a representative manufacturer)

Senior maintenance personnel have to judge by themselves where there is a problem and how to deal with it. It’s not something you can learn in a day or two, and naturally it’s impossible to teach you here, but there are indeed some principles that everyone will abide by.

To repair a board, you must understand the circuit diagram. Usually, we first look at the block diagram architecture diagram, and first understand which power, which reset#, which clock, and which IO/bus. Which GPIO. Next, look at the circuit diagram, gerber file, and BOM list. At least know what the whole board is doing. Google "intel motherboard block diagram" and you'll find a bunch. here is one:

Next, do visual inspection/comparison. Take a good board for comparison. Find out which component on the rigid board has scorch marks, exploded corners, crashed, and tin bridges. The components are missing, the connectors are not properly connected, the board is bent, the battery is leaking, the board is corroded... Advanced ones will use 5DX (a very expensive machine) X-ray to see the BGA solder balls , look for cold solder or broken balls.

If you can't find the reason, you have to turn on the power to check, first connect the power, and look for any overheating components. Next, look at each Is the level of a power correct, RESET is not given (usually low trigger), use an oscilloscope to see if the clock is there? Let's see if there is anything coming out of IO, and whether the GPIO level is correct.