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The blind holes are mostly small holes with a diameter of 0.05mm~0.15mm. The holes of the buried blind holes have laser holes, plasma holes and optical holes. The laser holes are usually used, and the laser holes are divided into CO2 and YAG UV laser machines (UV).
Blind vias/Laser Vias: Blind vias are the holes that connect the inner layer of the PCB to the surface layer of the PCB. The Blind vias do not penetrate the entire board.
Buried vias: Buried vias are only the type of holes connecting the wires between the inner layers, so they cannot be seen from the PCB surface.
The figure is a schematic diagram of an 8-layer slab sectional structure:
A: Through hole (L1-L8)
B: Buried hole (L2-L7)
C: blind hole (L7-L8)
D: blind hole (L1-L3)
Note: The following examples are all 8 PCB layers
Section structure diagram of 8 layers HDI circuit board
Blind embedded circuit board, also known as HDI circuit board, often used in mobile phones, GPS navigation and other high-end products on the application, the structure of the conventional multilayer circuit board, is containing the inner circuit and outer circuit, and then drilling, and the hole metallization process, to make the internal connection between the various layers of the circuit. Next, let's understand its precautions and maintenance.
Matters needing attention
Blind embedded circuit board if you want to copy the board, the difficulty is relatively high, the general mobile phone board and HDI board when reading the board will encounter blind embedded hole, so pay attention to the following matters:
1. Be careful and make preparations before copying the board;
2. The equipment must be advanced;
3. In the process of copying the board, keep comparing with the original board;
4. Check carefully and repeatedly.
Blind hole maintenance
In order to ensure the good working condition of the blind embedded circuit board and reduce the failure rate of the circuit board, it is necessary to carry out maintenance on the circuit board, including annual maintenance and semi-maintenance. The maintenance method is as follows:
1. Annual maintenance of blind burrowing
(1) Regularly spot check the electrolytic capacitor capacity in the circuit board, when the electrolytic capacitor capacity is found to be less than 20% of the nominal capacity, it should be replaced in time; Generally speaking, the working life of the electrolytic capacitor is about 10 years, so in order to ensure the normal work of the circuit board, the electrolytic capacitor should be replaced in about 10 years;
(2) For high-power devices coated with heat dissipation silicone grease, should check the heat dissipation silicone grease is not dry and solid, for dry and solid should be dry and solid heat dissipation silicone grease removed, coated with new heat dissipation silicone grease, in order to prevent the high power devices in the circuit board due to bad heat dissipation and burn;
(3) timely clean the dust on the circuit board to ensure the circuit board is clean.
2. Blind buried hole semi-maintenance
(1) Every quarter to clean the dust on the circuit board, the circuit board can be cleaned with special cleaning liquid, the dust on the circuit board is cleaned, the circuit board can be dried with a hair dryer;
(2) Observe the electronic components in the circuit board have no traces of high temperature, electrolytic capacitor has no bulge leakage phenomenon, if there should be replaced.
With the development of electronic products to high density, high precision, corresponding to the blind embedded circuit board put forward the same requirements, of course, also should pay attention to some matters, but also to maintain it, to ensure the use of the blind embedded circuit board.
