Welcome to Guangzhou Tongsen Electronic Technology Co., LTD. Website!
How do circuit boards work? (Part 2)
Power-on observation is a method of manual PCB inspection. After powering on the circuit board, instead of immediately testing, observe the changes. Any errors in the circuit board manufacturing or soldering process may cause smoking or unusual odors after power-on, which are uncommon circuit operation phenomena.
PCB Board Composition
This smartphone PCB actually consists of ten conductive layers, with the top and bottom layers used for mounting PCBA components and acting as multiple antennas. To make it work, each board includes power and ground planes. Additionally, the ground plane also functions as electromagnetic shielding and heat dissipation. The remaining four intermediate layers carry all communication lines or signal lines. Each conductive layer contains copper and insulating fiberglass and epoxy resin. This smartphone PCBA shown here only has 10 conductive layers, but in other applications they can have 2 to 50 layers. FS Technology can produce multilayer PCBAs with up to 56 layers.
In addition, there is a layer of colored solder resist on the top and bottom of the PCBA, which acts as electrical insulation, making the component pads usable. Above this is the silkscreen printing, including ink for markings and letters indicating component positions.
For the circuit board to function correctly, signals must pass through each conductive copper layer and the insulating material between them. This smartphone has ten separate conductive copper layers, each separated by insulating material. How does the signal propagate from one layer to another?
PCB layers achieve this by drilling or metal plating vias, or vertical interconnects, for signals. These vias interconnect the conductors of the various layers, thus connecting multiple components and enabling the operation of multilayer boards. Chinese manufacturers' PCB manufacturing technology can achieve three types of vias.
Through-hole: Holes from top layer to bottom layer
Blind vias: Blind vias connect the top or bottom layer to an inner layer
Buried vias: Buried vias connect inner layers
Because this process involves traversing many layers, when traversing unconnected conductive layers, the copper around the via in that layer is removed. If we X-ray the top of the PCB where the pads for mounting are located, we can see three sets of conductors running in different directions, with holes going through each layer.
These complex circuits exist on the PCB in the center of the phone, it's almost unbelievable. Each smartphone has a different shape and specification, so engineers need to use PCB design tools to design different types of PCBAs. For example, some phones have separate top and bottom PCB boards, the larger one is called the main board, and the smaller one is called the sub-board.
Another important detail is that the PCB is lighter, weighing only as much as a tablespoon of water, and fits perfectly into the phone. Engineers constantly innovate to make microchips, resistors, capacitors, inductors, and connectors as small as possible, some components are smaller than a flea.
In the past, PCBA board designs used components that occupied excessive board space and board area. Because the mounting mechanism for these components was pins through connection holes, these older designs were known as through-hole components. But here, these components are SMD components mounted using SMT assembly technology.
How to check if the PCB is working properly?
From PCB to PCBA is a complex process, both individuals and assembly companies need to thoroughly check the assembly quality of the PCB to ensure that the PCB can work properly. The working principle of the PCB circuit has been explained above, and now we will solve the problems that may be encountered in making your own circuit board, that is, how to check whether the circuit board is working properly.
Schematic Accuracy
Drawing schematics is a step in manufacturing a PCB. These schematics are used to show how electricity works and the function and connection relationships of various electrical components. Checking the schematics is an important part of ensuring that a homemade circuit board works properly.
First, check if the power supply of the IC chip and the labels of the network nodes are correct;
Check if the network nodes overlap;
The model of the component package, the pin order of the surface mount components;
Check if the wiring is correct, including wrong wiring, missing wiring, and multiple wiring.
Component Mounting Accuracy
As mentioned above, the function of a PCB is to provide a platform for electrical connections for electronic applications, while the PCBA is the core that enables the operation of electronic applications. After the PCBA is assembled, it is necessary to check the welding assembly quality of the polarized components on the board, such as whether the pins of LEDs, rectifier diodes, and transistors correspond. It is worth mentioning that even components with the same function but from different procurement channels have different pin arrangement orders. When making your own PCBA, you need to measure it with a multimeter after manual soldering, otherwise it will not work for PCBAs used for keyboards and mice.
Electrical Observation Method
The energized observation method is a method of manual inspection of PCBs, that is, after the circuit board is energized, do not rush to test but observe the changes after energization. Any mistakes in the circuit board manufacturing or soldering process may cause smoking or odor after energization, which is an uncommon circuit operation phenomenon.
RECOMMENDED NEWS
High-end Custom Services: SMT Chip Processing Meets Diverse Industry Needs
(Telephone contact)
Email:
Address： Room 502, Building 1, No. 13, Bohua 4th Road, Huangpu District, Guangzhou City
COPYRIGHT © 2025 Guangzhou Tongsen Electronic Technology Co., Ltd. All rights reserved.