PCB Tech - PCB board common sense and possible failures

Learn about the temperature and temperature of the circuit board

What is the temperature? What is humidity? What is the relationship between the printed circuit board and temperature and humidity? They have a great relationship. If it is not handled well, the circuit board will be charged. It does not matter if it costs. Anyway, the cost is not expensive, but it is a waste of time., If you don’t understand the temperature and humidity of the circuit board, it will be troublesome to print the circuit board. Let's talk about the circuit board repair experts below.

1. The temperature concept of the printed circuit board

In the early development of resistance thermometers, someone once conducted in-depth research on platinum resistance thermometers. Since this time, the resistance temperature measurement method has undergone a very big change. Platinum resistance thermometers are more accurate for high-precision temperature measurement. For temperature measurement, platinum resistance thermometers are the best choice.

Why do we choose platinum when we print circuit boards? What are its advantages? It is said that platinum has a very strong anti-oxidation ability at high temperatures. This is one of the reasons why it has become the choice for measuring high temperatures. Platinum is also a very good high temperature thermocouple material.

According to calculations, the resistance of platinum resistance thermometers is quite close to the square function of temperature.

2. Humidity of printed circuit board

The humidity of the printed circuit board includes humidity and relative humidity. They are quite different in use, and the concept is also far worse.

A. PCB relative humidity

As we all know, the amount of water vapor in the atmosphere is constantly changing, and the general range of change is between 0 and saturation. Humidity refers to the actual amount of water vapor in the air, and does not indicate the degree of saturation of the humid air or the ability to absorb water vapor in this state. Therefore, the degree of humidity is expressed in terms of relative humidity.

B. Printed circuit board humidity

Humidity refers to the mass of water vapor per 1m3 of humid air. This is quality, not quantity. Therefore, the humidity can be calculated by the formula. The value of humidity is equal to the value of the water vapor density ρv under the temperature "in the air" and the partial pressure of water vapor Pv.

Causes of circuit board failure

Ever since I came into contact with the circuit board repair industry, I have often heard someone say that some circuit boards often show ups and downs. Yesterday, a customer’s circuit board was broken. After exchanges, it turned out that this circuit board was faulty. It is this customer who often puts the circuit board in a damp place, which makes this circuit board unusable. Let me summarize the reasons for the circuit board failure below:

Reason one, software

Many parameters in the circuit are adjusted by software. The margins of some parameters are adjusted too low and are in the critical range. When the machine operating conditions meet the reason for the software to determine the fault, then the fault alarm will appear.

Reason two, there is moisture and dust on the circuit board.

Moisture and dust will conduct electricity and have a resistance effect, and the resistance value will also change during the process of thermal expansion and contraction. This resistance value has a parallel effect with other components. When this effect is strong, the circuit parameters will be changed and malfunctions will occur. ;

Reason three: poor circuit board contact

Poor contact between wire plugs and wiring terminals, poor contact between the board and the slot, failure when the cable is broken internally, and false welding of components are all of this type;

Reason four, the signal is interfered

For digital circuits, faults will only appear under certain conditions. It is also possible that individual component parameters or overall performance parameters of the circuit board have changed, making the anti-interference ability approach a critical point, and it is true that too much interference affects control. The system makes an error, thereby causing a failure;

The reason for PCB failure is nothing more than the four reasons mentioned above. If you do all of these four aspects, it is estimated that your circuit board will rarely have general failures, and it will be difficult to say major failures, such as improper use. Burned out, there are some natural factors, aging and other irresistible factors.