What is false soldering? What are his hazards and causes?
In the failure of electronic products, the failure of solder joints accounts for a large proportion. According to statistics, nearly half of the failures of electronic products are caused by poor welding, which almost exceeds the probability of failure of electronic components. It reduces the reliability of electronic products, increases the noise, degrades the technical indicators, and makes the circuit board unable to complete the design function, More seriously, it leads to the sudden collapse of the whole system without any warning, resulting in significant economic losses and reputation losses.
In the testing link and after-sales maintenance link of electronic product production, the fault caused by faulty welding causes great waste of time and energy for technicians. Sometimes it is not uncommon to spend a whole day looking for a faulty welding point.
In the production process and maintenance process of electronic products, even if efforts are made from all aspects, it can not eradicate the phenomenon of false soldering. Therefore, false soldering has always been the focus problem perplexing the electronic industry.
False soldering: one of the bad solder joints produced during the assembly and assembly of electronic products. Good intermetallic compound (IMC) is not formed on the welding interface of the solder joint, which makes the unreliable connection between components and substrate. (the false soldering defined here refers to the false soldering of solder joints on PCBA.)
Causes: the solderable surfaces of substrates and electronic components are oxidized or contaminated; Poor solder performance, poor flux performance and poor metal coating of substrate pad; Improper setting of welding parameters (temperature, time).
Impact: faulty soldering makes the solder joint into the connection state with contact resistance, resulting in abnormal circuit operation, or unstable phenomenon of power on and power off during electrical connection. The noise in the circuit (especially in the communication circuit) increases without regularity, which brings major hidden dangers to the debugging, use and maintenance of the circuit. In addition, there are also some false solder joints that maintain good electrical contact for a long time after the circuit starts to work, so it is not easy to find. However, under the action of environmental conditions such as temperature change, humidity change and vibration, the contact surface is gradually oxidized, and the contact slowly becomes incomplete, which makes the circuit "strike". In addition, the contact resistance of the false solder joint will cause local heating, and the local temperature rise will further worsen the incomplete contact solder joint, and finally even make the solder joint fall off, and the circuit can not work normally. This process can sometimes take as long as one or two years.
In the production and maintenance of electronic products, it is not easy to find the faulty solder joint from an electronic device with thousands of solder joints. Therefore, false soldering is a hidden danger of circuit reliability. We must pay attention to it, study its law and take measures to reduce its harm.
Characteristics of faulty soldering: from the perspective of electronic product testing, some faulty solder joints show the characteristics of being connected from time to time in the production testing link. Although it is troublesome to find the fault, the faulty solder joint can be solved before leaving the factory; On the other hand, the open circuit phenomenon often occurs in some false solder joints for a year or even longer, which makes the products stop working and cause losses.
False soldering has its concealment, contingency of failure and significance of system collapse loss, which can not be ignored.
To study the causes of false soldering and reduce its harm is an important subject that must be paid attention to in the development of China from a large electronic manufacturing country to a powerful electronic manufacturing country.
The causes of false soldering can be roughly divided into several aspects:
1、 Component factors;
2、 Substrate (usually PCB) factor;
3、 Flux and solder factors;
4、 Process parameters and other factors.
Contact Person: Mr. Ivan Zhu