Технология PCB - Факторы, влияющие на качество и толщину сварной сборки pcb

Factors affecting the welding quality and thickness of PCB assembly
Today I will share a topic, this topic is the factors that affect the quality and thickness of PCB assembly soldering. На самом деле, the quality and thickness of the intermetallic bonding layer in PCB assembly welding are related to the following factors, Подробнее см..
1. Alloy composition of solder
The alloy composition is a key parameter that determines the melting point of the solder paste and the quality of the solder joint.
исходить из общей теории смачивания, the ideal brazing temperature for most metals should be 15.5～71 degree Celsius higher than the melting point (liquid line) temperature. сплав на основе олова, the recommended temperature is about 30 to 40°C above the liquidus.
Пример оловянно - свинцового припоя, it is analyzed that the alloy composition is a key parameter that determines the melting point and solder joint quality.
(1) The melting point and welding temperature of eutectic alloy are the lowest
The melting point of 63Sn-37Pb eutectic alloy is 183 degree Celsius, 63SN - 37Pb эвтектические сплавы с температурой плавления 183°C.
температура сварки PCB также самая низкая, about 210～230 degree Celsius, сумма компонентов плата PCB will not be damaged during the soldering process. фазовая линия жидкости выше эвтектической температуры любого другого сплава. For example, the liquidus of 40Sn-60Pb (point H) is 232 degree Celsius, and the soldering temperature of SMT patch is about 260～270 degree Celsius, which obviously exceeds the endurance limit temperature of components and PCB printed boards.

(2) The eutectic alloy has the densest structure, which is beneficial to improve the strength of solder joints;
The so-called eutectic solder is the transition from solid phase to liquid phase or from liquid phase to solid phase at the same temperature, and the fine crystals of this composition
The granular mixture is called a eutectic alloy. когда температура достигает точки эвтектики, the solder is all in the liquid phase, when the temperature drops to the eutectic point
id solder suddenly becomes a solid phase, so the crystal particles formed when the solder joint is solidified are the smallest, наиболее плотное строение, and the solder joint strength is the highest. длительность затвердевания других сплавов, and the particles that crystallize first will grow up, это влияет на прочность сварной точки.
(3) The eutectic alloy has no plastic range or viscosity range during the solidification process, which is conducive to the control of the welding process;
As long as the eutectic alloy reaches the eutectic point temperature when the temperature is raised, Он мгновенно переходит из твёрдой фазы в жидкой; напротив, as long as the temperature drops to the eutectic point during cooling and solidification, Он сразу же из жидкой фазы в твёрдую, so the eutectic There is no plastic range when the alloy melts and solidifies.
The solidification temperature range (plastic range) of the alloy has a great influence on the welding processability and the quality of the solder joints. Wide plastic range
alloy,
формирование сварной точки при затвердевании сплава занимает много времени. If any vibration (including PCB deformation) occurs in the PCB and components during the alloy solidification process, it will cause "solder joint disturbance", Это может привести к растрескиванию точки сварки и к преждевременному повреждению оборудования.
From the above analysis, можно сделать вывод, что состав сплава является ключевым параметром, определяющим температуру плавления и качество флюса..
поэтому, whether it is a traditional Sn-Pb solder or a lead-free solder, легирующий компонент припоя требует максимально возможной эвтектики или близости к эвтектике.
Solder alloy
Second, the degree of oxidation of the alloy surface
The oxide content on the surface of the alloy powder also directly affects the solderability of the solder paste. Because diffusion can only enter clean metal surfaces
OK. Although the flux has the effect of cleaning the oxides on the metal surface. Но это не устраняет серьезную проблему окисления. The oxygen content of the alloy powder is required to be less than 0.5%, and it is best to control it below the minus 6th power of 80*10.
словом, regarding the factors that affect the welding quality and thickness of PCB assembly, электронное редактирование здесь вас познакомит, I hope to help you, Спасибо вам.