Classification of PCBA contaminants

PCBA板上的污染物种类很多，主要由物理键和化学键结合形成。

物理键结合：污染物与PCBA表面形成物理张力，通过分子间的表面张力结合。由于物理键合是物理效应，其物理键能较低，一般在0.8×103～2.1×104J/mol之间。 交钥匙 PCBA 公司 在组装过程中使用助焊剂。如果即使清洗干净了，附着在PCBA上的松香、树脂和残胶也会形成物理结合。

"化学键"结合：是指污染物与PCBA表面发生化学反应，两者的原子结合，发生化学反应后形成离子化合物或共价化合物。"化学键"的强度在（4.2～8.4）×105J/mol之间比较大。交钥匙 PCBA 组装公司使用松香酸有可能产生这种效果。松香酸腐蚀PCBA板表面，然后以空气中的水为介质，使电路板导电。电路板导电后，发生化学反应形成离子。

三种PCBA污染物极性污染物

极性污染物可分为无机污染物、离子残留物和离子污染物。PCB组装后 工作时，PCBA 上的这种污染物会在特定条件下电离，产生带正电或带负电的离子化合物，通常是卤化物、酸及其盐。这些不同的离子化合物具有不同的性质，因此在不同的溶液中会发生不同的反应。当组装公司不遵守规范时，当PCBA板放置在潮湿的环境中时，由于水的作用，电子元件产生电，极性污染物的离子会向极性相反的导体迁移. 焊接引脚将被视为导体。这些导电现象会导致绝缘电阻下降，增加焊点或导线之间的漏电流。如不及时处理

离子污染物的主要类型如下：

• 助焊剂活化剂
• 汗
• 离子表面活性剂
• 乙醇胺
• 有机酸
• 电镀化学

非极性污染物

非极性污染物主要包括有机污染物和非离子污染物。PCBA上的这种非极性污染物本身不能导电，FS Technology将其视为电路板上的电阻或绝缘体。这些非极性污染物会降低运行PCBA板的电流。如果这种物质的量太大，甚至会导致电流阻塞，也就是我们常说的停电。具体原因需要通过PCBA错误分析才能知道。最常见的是松香本身的树脂残渣、波峰焊中氧化还原反应产生的氧化保护膜、 SMT的油脂或蜡 placement machine or DIP insertion machine. Of course, the most difficult thing to avoid is the grease on the workers during manual welding. These non-polar contaminants are super viscous and adsorbent. It will absorb dust in the air, and when combined with machine residues, it will produce an insulating film, thereby preventing electrical contact on the surface of PCB components such as connectors, switches, and relays. Maybe you don't think you need to pay too much attention to these problems, but FS Technology can tell you responsibly that these effects are very serious. At the beginning, it may only be a short-term poor contact, but as time goes on, this situation will intensify, and the resistance value of the circuit board will gradually increase, and even cause an open circuit in severe cases. Sometimes the rosin covering the solder joints also hinders the PCBA test, especially the non-polar contaminants will aggravate the degree of contamination with the combination of polar contaminants.

The main types of ionic pollutants are as follows:

• Rosin
• Oils
• Greases
• HandLotion
• Silicone
• Adhesive

particulate pollutants

Particulate pollutants refer to dust, smoke, fiberglass filaments and lint that are visible to the naked eye. It also includes solder balls or tin bead dross caused by improper operation during soldering. These large particles of contaminants also cause poor current flow, which can cause short circuits that can be harmful to electronic assemblies.

Particulate pollutants can be removed by mechanical methods such as high-pressure gas injection, manual peeling, and cleaning.

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