The Test Of Wet Sulphur Vapour Was Developed To Verify The Resistance To PCB Crawling Corrosion

- Nov 17, 2018-

IST appropriate technology successfully developed resistance to environmental factors, and overcome the high-end products, such as 4 g/LTE, the cloud server) of the PCB crawling Corrosion (is Creep Corrosion) validation of the technology - wet Sulfur vapor Test (Flower of Sulfur Test, FOS).Appropriate, this is the 2012 developed mixed flow Gas Test (Mixing Flower Gas Test, MFG), another is more effective and cheap the validation of the crawling corrosion Test method. 

Creeping corrosion refers to the process of migration and growth of solid corrosion (usually sulphide and chloride) along the circuit surface. Most of the corrosion products (such as copper sulphide) occur on PCB boards. The corrosion products (such as copper sulphide) will crawl on the surface of the resistance welding layer, resulting in short circuit between adjacent welding pads and circuits. 

IST should be observed, due to the deteriorating environment, the haze allowed more of the sulfide in the air, the influence of electronic products in crawling on the PCB Corrosion is Creep Corrosion phenomena to a certain extent, will lead to the failure of electronic products, demand for these must have a long life, Gao Baogu netcom products, such as the Internet of things needed to cloud computing server, 4 g/LTE process equipment, etc., especially received extensive attention of the major international companies.

IST said it has been studying the creeping corrosion of PCB with international manufacturers for a long time.As early as in 2012, in iNEMI (international electronics makers federation) and netcom company - giant Huawei (Huawei) and well-known PCB - jian ding (Tripod) projects, international cooperation for PCB design, surface treatment, flux residues on PCB, resistance welding and resistance welding design and test conditions, MFG gas corrosion experiments, discusses the influence of different factors on the creep corrosion phenomena. 

This year, iST is more targeted at this issue. With the enterprises such as IBM, DELL and lenovo, it has developed another method to verify crawling corrosion test -- wet sulfur steam (FOS) test. Compared with MFG, this technology can verify PCB's crawling corrosion resistance at a lower cost and faster speed. 

For the FOS test, iist further explained.This test is mainly to test the corrosion resistance of metal circuits on PCB boards. According to the standards of ISA-71.04 (limits on the composition of environmental gases) and ASHRAE standards, the corrosion reaction rate of silver foil must be less than 20 nanometers/month.Copper foil is 30 nanometers/month. 

In order to know whether the metal circuits on the PCB board meet the requirements of this specification, the subsequent FOS test also requires pretreatment of the metal. Iist used two pretreatment methods -- "chemical etching" and "mechanical polishing pretreatment" to test, and found that "chemical etching" can more accurately understand the corrosion reaction rate.