A lead-free solder matrix
Looking for alternative SN-PB solder lead-free solder, the new lead-free solder still be able to complete traditional solder SN-PB functions, soldering permitted temperature range (less than 450 ° C) can be achieved with the base metal (mainly copper, or nickel-plated, silver-plated metal surface) a good connection. That is, the main consideration SN with CU, NI, AG, between the base metal to form intermetallic compounds, thus contributing to the solder wetting and spreading of the metal surface and the bonding between atoms and thus form a reliable connection.
Based on the solder melting point and the reactive wetting awareness of the need, the lead-free solder to SN as the matrix alloy. It has two meanings:
A SN is the matrix element of the lead-free solder as lead solder, metal compounds formed between the SN and the base metal is not guaranteed lead-free solder wetting and connections;
B lead-free solder is an alloy that is constituted to add some metal elements in pure tin. The addition of metal elements can inhibit the aforementioned phase transition of pure tin, can improve the strength and other physical properties.
Metal toxicity: Bi <Zn <In <Sn <Cu <Sb <Ag <Pb
Departure from the industry practical point of view, mainly in the following four points on the performance requirements of lead-free solder
(1) melting point - the solder melting point is the most fundamental parameters of the soldering temperature
(2) electrical properties - solder the formation of solder joints after major role in the transmission signal
(3) Mechanical Properties - Another main role of the solder joint is the mechanical connection
(4) wetting and spreading performance - good wetting and spreading to form a good solder joint
★ lead-free solder patents
China joined the WTO, more and more emphasis on patent and copyright infringement issues
Binary lead-free solder does not exist any patent issues. Japan has applied to the SN-CU-NI NI content must exceed a certain amount, that is, as elements of the matrix. Otherwise it can be seen as an impurity element.
The patent protection period of 20 years, the Chinese market is related to lead-free solder patents 28, 17 is the application of foreign companies in China, 11 is the country to apply.
The first patent of the Chinese market, "Samsung Korea