Common method of FPC Pad treatment

                                            Common method of FPC Pad treatment


         Compared with the method to deal with PCB pad,there are also a variety of methods to deal with FPC pads, such as the following:


        (1) Chemical nickel and gold is also called chemical leaching gold or settling gold. The thickness of non-electrolytic nickel layer on PCB copper surface is 2.5um-5.0um in general. The thickness of gold impregnated with 99.9% pure gold is 0.05um-0.1um. (it was previously reported that a PCB factory worker replaced the gold in the pcb pool with a replacement method). Advantages of this technique: flat surface. Long storage time, easy to weld; Suitable for thin spaced components and thin PCBs. For FPCs, they are more suitable for FPCs because they are thinner. Disadvantages: not environmentally friendly.


        (2) The advantages of electroplating lead tin (Tin-Lead platform): it can directly add flat lead tin to the pad, which has good solderability and uniformity. For some processing processes such as HOTBAR. FPC must be used in this way. Shortcomings: lead is easy to oxidize, the preservation time is short; Need to pull electroplated wire; It's not environmentally friendly.


        (3) Selective electroplating of gold finger PCB by electroplating gold electroplating, other areas are treated by another surface treatment method. Gold plating means that nickel coating is applied to the surface of PCB copper first. The thickness of nickel layer is 2.5um-5.0um. the thickness of gold layer is generally 0.05um-0.1um. the advantages are: the thickness of gold coating is thicker. Strong anti-oxidation and wear resistance. Golden finger is generally treated in this way. Disadvantages: no environmental protection, cyanide pollution.


        (4)Organic solderability Protective coating (OSP) this process refers to the surface coating of exposed PCB copper with specific organic compounds. Advantages: very flat PCB surface can be provided. Meet environmental protection requirements. Suitable for PCBs with fine spacing components.


        (5)Hot air leveling (HASL). This process refers to lead-tin alloy covered with 63/37 on the final exposed metal surface of PCB. The thickness of hot air leveling lead-tin alloy coating is required to be 1um-25um. the hot air leveling process can control the thickness of the coating. And pad graphics are more difficult. It is not recommended to use in PCBs with fine spaced elements because of the high flatness requirement of the padded pads of the fine spaced elements. The hot air leveling process has a great influence on the thin FPC, so it is not recommended to use this surface treatment method.