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PCB Fabrication Why Lead-free Solder
Jun 02, 2017

  PCB Fabrication Why lead-free solder

  Why lead-free solder?

  The harmful effects of lead-containing solder: The solder contains 1% weak (30,000/5 million tonnes) of the total use of lead, and the possibility of widespread diffusion is difficult to fully recover. Due to environmental pollution, worry about the impact of lead poisoning on the human body. In the PCB Fabrication industry, the application of halogen (fluorine F, cl, BR, iodine 1) is mainly on sheet and ink.

  1.1 Screening of materials

  PCB Fabrication final processing formed on the finished product, mainly contains three major categories of substances namely: plate, Surface treatment (metal) layer and ink.

  1.1.1 Plate

  Conventional plate FR-4, CEM-3, due to a large number of brominated epoxy resins, such as four bromine bisphenol, PBBs, bromine two benzene ether, in the combustion process, will emit very high toxicity substances, such as dioxins (TCDO), benzene furan, etc., once ingested by the human body will not be discharged, a great threat to human health. Therefore, PCB Fabrication CCL industry must be halogen-free substrate (CL, bromine BR is less than 0 respectively.) 9% Replace with phosphorus (p) Epoxy resin substituted for brominated epoxy resin, with nitrogen (n) Phenolic resins instead of the traditional double cyanide amine curing agent.

  In addition, environmental protection plate must have a strong heat resistance, can withstand the lead-free SMT project 260 degrees of high temperature, no discoloration, no layering, no deformation and bending.

  1.1.2 Surface Metal Layer

  At present, most of the industry uses environmentally friendly solder HASL "tin silver Copper" formula 95. 5sn-3. 9ag-0. 6CN) Replace PB-SN alloy, environmental protection PCB Fabrication surface lead-free coating should have high wetting fluidity, small thermal stress, low temperature oxidation and other characteristics, easy to lead-free SMT processing. In addition, the use of HASL flux also need to be synchronized with environmentally friendly recovery type, and SMT flux has a mutual melt.

  1.1.3 Ink

  Printing ink in the final PCB Fabrication include: solder ink, ink, female ink, ink ingredients and plates are very similar, mainly contains resin, bromine flame retardants and curing agent, at present many brands of ink has done not contain harmful substances, such as Japan's Sun, Taizhou, the new Korean ink. The choice of ink not only to meet environmental requirements, but also to withstand environmental lead-free SMT for a long time high temperature, do not occur layered discoloration, shedding, crack phenomenon.