Developed for environment resource management and cost reduction
Development History of Lower Silver Content Products
Nearly 20 years ago in Japan, Senju introduced ECO Solder as one of the industry's first environmentally-friendly Lead-Free products and by 2000 the Japan Electronics and Information Technology Industries Association (JEITA) recommended use of the Sn/Ag3.0/Cu0.5 alloy for Lead-Free applications. With the introduction of the EU's RoHS legislation in 2006, the Sn/Ag/Cu or "SAC" alloy family quickly became the global industry standard. Most alloys selected contained between 3.0 to 4.0% silver for the best soldering performance.
More recently, due to a significant metal cost increase, the electronics industry is forced to look for new materials and methods to reduce costs while maintaining the customer's high quality expectations.
As a result JEITA began its next generation standardization project investigating potential solutions to lower the material costs at the same time keeping the same soldering characteristics of the current materials. In 2007, JEITA recommended low silver content alloys for the next generation of flow soldering.
Comparing SnCuNi and other Low Ag Solders
The characteristics of SnCuNi, SAC305 and two promising Low Ag Content Alloys are compared in the charts below.
Thermal Properties
The Low Ag Content alloys have the same solid line temp as the SAC305 at 217 deg C, approximately 11 deg C lower than the SnCuNi solid line temperature at 228 deg C. Increasing the Ni content may further raise the liquid line temp, with +0.05% Ni creating a 250 deg liquid line temp, leading to potential bridging issues.
Wetting Ability
Adding Ag improves wetting. A drop in temperature, as this may occur on contact with the board, changes the wetting time significantly. Small Ag additions improve soldering ability and minimize bridge issues.
Tensile Strength
Ag improves tensile strength. Durability is depending on temperature changes. Selection must be according to temperature range of the environment the final product is to be used in.
Creep Characteristics
Ag improves creep characteristics. SnCuNi solder is not suitable for products exposed to long term stress.
