Copper-base filler metal & Application Cu- P filler metal According to Cu-P Diagram, copper can evidently lower the melting point of the filler metal. When the composition of P is 8.4%, the eutectic structure with low melting point 714°C ((Cu)+Cu3P) will be produced. In order to lower the melting point and improve the toughness, Ag could be the good candidate as the additional element, since the low melting eutectic phase (ω（Ag）=17.9%，ω(Cu)=30.4% and ω(Cu3P)=51.7%，ω(P)=7.3%，),whose eutectic point is 646°C will be formed. Phos-copper filler metal has several advantages, such as good fluency, low cost, and perfect performances. In addition, due to the self-flux character of Cu, this kind of filler metal could be used in resistance brazing, gas flame brazing, high frequency induction brazing and furnace brazing, etc. The joint strength is higher and the conductivity is better. However, flux is necessary while brazing copper or copper alloys. Phos-Copper-Silver brazing alloys with low melting point have good wettabilty, higher strength and toughness. The ramp rate should be as quick as possible while brazing. The joint is to be bright grey and will return to the original color of copper while dipped into 10% sulphuric solution.