SMTA International Conference Proceedings

Engineered Flux for Low Temperature Solders

Authors: Ramakrishna H V, Ph.D., Harish H S, Manjuvani J, Vangapandu Bhaskar, Ramesh Kumar , Vikas Patilz Siuli Sarkar, Ph.D. and Traian C. Cucu, Ph.D.
Company: Alpha Assembly Solutions, Alpha India Research Center
Date Published: 10/14/2018   Conference: SMTA International

Abstract: Low temperature solders are becoming more common in surface mount assembly. Critical SMT components cannot handle the temperatures used for lead-free soldering which typically reaches 240 – 250 °C. Sensitive critical components might be damaged by these high temperatures. High temperatures can also cause warpage and other damage to the assembly. Low temperature solder alloys can be used in many forms including solder paste, wire solder, pre-forms, and bar solder. The main motivation of low temperature soldering is driven by faster technology scaling, reduced energy and emissions. Increasing demand in electronics assembly materials like low temperature solder paste to meet and fulfil the requirements of today’s rapidly changing technology requires major innovation in developing new chemistry platform. A new and innovative chemistry platform needs versatile, multifunction capable chemical molecules as its building blocks to achieve desired solder paste processing properties. To achieve desired properties, a carefully engineered paste flux is used to study high speed printing and reflow properties of low temperature solders. The effect of viscosity and thixotropic index on high speed printability, reflow properties and other warpage defects like non- wet open (NWO) and head in pillow (HIP) were also compared to conventional flux system for low temperature solders. Fine feature printability is evaluated in both low (50mm/sec) and high speed (150mm/sec) printing methods to demonstrate the capability of newly engineered flux system.

Further, low temperature solders are finding its importance in fine feature application for advance packaging applications. The newly engineered flux is studied with finer particle size (Type 5) for printability, reflow ability and solder ability along with warpage defects and large area pad voids.

Key Words: 

Engineered Flux, Low temperature solders, High speed printability, Critical properties

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