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Feasibility of Low/No Silver Alloy Solder Paste Materials
April 23, 2014 |Estimated reading time: 1 minute
Abstract
Sn3.0Ag0.5Cu (SAC305) is the most popular near-eutectic lead-free alloy used in the manufacturing processes. Over the last several years, the price of silver has dramatically increased, driving a desire for lower-silver alloy alternatives.
As a result, there is a significant increase in the number of alternative low/no silver lead-free solder alloys available in the industry recently. In this paper, we’ll present the performance and process capability of various low/no silver alloy solder pastes. Data from printability, wetting test, slump test, solder ball test, voiding, etc., will be discussed and compared with the control SAC305 solder paste. Benefits and concerns of using low/no silver alloy solder paste materials will also be addressed.
Introduction
Sn3.0Ag0.5 solder paste is currently the common alloy for lead-free solder paste in the PCB assembly industry. However, the price of silver has kept increasing over the last several years. The silver price chart within the last five years is shown in Figure 1. This drives the desire for alternative low/no silver alloy materials and leads to the development of many alternative alloys. Today, many alternative low/no silver alloy solder pastes are available in the market. There are publications on the alternative lead-free alloys. However, most of the studies focus on the alternative alloys of the BGA solder balls and their reliability. There is very limited published information on the performance of low/no silver alloy solder pastes. In this article, we will discuss the process feasibility and challenges of low/no silver alloy solder pastes.
Figure 1: Five-year silver history chart.
Alternative Low/No Silver Alloy Solder Pastes
In the study, we evaluated 11 different alternatives alloys and compared their performance with the control SAC305 solder paste (Table 1). Type 3 was used in the evaluation. Sn3.0Ag0.5Cu alloy typically melts at ~217°C. Alternative low/no alloys have about 10°C higher melting temperature than SAC305 solder paste. Its liquidus temperature ranges from 225°C to 228°C.Read the full article here.Editor's Note: This article originally appeared in the March 2014 issue of SMT Magazine.