Reliability assessment of high temperature lead-free device attach technologies

Abstract

The demand for electronics capable of operating at temperatures above the traditional 125°C limit continues to increase. Devices based on wide band gap semiconductors have been demonstrated to operate at temperatures up to 500°C, but packaging them remains major hurdle to product development. Recent regulations, such as RoHS and WEEE, increase the complexity of the packaging task as they prohibit the use of certain materials in electronic products such as lead, which has traditionally been widely used in high temperature solder attach. In this investigation, a series of Pb-free die attach technologies have been identified as possible alternatives to Pb-based ones for high temperature applications. This paper describes the fabrication sequence for each system and assesses their long term reliability using accelerated thermal cycling and physics-of-failure modeling. The reliability of the lead rich alloy was confirmed during this investigation while early failures of the silver filled epoxy demonstrated their inability to survive high temperatures. An empirical damage model was developed for the silver nanoparticle paste based on fatigue induced failures. Encouraging reliability data has been presented for the goldtin SLID system where bond quality was demonstrated to be a critical factor on its failure mode and mechanism. IntroductionThe development of electronics and microsystems that can operate at temperatures in excess of the traditional maximum [1] of 125°C is a critical enabling technology for the creation of next generation electronic systems for a wide range of military and commercial applications; including avionics, hybrid-electric automotive electronics, deep well drilling, chemical processing systems, and space/earth explorations. Critical elements of these systems are the sub-assemblies for power control, distribution, and management. The last several years have seen the advent of silicon carbide (SiC) power devices operating at temperatures well above 125°C [2]. These devices provide higher switching speed and lower on-state losses with higher thermal conductivity. Developing reliable technologies for packaging is now the main hurdle to successful operation of SiC based power electronics at high temperature.This work focuses on the first-level interconnection process known as die attach, the primary function of which is to mechanically secure the semiconductor chip to a lead frame or substrate, and to ensure it does not detach or fracture over an operational lifetime that may include power and temperature excursions. One of the most common approaches for packaging SiC devices is to mount the back of the chip on a ceramic substrate with a suitable die attach and route the

Silver-Indium Transient Liquid Phase Sintering for High Temperature Die Attachment

“…From these observations it was revealed that the proposed Ag-In TLPS attach material outperformed the DBC substrates during the thermal cycling test. Results obtained from life cycle data (cycles), were comparable to the observed performance of the Pb-rich solder, the most widely used material for high temperature electronics applications [7,21]. When compared with lead-free alternatives, it outperformed technologies such as sintered Ag-nanocolloids as well as sintered Ag nanoparticle pastes [7,21].…”

“…This technique utilizes a reduction of total free energy as the driving force for the sintering reaction. However, this approach has been shown to have reliability limitations [7].…”

Shear strength of die attachments prepared using dry nanosilver film by a time-reduced sintering process

“…With increasing demand for high power density and high performance power electronics systems, conventional Sn-based solders are no longer considered acceptable for power die attachments or other interconnects where the operating temperature s are expected to rise above 175°C. The use of high lead solders with a Pb content of 85-97 wt.% is a standard and widely accepted approach for improving the reliability of conventional Sn-Ag solder joints [1]. However, lead is restricted in the application of electronics packaging owing to environmental concerns.…”

An Assessment of Validity of the Bathtub Model Hazard Rate Trends in Electronics

“…White et al [75] found the main failure distribution in DRAMs has an increasing hazard rate. Quintero et al [76] conducted reliability and life studies on semiconductor diesubstrate assemblies of different sizes under different temperatures. They observed that the Weibull shape parameter was always greater than 1, showing an increasing hazard rate existed rather than a constant hazard rate.…”