Advances in Producing Functional Circuits on Biodegradable PCBs

2020 43rd International Spring Seminar on Electronics Technology (ISSE)

Batorfi

Hurtony

et al. 2020

In this study, the whisker growth from SAC0307-Mn07 solder alloy was investigated. To get fast information, an ultra-thin film was vacuum evaporated from the examined solder alloy onto Cu substrates. The evaporated layer was ~100-150nm thick in average with the same grain size. The layers were kept at room temperature for 28 days. Whisker growth was monitored by scanning electron microscope with some days frequency, and the layer structure under the whisker was examined on focused ion beam cuts. The large mechanical stress on the Sn layer due to the intermetallic layer growth initiated the whisker growth right after the layer deposition. However, it stopped after 2 weeks since the intermetallic grains consumed the ultra-thin Sn layer. The whisker density was extremely high (~24000 pcs./mm 2). Most of the whiskers were the short nodule and hillock type, which does not mean risk in microelectronics. Therefore, the alloying of Mn into the high Sn content solder alloys have a positive effect on the reliability of the solder joints.

Section: Introductionmentioning

confidence: 99%

Whisker Development from SAC0307-Mn07 Solder Alloy

2020 43rd International Spring Seminar on Electronics Technology (ISSE)

Batorfi

Hurtony

et al. 2020

“…Sn whiskers can cause serious reliability problems in microelectronics, since they can form short circuits in fine pitch electronics. Transition to lead-free electronics in 2006 resulted in the application of pure Sn as surface finishes on Cu wirings, and high Sn content solder alloys (>98%wt) [3][4][5]. Unfortunately, the Cu-Sn layer structure is very sensitive to whisker development due to the Cu6Sn5 Intermetallic Layer (IML) growth at the interface, which yields in compressive stress in the Sn layer [6].…”

Section: Introductionmentioning

confidence: 99%

Early Stage Whisker Development from Sn Thin Film on Cu Substrate

2019 42nd International Spring Seminar on Electronics Technology (ISSE)

Hurtony

Krammer

et al. 2019

The Sn thin film on Cu substrate has high Sn whisker growth susceptibility because of the intensive Cu6Sn5 intermetallic formation at the Sn-Cu interface. In this study, the whisker development on vacuum evaporated Sn thin film deposited on Cu substrates was investigated, starting directly from the Sn deposition. The aim was to obtain more information about the whiskering behavior of Sn thin film in the early stage of the life cycle. For the study, 99.99% pure tin was vacuum evaporated onto Cu substrates. Two different Cu substrates were applied with different surface roughness to investigate the effect of surface roughness on the whisker development. The average thickness of the evaporated Sn layer was ~2 μm. Samples were stored at room temperature for 10 weeks. Whisker development was observed by scanning electron microscope. It was found that the large compressive stress in the Sn layer because of the intermetallic formation initiates the whisker development even after 1 day of the Sn layer deposition. Almost only filament type whiskers were detected. The characteristics of the whisker density showed exponential saturation up to 10 days of the study, while the length of the whiskers was growing further still the end of the study. It was also found that the surface roughness of the Cu substrate affects the rate of whisker growth.

“…Future trends in the electronics industry show that these interconnect materials will be required for use in mobile, miniaturized, integrated and wearable consumer electronics devices. Other possible uses for these materials are in heatsensitive units such as optoelectronic components (Guang et al, 2016) or biodegradable substrates (Géczy et al, 2011;Kovács et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Reliability studies of InnoLot and SnBi joints soldered on DBC substrate

Skwarek

Witek

et al. 2018

SSMT

Purpose This paper aims to investigate the quality and reliability of solder joints prepared from Pb-free alloys on direct bounded Cu (DBC) substrates. Two types of solder alloys were studied: Sn90.95Ag3.8Cu0.7Sb1.4Ni0.15Bi3.0, with a high melting point of 225°C, and Sn42Bi58, with low a melting point of 138°C. Design/methodology/approach Capacitor components of size 1806 were soldered on DBC substrates by using convection reflow soldering and vacuum vapor-phase soldering technologies. A part of the samples was subjected to the thermal shock test. The structure of the solder joints and the content of the voids were investigated using three-dimensional X-ray tomography. The mechanical strength of the joints was evaluated using the shear force test, and the microstructure of the joints was studied on metallographic cross sections by using scanning electron microscopy. Findings It was found that the number of voids is not related directly to the mechanical strength of the solder joints. The mechanical strength of the solder joints depends more on the amount of Ag3Sn precipitation, Au precipitation and the intermetallic layer in the solder joints. In some cases, the thermal shock test caused micro-cracks around the Au precipitation because of a mismatch of Au, AuSn4 and Sn in terms of coefficients of thermal expansion. Originality/value DBC substrates are usually used for power electronics, where the quality of the solder joints is even more important than in the case of commercial electronics.