Embedded Components

“Industrial PCB Development Using Embedded Passive and Active Discrete Chips Focused on Process and DfR”

Author: Arnaud Grivon; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
Abstract: This paper discusses aspects of the PCB embedding technology developed in the frame of the HERMES project, a Europe-funded research program to establish an industrial platform capable of producing PCBs with two layers of embedded components, including large die sizes. The focus is on the main embedding process steps and prerequisites such as chip thinning and plating. DfR through base material and board architecture optimization also is reviewed. Impact of buildup and chip positioning is studied through use of torsion testing and in situ PCB strain measurement. (IPC Apex, April 2010)

Market Trends

“Trends, Business Models and Entry Modes in MedTech Manufacturing – China”

Author: Tsz-Yin Chang; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
Abstract: China’s medical equipment market was $6.16 billion in 2009 and is expected to reach $10.18 billion in 2014, an 11.2% compound annual growth rate. Exports reached $5.3 billion in 2007, up 28% over 2006, mainly to the US (25.3%) and Japan (12.6%). Some 13,400 companies were building medical equipment in China as of 2008, and laws passed in 2009 push for a new infrastructure to address chronic domestic medical industry concerns. More than 2,000 hospitals will be established, as well as three medical science/biotech research parks. Siemens, Philips and GE are among the major multinational companies setting up large medical product development campuses in the country. (MedTech Manufacturing Conference, March 2010)

PWB Reliability

“Effects of Solder Mask on Electrochemical Migration of Tin-Lead and Lead-Free Boards”

Authors: Xiaofei He, Michael H. Azarian and Dr. Michael G. Pecht; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
Abstract: Solder mask’s mechanical and thermal properties have been widely reported, but systematic studies of their influence on electrochemical migration have been few. This paper presents results of temperature-humidity-bias (THB) testing of more than 1000 hr. duration at 40V, 65°C, and 88% relative humidity for comparative evaluation of ECM on circuit boards with and without a solder mask. The boards were HASL-finished and wave-soldered using a no-clean, low-solids flux. Besides primarily assessing effects of solder mask on ECM, effects of solder alloy composition (eutectic SnPb versus Sn3.0Ag0.5Cu) were also investigated. In situ monitoring of SIR was performed throughout these tests. Optical microscopy and scanning electron microscopy were employed to examine the correlation between the physical attributes of dendrites and the measured SIR, as well as to evaluate the effects of solder mask and solder alloy on ECM. Ion chromatography was conducted to measure contaminant levels on the surface of the PCBs. Elemental mapping by energy dispersive x-ray spectroscopy was employed to identify the migrating species and their distributions and morphologies within the dendrites. As expected, the use of a solder mask resulted in higher SIR, but a dramatic difference was observed in its effect on dendritic growth and characteristic life. (IPC Apex, April 2010)

Wave Solder Joint Troubleshooting

“Copper Tin Intermetallic Crystals and Their Role in the Formation of Microbridges between the Leads of Hand Reworked Fine Pitch Components”

Author: Jeff Kukelhan
Abstract: During wave-soldering exposure, copper from through-holes, surface-mount lands and component leads continually dissolves into the molten solder. Unless solder in the reservoir is regularly changed, dissolved copper eventually reaches a point of saturation, and orthorhombic Cu6Sn5 crystals begin to precipitate out of the molten solder, causing it to become gritty and sluggish. Solder drawn from such a saturated wave solder pot can solidify into joints whose surface finish exhibits many needle-like metallic protrusions. These protrusions are, in fact, orthorhombic Cu6Sn5 crystals. BAE Systems has determined that this same phenomenon is responsible for the formation of nearly invisible intermetallic microbridges between fine-pitch surface-mount component leads. They form when a solder bridge from a surface-mount paste reflow operation is hand-reworked with a soldering iron and copper desoldering braid. This paper documents several short circuit failures caused by this phenomenon, the investigation that identified the root cause of the problem, and the rework techniques that can be used to prevent it. (IPC Apex, April 2010)

This column provides abstracts from recent industry conferences and company white papers. With the amount of information increasing, our goal is to provide an added opportunity for readers to keep abreast of technology and business trends.