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Monday, 31 March 2008 19:00
Technical Abstracts Circuit Design

“50 GHz End Launch Connector Test Boards”

Author: Bill Rosas

Abstract: The methodology for broadband (50 GHz) transitions from coax to GCPWG is explained through following the development of connector test boards. How to create broadband GCPWG lines is explained and verified through 3-D simulation and actual measurements, including an explanation and verification of the purpose of the vias. The difference between microstrip and GCPWG on 0.030" RO4350 material, especially relating to bandwidth and loss, is examined through measurement of boards. The effect of the connectors is removed from all of the measurements by using identical connectors for all measurements. For 0.030" RO4350 substrates used for up to 50 GHz, properly designed GCPWG has been shown to have some advantages. But for loss, there are applications where microstrip would be the better choice. This means the application would determine which structure is best to use. If loss is the only concern, for longer lines microstrip will be the better choice. For bandwidth, isolation and if lines are very short, GCPWG would be the better choice. (DesignCon, February 2008; edn.com/contents/images/12-WA2--Bill_Rosas.pdf)

Component Assembly

“Process and Assembly Methods for Increased Yield of Package on Package Devices”

Authors: Dr. Brian Toleno and Dan Maslyk; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Abstract: Package on package (PoP) is subject to known good die issues and other challenges that can drive up cost. In addition, this limits the designer as to what functionality can be “stacked,” as these come packaged in a single unit. Stacking packages offers significant advantages from a design standpoint. As long as the pad designs are compatible, different device types can be stacked, permitting more versatility in the design and assembly. On the other hand, assembling these devices on a standard SMT line can present challenges. Some assemblers purchase or acquire these devices preassembled, but the trend is toward assembling these on the PCB using a standard SMT process. Once solder paste is printed on the PCB and the first-level component placed, the attachment methodology of the second-level device is not as clear. Therefore, to reflow all these in one pass, alternative measures need to be investigated. This paper compares the process conditions and yield achieved when assembling package on package devices using different materials and methodologies. In all cases, the devices were Pb-free with solder paste used for the bottom package. The process and materials were varied for the top package. The materials used for the top package assembly included tacky flux, solder paste and an epoxy flux system. Once assembled, the devices were tested for electrical yield, solder joint metallurgy integrity, and standoff height. (SMTA Pan Pac Symposium, January 2008)

Supply Chain Management

“Corporate Social Responsibility in China’s Information and Communications Technology (ICT) Sector”

Author: United Nations Environment Programme

Abstract: Corporate social responsibility (CSR) efforts within global supply chains have improved social and environmental conditions around the world. There is growing recognition of a connection between CSR and a company’s ability to attract and retain international customers. FIAS launched a project in October 2006 to develop a capability-building strategy in Shenzhen designed to identify and test strategies and activities that will most likely improve social and environmental conditions, and also provide business benefits to the ICT supply chain. Participants included Celestica, Flextronics and Foxconn, among others. Since employee retention is a major challenge in Shenzhen, factories are extremely concerned with losing workers due to insufficient overtime. Among the suppliers interviewed, turnover ranged from 3% to 20% per month. Many suppliers felt workers demanded at least 60 to 80 hrs. of overtime per month, and that overtime only became unwelcome above 100 hrs. per month. Meanwhile, external audits are uncommon: Only one or two of the suppliers interviewed had been audited for more than three years, and less than half of the suppliers had been audited exclusively for CSR rather than as part of a quality audit. (July 2007; bsr.org/reports/2007_China-ICT-Report_English.pdf)

Thermal Interface Materials

“Electrical and Thermal Interface Materials”

Authors: Rob Emery and Tanawan Chaowasakoo; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Abstract: Thermal design is limited by the need for easy assembly, which can result in high resistances between different elements of the thermal management system.

TIMs are used to minimize these resistances and a broad range of materials used: greases, gels, putty, phase-change materials (PCMs), pads, tapes, adhesives and solders. A simple setup based on ASTM D5470 for testing TIMs is presented. Performance and tradeoffs (ease of application, pressure effects, reworkability, environmental resistance) between the different material types are shown. (SMTA Pan Pac Symposium, January 2008)

Circuits Assembly provides abstracts of papers 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.
 

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