Circuits Assembly - February 2008 - (Page 34)

Tech Tips board warpage. In addition, components that are localized to the area directly heated by a chimney heater on the bottom side may also attain liquidus temperatures. The EMPF has conducted profile experiments that varied the top and bottom heaters and measured temperatures at the chip top, board bottom, and target (internal thermocouple at solder ball area). The goal of the profile was to attain the liquidus temperature of the SAC 305 alloy (217°C) and then attain a peak that is 20°C higher. From the data, several conclusions can be made to fine-tune the profile. The most interesting and useful observation was that the average temperature (between the top and bottom heaters) approximated the target temperature at the interface. For example, when the top heat was 280°C and the bottom heat 200°C, the target thermocouple measurement at the BGA interface was 238°C, and the TC measurement at the top of the component was safe at 248°C. There were also many useful small empirical observations. For instance, the bottom board TC was on average 15°C lower than the average heat input. Based on The fourth edition of these observations and Printed Circuit Board Basics: the desire not to reflow the board bottom side, An Introduction to the PCB Industry the target temperatures by Dan Beaulieu and average heat inputs were determined. The time and duration of each stage is Order your copy of PCB Basics today! another consideration. The preheat stage Finally there’s an easy-to-read handbook depends on the mass of that explains the process and business the substrate, the preof printed circuit board manufacturheat temperature and ing in simple terms that anyone can airflow rates. When the understand! TC response becomes A must-read for those who are new to the industry and a valuable resource asymptotic (the temfor those who work in the industry, perature is no longer Printed Circuit Board Basics: An increasing rapidly and Introduction to the PCB Industry has flattened off ), the is the perfect book to help your cuszone duration may be tomers and employees understand the decreased. services your company provides to the Using thermocouPCB industry. ples to monitor the Authored by Dan Beaulieu, a 30-year industry veteran and a founding parttemperature response ner of D.B. Management Group, and edited by Mike Buetow, editor-in-chief of Printed Circuit Design & Manufacture magazine, the fourth edition of Printed of electronics being Circuit Board Basics contains: reworked, observa• An updated primer on single-sided, double-sided and multilayer tions can be made PCB manufacturing processes; such as end-of-zone • A review of new technologies such as embedded components and microvias temperatures and peak (HDI); temperatures. Using • Updated PCB specifications; these observations, • A history of the industry; modifications to the • Detailed, updated graphics – including over 45 color photos and illustrations; system heaters can be • An updated glossary of terms and definitions (twice the size of the glossary in previous editions); adjusted incrementally • And much more! to improve the attachment process. These Order your copy of Printed Circuit Board Basics today are key elements to for only $34.95 plus shipping and handling! proper temperature profiling. ■ Now Available! ONLY $34.95 To order, visit: pcdandf.com/cms/basics 34 Circuits Assembly FEBRUARY 2008 Printed Circuit Board Basics • 81 pages • ISBN 0-9743561-0-7 circuitsassembly.com http://www.pcdandf.com/cms/basics pcdandf.com/cms/basics http://www.pcdandf.com/cms/basics circuitsassembly.com

Table of Contents Feed for the Digital Edition of Circuits Assembly - February 2008

Circuits Assembly - February 2008 Contents Caveat Lector Letters Industry News Market Watch Global Sourcing Better Manufacturing Maximizing Lean Copper As a Viable Solution for IC Packaging Embedded Active Components for High-Rel Products Cover Story: XRF Equipment As a RoHS Screening Tool Tech Tips Selective Soldering Test and Inspection Process Doctor Pb-Free Lessons Learned Product Spotlight Ad Index Assembly Insider Technical Abstracts

Circuits Assembly - February 2008

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