August, 2014
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Implementing Warpage Management: A Five-Step Process Continued from previous page
agement program involves under- standing appropriate standards and, currently, no international standard directly addresses stacked package or package-to-board assembly relat- ed to collecting warpage data or how to use that data from more than one surface. Some companies may have proprietary standards related to warpage. But, for now, all relevant public standards address warpage of packages and their corresponding land areas separately.
Addressing Warpage Standards Traditionally, warpage stan-
dards have addressed only the “pack- age side” of a design, typically setting limits on the maximum coplanarity of a package at a peak reflow temper- ature. But standards bodies have more recently begun to address how warpage of package land areas on printed-circuit boards (PCBs) can affect assembly yield and reliability. The most relevant current public
standards include IPC-9641, JESD22- B112A, and ED-7306 from the Japan Electronics and Infor mation Technol - ogy Industries (JEITA). The IPC-9641 standard, “High
Temperature Printed Board Flatness Guideline,” from the IPC (www.ipc. - org), provides explanations about why
dards, EMS companies are often guided by customer requirements for warpage-related issues. Custom-pro- vided guidelines and design-specific requirements should be considered in any efforts to establish a warpage management program. Sharing data is an important
part of any warpage management program. By sharing data, supply- chain partners can improve their designs and develop products that can be assembled with fewer defects and perform more reliably for cus- tomers. Any EMS company consider- ing a warpage management program or upgrading their existing surface measurement data collection and analysis system should consult with supply-chain partners on which data
is useful and should be shared. They must also learn how to best share the appropriate data, upstream and downstream, with their partners. Such sharing can help improve prod- uct designs, enhance assembly plan- ning, and lead to continuous process improvements. In establishing warpage man-
agement capabilities, an EMS provider will need people and equip- ment to perform these measure- ments in-house. While it is possible to outsource warpage measurements and reporting, by means of outside test laboratories, it is typically not done due to confidentiality require- ments. As a result, it is essential to install the needed measurement equipment at the location where
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components are received and assem- bly is being performed, and to have the right people trained and ready to perform the warpage measurements. A number of measurement tech-
nologies are available for obtaining surface warpage data. Selecting the appropriate tools should take into account factors such as the measure- ment volume (how many samples per day), the measurement resolution required, which people will be using the equipment (for ease-of-use requirements), and which types of tools are already in use by supply- chain partners (for compatibility).
Warpage Measurement Systems Warpage measurement systems
Continued on page 55
Phase image from PCB, shadow moiré acquisition.
measuring PCB land areas is impor- tant, guidelines for selecting measure- ment equipment, and an introduction to collecting warpage data so it can be correlated with other companies’ results. The JESD22-B112A standard
from JEDEC (
www.jedec.org), “Pack - age Warpage Measurement of Sur - face-Mount Integrated Circuits at Elevated Temperature,” released in 2009, is the electronic industry’s main reference for package warpage meas- urements. It defines warpage and how to measure it, introduces relevant measurement technologies such as shadow moiré, DIC, and fringe projec- tion, and provides example measure- ment processes and results. It is a good starting point for understanding the warpage performance of electronic components. JEITA’s (
www.jeita.or.jp) ED-
7306 standard, “Measurement Meth - ods of Package Warpage at Elevated Temperature and the Maximum Permissible Warpage,” was pub- lished in 2007. Although this docu- ment is often used, the warpage lim- its presented in ED-7306 are best considered guidelines rather than absolute “pass/fail” specifications.
Customer Requirements In addition to these public stan-
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