Printed Circuit Design & Fab - January 2009 - (Page 29)

not aces. For only $995 US per article, you’ll receive an electronic reprint (in Adobe Acrobat .PDF fomat) that has the following features: • A cover page with your company’s Figure 1. PCB defect - exposed copper traces. marketing copy and “as seen in the pages of Printed Circuit Design & Fab” text. • Your article in full color, formatted as it appeared in the print issue. Figure 1B. Angle view Ð exposed copper traces • A back page containing marketing are visible. copy that you select or provide. • Calculations. Figure 3A. Chevron solder mask registration feature design. Figure 3B. The right to post and distribute Figure 2A. X-ray detection issue of Ò whisker Figure 3B Enlarged view of Ò whisker 2B. Figure 3. Chevron solder mask registration feature design and calculation.the article – for life! shortÓ . shortÓ . Figure 2. Difficulty in Ò whiskerÓ short assembly defect detection using x-ray equipment. a solder joint with whisker short and Solder Mask Registration with x-ray examinations. The whisControl ker short could not be detected using A special solder mask registration 2D transmission x-ray because the feature called a “chevron”, as shown image density of the solder ball diamin FiGurE 3a, has since been impleeter would overshadow the whisker mented on designs with 0.8-mm or short. Similarly, laminography x-ray smaller pitch area array devices to (5DX) could not reveal the whisker assist with solder mask registration short. Therefore, whisker shorts to verification. This registration feature adjacent traces or vias are very difconsists of two 0.005-inch copper ficult to detect following fine-pitch traces and a 0.010-inch solder mask BGA/CSP assembly; the only solution opening slot. The solder mask slot would be to remove the components is placed between the copper traces, and inspect the fine-pitch BGA/CSP and all three features are laid out in site. This solder short defect may an “L” shape. A 0.005-inch space require many hours to diagnose, and is designed between the solder mask was observed only after the fine-pitch slot and each copper trace. The BGA had been removed. recommended overall dimension To resolve solder mask misregisfor chevron design is 0.080 square tration concerns during PCB fabricainches. However, the dimensions can tion, companies must create specbe adjusted to any reasonable size as ifications in the fabrication notes long as the “L” feature is observable to explicitly indicate unique solder and the spacing is equal to or greater mask registration requirements. Also, than 0.005 inches between the copcritical areas such as fine-pitch BGA/ per trace and solder mask slot. This CSP sites must be identified to the allows for standard copper etch or PCB fabrication vendors and assemsolder mask process variations such bly providers requesting a thorough that measurements can still be made inspection of those areas. The IPCif the copper trace or solder mask A-600 specification2 can be used as a opening is over or under etched. An additional silkscreen trace is added supplement to a company’s specificaalong the outside corner of the “L” tions. Additionally, this solder mask shape to evaluate the silkscreen misregistration feature can be used as dimension and registration. This silka quick diagnostic if an assembly has an electrical short at the fine-pitch BGA/CSP component location that is 3a Figure 1A. Top view Ð exposed copper is not Figure 1B. Angle view Ð exposed copper traces not detected by x-ray processes. are visible. visible. Expand your global reach with electronic reprints! Your company took the time to write and submit a great article to Printed Circuit Design & Fab. Following publication, how can your company capitalize on the hard work you put into an article beyond the reach and lifespan of a single monthly issue? The answer: electronic reprints! With an electronic reprint, it’s easy to show your clients, partners and employees that you have been recognized in a well-respected industry magazine. An electronic reprint also serves as an attractive endorsement, adding credibility to your company and its products and services. Figure 2. Enlarged in “whisker” short FiGurE2B. Difficulty view of Ò whisker shortÓ . assembly defect detection using x-ray ssembly defect detection using x-ray equipment. equipment. JANUARY 2009 sker FiGurE 3. Chevron solder mask regisFigure design and calculation. tration feature4. Chevron solder mask registration feature location. To purchase or inquire about electronic reprints today, send an e-mail to: pcdf_reprints@ upmediagroup.com PRINTED CIRCUIT DESIGN & FAB 29 Figure 3A. Chevron solder mask registration feature design. Figure 3B. Calculations. Figure 3. Chevron solder mask registration feature design and calculation.

Table of Contents Feed for the Digital Edition of Printed Circuit Design & Fab - January 2009

Printed Circuit Design & Fab - January 2009 Contents Our Line Market Watch Around the World Happenings ROI The Signal Doctor Positive Plating Final Finish Forum Making Sense of Laminate Dielectric Properties Design and Fab Tips for Improving Solder Mask Registration Automating the DDRx Interface Verification Process Printed Circuit Design & Fab Annual Buyers Guide: Special Suppliers Section Printed Circuit Design & Fab Annual Buyers Guide: Guide to Products and Services Off the Shelf Marketplace Ad Index BGA Bulletin

Printed Circuit Design & Fab - January 2009

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