Circuits Assembly - June 2008 - (Page 4)

Letters Send your thoughts to Editor, CirCuits Assembly, email: mbuetow@upmedia group.com. Letters must include the writer’s name, address and company affiliation and may be edited for length and clarity. Black Pad Has Multiple Causes Phil Zarrow’s April column narrowly assumes causes of black pad. And recommending more gold as mitigation is harmful advice (assuming many readers may miss his 4 µin maximum as the reasonable upper limit). Japanese science has proven, in this case, less is better. Black pad has several causes. The mistake assumes all ENIG chemistries are created equal. We have proven that is not true. Black pad is rare, but can be created by 1) an electroless nickel with less than 5.5% phosphorus content in the plated layer; 2) an overly aggressive gold chemistry (either the chemistry is too acidic, or the gold is permitted to run below recommended levels in the bath, or boards are simply left in the bath too long); 3) the gold layer is too thick (gold deposits by replacing nickel; if this is permitted to continue too long, then the surface is compromised and black pad is guaranteed). We still fight standards (even military: “But that is what the spec says”) that require a minimum 8 µin of immersion gold. Hopefully, such specs also accept total responsibility for black nickel! We also fight erroneous thinking that the solution is high phosphorus nickel (so much for good solderability). The key steps are a consistent nickel and gentle gold that give complete coverage (porous gold layers do not protect the nickel surface) with limited thickness. We prefer two or three µin. As a supplier, this reduces our sales but saves customers money and, most important, it is based on years of research and field service. Another battle fought over the years was the concept of ENIG with a layer of electroless palladium between the nickel and gold (ENEPIG) as the universal finish. However, this does not create as strong a solder joint as regular ENIG, provided leaded solders are used. For non-leaded solders, ENEPIG offers better solderability and eliminates black pad, as the palladium layer acts as a protective barrier between nickel and gold. Another flexible alternative is adding a layer of electroless (autocatalytic) gold over ENIG (a process called ENAG), for purposes of gold wire bonding. Don Walsh Director of Operations Uyemura International Corp. circuitsassembly.com Editorial Office Circuits Assembly 2400 Lake Park Drive, Ste. 440, Smyrna, GA 30080 678-589-8800 Editor-in-Chief: Mike Buetow (617) 327-4702, mbuetow@upmediagroup.com Senior Editor: Chelsey Drysdale (678) 589-8846, cdrysdale@upmediagroup.com Production Manager/Managing Editor: Javier Longoria Director of Audience Development: Jennifer Schuler Special Projects Manager: Ronda Faries Publisher: Pete Waddell Group Sales Director: Susan Jones (404) 822-8900, sjones@upmediagroup.com Sales Associate: Krista Fabian (678) 589-8840, kfabian@upmediagroup.com Asia (except Korea): Susan Jones, (404) 822-8900, sjones@upmediagroup.com Korea: Young Media 82 2 756 4819, ymedia@ymedia.co.kr Circulation Inquiries: email: jschuler@upmediagroup.com fax: (918) 496-9465 Reprints: Electronic: ca_reprints@upmediagroup.com Print: Edward Kane, FosteReprints 866-879-9144 ext 131; fax: 219-561-2009 ekane@fostereprints.com List Rental: Jennifer Schuler, (918) 496-1476; fax (918) 496-9465 Editorial Advisory Board: John D. Borneman, Delphi Delco Electronics Heather McCormick, Celestica Curt Williams, Morey Corp. Chrys Shea, Cookson Electronics UP Media Group, Inc. President: Pete Waddell Vice President, Sales and Marketing: Frances Stewart Vice President, Editorial and Production: Mike Buetow PCB Show Group: (678) 589-8800 Subscription Policy Circuits Assembly (ISSN 1054-0407/GST124513185/Agreement #1419676) is distributed without charge to qualified subscribers. To all others in the USA and Canada: US$80 per year. Other countries: US$145 per year (air service included, payment required in advance). Single copies US$8.50. Send requests for qualification forms and changes of address (include old label) to: CIRCUITS ASSEMBLY, P.O. Box 35646, Tulsa, OK 74153-0646, email: jschuler@upmediagroup.com, fax (918) 496-9465. Periodicals postage paid at Atlanta, GA 30339 and additional mailing offices. Reproduction of text and illustrations is not allowed without express written permission. Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by UP Media Group, Inc. for libraries and other users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided that the base fee of $2.00 per copy, plus $0.25 per page is paid directly to CCC, 21 Congress St., Salem, MA 01970. 0009-7306/86, $2.00 + $0.25. 16mm microfilm, 35mm microfilm, 105mm microfiche and article and issue photocopies are available from University Microfilms International, 300 N. Zeeb Rd., Ann Arbor, MI 48106 (313) 761-4700. Canadian GST Permit 124513185. Opinions expressed by authors are not necessarily those of the publisher, and this publication can accept no responsibility in connection with any liability that might develop as a result of articles published. Circuits Assembly is published monthly by UP Media Group, Inc., 2400 Lake Park Drive, Suite 440, Smyrna, GA 30080. POSTMASTER: Please send changes of address to CIRCUITS ASSEMBLY, P.O. Box 35646, Tulsa, OK 74153-0646. Corrections Due to an editorial error, the April 2008 Better Manufacturing column incorrectly stated the IPC standards for gold plating volume in µm. The correct volume is µin. We regret the error. 4 Circuits Assembly JUNE 2008 circuitsassembly.com http://circuitsassembly.com http://circuitsassembly.com

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

Circuits Assembly - June 2008 Contents Letters Caveat Lector Industry News Market Watch Talking Heads Screen Printing Better Manufacturing China Goes ‘Upmarket’ Out of the Garage Improving Production Line Performance Manufacturing Steps Onto the Enterprise IT Stage Measuring and Controlling Wave Height and Dwell Time Wave Soldering Tech Tips Test and Inspection Process Doctor Pb-Free Lessons Learned Getting Lean Eastern Advances Semicon West Product Preview Product Spotlight Ad Index Assembly Insider Technical Abstracts

Circuits Assembly - June 2008

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