Circuits Assembly - December 2008 - (Page 41) Table 2. IPC-4781, Table 3.3 Test Responsibility for Qualification defines the requirement and the right side specifies the materials and the tests to be performed. Requirement Material Supplier Fabricator End User Other aspects found in the complete version of Physical Hardness X X N/R the chart include chemical resistance, electrical Adhesion to requirements, environmental requirements and Solder Mask X X N/R materials. Table 2 features the top of Table 3-2, Materials depicting who is responsible for each test and Conformal Coating N/R AABUS* X qualification. Adhesion Military adoption? The significant issue to be Flammability X N/R N/R decided is whether the US military will adopt *AABUS: As agreed between user and supplier. the new specification. Three government specifications (MIL-I-43553, A-A-56032 and MIS37271) predate IPC-4781, but in our opinion do not meet regard to legend inks. These definitionsPage 1 are important, as roject2:Layout 1 4/14/08 11:42 AM industry needs. much confusion has arisen over language issues. IPC-4781 will be useful for the commercial sector, but The heart of IPC-4781 is Table 3-1. IPC-TM-650, Test for companies that fabricate boards for the DoD, military Methods Manual, is referenced for testing and measurrequirements dominate legend and marking ink selection. ing performance in a broad range of characteristics. No It is hoped the Defense Department will adopt IPC-4781. specific chemistry or application method is called out or IPC-4781 mirrors other IPC specifications in terms excluded; any that meet the requirements are approved for of material qualification and conformance, such as IPCuse. Material compatibility of all inks is documented. Of SM-840 and IPC-CC-830 for conformal coatings, so commajor significance is assignment of responsibility between pliance should be user friendly. vendor and user for each specified formulation or varian tion of legend or marking ink material. In some cases, a designation of AABUS (as agreed between user and supAcknowledgments plier) is given, ensuring these issues are defined in the user/ supplier contract. A sample of the top of the chart, physical Doug Pauls of Rockwell Collins, Henry Sanftleben of Delphi Electronics & aspects, can be seen in Table 1. In this table, the left side Safety and Dave Vaughan of Taiyo America contributed to this column. Column A Column B Column C Standards circuitsassembly.com Circuits Assembly DECEMBER 2008 41 http://www.powell-muchaconsulting.com/ http://www.powell-muchaconsulting.com/ http://www.circuitsassembly.com
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