Technical Library | 2013-04-04 15:28:39.0
This paper will outline and define what requirements must be adhered to for the OEM community to truly achieve the IPC class product from the Electrical Test standpoint. This will include the test point optimization matrix, Isolation (shorts) parameters and Continuity (opens) parameters. This paper will also address the IPC Class III/A additional requirements for Aerospace and Military Avionics. The disconnect exists between OEMs understanding the requirements of their specific IPC class design versus the signature that will be presented from their design. This results in many Class III builds failing at Electrical Test... First published in the 2012 IPC APEX EXPO technical conference proceedings
Technical Library | 2017-10-12 15:45:25.0
The risk associated with whisker growth from pure tin solderable terminations is fully mitigated when all of the pure tin is dissolved into tin-lead solder during SMT reflow. In order to take full advantage of this phenomenon, it is necessary to understand the conditions under which such coverage can be assured. A round robin study has been performed by IPC Task group 8-81f, during which identical sets of test vehicles were assembled at multiple locations, in accordance with IPC J-STD-001, Class 3. All of the test vehicles were analyzed to determine the extent of complete tin dissolution on a variety of component types. Results of this study are presented together with relevant conclusions and recommendations to guide high reliability end-users on the applicability and limitations of this mitigation strategy.
Technical Library | 2019-09-04 21:35:53.0
Since the European Directives, RoHS (Restriction of Hazardous Substances) and REACH (Registration, Evaluation, Authorization and Restriction of Chemicals), entered into force in 2006-7, the number of regulated substances continues to grow. REACH adds new substances roughly twice a year, and more substances will be added to RoHS in 2019. While these open-ended regulations represent an ongoing burden for supply chain reporting, some ability to remain ahead of new substance restrictions can be achieved through full material declarations (FMD) specifically the IPC-1752A Class D Standard (the "Standard"), which was developed by the IPC - Association Connecting Electronic Industries. What is important to the supply chain is access to user-friendly, easily accessible or free, fully supported tools that allow suppliers to create and modify XML (Extensible Markup Language) files as specified in the Standard. Some tools will provide enhancements that validate required data entry and provide real-time interactive messages to facilitate the resolution of errors. In addition, validation and auto-population of substance CAS (Chemical Abstract Service) numbers, and Class D weight rollup validation ensure greater success in the acceptance of the declarations in customer systems that automate data gathering and reporting. A good tool should support importing existing IPC-1752A files for editing; this capability reduces the effort to update older declarations and greatly benefits suppliers of a family of products with similar composition. One of the problems with FMDs is the use of "wildcard" non-CAS numbers based on a declarable substance list (DSL). While the substances in different company's lists tend to have some overlap, no two DSL’s are the same. We provide an understanding of the commonality and differences between representative DSLs, and the ability to configure how much of a non-DSL substance percent is allowed. Case studies are discussed to show how supplier compliance data, can be automatically loaded into the customer's enterprise compliance system. Finally, we briefly discuss future enhancements and other developments like Once an Article, Always an Article (O5A) that will continue to require IPC standards and supporting tools to evolve.
Technical Library | 2021-07-20 20:02:29.0
During the manufacturing of printed circuit boards (PCBs) for a Flight Project, it was found that a European manufacturer was building its boards to a European standard that had no requirement for copper wrap on the vias. The amount of copper wrap that was measured on coupons from the panel containing the boards of interest was less than the amount specified in IPC-6012 Rev B, Class 3. To help determine the reliability and usability of the boards, three sets of tests and a simulation were run. The test results, along with results of simulation and destructive physical analysis, are presented in this paper. The first experiment involved subjecting coupons from the panels supplied by the European manufacturer to thermal cycling. After 17 000 cycles, the test was stopped with no failures. A second set of accelerated tests involved comparing the thermal fatigue life of test samples made from FR4 and polyimide with varying amounts of copper wrap. Again, the testing did not reveal any failures. The third test involved using interconnect stress test coupons with through-hole vias and blind vias that were subjected to elevated temperatures to accelerate fatigue failures. While there were failures, as expected, the failures were at barrel cracks. In addition to the experiments, this paper also discusses the results of finite-element analysis using simulation software that was used to model plated-through holes under thermal stress using a steady-state analysis, also showing the main failure mode was barrel cracking. The tests show that although copper wrap was sought as a better alternative to butt joints between barrel plating and copper foil layers, manufacturability remains challenging and attempts to meet the requirements often result in features that reduce the reliability of the boards. Experimental and simulation work discussed in this paper indicate that the standard requirements for copper wrap are not contributing to the overall board reliability, although it should be added that a design with a butt joint is going to be a higher risk than a reduced copper wrap design. The study further shows that procurement requirements for wrap plating thickness from Class 3 to Class 2 would pose little risk to reliability (minimum 5 μm/0.197 mil for all via types).Experimental results corroborated by modeling indicate that the stress maxima are internal to the barrels rather than at the wrap location. In fact, the existence of Cu wrap was determined to have no appreciable effect on reliability.
Technical Library | 2016-07-28 17:00:20.0
Packaging trends enable disruptive technologies. The miniaturization of components reduces the distance between conductive paths. Cleanliness of electronic hardware based on the service exposure of electrical equipment and controls can improve the reliability and cost effectiveness of the entire system. Problems resulting from leakage currents and electrochemical migration lead to unintended power disruption and intermittent performance problems due to corrosion issues.Solvent cleaning has a long history of use for cleaning electronic hardware. Limitations with solvent based cleaning agents due to environmental effects and the ability to clean new flux designs commonly used to join miniaturized components has limited the use of solvent cleaning processes for cleaning electronic hardware. To address these limitations, new solvent cleaning agents and processes have been designed to clean highly dense electronic hardware.The research study will evaluate the cleaning and electrical performance using the IPC B-52 Test Vehicle. Lead Free noclean solder paste will be used to join the components to the test vehicle. Ion Chromatography and SIR values will be reported.
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