IPC standards are electronic design, manufacturing and inspection standards published by IPC, a global trade and standards setting association focused on the electronics industry.\u00a0 IPC\u2019s standards are used worldwide and have been essential to the globalization of the electronics industry. Anyone who designs or manufactures PCB assemblies needs to be familiar with the standards.<\/p>\n

Most engineers and designers first encounter the IPCstandards in the fabrication notes on PCB drawings or because they have been trained on ubiquitous IPC-A-610 \u201cAcceptability of Electronic Assemblies\u201d which illustrates quality standards for PCB soldering and cleaning.<\/p>\n

The IPC publishes standards for every aspect of PCB design<\/a>, manufacturing, and inspection<\/p>\n

The major categories of the standards are:<\/p>\n

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• General documents<\/li>\n
• Design specifications<\/li>\n
• Material specifications<\/li>\n
• Performance and inspection standards<\/li>\n
• Flex assembly and materials standards<\/li>\n<\/ul>\n

  The General Documents <\/strong>cover terms and definitions, PCB tolerances, PCB documentation, and bare PCB testing standards.<\/p>\n

  The Design Specification Section<\/strong> focuses on guidelines for the electrical engineer and PCB layout designer.Perhaps the two best known design standards are IPC-2221 \u201cGeneric Standard on Printed Board Design\u201d and IPC-7351B Generic Requirements for Surface Mount Design and Land Pattern Standards.\u00a0 Fortunately for the PCB designer, these generic standards are encoded in the PC Board<\/a> layoutsoftware\u2019s internal design rules, so it is not necessary to have them memorized when laying out a PCB.<\/p>\n

  The Material Specifications<\/strong>define the specifications for everything in the electronics supply chain from the pre-preg to the silkscreen. These specifications are often referenced in the notes on a PCB drawing.\u00a0 One typical example is IPC-4552\u201cPerformance Specification for Electroless Nickel\/Immersion Gold (ENIG) Plating for Printed Boards\u201d which sets requirements for the gold plating of PCBs.<\/p>\n

  The Performance and Inspection Documents<\/strong> contains one of the most important standards, IPC-6011 \u201cGeneric Performance Specification for Printed Boards.\u201d\u00a0\u00a0 IPC 6011 establishes the requirements for PCBs and defines the level of quality ultimately reliability for PCBS the IPC-6011 standards cover the following topics:<\/p>\n

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  • PCB design<\/a><\/li>\n
  • PCB assembly<\/li>\n
  • PCB testing<\/li>\n
  • PCB inspection<\/li>\n
  • PCB documentation<\/li>\n<\/ul>\n

    Flex assembly and materials standards<\/strong>covers both the materials and the assembly standards for flexible printed circuits<\/p>\n

    IPC Electronic Product Classes<\/strong><\/p>\n

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    The most important part of IPC-6011 is the definition of classes of electronic products.\u00a0 The definition of classes is then used to determine the PCB design, manufacturing, and inspection rules.<\/p>\n

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    IPC 6011 defines three classes of electronic products<\/a> and one subclass.<\/p>\n

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    • Class 1 \u2013 general electronic products:<\/strong> Class 1 products are for applications in which the functionality and low cost primary drivers, and reliability is secondary. This class includes most low-cost electronic products. PNC and most U.S suppliers do not manufacture class 1 PCBs.<\/li>\n<\/ul>\n

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      • Class 2 \u2013 dedicated service electronic products:<\/strong> Class 2 products put more emphasis on high reliability and extended life. Uninterrupted service is preferable, but not mission critical. The use environment of the class 2 product is not extreme enough to cause Printed Circuit Board<\/a> This is typically the default standard for layout application design rules and for U.S. manufacturers.<\/li>\n<\/ul>\n

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        • Class 3 \u2013 high-performance electronic products:<\/strong> Class 3 products must provide continuous performance or performance on demand with no downtime or performance degradation. The end-use environment may include temperature extremes, vibration, and high altitudes. This category includes critical systems such as medical life support systems.<\/li>\n<\/ul>\n

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          • Class 3\/A -space and avionics: <\/strong>Class 3\/A is a new subclass of class 3 specifically for military and aerospace electronics. They are considered mission critical and failure could result in the loss of the spacecraft or aircraft. It is the highest class for PCBs, and class 3\/A PCBs have very stringent (and expensive) manufacturing and inspection criteria.\u00a0 When selecting a manufacturer for class 3\/A PCBs it is essential to choose a company like PNC with extensive military and aerospace experience.<\/li>\n<\/ul>\n

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            Differences Between Class 2 and Class 3 PCBs<\/strong><\/p>\n

            \u00a0<\/strong>From an engineer’s standpoint, the selection of product class affects the design rules used by the layout software, the PCB construction and most importantly from a cost standpoint, the level of inspection and reject criteria at the bare PCB and finished assembly level.\u00a0 Oneof the most consequential decisions for the final unit cost of the PCB assembly<\/a> will be the decision to go with either an IPC class 2 or class 3 quality level.<\/p>\n

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            At the PCB design stage, there are different design rules for class 2 and class 3.The design rule that has the most effect on the layout is that the difference in the size of via pads and drill holes specified for plated through holes.<\/p>\n

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            Larger pad and drill sizes are required on IPC class 3 PCBs to ensure the a 360 deg connection between the pad and the hole plating, and to minimize the potential for drill breakouts from the annular ring on the far side of the hole due to drill drift.\u00a0 \u00a0Besides taking up more PCB real estate, the larger via pad specification for IPC class 3 PCBs limit the fan out of BGAs to 0.8 mm pitch and larger. Smaller pitch BGAs cannot be accommodated by class 3 design rules, because traces cannot be routed between the larger pads.<\/p>\n

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            In manufacturing, there are tighter inspection criteria for defects to the bare PCB that increases inspection time and decreases bare PCB yield. Both increase costs.\u00a0 Similar inspections and occur after soldering and cleaning, and again, the tighter inspection criteria decrease PCB yield.<\/p>\n

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            PNC can help you keep IPC class 3 costs in control<\/strong><\/p>\n

            \u00a0<\/em>The best way to keep IPC class 3 PCB costs under control is to work with a manufacturer who has the expertise and equipment to keep yields high.\u00a0\u00a0 PNC has deep experience in fabricating space and avionics rated PC Board assembly<\/a>. Ask the experts at PNC to work with you on your next mission critical design.<\/p>\n

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