IPC 2221 Generic Standard On Printed Board Design.pdf __TOP__
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IPC-2221B is the foundation design standard for all documents in the IPC-2220 series. It establishes the generic requirements for the design of printed boards and other forms of component mounting or interconnecting structures, whether single-sided, double-sided or multilayer. Among the many updates to Revision B are new criteria for conductor characteristics, surface finishes, via protection, board electrical test, dielectric properties, board housings, thermal stress, compliant pins, panelization and internal and external foil thicknesses. Appendix A provides new test coupon designs used for lot acceptance and quality conformance testing.
IPC-2221 establishes standards for PCB design aspects such as schematic, material selection, thermal management, DFM, DFA, DFT, and quality assurance. Some of the primary design requirements of high-voltage boards are defined in IPC-2221B.
IPC standards are established for the electronic manufacturing industry and are issued by a trade association named IPC. It lays the foundation for the design, assembly, packaging, interconnection, material, performance, and inspection specifications for the electronic industry. These global standards are pivotal to achieving high-yield circuit boards. Adhering to these standards can reduce the communication between the designer and the manufacturer.
IPC-2221 sheds light on the prerequisites for designing organic circuit boards with effective component placement, and interconnection structures. These boards are built using organic PCB materials or a combination of organic and inorganic substrates.
IPC-2221 is the bedrock of the IPC-2220-FAM design series, based on which the design principles and recommendations for different kinds of boards are established. The hierarchy of the 2220 series is shown below.
You need to consider the generic standards established by IPC-2221 in conjunction with the detailed requirements specific to your design. For example, to design a rigid board, the regulations mentioned in IPC-2221 should be referred to alongside the ones laid out in IPC-2222.
IPC-2222 mentions the optimized rules for efficient component placement, routing density, and superior electrical performance to achieve a flawless design. Used in conjunction with IPC-2221, IPC-2222 sets standards for the following factors to increase the manufacturability of a rigid circuit:
The IPC-2224 standard is a set of requirements for designing PC cards. The standard also guides you to secure passive and active components such as through-hole, fine-pitch BGAs, unpackaged bare die, array mount, and surface mount devices. The material specifications ensure faultless physical, thermal, and electrical functions of the following types of boards:
The minimum spacing details required to allow high voltage between two conductors are specified in the standard. These values are evaluated with respect to peak DC or AC voltage. A point to be observed is that IPC-2221 mentions the exact minimum spacing required to pass voltage at around 500 V. If the voltage exceeds 500V, per-volt clearance calculation will help you obtain the necessary minimum spacing.
Clearance and creepage are two parameters that are related to the distance required between conductors on a circuit board. The distance between two conductors or nodes, measured in air, is referred to as the clearance distance. IPC-2221 defines optimum clearances related to different aspects of the circuit board. Let us have a look at a few of the important ones mentioned in this standard.
The clearances mentioned in IPC-2221 require rechecking when it comes to high-voltage circuit boards. This is because there are more chances of a flashover in high-voltage designs than in a standard one. Therefore, different regulations should be considered in the case of high-voltage PCBs.
With the increase in voltages, it is obvious that the clearance and creepage distance between traces and conducting features on the PCB should be increased. But we are working on circuit boards here, and hence there is a limit to which these distances can be increased. The minimum creepage and clearances defined by the IPC-2221 will not be enough to prevent a flashover in this case. Therefore, different methods should be adapted to increase the clearance and creepage distances for a high-voltage design. They include:
IPC-2221 is a reference document that lays down a number of design standards while designing a PCB. Adhering to these standards is crucial to realize DFM, DFA, and DFT specs. Let us know in the comments section if you require any assistance to make your board manufacturable in the first go. Our design and manufacturing experts will be happy to help you.
Charts IPC standard 2221 "Generic Standard on Printed Board Design" (pdf, IPC web-site paid) (page 41) provides the following relationships between current carrying capacity and copper trace width:
What is 1 oz copper?The measure for the copper thickness on a printed circuit board. It's the resulting thickness (height) when 1 oz of copper is pressed flat and spread evenly over a one square foot area. It corresponds to copper thickness of 1.37 mils (34.79 um).
IPC-2221 is the foundation design standard for all IPC-2220 design series. It establishes the generic requirements for the design of PCBs and other forms of component mounting or interconnecting structures, whether single-sided, double-sided or multilayer. This standard also provides test coupon designs used for lot acceptance and quality conformance testing.
In high voltage PCB design, the important generic standard for PCB design is IPC-2221. Many important design aspects are summarized in this design standard, some of which boil down to simple mathematical formulas. For high voltage PCBs, an IPC-2221 calculator can help you quickly determine appropriate spacing requirements between conductive elements on your PCB, which helps ensure your next high voltage board will remain safe at its operating voltage. When your design software includes these specifications as automated design rules, you can remain productive and avoid making layout mistakes as you build your board.
IPC-2221 (Revision B effective 2012) is a generally accepted industry standard that defines a multitude of PCB design aspects. Some examples include design requirements on materials (including substrates and plating), testability, thermal management and thermal reliefs, and annular rings, to name a few.
Some of the design guidelines are superseded by more specific design standards. For example, the IPC-6012 and IPC-6018 provide design specifications on rigid PCBs and high-frequency PCBs, respectively. These additional standards are meant to be largely consistent with the IPC-2221 standards for generic PCBs. However, IPC-2221 is not typically the qualification standard used to assess product reliability or manufacturing yield/defects. For rigid boards, either IPC-6012 or IPC-A-600 will normally be used for qualifying fabricated rigid PCBs.
The first point is most important as it can be most easily controlled by setting the right minimum clearance between conductors in the PCB. The second effect can also be suppressed with appropriate trace spacing, as well as material selection and general cleanliness in processing. The required spacing needed to prevent these effects is summarized as a function of the voltage between two conductors in the IPC-2221 standard.
The image below shows Table 6-1 from the IPC-2221 standards. These values list minimum conductor spacing as a function of the voltage between the two conductors. These values are specified in terms of either the peak AC or DC voltage between the conductors. Note that IPC-2221 only specifies fixed minimum conductor spacing values for voltages up to 500 V. Once the voltage between two conductors exceeds 500 V, the per-volt clearance values shown in the table below are used to calculate the minimum conductor spacing. Each volt above 500 V will add to the required minimum clearance by the amount shown in the bottom row of the table.
To determine the best cross-sectional area, calculators based on data published in IPC-2221 and IPC-2152 standards can be used. The dataset used in an IPC-2152 calculator is more complex, but it can provide more accurate results than an IPC-2221 calculator.
The IPC-9592B standard provides conductor spacing requirements specifically for power conversion devices. These standards are quite consistent when graphed alongside the required conductor spacing specified in IPC-2221. The table below specifies the spacing requirements under IPC-9592B. This defines the minimum required trace spacing as a function of peak voltage values; the difference is that this standard scales the minimum conductor spacing values with applied voltage below the 500 V limit shown in the above table.
The calculator below provides a safe clearance calculation based on the standards cited above. To use this calculator, enter the working voltage at which your board will operate, and the calculator will return clearance requirements for internal, external, and coated traces in the PCB layout. The calculator will also return results for IPC-9592 compliant power conversion devices.
Note that the IPC-2221 standards are voluntary. However, for products covered by safety standards as defined in building and electrical codes, creepage and clearance requirements in the relevant UL or IEC standard may become mandatory. As an example, the relevant set of safety requirements on IT and telecom products with AC mains and battery power can be found in the IEC 62368-1 standard (this replaced the IEC 60950-1 standard). For creepage, the spacing specified under IPC-2221B depends on RMS working voltage, pollution degree (numbered 1 through 3), and material group. The definitions of the latter two terms can be found in the UL 62368-1 standards. Whether you need to comply with IEC, IPC, or other required safety standards, you can specify your design requirements as design rules when you use the right PCB design software. 2b1af7f3a8