The electronic world demands precision, uniformity and dependability attributes of conforming to laid down standards. Regardless of whether you are designing consumer equipment, medical equipment, or aerospace equipment, knowledge of PCB fabrication standards is an absolute must. These standards guarantee that your designs do not only comply with specifications, but also take the quality levels that your application requires. The following are five standards of PCB fabrication that no engineer would not want to know.
1. The Visual Acceptability Standard, IPC-A-600
The quality of PCBs is based on IPC-A-600. This standard stipulates visual and mechanical acceptability parameters of printed circuit boards, what is acceptable and rejectable boards. Instead of a prescriptive way of manufacturing, IPC-A-600 gives a specification of how the final product should appear.
The standard classifies PCBs into three classes of quality:
- Class 1 (General Electronics): Consumer goods with lowest cost taking the first seat and performance being the least important.
- Class 2 (Dedicated Service): Commercial and industrial products that need a constant performance with unintensive access to the service provision.
- Class 3 (High-Reliability): The Military, medical, and aerospace systems that can not allow failure. The Class 3 requires minimum cosmetic flaws and the narrowest tolerances.
Board edges, base material, conductive patterns, plated-through holes, solder mask, surface finishes, and marking are included in IPC-A-600. When working with pcb fabrication materials, checking the order of the right class helps the engineer to avoid expensive respins and failure in the field.
2. IPC-2221: The PCB Design Standard
IPC-2221 defines design guidelines which make PCBs reliable and manufacturable. This standard gives important advice on the choice of the material, calculation of trace width, spacing, and positioning of components.
Important Requirements IPC-2221:
- Trace width is based on current carrying requirement. The current capacity charts of the standard will avoid overheating and burnout of traces. IPC-2221 gives specific width values depending on the trace size and current density when the trace supports 1 ampere of current at 10 o C increase in temperature.
- There is a voltage dependent conductor spacing. Minimum spacing of 0.25mm (10 mils) is acceptible to traces with less than 50V traces. Nonetheless, above 300 V, separation should be 10-fold or more than the trace width in order to avoid arcing and dielectric breakdown. These requirements are usually underestimated by engineers resulting in failure of the fields.
- The rules of component placement guarantee appropriate thermal management, feasibility of assembly and screen integrity. IPC-2221 gives specifications of minimum distance between components, traces and the sides of the board.
This is because engineers undertaking pcb board projects need to refer to IPC-2221 when reviewing the schematic, not when at layout, when it becomes costly to correct.
3. IPC-6012: Rigid PCB Performance Standard
Although the concept of visual acceptability is set by the IPC- A-600, IPC- 6012 defines accepted standards and performance attributes of rigid PCBs. His standard stipulates the material requirements, accuracy of drilling, plating thickness, testing method and electrical performance.
IPC-6012 requires:
- Minimums of copper plating thickness (usual after all processing 0.0008 inches)
- Standards of plated-through hole wall coverage.
- Electric continuity testing on all the layers.
- Stress tests on adhesion of the layer.
Certain checking methods and acceptance levels
The manufacturers which have certified themselves as IPC-6012 have the ability to manufacture boards which can be at specific levels of performance at all times. This means that by specifying this standard at the stage of pcb fabrication process selection, you will be guaranteeing that your manufacturer works with strict quality guidelines.
4. Customer Services: ISO 9001:2015 Certification of Quality Management System
The ISO 9001 certifies that a PCB manufacturer has adopted an institutionalized quality management system (QMS) that involves design, procurement, production, inspection, and the continuous improvement. This certification will guarantee a uniform quality of the products, written procedures, and a methodical elimination of defects.
To select a manufacturer of pcb fabrication, ISO 9001:2015 certification will imply:
- Recorded and managed production methods.
- Consistent internal audit and review by the management.
- Constant process enhancement projects.
- Non-conformance root cause analysis.
- All the critical manufacturing parameters can be traced.
Although ISO 9001 does not ensure flawless boards, it illustrates organizational dedication to organization with the management of quality as it is vitally needed; mission-oriented applications require it.
5. J-STD-001: Assembly and Solderability Standards
J-STD-001 is a standard which stipulates the requirements of solder joints, assembly processes, and acceptance. The minimum pad sizes, the distance between the parts of the assembly and the thermal requirements during the soldering process are defined by this standard.
The spatial requirements of the standard are:
- Spacing between pads and traces in Class 1 and 2 PCBs Minimum 0.25mm (10 mil) spacing between pads and traces.
- At least 1.5mm (60 mil) between parts and neighboring traces to allow reflow lobbing to be avoided.
Thermal profiles of various kinds of components
J-STD-001 is usually not considered when laying a PCB, which causes assembly complexities and defects at the end of the pcb fabrication supplies chain. Co-ordinating of pcb fabrication ties down specifications to assembly partners so as to maintain source.
Practical Implementation
Choose the right class (1, 2 or 3) according to the importance of the application and make it known in your manufacturing document. In design, reference IPC-2221 is required not after design layout. Check certifications of manufacturers (IPC-6012, ISO 9001) and then commit to production. Arrange with the assembly partners on the J-STD-001 compliance at the design stage.
Conclusion
The five standards that comprise IPC-A-600, IPC-2221, IPC-6012, ISO 9001 and J-STD-001 are the pillars of consistent PCB fabrication. The development and application of these standards turn abstract design points into a manufacturing and reliable commodity that is capable of meeting performance requirements of the real world. When making your first board or your hundredth board, these are the basic standards that you should stick to and there can be no compromise on these.