Continuous improvement methods that include analyzing re-engineered processes, influencing the specification and standards, benchmarking, tracking, controlling and communicating. The NASA Workmanship Program is taking the following actions to develop assurance guidance and requirements that can be applied Agency-wide in the following manner:. The NASA PCB Working Group is a resource for printed circuit board technology assessment and provides policy recommendations for printed circuit board quality assurance. The Working Group also communicates lessons learned technical recommendations and shares observations on new and altered printed circuit board products.
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Reviewing industry data, literature and experiences. Once published in a technical standard the guidance, requirement, or the standard as a whole, can be referenced and imposed by NASA hardware developers in their procurement contract statements of work, in purchase orders or other procurement vehicles where technical requirements are established. Independent Technical Evaluations. Routinely NASA Centers conduct independent technical evaluations on printed circuit board materials, designs, and fabrication principles in an attempt to learn how to maintain control over all of the factors that may affect the quality and reliability of PCBs used in missions.
Using an experimental design approach enables the NASA Center to test the hypothesis by reaching valid conclusions about relationships between, for example design specifications, magnitudes of applied stress and reliability, or between any other independent and dependent variables. Some examples of ongoing or recently completed independent studies are provided below. Copper Wrap Plating Requirements. Temperature cycling and thermal shock tests on test coupons fabricated with polyimide and FR4 materials suggest that copper wrap thickness is not a dominant failure site in PTH geometries.
Destructive physical analysis of test coupons from interconnect stress testing IST , which was performed at stress levels far exceeding any reasonable qualification level, suggests that the failure sites are located in the barrels, away from the copper wrap plating location. Software simulation also confirmed the IST test observations. The study further showed that procurement requirements for wrap plating thickness from IPC Class 3 to Class 2 would pose little risk to reliability. Experimental results corroborated by modeling indicate that the stress maxima are internal to the barrels rather than at the wrap location.
The goal of the test plan is to design-in variations in the internal annular ring geometries in printed circuit boards and correlate the effects of these variations to risk of PCB failure in relevant test and mission environments for earth-orbiting robotics missions. Reliability tests such as temperature cycling and mechanical flexure will be conducted on test samples constructed with controlled IAR widths, sub-optimal IAR widths and other configurations such as teardrops.
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For further information, contact Bhanu Sood, email: bhanu. Each NASA Center is responsible for ensuring manufacturing readiness for each PCB design, that the design will meet performance requirements and that it will be reliable in the context of the given mission. The following industry standards are commonly used to guide design for high reliability PCBs:.
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Not all of these companies are expert in the same range of technologies and products and careful supplier risk assessment is necessary to ensure orders are placed with companies who can readily deliver verified high-quality product without multiple rebuilds. There are no specific minimum technical requirements that are unique for assuring PCB quality imposed at the Agency level.
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Each NASA Center is responsible for ensuring PCB manufacturers used, or used by their prime contractors and system developers, are capable of complying with the minimum generic quality control requirements identified in NPD These organizations maintain lists of suppliers who have demonstrated compliance to those standards and met minimum audit criteria. Many high reliability system developers will qualify PCB suppliers based on their demonstrated ability to comply with the following technical standards:.
Some PCB evaluations are performed visually, others are done through a series of destructive and nondestructive tests. Nondestructive tests include evaluation of warp, visual examinations for surface defects, and electrical probing to ensure the circuit connections have been correctly realized from the computer aided design CAD files that the PCB designer provides to the PCB manufacturer. Destructive tests are performed on a representative sample called a test coupon.
Also on this page:. Printed Circuit Boards. Webmaster: Carl M. This is an inspection criterion due to which the level of acceptance criteria is realized for each class of product. This guideline helps the manufacture understand what the minimum requirements are to be for each printed board specification.
In fact, it is used more often as a tool to inspect the internal and external mechanism for printed circuit boards. This guideline helps to define and establish the standard performance and qualifications requirements that manufacturers should meet fabricating rigid circuit boards. With the help of this standard, manufacturers know which requirements they have to meet during the fabrication process for the 3 performance class of printed boards, i. Class 1, 2 and 3, 3A. Class 1 circuit boards are manufactured where the function of the end use product is usually the requirement.
For example: a garage door opener. This class of circuit board is manufactured and needed when continued performance, an extended life and uninterrupted service are desired features; however, it is not of critical importance. This is the highest class of printed boards and will include any end use where performance on demand or high performance is absolutely necessary.