IPC Day Netherlands: A Focus on U.S. and EU Aerospace Electronics

Estimated reading time: 14 minutes

He asked and explored: “What is risk, and why do we worry about it?” He defined risk as an expectation of loss in statistical terms, a combination of the probability that an undesired event would occur and the consequence or impact of the undesired event. Consequences can be technical failure, cost of fixing the problem, time to fix the problem, or safety considerations. 

Sood said communicating risk is key to portraying the status of a new technology and that an important guide to space mission development is the NASA risk classification system, which also forms the basis for programme and project managers to develop and implement mission assurance and risk management strategies. His graphic indicated risk profiles for a range of missions, where Class A represents minimum practical risk, Class B low risk, Class C moderate risk, and Class D as the highest risk profile. 

He also discussed the relationship between risk and possibility. Failure modes and mechanisms all constitute possibilities, and there is a tendency to take action to eliminate severe consequences regardless of the probability of their occurrence, although a lack of careful and reasoned analysis of each possibility can result in excessive cost and increased overall risk. He used the analogy of a waterbed to illustrate the importance of a systems approach to ensure that mitigating or eliminating a particular risk does not cause a much greater risk elsewhere in the system. “Try to maintain a level waterbed,” he said. 

As an introduction to the topic of “quality versus reliability,” Sood discussed emerging technologies and applications, remarking that space systems are complex, full of competing failure mechanisms. He defined “quality” as the totality of features and characteristics of a product or service that bear upon its ability to satisfy given needs, whereas “misguided quality” is defined by specifications that don’t actually link to performance, or specifications that are egregiously more stringent than the application warranted. The “reliability” of a system is its ability to perform the necessary functions within expected life exposure conditions for a required period. Often the quality definition for a product has lost its meaning over time, or the evolution of the product design has surpassed the quality definitions.

On the significance of PCB and PCBA requirements, he remarked that in most cases NASA uses IPC standards which are codified within NASA’s specifications and procedures, although in certain cases MIL, ESA, or in-house standards are applied. Inspection includes microsection evaluation and the evaluation of surface finish. Tests include external, visual, electrical continuity and isolation, solderability, and cleanliness. He was concerned that one of the challenges of next-generation PCB technologies was to avoid them being evaluated with old standards, and he used the example of NASA’s SpaceCube family of high-performance in-flight reconfigurable systems designed for advanced CubeSat applications based on hybrid data-processing. The stackup was designed and fabricated to IPC-6012DS, the Space and Military Avionics Applications Addendum to IPC-6012D, which introduced many challenges but was mainly focused on vias.

Along with specific board-level design requirements, NASA also examined non-conformance data and Goddard had identified 21 distinct non-conformance types among their 10 leading suppliers. Of these, the top five were:

• Innerlayer separations or inclusions
• Separations or inclusions between plating layers
• Copper wicking in excess of 2.0 mil
• Internal annular ring less than 2.0 mil
• ENIG less than minimum requirements

The risks associated with these top-five non-conformances were assessed and categorised, and the risk-based approach was used to identify and communicate risks to stakeholders. 

A recommendation from the study of risk of conformance vs. risk of non-conformance was to not reject a non-conforming item without understanding the risk and to determine the cause of the non-conformance before rejecting the item. 

In his conclusions, Sood remarked that standards play a multi-faceted role in advanced technology development and promote interoperability and innovation while also supporting quality. He believes that partnering and collaboration play a key role in technology development and enable future missions and discoveries. Strategic technology investments are focused on NASA priorities, particularly on technologies or capabilities that differentiate NASA from other organisations. As technology continues to advance, the role of standards in ensuring its successful development and adoption becomes increasingly significant. 

We heard NASA’s appraisal of the role of standards in shaping the future of aerospace technology, but how is PCB technology advancing for European space applications? Stan Heltzel, ESA’s materials and processes engineer, brought us up-to-date. 

Beginning with ESA itself, “Europe’s gateway to space,”,Heltzel gave a few basic facts and figures:

• 22 member states and 5,000 employees
• Objective: the exploration and use of space for exclusively peaceful purposes
• Headquartered in Paris with seven sites across Europe and a spaceport in French Guiana
• Annual budget about 6.5 billion euro

The ESTEC site in Noordwijk is the European Space Research and Technology Centre, the largest ESA site, and the incubator of the European space effort, where most ESA projects are born, developed, and scientifically exploited.

• Heltzel gave a flavour of ESA projects with a brief run through a few current and future missions:
• BepiColombo on its way to Mercury
• Solar Orbiter
• Rosetta the comet chaser
• JUICE on its way to Jupiter’s moons
• The Galileo constellation medium Earth orbit global navigation satellite system
• A whole range of geostationary telecommunications systems
• Human spaceflight missions include the International Space Station and the Lunar Gateway

Turning to the specific area of printed circuit boards, his flow chart illustrated the life cycle of a PCB in a space project step-by-step, in colour-coded groups representing the procurement cycle, project review, the assembly cycle, and final integration into a system. Electronic packaging levels progressed from bare chip at Level 0 through back-end packaging at Level 1, PCB assembly at Level 2, modules integrated at Level 3, to system at Level 4.

Describing the anatomy of a spacecraft, Heltzel commented that printed circuit boards and electronic assemblies are a complex combination of materials and processes to provide a stable mechanical and thermal platform for the electrical interconnection of components, acting as the nerves and veins of the spacecraft. 

How are PCBs qualified for space applications? Heltzel explained that ESA and the French Space Agency CNES are the qualification authorities, using the European Cooperation for Space Standardisation ECSS-Q-ST-70-60C standard for qualification and procurement of printed circuit boards. The ESCC Qualified Manufacturers List (ESCC QML) and Qualified Parts List (ESCC QPL) can be found on the European Space Components Information Exchange System website https://escies.org. There is one qualified PCB manufacturer in UK, two in France, one in Belgium, one in Germany, and one in the process of gaining qualification in Italy.

Under his heading “quality,” Heltzel listed capability, quality, reliability, and robustness. Capability denoted ability to manufacture a design; quality denoted as-manufactured build integrity; reliability related to performance under operational environmental stress; and robustness to performance under excessive environmental stress. Failure could occur “stable” as-manufactured or “latent” intermittent and evolving. PCB acceptance was based on dozens of quality indicators that influence its reliability and thus the probability of failure. Considering the cost of quality, the cost of conformance needs to be balanced against the cost of non-conformance. The later a problem is detected, the more expensive it becomes, and significantly, if the cost of good design is considered expensive, the cost of bad design can be much more expensive. There is a triangle of constraints in project management; the three parameters being “good,” “fast,” and “cheap.” Any two can be achieved in combination, but to achieve three together is impossible.

Other topics he discussed included six-sigma in the context of process engineering and confidence intervals in stress-strength analysis for predicting infant mortality, useful life, and wear-out. 

From a design point of view, he assessed the relationship between functionality and reliability, commenting that operational performance requirements at equipment level might not be consistent with reliability requirements at the PCB level. He stressed the importance of “designing with margin,” noting that designing with several technology features that are each within, but at the limit of, the capability of the manufacturer is a pitfall that can generate an unqualified, unreliable or even unmanufacturable PCB.

Turning his attention to developments in PCB technology, Heltzel discussed ESA’s HDI roadmap and emphasised the importance of making the PCB manufacturer a partner in the supply chain because complex designs require early involvement and technology developments needed expertise and resourcing on both sides of the supply chain. Qualification and continuous improvement need support from the supply chain and problem areas can be addressed by supplier-development programmes. PCBs can’t be treated as a commodity and there are properly structured procedures in place for their successful procurement. For example, a Manufacturing Readiness Review checklist is issued on ESCIES for use by the procurement authority. 

There is currently a high level of activity in the market for PCBs for space applications, with high order levels and long lead times, but there has been a steep decline in the number of PCB manufacturers in the EU, together with an incomplete local supply chain for resin, glass, copper foil, chemistry, equipment, and educated personnel. A review of the PCB and advanced packaging supply chains in Europe for critical applications, such as space and defence programmes, published as a Eurospace PCB supply chain white paper, “Supporting electronic assemblies and PCBs for a resilient and competitive EEE components supply chain in Europe,” requests support from the European Commission for the broad development of the PCB supply chain.

Returning to the theme of technology and reliability, Heltzel detailed the work of the EU IPC Microvia Working Group, whose main objective has been to strengthen European industry presence in IPC microvia standardization. The conclusion is that that advanced PCB technologies can be used reliably, with manufacturing processes optimised through mutual assessment among the supply chain. 

A visit to ESA’s materials laboratory and a guided tour of the Erasmus Human Spaceflight Visitor Centre put a context of realism on the event and brought an extremely interesting day to a meaningful conclusion. My grateful thanks to IPC and ESTEC.

IPC will be holding a series of these IPC Day events at various locations in Europe, with the objective of engaging more people and lowering the barrier to accessing IPC activities.

• < Previous Page