Test, Inspection and Measurement
Introduction
As printed circuit complexity and design demand increases, the need for coincident evolution of test, measurement and inspection methodologies and capability must increase as well in order…
to monitor and control processes,
confirm product attributes and life,
provide certification of finished properties mechanically and electrically.
The technology issues discussed below mainly fall into three categories.
Test, Measurement, and Inspection Equipment evolution:
Sensitivity, speed, and automation are continually being added to the PCB process inspection evolution, allowing for better feedback and control and capability of processes to meet increasing product demands. Specifically, attribute and variable measurements are combined for non-destructive fast feedback (smart automatic optical inspection) are increasing needed to advance the state of the art.
Data Handling, Testing protocols and Traceability:
Data management and handling become a key element of inspection and test, since the data gathered can be further intelligently utilized to control processes and the product data collected for analysis and traceability.
Reliability:
With product applications growing in challenging environments, hotter, faster, smaller, assessment of reliability and predicted product life is equally more challenging to the PCB supplier, putting pressure on laboratory and accelerated life knowledge and testability further up the supply chain. Coincidentally, the evolution of failure analysis must keep pace with increasing demand for product performance.
Technical Needs, Gaps and Solutions
The technology issues surrounding Test, Inspection and Measurement, the associated needs, technology status of those needs, as well as gaps and challenges to overcome, are summarized below. The time period considered is from 2023 to 2033.
Some definitions:
Term | Definition |
|---|---|
GAP | This is what is missing or what below in performance, in today’s technology, to meet the need for year X. |
CHALLENGE | Why is it difficult to meet the need in year X? Typically, this is some particular technical consequence of that need that is inherently difficult. |
CURRENT TECHNOLOGY STATUS in year X | How well does today’s technology and solutions meet the need in year X? |
Technology Status Legend
For each need, the status of today’s technology is indicated by label and color as follows:
In-table color + label key | Description of Technology Status |
|---|---|
Solutions not known | Solutions not known at this time |
Solutions need optimization | Current solutions need optimization |
Solutions deployed or known | Solutions deployed or known today |
Not determined | TBD |
Table 1. Test, Inspection and Measurement Needs, Gaps, and Today’s Technology Status with Respect to Current and Future Needs
| ROADMAP TIMEFRAME | |||
TECHNOLOGY ISSUE | TODAY (2023) | 3 YEARS (2026) | 5 YEARS (2028) | 10 YEARS (2032) |
[Equipment] Electrical Testability (e.g., Needs like small features, in process, final, capability, architectures, known good die (KGD)-like, etc.) | ||||
NEED | Flying probe 4-wire and fine pitch for functional testing | Flying grid, faster test | Non-contact testing | Non-contact testing evolution |
CURRENT TECHNOLOGY STATUS | Deployed | |||
NEED | Continuity with Impedance, volumetric control of conductor and stub | 100% continuity, more involved testing. Impedance, volumetric control of conductor
| Able to address more complexity, specialization like embedded die and waveguide. Requires test methods to be developed. | |
CURRENT TECHNOLOGY STATUS | ||||
GAP | Available equipment | Available equipment | ||
CHALLENGE | More data from test | TBD based on market, product, competition and demand | ||
CHALLENGE | Layout and design, and modeling for test (DFT) | |||
CHALLENGE | Pitch | |||
CHALLENGE | Test speed | |||
[Equipment] Measurability (e.g., Needs like features size, coplanarity, roughness, placement, ) | ||||
NEED | Adaptive control with some dynamic in place | Dynamic control capability w feedback (For mechanical, chemical, optical) | Full automation with factory artificial intelligence (AI) | |
CURRENT TECHNOLOGY STATUS
| ||||
NEED | 100% measurability needed, (at pass/fail) | 100% measurability signal integrity (SI) | 100% traceability attribute measurements (e.g., electrical, etc.) | |
CURRENT TECHNOLOGY STATUS
| Limited 100 % sampling and some batch testing | |||
GAP | Availability and cost of equipment | |||
CHALLENGE | Keeping pace with design evolution and change | Greater sensitivities with 6G, new functionalities, as well as conventional techs (low tech is no longer “low tech”) | ||
CHALLENGE | High-end technology pressure, less flexible market | |||
[Equipment] Back Drill | ||||
NEED | 100% measurement of holes | 100% measurement of holes for optical and Xray | New technology innovations | TBD based on new techs |
CURRENT TECHNOLOGY STATUS | Available: Flying-probe capacitance check for stripes or extra copper | In development: Upstream optical feedback in process |
|
|
GAP | Limited coverage, not at 100% | Availability of optical test equipment | More complex PCB design | |
GAP | Need to define in which stage the measurement is done e.g. measurement during PCB manufacturing or ready product | |||
CHALLENGE | Tight stub (near-zero tolerance) | Zero stub and alternative structure of PCB | ||
| ||||
CHALLENGE | Small-hole variation | |||
CHALLENGE | Complexity with sizes and aspect ratio | |||
[Equipment] Inspection (Automatic optical inspection (AOI) and automated visual inspection (AVI)) | ||||
NEED: Faster and less false calls with high resolution with automation
| Scanning both sides at same time | Software (SW) improvements and Factory Automation, increasing speed | Machine learning (ML) and Automation and more use of AOI & AVI | |
CURRENT TECHNOLOGY STATUS | ||||
GAP | Equipment procurement and retooling transition | New methodologies for inspection to be developed | ||
CHALLENGE | Verification is complex | Products’ evolutions adds machine AOI | ||
CHALLENGE | Materials mix adds complexity | |||
[Data & Protocols] Automation | ||||
NEED | Continuous inline inspection, adaptive process feedback | Continuous inline inspection, adaptive process feedback, and high investment | ||
CURRENT TECHNOLOGY STATUS | Batch judgements based on sampling | |||
GAP | Equipment procurement and retooling transition | New methodologies for inspection to be developed | ||
GAP | Equipment needs to be developed for specific PCB processes | High cost of equipment needs to be developed for specific PCB processes | ||
CHALLENGE | Product variation and yield loss | |||
CHALLENGE | Sophistication of tools and specific testing including data collection and SW development | |||
[Data & Protocols] Traceability | ||||
NEED | Lot/batch code traceability | Individual board bar code traceability, smaller and more precise | Individual board bar code traceability embedded inside by radio frequency identification (RFID); solutions needed for low-end lower tech boards, to be more the “norm” | TBD - Individual board bar code traceability embedded inside by RFID; solutions needed for low-end lower tech boards, to be more the “norm” |
CURRENT TECHNOLOGY STATUS | Deployed | Existing on high-end boards (few layers) | ||
GAP | No forward and backward traceability | |||
CHALLENGE | Cost of assembly failure | Costs need to be lower | ||
CHALLENGE | Solder mask and copper inside board indexing | Development of hardware (HW), SW and data systems | ||
CHALLENGE | Readers’ technology: Data Systems, No standard placement, Lot definition / overlap and Laser resolution not scannable | Product complexity | ||
[Data & Protocols] Test protocols and procedures | ||||
NEED | Adequate testability of new designs (with smaller pitch, new functions to test) and continuity (down to the milliohm regime) | Non-contact testing | ||
CURRENT TECHNOLOGY STATUS | Tech needs optimization – extend beyond 10% coverage | Development needed for commercial solutions | ||
GAP | Today – continuity and resistance testing at 1 ohm, not milliohm | No commercial solutions to date | ||
CHALLENGE | Cost prohibitive for lower resistances | Low correlation between the indirect measurements and resistance | ||
NEED | For high-density interconnect (HDI) and fine pitch substrates esp. in hostile environments, repeated real-time certification of outputs, instead of testing one-off coupons/sample. Needed to ensure continued process reliability. | Extend from substrates (today) to testing of 3D stack-ups. | Extend from substrates (today) to PCBs for HDI products | |
CURRENT TECHNOLOGY STATUS | Tech needs development | |||
GAP | Getting to a repeatable, semi-real-time solution | New methodologies for inspection to be developed | ||
CHALLENGE | Time for test and capital investment in the testing equipment | |||
[Reliability] Accelerated Test | ||||
NEED | Demand for more frequent product testing certification | |||
CURRENT TECHNOLOGY STATUS | Needs to be optimized | |||
GAP | Expense, legal aspects to certification and change control issues | |||
GAP | New products and materials constantly developed | |||
CHALLENGE | Less accurate and need for standards across the industry sectors (automotive, telecom, data center, consumer electronics., aerospace and defense (A&D), etc.) | More complexity with products | ||
CHALLENGE | High power applications and new failure mechanisms | |||
CHALLENGE | Automation and identification | |||
[Reliability] Product Reliability (e.g., variations, specs, etc.) | ||||
NEED | Simulate functional tests based on the bare board tests – starting with impedance and loss predictions | Increased sophistication of functional tests coverage: channel simulation, jitter simulation, length matching, timing, channel compliance, misalignment with line cards, crosstalk, etc. | ||
CURRENT TECHNOLOGY STATUS | Tech exists – needs development and commercial solutions | |||
GAP | Need a smarter “flying probe” | New methodologies for inspection to be developed | ||
CHALLENGE | Cost prohibitive for commercial availability | |||
[Reliability] Failure Analysis (e.g, equipment investment, end-process and data handling, etc.) | ||||
NEED | For high-speed computing, for mobile handsets: Move beyond SEMI-Enhanced Digital Access Communication System (EDACS) towards more sophisticated tools such as surface analysis, focused ion beam (FIB) , X-ray photoelectron spectroscopy (XPS). Simulation of soldering process (Ackromatrix) | Automation of the same | Faster testing | In-situ testing |
CURRENT TECHNOLOGY STATUS | Extending techniques from semi into PCB | |||
GAP | Currently in-lab – need to be in-situ. Training and in-factory equipment needed. | |||
CHALLENGE | Affordability of new labs and equipment (in-house or out-source decisions) | |||
[Reliability] Failure Analysis (e.g, equipment investment, end-process and data handling, etc.) | ||||
[Repeatability] All Test Processes | ||||
NEED | Repeatable and correlative testing between sources (between fabricators and between fabricator and customer and lab) | Third party certification and validation of lab test results | ||
CURRENT TECHNOLOGY STATUS | Solutions need optimization | Solutions need optimization | ||
GAP | Test methods are standardized and documented but requirement for correlation is not. | Supplier labs will be required to achieve third party validation | ||
CHALLENGE | Lack of industry standard to address test result validation | |||
Approaches to address Needs, Gaps and Challenges
Table 2 considers approaches to address the above needs and challenges. The evolution of these is projected out over a 10-year timeframe using technology readiness levels (TRLs).
In-table color key | Range of Technology Readiness Levels | Description |
|---|---|---|
2 | TRL: 1 to 4 | Levels involving research |
6 | TRL: 5 to 7 | Levels involving development |
9 | TRL: 8 to 9 | Levels involving deployment |
Table 2. Test, Inspection and Measurement Potential Solutions
|
| EXPECTED TRL LEVEL | |||
TECHNOLOGY ISSUE | POTENTIAL SOLUTIONS | TODAY (2023) | 3 YEARS (2026) | 5 YEARS (2028) | 10 YEARS (2033) |
[Equipment] Electrical Testability | Existing machine development (software and mechanics) | 6 | 8 | 9 | 9 |
| More comprehensive testing with software and hardware upgrades | 5 | 6 | 8 | 9 |
| New testing machine development (e.g., non-contact, etc.) for smaller dimensions, finer pitch, speed, data handling… | 5 | 5 | 6 | 8 |
[Equipment] Measurability | Increase in-process automated measurement and feedback for control of machine and chemical parameters (close-loop, realtime) | 5 | 5 | 6 | 8 |
| Improve ML to reduce variation and optimize process | 4 | 5 | 6 | 8 |
| AI utilized to optimize machine control and data handling | 3 | 4 | 5 | 6 |
[Equipment] Back Drill | Existing machine development (software and mechanics) | 6 | 8 | 9 | 9 |
| More comprehensive testing with software and hardware upgrades for i.e., impedance | 5 | 5 | 6 | 9 |
| New testing machine development for smaller dimensions, finer pitch, speed, data handling | 4 | 5 | 6 | 8 |
| Eliminate need for backdrill completely with zero-stub design (including in HDI) | 5 | 6 | 7 | 8 |
[Equipment] Inspection (AOI & AVI) | ML improvements to reduce false calls, capability for both sides | 6 | 7 | 8 | 9 |
| HW and SW development to reduce false calls, capability for both sides | 6 | 7 | 8 | 9 |
| Inspection machines optimization and customization | 5 | 7 | 8 | 9 |
[Data & Protocols] Automation (HW & SW) + Traceability | In-line measurement and test with automated feedback/adjustment for the process | 6 | 7 | 8 | 9 |
| Comprehensive testing, including product test, of individual units produced, including product tracing | 5 | 6 | 7 | 8 |
[Data & Protocols] Test protocols and procedures | Full, accurate electrical characterization of the net and node (more than just open and shorts), at product level | 6 | 7 | 8 | 9 |
| High-accuracy semi-conductor-level line probes for smaller feature sizes, with non-contact testing | 4 | 5 | 6 | 8 |
[Reliability] Accelerated Test for Product Function and Reliability | System environment and aging emulation combined with high-accuracy rate-of-rise and continuity resistance testing | 4 | 4 | 6 | 7 |
[Reliability] Failure Analysis | Surface analysis (electron spectroscopy for chemical analysis (ESCA), AUGER, scanning electron microscopy/energy dispersive X-Ray (SEM/EDX)) | 5 | 6 | 8 | 9 |
| FIB | 5 | 6 | 8 | 9 |
| XPS | 5 | 6 | 8 | 9 |
| Simulation of soldering process (shadow moiré) | 5 | 6 | 8 | 9 |
Conclusions
With ever increasing developments in artificial intelligence, augmented reality, connected factories and robotics, the future PCB factory must keep pace to effectively compete since automation is becoming a key component of company differentiation and efficiency. Furthermore, advances in field simulation testing are necessary to have successful certification of product quality over increased lifetimes.