Overcoming the challenge of testing electromechanical assemblies

When it comes to mechatronics, small defects can trigger big failures. A single solder crack on a printed circuit board (PCB), a hairline fracture in a mounting bracket, tolerance errors, and software compatibility issues can bring down satellites and stop robots in their tracks. Here’s why electromechanical assembly testing can be the hardest to coordinate and the most important to get right. 

Whether it’s precision robotics, medical infusion pumps, or automotive control units, manufacturers and OEMs cannot afford to treat electromechanical assembly testing as an afterthought.

Faults hidden deep within the complex interplay of mechanical assemblies, electronic components, and software are among the hardest to detect. And testing gaps often only become visible when it’s too late. Testing and testability must be designed into every stage of development.

What are the major testing challenges for electromechanical assemblies?

Managing testing complexity

Electromechanical systems merge multiple engineering disciplines. Faults can originate from:

• Electronic circuits: solder joints, PCB assembly layout errors, electronic component failures.
• Mechanical assemblies: misalignments, torque inconsistencies, or material fatigue.
• Software control loops: incorrect feedback processing or signal delays.

An effective testing approach must consider not only the individual elements but how they interact dynamically.

Uncovering hidden defects

Defects that pass traditional visual inspections and functional testing can surface later under stress. These can include:

• Micro-cracks in solder joints beneath BGAs on a printed circuit board assembly.
• Internal fractures in plastic or mechanical components
• Intermittent contact issues in cable assemblies and wire harness assemblies

Identifying these potential weak spots requires advanced inspection methods that look beyond the surface, such as X-ray inspection.

Ensuring real-world reliability

Electromechanical products often operate in challenging environments:

• Automotive systems endure constant vibration and thermal cycling.
• Industrial equipment faces mechanical loads and dust ingress.
• Medical devices demand precision under temperature shifts and sterilisation 

Your testing methods need to reflect these real-world conditions - ensuring the ruggedisation of designs.

Designing for testability (DfT): The critical foundation

Testing challenges often trace back to design decisions. The right manufacturing partners will embrace Design for Testability (DfT) as a core principle of DfX, extending beyond PCBs to the entire electromechanical assembly project. Key DfT practices include:

• Electrical access points: Test pads and probe points for non-intrusive circuit validation.
• Modular subassemblies: Breaking systems into testable units (e.g., motors, sensors, actuator modules) before full electromechanical assembly service integration.
• Mechanical access for inspection: Designing mechanical assemblies to allow for torque measurements, alignment checks, and movement analysis.
• Built-in diagnostic feedback: Integrating position, force, and current sensors that assist both in-field performance monitoring and end-of-line testing.

Without DfT, the most sophisticated testing technologies can be rendered ineffective due to limited physical access or poor fault isolation.

The ideal testing process for electromechanical assemblies

The right manufacturer will implement a multi-stage testing strategy designed to uncover faults across electronic, mechanical, and environmental dimensions. This process minimises production defects, reduces field failures, and accelerates time-to-market.

Real-world functional testing

Functional testing should simulate actual operating conditions, moving beyond simple validation to assess system performance under load:

• Torque and load testing: Validating motor performance under varying torque conditions.
• Closed-loop system checks: Evaluating sensor feedback and electronic control unit responses during mechanical movements.
• Current signature analysis: Detecting mechanical friction, motor imbalance, or gear wear through current consumption patterns.

This ensures that electromechanical interactions are validated as a whole system.

Advanced inspection techniques

Surface inspections alone are insufficient. The right manufacturer will employ advanced testing methods to detect hidden defects:

• X-ray inspection: Revealing solder fractures or misaligned components beneath the circuit board surface.
• Acoustic emission testing: Identifying internal structural defects, such as cracks or bearing wear, during operation.
• Force and torque measurement: Ensuring mechanical systems function correctly under physical stress. 

Combining electrical testing, mechanical evaluation, and structural assessments minimises the risk of latent defects.

Flexible testing for low-volume and complex 

Electromechanical products often involve high-mix, low-volume production, making traditional ICT fixtures costly and inflexible. Manufacturers capable of rapid adaptation use:

• Flying probe testing (FPT): Allowing non-contact electrical testing without the need for custom test fixtures.
• Custom functional test rigs: Combining electrical and mechanical validation in one setup, adaptable to product variants.

Flexibility in testing infrastructure is essential for manufacturers supporting product development cycles or multiple product configurations.

Environmental and lifecycle testing

Leading manufacturers incorporate environmental stress validation into both product development and production:

• HALT (Highly Accelerated Life Testing): Exposing prototypes to extreme conditions to reveal weak points early.
• HASS (Highly Accelerated Stress Screening): Screening production units for early-life defects.
• Soak testing: Running assemblies for extended periods under load to validate endurance.

Environmental testing ensures electromechanical assemblies maintain performance over their entire lifespan.

Testing as a competitive advantage

In electromechanical systems, rigorous testing is not merely a safeguard—it is a strategic advantage. An ideal manufacturer recognises that robust validation processes:

• Prevent costly product recalls and warranty claims.
• Accelerate time-to-market by catching issues early.
• Build brand reputation through product reliability.
• Support innovation by enabling rapid iteration and testing.

Test capabilities; what to look for in an EMS partner

OEMs seeking a manufacturing partner for electromechanical assemblies should prioritise suppliers with:

• Expertise in both electrical and mechanical system testing.
• A DfT philosophy baked into their engineering process.
• Multi-domain testing capabilities, including electrical, mechanical, and environmental validation.
• Advanced inspection technologies, from X-ray analysis to real-time torque measurements
• Flexible, automated test systems capable of supporting both prototype and production volumes
• Robust supply chain quality controls and traceability systems.
• Advanced manufacturing processes that foreground quality assurance to prevent failure

Bespoke testing strategies - a mechatronic case study

ESCATEC, as a leading EMS provider, collaborated with a global test and measurement manufacturer to develop a customised testing strategy for a complex control cabinet used in coordinate measurement machines (CMMs). 

Given the precision demands of the industry, a multi-stage testing process was implemented to ensure reliability from assembly to deployment.

The main PCBA, a highly complex assembly, underwent flying probe testing to verify build quality and catch potential manufacturing defects early. Once integrated into a 19” rack enclosure, the functional testing phase validated that signals flowed correctly between the main board and the back panel. To ensure robust electrical integrity, cable assemblies were continuity tested before installation into the cabinet.

Before final deployment, PAT (Portable Appliance Testing) was carried out to verify electrical safety before applying mains power. A final functional test was then performed, ensuring seamless integration with the servo rack, power supply, and all subassemblies.

With projects like these, ESCATEC’s end-to-end design, build, and test capabilities provide OEMs with confidence in product performance, proving that testing is not just a checkpoint - it’s the foundation of reliability.

Conclusion

By choosing manufacturing partners with the skills to devise bespoke testing strategies using a range of in-house testing equipment, OEMs can mitigate risks, enhance product quality, and position themselves for long-term success in increasingly complex and demanding markets.