The Critical Role of Fully Automated Probe Card Testing in Semiconductor Manufacturing

In semiconductor testing, fully automated systems manage every step of the process. Each phase of integrated circuit (IC) production is costly, making it essential to identify defective dies early in the production cycle. This ensures cost optimization and scalability in manufacturing.

The production of wafers involves a meticulous, step-by-step process to create electronic circuits. In simplified terms, multiple circuits—often hundreds or thousands—are fabricated on a single semiconductor wafer during IC manufacturing. These circuits are then equipped with soldering bumps or prepared for wire bonding, followed by singulation and encapsulation in a molding package.

Given the delicate and fragile nature of wafers, manual handling is impractical. Automated systems are deployed across all stages of semiconductor manufacturing and testing to ensure precision and efficiency. These systems employ advanced electrical and inspection technologies to select appropriate wafers for further processing. Electrical testing of individual circuits is conducted using Automatic Test Equipment (ATE), which connects to the wafers via a probe card. These tests verify analog, digital, and mixed-signal functionalities.

Wafer testing is a critical step in IC production, as it validates the functionality of each semiconductor device and identifies defective ones. Known as “Known Good Die” (KGD), functional circuits are marked and advanced to subsequent production stages. The testing process generates a digital map to indicate the pass/fail status of each die. This step is indispensable, considering the fragility and microscopic scale of silicon wafers, which have a thickness of about 0.4–0.5 mm and diameters ranging from 4 to 12 inches. Each die’s circuit dimensions are measured in microns, underscoring the need for precision.

Probe Card Testing

Probe card testing systems are designed to perform various tests, including:

1. Bare Board Test (BBT): Testing unassembled MLO and PCB boards.
2. Continuity Testing: Verifying connections between the MLO and PCB.
3. In-Circuit Testing (ICT): Testing assembled PCBs for circuit continuity and functionality.
4. Functional Testing: Assessing the performance of the entire probe card assembly.
5. Integrity Connection Certification Test (ICCT): Ensuring reliable connections between the MLO and PCB.

To ensure cost-effectiveness and efficiency, automated systems must offer high flexibility and swift setup times. A comprehensive solution requires mechanical adaptability paired with user-friendly software, attributes central to advanced flying probe systems.

Advanced Testing Specifications

Modern systems for probe card testing handle incredibly fine specifications:

• Pad Sizes: Ranging from 40–80 µm on the MLO.
• Bump Diameters: Between 250–500 µm.
• Probe Pitch: Approximately 70 µm with ultra-fine movement resolution of 1 µm.

To protect delicate boards, probing force must be carefully controlled to prevent damage, such as scratches or marks. Vertical Z-axis movement during probing minimizes the risk of pad damage, ensuring smooth contact without leaving traces.

Probing Variations

• MLO Testing: Probes with diameters around 15 µm and contact forces of 2–6 grams are ideal.
• PCB Testing: Probes generally have diameters of 30 µm.

After assembly, ICCT tests are conducted to confirm all MLO-PCB connections are intact.

Comprehensive Testing Requirements

A robust probe card testing system should handle the following tests:

• Electrical Tests: Open/short circuits, ultra-fast capacitive tests, Kelvin tests, and leakage tests (current values < 1 nA).
• Voltage Isolation: Up to 1000 volts.
• Parametric Testing: Evaluating passive components (e.g., resistors, capacitors, inductors) and active components (e.g., Zener diodes).
• Functional Component Testing: Powering up boards to test integrated circuits, relays, and other embedded components.

The goal is to deliver accurate, efficient, and comprehensive testing capabilities, ensuring reliability and performance in IC production.

Seica’s Pilot VX HR XL: A Leading Solution

Seica’s Pilot VX HR XL platform is an advanced flying probe system designed to address the diverse needs of probe card testing. This system integrates cutting-edge hardware and software to provide a turnkey solution for all phases of testing.

Key Testing Capabilities

• Pre-Assembly Testing: Validates MLO and PCB boards individually.
• In-Circuit and Functional Testing: Assesses PCBs post-assembly.
• Final Testing: Verifies the integrity of the fully assembled probe card.

For final tests, the system performs ICT to evaluate every connection between the MLO and PCB interface. The platform can account for variations in network resistance and component placement, enhancing testing accuracy.

Pilot VX HR Hardware Highlights

1. Vertical Architecture: Facilitates easy loading, including round probe cards.
2. Independent Axes: Features 8 axes with 1 µm movement resolution.
3. Probe Configurations: Includes standard and high-resolution probes, ensuring flexibility.
4. Large Testing Area: Accommodates boards up to 800×650 mm.
5. Planarity Control: Utilizes a laser sensor to detect defects like chip tombstoning.
6. Soft Landing Profile: Minimizes contact force, protecting delicate surfaces.

Advanced Measurement Capabilities

Seica’s system integrates real-time measurement technologies powered by DSP. This enables high-speed, precise resistive, capacitive, and inductive tests. Unique features include:

• Ultra-Fast Capacitive Testing: Reduces testing time without compromising accuracy.
• High-Resolution Cameras: The front camera offers 12 MP with 0.9 µm optical resolution, while the rear camera provides 10 µm resolution. Both cameras include motorized focus.
• Automatic Stamper Option: Marks boards pass or fail using soft-kiss technology.

VIVA Software Integration

The VIVA software platform simplifies test program generation and execution. Key features include:

• Automated Program Generation: Supports BBT and ICT test creation using CAD/CAM data in formats like IPC-D356A.
• QUICK TEST (QT): Provides a graphical interface for creating functional tests without deep technical knowledge.
• Remote Management: Offers web-based control, enabling centralized operation and compliance with Industry 4.0 standards.

Conclusion

Wafer and probe card testing play a pivotal role in ensuring the quality and reliability of IC production. Advanced systems like the Pilot VX HR XL exemplify how innovation in automation and precision can meet the rigorous demands of modern semiconductor manufacturing. These systems not only streamline testing but also enhance scalability and cost efficiency.