Applications

The Scanning Acoustic Microscope (SAM) plays a critical role in Plastic Ball Grid Array (PBGA) packaging. It ensures packaging quality and reliability through non-destructive imaging of the internal packaging structure. Its main applications are as follows:

1. Solder Joint Quality Inspection

Detects solder joint defects between the chip and substrate, such as cold solder, voids, cracks, or insufficient solder. By analyzing differences in the energy of ultrasonic waves reflected at material interfaces, abnormal soldering areas can be precisely located.

2. Delamination Defect Identification

Identifies delamination between the plastic encapsulant and the chip, substrate, or copper wires. Ultrasonic waves reflect strongly at delamination interfaces (air gaps), generating clear C-scan images that visually display the location, area, and morphology of delaminations.

3. Void Defect Detection

Finds micro-voids inside the plastic encapsulation material or at interfaces. These voids appear as bright highlight signal points in acoustic images. Their size and distribution density can be evaluated via C-scan or T-scan modes.

4. Material Interface Integrity Assessment

Analyzes the bonding state between different material layers (e.g., chip, solder, substrate, plastic encapsulant). Differences in the response of ultrasonic waves to interfaces of materials with varying acoustic impedances can reveal potential poor bonding or contamination issues.

5. Technical Advantages Over Traditional Methods

Non-destructive: Requires no physical cutting or chemical etching, preserving sample integrity and electrical performance.

High-resolution imaging: Provides micron-level precision internal 2D (C-scan) or 3D tomographic images for precise defect localization.

Quantitative analysis: Accurately measures defect area, depth, and position, supporting quality classification standards.

Efficiency and applicability: Suitable for mass production line testing. More sensitive to interface delamination compared to destructive methods (e.g., sectioning) or X-ray inspection.

6. Progress in Domestic Production

Chinese enterprises have achieved significant breakthroughs in SAM core technology, breaking foreign monopolies.

Jiao Cheng Ultrasonic: Developed 2.5D/3D advanced packaging SAM, mastering high-frequency sound generation, signal processing, and imaging algorithms.

Shan Tou Ultrasonic: Independently developed the CTS-SAM series with self-developed high-frequency pulse transceivers, achieving full localization of core components.

Core Technology Breakthrough: Domestic SAMs have exceeded 100 MHz operating frequency, reaching up to 175 MHz, enabling micron-level defect detection.

Market Impact: Domestic equipment is 40% lower in price than imported brands, accelerating penetration in the mid-to-low-end market and supporting the localization of semiconductor advanced packaging testing.