In today's technological landscape, semiconductor packaging plays a crucial role in chip manufacturing, ensuring both performance and reliability. But how exactly does traditional packaging transform raw wafers into market-ready chips? This article explores the complete traditional packaging workflow, revealing the intricate technical processes involved.
1. Wafer Thinning Process
The first step in traditional packaging involves wafer thinning. Through backside grinding, the wafer thickness is reduced from 600-800μm to just tens of micrometers, enabling smaller chip sizes to meet packaging requirements. This thinning process not only enhances thermal dissipation but also improves electrical performance by reducing parasitic capacitance and conduction resistance. However, excessive thinning risks wafer fracture, making the CMP (Chemical Mechanical Planarization) process critical for maintaining structural integrity.
2. Dicing Technology
After thinning, the wafer undergoes dicing. A protective blue tape is applied to prevent damage during this process. While mechanical dicing was historically common, its precision limitations and slow speed have led to widespread adoption of laser cutting. Laser dicing comes in two forms: full-cut (faster but generates heat) and stealth-cut (creating internal micro-cracks to avoid surface damage, ideal for ultra-thin wafers). Plasma dicing has also emerged as a high-speed, low-damage alternative for small-sized chips.
3. Die Attach Process
Following dicing, individual dies are bonded to packaging substrates using one of three methods:
- Adhesive bonding: Epoxy resin provides strong adhesion through thermal curing
- Solder bonding: Molten solder connects die to substrate
- Eutectic bonding: More complex but offers superior thermal conductivity
Precise die placement is crucial to prevent chip failure from misalignment.
4. Wire Bonding
Wire bonding creates electrical connections between die and substrate. Material selection (gold, silver, copper, or aluminum) significantly impacts connection quality. The process combines heat, pressure, and ultrasound to break surface oxide layers and form stable bonds. While gold offers superior performance, cost considerations have increased adoption of copper and aluminum for mid-to-low range products.
5. Cleaning and Optical Inspection
Post-bonding, chips undergo thorough cleaning and inspection using low-power microscopes and Automated Optical Inspection (AOI) systems. AOI enables quantitative defect detection across multiple stages:
- Wafer inspection
- Die surface defect detection
- Bonding and encapsulation quality checks
6. Molding Process
Encapsulation represents a critical phase in traditional packaging. While cost-effective plastic molding dominates consumer applications, ceramic and metal packaging remain essential for aerospace and military uses. The process involves injecting epoxy molding compound into precise molds to protect the chip.
7. Deflashing, Post-Curing, and Ball Attachment
Deflashing removes excess material through weak acid immersion and high-pressure washing. Post-curing then enhances the molding compound's mechanical strength. For BGA (Ball Grid Array) packages, precise solder ball placement ensures optimal electrical connections.
8. Plating and Forming
Chemical plating (typically tin) improves conductivity and corrosion resistance on package leads. The framework then undergoes cutting and forming to accommodate different package types.
9. Final Testing and Marking
Completed packages undergo rigorous Automated Test Equipment (ATE) verification to ensure functionality meets specifications. Approved units receive laser marking for identification and traceability.
10. Shipping
The final step involves packaging tested products according to customer requirements, with shipping efficiency directly impacting market performance.
Traditional semiconductor packaging represents a complex, interdependent sequence where each step critically impacts the final product's performance and reliability. As technology advances, new packaging innovations continue to emerge—a topic we'll explore in future coverage.