Semiconductor Die Attach (Step 3)
Die attach is the process of mounting individual semiconductor dies onto a package substrate, lead frame, or interposer after dicing. It establishes the physical and thermal interface between the chip and its package, providing mechanical stability, thermal dissipation, and electrical connectivity for subsequent bonding steps.
Process Overview
- Purpose: Secure the die onto its package or carrier for electrical interconnection.
- Methods: Adhesive bonding (epoxies, films), eutectic solder attach, or sintered silver for high-performance applications.
- Sequence: Die pick-and-place ? attach with adhesive, solder, or sinter ? curing or reflow process.
- Integration: Critical for thermal performance and reliability; precedes wire bonding, flip-chip, or TSV connections.
Die Attach Techniques
| Method | Process | Advantages | Constraints |
|---|---|---|---|
| Epoxy Adhesive | Die is bonded with conductive or non-conductive epoxy; cured at elevated temperature. | Low cost; flexible; widely used in consumer devices. | Limited thermal conductivity; long curing times. |
| Eutectic Solder Attach | Gold-silicon or gold-tin solder reflow bonds die to package. | High reliability; strong mechanical and thermal performance. | High process temperatures; expensive materials. |
| Sintered Silver | Silver particles sintered under pressure form high-conductivity bond. | Excellent thermal/electrical conductivity; ideal for power and automotive devices. | Higher equipment cost; process control challenges. |
| Die Attach Films (DAF) | Pre-formed films laminated onto substrates before die placement. | Uniform thickness; good for thin dies; fast processing. | Less flexible for varied die sizes; specialized storage/handling. |
Major Equipment Vendors
- ASMPT (Singapore): Advanced die attach equipment for high-volume and advanced packaging.
- Kulicke & Soffa (U.S.): Die bonders, flip-chip bonders, and advanced packaging tools.
- Besi (Netherlands): Die attach platforms for automotive, power, and AI packages.
- Palomar Technologies (U.S.): Specialized die attach solutions for optoelectronics and defense.
Process Consumables
- Adhesives: Epoxy resins, silver-filled conductive adhesives, die attach films (DAF).
- Solders: Gold-tin, gold-silicon, lead-free alloys.
- Silver Pastes: For sintered silver attach in high-power devices.
- Carrier Substrates: Organic laminates, lead frames, or silicon interposers.
Cleanroom & Environment
- Typically performed in Class 1000 or less stringent assembly cleanrooms.
- Die placement precision must be controlled within microns for advanced packages.
- Thermal cure, sintering, or solder reflow steps require precise atmosphere control (N2, forming gas).
Advantages & Constraints
- Advantages: Provides both thermal and mechanical stability; multiple bonding options for different performance tiers.
- Constraints: Thermal management limitations in consumer-grade adhesives; cost of advanced methods like sintered silver; reliability under thermal cycling.
Market Outlook
Die attach is evolving with demand for advanced packaging in automotive, AI, and 5G applications. Sintered silver and die attach films are gaining traction for power semiconductors, EV inverters, and high-performance computing. Automation and precision placement are increasingly critical as chiplets and 3D packages proliferate.