scope:

This document provides users of underfill material with guidance in selecting and evaluating underfill material for assembly solder joints second level interconnects. Underfill material is used to increase reliability of electronic devices by two methods: alleviate coefficient of thermal expansion (CTE) mismatch (between the electronic package and the assembly substrate) and/or increase mechanical strength. Underfill materials are also used for environmental protection, mechanical shock or vibration, and anti-tampering uses. Materials used in underfill applications should not adversely affect device reliability nor degrade electrical performance (e.g., ionic impurities). When correctly selected and applied, underfill material should increase the life of the assembly solder joints.

Types of underfill materials currently available in the market include:

• Capillary Flow Underfill

- Primary UFs (Package level not within the scope of this document)

- Secondary (Board level)

• No-Flow/Fluxing Underfill

- Thermal Compression Bonding (TCB) Epoxies (not within the scope of this document)

- Non-Conductive Paste (NCP)

- Non-Conductive Film (NCF)

• Removable/Re-Workable Underfill

• Corner Bonding/Glue Bonding

• Molded Underfill (not within scope of document)

• Wafer Applied Underfill (not within scope of document)

• Vacuum Underfill (not within scope of document)