Single-Component Underfill

LETBOND® Single-Component Underfill Adhesives

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Description

The LETBOND® Single-Component Underfill series is a high-performance epoxy resin adhesive specifically developed for chip packaging such as BGA and CSP. It offers excellent permeability, reliability, and encapsulation reinforcement, effectively preventing moisture ingress while absorbing thermal stress and mechanical shock.

  • 3517: A high-strength type with moderate viscosity and rapid curing. It features high hardness and mechanical strength, making it ideal for single-use encapsulation requiring long-term reliability.
  • 3577: A reworkable type characterized by excellent toughness after curing. Its low-hardness design helps mitigate cracking and impact, making it suitable for high-value electronic products that require disassembly and repair.

Features

  • One-Component Design: Ready to use with no mixing required.
  • High Reliability: Exceptional moisture resistance and strength with low impurity levels to ensure no interference with electrical performance.
  • Superior Permeability: Capable of deep penetration into the gaps between chips and substrates for complete coverage.
  • Robust Encapsulation: Resistant to thermal cycling stress and drop-impact.
  • Reworkability: Supports component removal and maintenance through heating (Model 3577 performs exceptionally well in this area).
  • Environmental Compliance: Model 3577 is a solvent-free formulation meeting RoHS and halogen-free standards.

Applications

  • 3517: Used in encapsulation processes for smartphones, PCs, and LCD monitors that require high strength and environmental durability. It specializes in BGA underfill to provide reliable moisture proofing and impact resistance.
  • 3577: Applied to BGA and CSP packaging and reinforcement, particularly for server modules and communication equipment that require reworkability. It features excellent crack resistance to effectively buffer mechanical shock and thermal cycling stress.

Selection Specifications

Model Color Viscosity
(cps)		 Cure Time Hardness
(Shore)		 Tensile Strength
(MPa)		 Shear Strength
(MPa)		 Thermal Conductivity
(W/mK)
3517
Black
1,280 – 1,920
Gel: 16 sec (@ 150°C)
Full Cure: 10 min (@ 120°C)
D 84
30
16
0.22
3577
Black
800 – 1,200
Full Cure: 20 min (@ 130°C)
D 50
45
> 10
0.30

Notes:

  • The values above are for reference only; actual values are based on the Certificate of Analysis (COA) of the shipped batch.