LINQBOND UF3550R | Reworkable Underfill


Main features
  • Low stress, high fatigue and crack resistance
  • Low viscosity, solvent-free
  • Fast cure

Product Description

UF3550R is a reworkable one-component epoxy adhesive designed for electronic device bonding. It is easy to use and suitable for various electronic components, including casting and sealing. This resin cures quickly at high temperatures, reducing working time and increasing efficiency simultaneously.

UF3550R forms tough, strong structural bonds with excellent shear, peel, and impact strength. The resin's durability is exceptional, passing numerous environmental tests. When used for underfilling CSP and BGA chips, it buffers the expansion and contraction stress of solder ball contacts and mitigates the shear force generated by reaction forces during drop tests.

Product Family
UF3550R  
50ml syringe 30ml syringe 10ml syringe

Catalog Product

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Packaging
TDS, SDS & Technical documents

Technical Specifications

General Properties
Pot Life
Pot Life
Pot life is the amount of time it takes for the viscosity of a material to double (or quadruple for lower viscosity materials) in room temperature after a material is mixed.

It is closely related to work life but it is not application dependent, less precise and more of a general indication of how fast a system is going to cure.
 168 hours
Specific Gravity
Specific Gravity
Specific gravity (SG) is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume.

For liquids, the reference substance is almost always water (1), while for gases, it is air (1.18) at room temperature. Specific gravity is unitless.
 1.16
Work life @25°C
Work life @25°C
Work life is the amount of time we have to work with a material until it is no longer able to be easily worked and applied on a substrate.

It is based on the change in viscosity and it can rely on the application requirements.
 168 hours
Shelf Life
Shelf Life
Shelf life is the amount of time after manufacturing that a product is guaranteed to retain its properties.

It differs vastly per product and it is based on temperature and storage conditions.

The properties can be guaranteed for the temperature and time range indicated on the TDS since those are the ones tested to be the best for the product.
Shelf Life @ -20°C 243 days
Physical Properties
Viscosity
Viscosity
Viscosity is a measurement of a fluid’s resistance to flow.

Viscosity is commonly measured in centiPoise (cP). One cP is defined as
the viscosity of water and all other viscosities are derived from this base. MPa is another common unit with a 1:1 conversion to cP.

A product like honey would have a much higher viscosity -around 10,000 cPs-
compared to water. As a result, honey would flow much slower out of a tipped glass than
water would.

The viscosity of a material can be decreased with an increase in temperature in
order to better suit an application
 550-850 mPa.s
Electrical Properties
Dielectric Constant
Dielectric Constant
Dielectric Constant (k), commonly known as relative permittivity, is a number relating the ability of a material to carry alternating current to the ability of vacuum to carry alternating current.

It determines the ability of an insulator to store electrical energy and is the ratio of electric permeability in vacuum against the electric permeability of a material.

The lower the dielectric constant (κ) and dissipation factor, the less energy is absorbed from an electric field, making it a much better insulator.

It is a dimensionless property that can be affected by various factors such as the
thickness uniformity of a material, insufficient contact between the sample and electrodes, water adsorption and contact resistance.
Dielectric Constant @ 1000 kHz 3.4
Volume Resistivity
Volume Resistivity
Volume resistivity, also called volume resistance, bulk resistance or bulk resistivity is a thickness dependent measurement of the resistivity of a material perpendicular to the plane of the surface.
 4.5x1015 Ohms⋅cm
Mechanical Properties
Storage (DMA) Modulus
Storage (DMA) Modulus @ 25°C 2 N/mm2
Thermal Properties
Coefficient of Thermal Expansion (CTE)
Coefficient of Thermal Expansion (CTE)
CTE (Coefficient of thermal expansion) is a material property that is indicative of the extent to which a material expands with a change in temperature. This can be a change in length, area or volume, depending on the material.

Knowing the CTE of the layers is helpful in analyzing stresses that might occur when a
system consists of an adhesive plus some other solid component.
Coefficient of Thermal Expansion (CTE), α1
Coefficient of Thermal Expansion (CTE), α1
CTE α1 (alpha 1) is the slope of the Coefficient of thermal expansion in a temperature range below the Glass transition temperature (Tg).

It explains how much a material will expand until it reaches Tg.
 60 ppm/°C
Coefficient of Thermal Expansion (CTE), α2
Coefficient of Thermal Expansion (CTE), α2
CTE α2 (alpha 2) is the slope of the Coefficient of thermal expansion in a temperature range above the Glass transition temperature (Tg).

It explains the extent to which a material will expand after it passes Tg.
 215 ppm/°C
Glass Transition Temperature (Tg)
Glass Transition Temperature (Tg)
The glass transition temperature for organic adhesives is a temperature region where the polymers change from glassy and brittle to soft and rubbery. Increasing the temperature further continues the softening process as the viscosity drops too. Temperatures between the glass transition temperature and below the decomposition point of the adhesive are the best region for bonding.

The glass-transition temperature Tg of a material characterizes the range of temperatures over which this glass transition occurs.
 35 °C

Additional Information

Instructions for Use:

  1. Before use, thaw the product to reach room temperature for 1–2 hours. The syringe should be placed vertically while thawing. Keep the container airtight until room temperature is reached.

  2. Ensure the surface to be bonded is clean and free of contaminants like dirt, grease, or mold release agents. A simple solvent wipe is often sufficient.

  3. Cure time may vary based on the actual part geometry, material volume, and equipment. It is recommended to test on actual parts and equipment.

  4. For large-scale applications, consider a staged curing process: start with a lower temperature pre-cure, followed by a full cure at a higher temperature to effectively manage heat release.

  5. Cool down gradually after curing to minimize thermal stress.

  6. The epoxy cannot be refrozen once exposed to room temperature.

 

Rework Process:

  1. Component Removal. Component solder joints must be heated above their reflow temperature (260°C to 280°C). At this temperature, the underfill will be soft and easy to remove. The component may then be pulled or removed by twisting or with a use of a vacuum pick-up nozzle.

  2. Site Preparation. After component removal, cleaning of residues may be done by the following methods

    • Scraping. Heat the site to 250°C to 300°C and scrape off the underfill carefully avoiding damage of pads on the substrate. Alternatively, heating can also be done from the bottom of the substrate.

    • Rotating Brush. Apply a sufficient amount of pressure onto the brush to clean the residues. Care should be taken to avoid damage to the substrate.

  3. Component Replacement. Isopropanol or a flux pen may be used to ensure no residue remains on the circuit board after cleaning. Brush solder paste or flux on the board and align the new component using a vacuum and reflow using hot air. Underfill will likewise be applied followed by the cure step.

 

Storage and Handling

Store and transport below -5°C Temperature. Keep away from moisture and heat sources. It is strictly forbidden to store in outdoor environments.