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Harmonization Code : 3907.30.00.90 |   Polyacetals, other polyethers and epoxide resins, in primary forms; polycarbonates, alkyd resins, polyallyl esters and other polyesters, in primary forms : Epoxide resins : Other
Main features
  • Snap curable
  • Halogen free
  • Reworkable

Product Description

LOCTITE ECCOBOND UF 3915 reworkable underfill is specially designed for WLCSP (Wafer level chip scale packages) and flip chip device applications. It is a Halogen free, one component underfill that can be snap cured @ 160°C.

LOCTITE ECCOBOND UF 3915 has a High Glass transition temperature of 125°C while also demonstrating high fracture toughness and excellent thermal cycle performance. It is electrically stable under thermal and humidity bias and it is compatible with most Pb free solders

Recommended Snap cure schedule

  • 7 minutes @ 160 °C
  • Alternate cure schedule

  • 20 minutes @ 130 °C OR
  • 10 minutes @ 150 °C
  • Product Family
    30cc Syringe

    Catalog Product

    Unlike other products we offer, the products listed on this page cannot currently be ordered directly from the website.
    Not Available Shipping in 8 - 12 weeks

    Technical Specifications

    General Properties
    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.
    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.
    24 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 @ -40°C 270 days
    Mechanical Properties
    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
    Viscosity 5,500 mPa.s
    Thixotropic index
    Thixotropic index
    Thixotropic Index is a ratio of a material s viscosity at two different speeds in Ambient temperature, generally different by a factor of ten.

    A thixotropic material s viscosity will decrease as agitation or pressure is increased. It indicates the capability of a material to hold its shape. Mayonnaise is a great example of this. It holds its shape very well, but when a shear stress is applied, the material easily spreads.

    It helps in choosing a material in accordance to the application, dispense method and viscosity of a material.
    Storage (DMA) Modulus
    Storage (DMA) Modulus @ 25°C 7,600 N/mm2
    Thermal Properties
    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.
    125 °C
    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.
    25 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.
    100 ppm/°C