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LOCTITE ECCOBOND UF 3820

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

Reworkable uunderfill before and after cleaning

Main features

High Tg
Easy rework
Stable electrical performance

Product Description

LOCTITE ECCOBOND UF 3820 reworkable underfill is specially designed for CSP, WLCSP and BGA applications. It is formulated to cure quickly at moderate temperatures to minimize stress to other components. This material's high glass transition temperature and high fracture toughness enables excellent protection of solder joints during thermal cycling.

LOCTITE ECCOBOND UF 3820 is a high TG, easy to rework epoxy that cures fast at moderate temperatures. It is capable of flowing at room temperature and offer high fracture toughness and excellent thermal cycle performance.

Cure Schedule

10 minutes @ 130°C
5 minutes @ 150°C or
3 minutes @ 160°C

Technical Specifications

General Properties

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	180 days

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.

1.24

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

Mechanical Properties

Storage (DMA) Modulus
Storage (DMA) Modulus @ 100°C	2,070 N/mm2
Storage (DMA) Modulus @ 200°C	25 N/mm2
Storage (DMA) Modulus @ 25°C	2,560 N/mm2

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
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.	1.1
Viscosity	340 mPa.s

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.	51 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.	172 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.

133 °C

Additional Information

Why do we need a reworkable underfill?

It is desirable to have a material that is re-workable:

In production where expensive mother boards can be repaired.
At the end of the assembly process (finished part).

This way we can avoid damage that can occur by:

Component removal /de-bonding
Surface cleaning/scraping of remaining underfill on board

The rework process is fairly straightforward. We need to locally go above the reflow temperature of the solder and then mechanically remove the component