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LOCTITE ABLESTIK ABP 8068TB

Harmonization Code : 3506.91.90.99 | Prepared glues and other prepared adhesives, not elsewhere specified or included; products suitable for use as glues or adhesives, put up for retail sale as glues or adhesives, not exceeding a net weight of 1 kg ; Adhesives based on polymers of headings 3901 to 3913 or on rubber; Other ; Other

Main features

Good workability
High thermal stability
Solder replacement

Product Description

LOCTITE ABLESTIK ABP 8068TB is a silver-filled semi-sintering die attach adhesive designed for semiconductor packages with high thermal and electrical requirements. It is formulated with a more enhanced resin bleed control than its predecessor LOCTITE ABLESTIK ABP 8068TA and it is designed to replace Pb Solder in Power and Low noise amplifier (RF SiP) type consumer applications.

LOCTITE ABLESTIK ABP 8068TB is designed to provide high adhesion and low stress which are essential for the thermal and reliability performances of high end power packages. The thermal performance of this material is comparable to that of a solder paste product (>100 W/mK thermal conductivity). It passes MSL 2A and MSL3 tests

LOCTITE ABLESTIK ABP 8068TB is not compatible with bare copper but it works fine and provides good sintering with Ag or Au electroplated Cu, Ag and PPF leadframes. It is an ideal solution for dies that are smaller than 2x2 mm and it can be fast and easily processed with standard die attach equipment

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	365 days

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.

16 hours

Chemical Properties

Extractable Ionic Content, after 20 hours
Chloride (Cl-) Chloride (Cl-) The amount of Chloride (Cl-) ion extracted from the product in parts per million (ppm)	20 ppm
Sodium (Na+) Sodium (Na+) The amount of Sodium (Na+) ion extracted from the product in parts per million (ppm)	1.5 ppm
Potassium (K+) Potassium (K+) The amount of Potassium (K+) ion extracted from the product in parts per million (ppm)	0.5 ppm

Moisture Absorption

Moisture Absorption
Moisture absorption shows the capacity of a polymer to absorb moisture from its environment.

Absorbed moisture can reduce the glass transition temperature and strength of a polymer and can also result in popcorning, unreliable adhesion or voids in the bond line due to moisture desorption or entrapment.

Moisture absorption should always be mentioned with the test conditions to provide a meaningful frame of reference.

Moisture absorption - 168h @ 85ºC | 85% RH

0.21 %

Mechanical 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
Viscosity	11,500 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.	5.5

Die Shear Strength Die Shear Strength Die Shear Strength is the force that has to be applied to the side of the semiconductor die before it shears from its mounting. Shear strength is measured for various die sizes, substrates and operating temperatures so check the Technical data sheet for your intended usage.
2x2mm @260°C	6.5 kgf
3x3mm @260°C	10.8 kg-f

Tensile Modulus Tensile Modulus Tensile modulus is a mechanical property that measures the stiffness of an elastic material. It is the slope of stress / strain curve of a material under direct tensile loading. It can be used to predict the elongation or elastic deformation of an object as long as the stress is less than the tensile strength of the material. Elastic deformation is caused by stretching the bonds between atoms and the deformation can be reversed when the load is removed. Tensile modulus is affected by temperature and is an important engineering attribute since we generally want to keep elastic deformation as small as possible.
Tensile Modulus @25°C	12,500 N/mm2
Tensile Modulus @150°C	1,100 N/mm2
Tensile Modulus @250°C	650 N/mm2
Tensile Modulus @-65°C	15,600 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.

25 °C

Thermal Conductivity

Thermal Conductivity
Thermal conductivity describes the ability of a material to conduct heat. It is required by power packages in order to dissipate heat and maintain stable electrical performance.

Thermal conductivity units are [W/(m K)] in the SI system and [Btu/(hr ft °F)] in the Imperial system.

100 W/m.K

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.	103 ppm/°C

Additional Information

LOCTITE ABLESTIK ABP 8068TB can be used for Screen printing. But what is the process and what should you be careful of?

What stencil material should we use?

We have found that it is easier to achieve good results with a metal stencil (50um thickness seems ideal), compared with screen printing with a mesh (which tends to give a lower thickness and a rougher surface to the adhesive). Laser cut stainless is OK for a quick feasibility study, but I would recommend electroformed Nickel for good quality , high volume manufacturing.

Bleeding under the stencil?

It might be caused by too hard stencil unable to make a perfect fit with the substrate, due to the surface morphology. Using a mesh screen with an emulsion backing would probably solve this, but bring other processing issues.

Are there dimples?

Those can be caused as the stencil separates from the substrate, pulling up the edges of the printed adhesive. This can be improved by polishing the stencil apertures. Lower viscosity ABP 8068TA may be also worth testing in parallel if you observe dimple effects (although 8068TA also has a high thixotropic index of 6 for dispensing purposes)

Recommendations for aperture reduction and post cure cooling rate?

Aperture reduction needs to be established by DOE trials, as it depends on component size, stencil thickness and customers inspection requirements. Regarding cooling rate, we do not believe this is critical, but thermal shock should be avoided. Normal practice is to allow parts to cool fairly slowly in the oven until below about 70C (when they are safe to handle).

What are the optimal Printing parameters?

Those will depend on the design of the print pattern and the equipment used, but the following will be a good starting point:

Print speed: 30 mm/s
Force: 12 kg
Print gap: The Print Gap should be set to Zero mm (stencil is in contact with substrate during print). And the Separation Speed (the rate at which the palette drops away from the stencil) should be set to 2 or 3 mm/sec. The Separation distance should be at least 2mm.
Squeegee material: Stainless is good. Rubber will deform into stencil opening & reduce the glue thickness. Rubber is good with a mesh screen, but not usually suitable for metal stencil.
Squeegee angle: Not really critical. Use what is available – typically 45 or 60 degrees.
Die placement force: This depends on the component size. Suggest to start with parameters for conventional silver filled die attach paste. Aim for BLT = 25 um after cure (and a minimum of 10um).