BioSciences - Polysciences, Inc.

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Electronic Adhesives & Encapsulants
CONFORMAL COATING: Low viscosity polymer coating typically
spun or sprayed onto a device or semiconductor. These coatings
protect the devices from the environment or provide electrical
insulation value. They do not protect well against physical shock as
they are only a thin coating.
CTE (Coefficient of Thermal Expansion): How much a
material grows when heated (and shrinks when cooled). The unit
of measure is parts per million/per degree centigrade. The CTE
differences (CTE mismatch) among the materials in a semiconductor
package will cause stresses as the part is exposed to temperature
changes in its working life. In most cases, it is useful for an epoxy
connecting two materials to have a CTE that falls between the
CTE’s of the materials being joined.
CTE’s of Common Materials ppm/C
Silica 1
Silicon Die 2.5 to 4
Alumina 6.5
Gold 14
FR4 Substrate 14
Copper 17
BT Laminate 20
Solder Ball 25
Unfilled Polymer 60 or higher
CURE: Non-specific term that is widely used to mean the solidification
of a polymer. Curing can be accomplished by applying heat or UV
light. Several intermediate steps take place during curing that also
have non-specific definitions. When the outside layer of the liquid
forms a rubbery coating this is called skinning. When the entire
liquid material is solid, but has not yet achieved stable mechanical
properties this is called gelling. When the material reaches its final
mechanical properties it is said to be cured.
CURING PROFILE: Sometimes referred to as cure cycle or cure
schedule, defines the time and temperature required to change
the state of a material to achieve its best-desired performance
characteristics.
DAM: A wall of material around the perimeter of a device. The
dam is formed by dispensing a high viscosity material through a
single nozzle that traces a pattern around the device. The dam’s
main function is to contain a low viscosity fill material that is
applied to encapsulate the device.
DIE: A single semiconductor cut from a wafer.
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DIE ATTACH: Adhesive that bonds the semiconductor die to
the substrate. Can be thermally conductive or nonthermally
conductive.
DIELECTRIC CONSTANT: Ratio of the capacitance of a material
(materials that do not conduct electricity) to the capacitance of air.
A measure of the insulating strength of a dielectric material.
DIELECTRIC LOSS: Electric energy transformed into heat in
a dielectric subjected to changing electric fields. The amount of
electrical energy lost to the dielectric.
DSC (DYNAMIC SCANNING CALORIMETER): Analytical
instrument that measures the heat absorbed or released by a
material as it’s temperature is raised at a controlled rate. A significant
change in the graph of this measure indicates a chemical reaction
is occurring. This measure is used to determine the temperature
at which an epoxy material will change from liquid to solid. This
instrument also measures the percentage cure of epoxy materials.
DTA (DYNAMIC THERMAL ANALYSIS): DTA is an analytical
instrument used to measure the effects of temperature on the
performance of materials. It is key to determining the temperature
at which a material changes phase, such as from a glass-like
solid to a soft, rubbery condition. The temperature at which this
transition occurs is referred to as the glass transition temperature,
or Tg. This instrument can also measure modulus. It is an extension
to the older means of using a TMA (Thermal Mechanical Analyzer)
for some of these measurements.
ENCAPSULANT: A material that seals or covers a semiconductor
to provide mechanical and environmental protection. Typical
materials are: molding compound, glob top, dam & fill and potting
compound.
EPOXY: Family of thermosetting resins that are used as the media
for bonding and protecting semiconductor devices. The main
advantages of epoxy are the ability to form strong bonds to many
surfaces, low processing temperature and low cost. Epoxies come
in many variations with many different properties.
EPOXY ANHYDRIDE: Anhydride is the curing agent most
commonly used in semiconductor materials such as die attach
adhesive. As a curing agent, it not only causes the polymerization
reaction to occur, it becomes a part of the finished compound. The
nature of the anhydride reaction is such that it starts to cause the
epoxy to change to a solid (gel) at room temperature without the
addition of heat.