Datasheet

102
www.lairdtech.com
103
www.lairdtech.com
EMI ESSENTIALSEMI ESSENTIALS
AUTOMATED FORM-IN-PLACE
EMI GASKET TECHNOLOGIES
INTRODUCTION
Laird form-in-place is an automated system for dispensing
conductive elastomer EMI shielding and grounding gaskets onto
metal or plastic substrates. Form-in-place is particularly well
suited for cellular phones, PDAs, PC cards, telecom base stations,
radios, and many other compartmentalized cast or plastic
enclosures and packaged electronic assemblies.
Utilizing programmable 3-axis CNC dispensing equipment,
the compound is dispensed accurately onto the substrate and
creates a secure bond during the curing process. The repeatable
computer-controlled dispensing pattern insures consistency
between parts and rapid part program changes. In addition, it
supports all levels of volume – from prototyping to high-volume
electronic component production – via the use of one or multiple
dispensing heads. The system is programmed to apply custom
gasket congurations onto parts, to form multiple levels on the
part, and on slopes up to approximately 70°.
Laird RXP compounds are Room Temperature Vulcanizing
(RTV) elastomers and HXP compounds are High Temperature
Vulcanizing (HTV) elastomers, both lled with proprietary
conductive particles. Dispensed gasket beads of RXP compounds
may be handled in 3 hours, and are cured in 24 hours, under
conditions of standard temperature and 50% Relative Humidity.
Dispensed gasket beads of HXP compounds can be handled
after the materials are cured in an oven. The compounds have
a working compression range from 10% to 50% of the gasket
height, with a recommended design compression of 30% against
a mechanical compression stop. Our product is designed to
support low closure forces and is compatible with plastic, metal,
and plated or chromate nished substrates.
The required force to compress a given bead is a function of the
compound and the gasket size; i.e. smaller gaskets require less
force than larger gaskets. Please refer to our technical data for
details. Gaskets are dispensed on substrates within a placement
tolerance of ± 0.001 inches and gasket cross-sectional tolerances
from ± 0.003 to 0.007 inches. Refer to Table 1 on page 104 for
typical gasket dimensions and tolerances. As a normal course of
equipment operations, starting points and termination ends of the
gaskets will have proles that are approximately 25% larger than
the running gaskets.
FORM-IN-PLACE GASKETING
FEATURES AND BENEFITS
• Form-in-place gasketing offers a total cost savings in the
form of reduced raw materials, labor or assembly time
• Room temperature cure gasketing materials eliminate the
need for costly heat curing systems, allowing the use of
inexpensive plastic or metal substrates
• Single-component compounds eliminate the need for mixing
ingredients, thereby shortening production cycles and
eliminating related waste
• Easy to program operating system allows for quick part-to-
part change-over, minimal tooling investment for new designs,
and prototype development in 24 to 48 hours
• High shielding effectiveness: 85–100 dB up to 10 GHz
• The dispensing system supports prototyping and high volume
production schedules in a space saving 4’ x 3’ [12 sq. ft.] (1,2
m x 0,9 m [1,1 sq. m]) footprint
• Form-in-place gaskets provide more critical packaging space
for board level components and smaller package dimensions
• Excellent adhesion on a wide variety of metal and plastic
substrates including:
- aluminum and other casting alloys
- stainless steel
- nickel copper plating (on plastics)
- copper, silver, and nickel lled paint (on plastics)
• Low compression force makes SN compounds an
excellent selection where the mating surfaces lack
mechanical stiffness
TYPICAL APPLICATION FOR FORM-IN-PLACE GASKETS:
ON A SIDE ON A RIDGE IN A GROOVE ON A FLAT
SURFACE
Automated dispensing of compound is
controlled by sophisticated computer software,
which is user-friendly and easy to work with.
SPECIALTY PRODUCTS
ELECTROCOAT™
ElectroCoat is a thin, exible surface coating consisting of a
silver-lled silicone elastomer. The versatile coating can be easily
applied to die-cut or molded foams for both gasket and non-
gasket applications. It can also be applied to molded or extruded
elastomers, other polymers, and a wide range of other materials.
• Excellent shielding effectiveness — greater than 90 dB
measured by transfer impedance
• Solid, continuous, conductive coating over the entire gasket
surface, including the inner die-cut surfaces of foam gaskets
• Coated foam gaskets have very low compression force
• Exceptionally wide compression range from 10% to 70%
deection to accommodate uneven gaps in enclosure
housings
• Flexible coating withstands gasket compression with no
decrease in shielding effectiveness after 1000 cycles of 40%
compression
• Extruded proles shown on pages 87-92 are available with
neoprene core.
ORDERING INFORMATION
1. Determine if PSA is needed. If so, replace the 5th digit in the
part number with “9”.
2. Select desired core material from Table 1 and insert in place
of YY.
3. Select two digit ElectroCoat from Table 2 and insert in place
of ZZ.
4. A unique custom identication number will be assigned by
sales.
8550 -X XXX -YY -ZZ
Standard
Series
Number
9
w/PSA
Unique identication
number assigned
by Laird
Core
Material*
ElectroCoat
(Coating
Material)
TABLE 1
YY # CORE MATERIAL*
50 Silicone Foam
51 Solid Silicone
52 Neoprene Foam
TABLE 2
ZZ COATING # MATERIAL
10 Silver/Silicone
* Other core materials may be available.
Consult Laird sales department.