CHOFORM

and ParPHorm

Robotically Dispensed

Form-In-Place EMI Gaskets

Customer Value

Proposition:

Parker Chomerics CHOFORM Automated EMI

Gasketing System is ideal for today’s densely

populated electronics packaging, particu-

larly where intercompartmental isolation is

required to separate processing and signal

generating functions. CHOFORM is direct-

ly dispensed on castings, machined metal

and conductive plastic housings and board

shields. It provides excellent electrical con-

tact to mating conductive surfaces includ-

ing printed circuit board traces. CHOFORM

is widely used in compartmentalized enclo-

sures and other tightly packaged electronic

devices in military, telecom, transportation,

aerospace and life science applications.

Product Features:

• Up to 60% space saved -ﬂanges

as narrow as 0.025” (0.76mm)

can be gasketed.

• More than 100 dB shielding

effectiveness from 200 MHz to 12

GHz with very small gasket beads.

• Excellent adhesion to common

housing substrates and coatings.

• Highly compressible gaskets,

ideal with limited deﬂection force.

• Quick turn-around of prototypes

and samples. Parts typically

prototyped and shipped within

several days and typically do

not require tooling.

With gasket dispensing primarily

software driven, CHOFORM technology

permits rapid prototyping, changes in

design, and production scale-up at

nominal cost. Its inherent ﬂexibility

accommodates batch runs or continuous

production, from ten to ten million

parts. Wide acceptance of the CHOFORM

automated gasket dispensing system

can be attributed to a successful blend of

manufacturing and materials expertise.

The CHOFORM technology combined

with a Parker Chomerics supplied metal

or conductive plastic housing or board

shield provides an integrated solution

ready for the customers’ highest level

of assembly. Individual compartment

shielding or grounding is often enhanced

by placement of a secondary EMI product

such as a short length of ﬁngerstock,

fabric over foam, conductive extrusion

gasket or a microwave absorber. Thermal

transfer from the printed circuit boards’

heat generating devices to a metal

housing wall or board shield can be

accomplished by placement of a soft

thermally conductive gap ﬁller, dispensed

thermal compound or gel.

The CHOFORM technology allows dispensing

of precisely positioned, conformable gaskets

in very small cross sections that free valuable

package space. They provide the lowest total

cost of ownership for small cross section

and complex pattern applications. Parker

Chomerics CHOFORM and ParPHorm

Form-In-Place (FIP) materials can reduce

installed cost of an EMI gasket by up to

60%. The durable, highly conductive seals

have low compression set, ensuring years

of effective EMI shielding and mechanical

performance.

Parker Chomerics has the

technology to support all of

these application needs in a one

stop integrated solution. Contact

Parker Chomerics Applications

for further details and assistance.

Excellent Shieiding Effectiveness, even in

small cross sections, shielding effectiveness

of CHOFORM gaskets exceeds 100 dB between

200 MHz and 12 GHz. Shielding performance

increases with cross sectional dimensions.

Results shown for various CHOFORM materials

were obtained using Parker Chomerics

standard bead size of 0.034 inch high by 0.040

inch wide (0.86 mm high by 1.0 mm wide)

Denser Packaging is Possible CHOFORM

gaskets can be applied to walls or ﬂanges as

narrow as 0.025” (0.76 mm), and don’t require

mechanical retention. Compared with groove

and friction-ﬁt designs, the positional accuracy

and self adhesive properties of CHOFORM

gaskets will typically save 60% or more space.

This frees additional board space, and allows

for smaller overall package dimensions.

Small Cross Sections, Complex Geometries

Virtually any gasket bead path can be

programmed using CHOFORM application

technology. In addition to simple straight

lengths, the system applies continuous 360

perimeter gaskets in combination with any

required number of internal subpaths that

form “T” joints wifh the perimeter seal. The

system produces reliable junctions between

bead paths that provide continuous EMI

shielding and environmental sealing.

Low Closure Force Not a Problem CHOFORM

gasket materials are ideal for low deﬂection

force designs, or those whose mating

surfaces have low mechanical rigidity.

Nominal deﬂection of 30% using a mechanical

compression stop is recommended. Deﬂection

below 20% or above 40% is not recommended.

An example of typical compression-deﬂection

data for for CHOFORM materials appears in

Figure 1.

Gasket Application Fully

Programmable in 3 Axes Full 3-axis

motion of the CHOFORM application

technology accommodates uneven

surfaces (with a maximum slope

of 60

common in castings or

injection-molded parts. The result

is enhanced control of the gasket

cross section.

Tight Dimensional Control and

Terminations CHOFORM gasket

beads are dispensed with an

accuracy of 0.001 inch (0.025

mm), and a cross-sectional height

tolerance of 0.006 inch (0.15 mm).

This innovative technology produces

clean bead ends minimizing the “tail”

characteristic of other processes.

The key is precise management

of ﬂow rate of material through

the nozzle, material viscosity and

dispensing speed.

* CrO

, black chrome, black nickel, bright nickel, tin

Note: Gasket cross section and

tolerances will vary slightly at the

site of ‘start’ or ‘stop’ events in the

dispense bead length.

Figure 1

Deﬂection vs Applied Load

Gasket application to sloped surfaces is fully

programmable

Robotically Dispensed Form-In-Place EMI Gasketing

Secure Gasket Adhesion CHOFORM gaskets

typically exhibit 4-12 N/cm of shear adhesion

to a variety of common housing substrates,

Including:

• cast aluminum, magnesium

or zinc alloys with various platings*

• nickel-copper plating on plastic stainless

steel (300 series)

• CHO-SHIELD

2056, 610, 2040 or 2044

conductive coatings

• Vacuum metallized aluminum

0 5 10 15 20 25 30 35 40 45

Load (lbf / in)

Deﬂection (%)

50 kg Load Cell Operated 0.025 in/min using a 1.00" x 1.00" Ag probe

CHO-FORM® 5560 ( 0.040" x 0.045") CHO-FORM® 5560 ( 0.062" x 0.073")

PTL Serial #: 120409-071903

High levels of Quality Control

Parker Chomerics has the capability to

perform automated dimensional veriﬁca-

tion of gasket bead placement and height

for statistical process control, using fully

programmable optical coordinate mea-

suring technology and vision systems.

Electrical resistance of cured gasket ma-

terial is tested with a multimeter capable

of measuring to 0.001 ohm. Typical C

and C

values are approximately1.5.

CHOFORM materials typically establish 4-12 N/cm adhesion to many substrates,

including magnesium and aluminum alloys and commonly used conductive

ﬁlms such as Ni/Cu plating, vacuum metallized coatings and conductive paints.

Producing durable, conformable gaskets, all CHOFORM materials can be

applied as small as 0.034 inch high and 0.040 inch wide (0.86 mm high and 1.02

mm wide), delivering Cpk values >1.33.

(Exception: CHOFORM 5560 has a minimum applied height of 0.039 inch

high and 0.045 inch wide (0.99 mm high and 1.14 mm wide).

Refer to Table 2a “Typical Properties of CHOFORM Materials” for all minimum

and maximum bead sizes.

A Choice of Materials Formulated for

Automated Dispensing

CHOFORM 5575 — One component,

moisture cure silicone system,

which requires a minimum cure

of 18 minutes at 22°C (72°F) at

50% relative humidity. The silver-

aluminum ﬁller makes 5575 an 80 dB

shielding material, while providing

high corrosion resistance against

aluminum.

CHOFORM 5513 — Two-component,

thermal cure silicone system, which

requires a minimum cure of 30

minutes at 140°C (284°F). The Ag/Cu

particle ﬁller makes 5513 a > 70 dB

shielding material while also having

the best adhesion to chromate coated

aluminum and most other substrates.

CHOFORM 5541 — One-component,

thermal cure silicone system, which

requires a minimum cure of 30

minutes at 150°C (302°F). The low

cost Ni/Graphite ﬁller makes 5541 a

>65 dB shielding material while also

providing a good galvanic corrosion

resistant gasket when mated with

aluminum for outdoor applications.

5541 has very good adhesion

properties.

CCHOFORM 5550 — One-component,

thermal cure silicone system, which

requires a minimum cure of 30

minutes at 150°C (302°F). The low

cost Ni/Graphite ﬁller makes 5550 a

>65 dB shielding material while also

providing a good galvanic corrosion

resistant gasket when mated with

aluminum for outdoor applications.

The key property in 5550 is its lower

hardness than 5541, however this

softer material requires a larger

minimum bead size.

CHOFORM 5526 — One-component,

room temperature, moisture cure

silicone system, which requires a

full cure of 24 hours at 50% relative

humidity. The pure silver ﬁller makes

5526 our best shielding material at

> 100 dB, while providing a soft, low

closure force gasket.

CHOFORM 5528 — One-component,

room temperature, moisture cure

silicone system, which requires a full

cure of 24 hours at 50% relative humidity.

The Ag/Cu ﬁller makes 5528 a >70 dB

shielding material, while providing a

soft, low closure force gasket.

CHOFORM 5538 — One-component,

room temperature, moisture cure

silicone system, which ONLY requires

a full cure of 4 hours at 50% relative

humidity. The low cost Ni/Graphite ﬁller

makes 5538 a >65 dB shielding material

while also providing a good galvanic

corrosion resistant gasket when mated

with aluminum for outdoor applications.

5538 is also capable of the smallest

possible bead size.

CHOFORM 5560 — One-component,

thermal cure silicone system, which

requires a minimum cure of 30

minutes at 150°C (302°F). The Ni/Al

ﬁller makes 5560 a very good >90 dB

shielding material while also providing

the best galvanic corrosion resistant

gasket when mated with aluminum for

even the harshest salt spray / salt fog

environments.

Robotically Dispensed Form-In-Place EMI Gasketing

ParPHorm Form-In-Place Sealing Compounds

ParPHorm is a family of non-conductive, thermal and moisture

cure, form-in-place, elastomeric sealing compounds. These

silicone and ﬂuorosilicone materials provide environmental,

ﬂuid, and dust sealing of small enclosures. The product

line consists of state-of-the art compounds designed to be

robotically dispensed onto small housings and then cured.

Curing of the dispensed materials is done via in-line ovens at

284

F (140

C) for 30 minutes. Dispensed bead heights range

from 0.018 in. (0.46 mm) to 0.062 in. (1.57 mm). Application

advantages of the materials are resistance to a wide variety

of ﬂuids, excellent substrate adhesion, low hardness, and

outstanding compression set properties. Refer to Table 2b.

DESCRIPTION - Moisture Cure Materials

ParPHorm 1800

ParPHorm 1800 is a non-conductive, moisture cure,

form-in-place (FIP), silicone elastomer sealing material.

The material provides environmental, ﬂuid, and dust

sealing of small enclosures via a compound designed to

be robotically dispensed onto small housings. Curing of

the dispensed material is via moisture cure for 48 hours.

Minimum bead size is 0.018” (0.46 mm) tall by 0.022”

(0.56 mm) wide. Maximum bead size is .062” (1.57 mm)

tall by 0.075” ((1.91 mm) wide. Application advantages of

the material are excellent adhesion, low hardness, and

excellent compression set properties. Applications for

ParPHorm 1800 material include handheld electronic

module housings, battery cases, industrial gauges, fuel

cells, and other enclosures requiring small dispensed

elastomer seals for environmental or ﬂuid sealing. Parker

Chomerics offers worldwide capabilities for dispensing

of this material onto customer supplied housings. Parker

Chomerics can also provide supply chain management of

the process and source the housings along with ParPHorm

dispensing and ﬁnishing operations such as painting and

minor mechanical assembly.

FEATURES

• One component thermal cure materials

• Excellent resistance to a wide variety of ﬂuids

• Excellent adhesion to a wide variety of substrates

• Low material and installation costs

DESCRIPTION - Thermal Cure Materials

ParPHorm S1945

ParPHorm S1945 is a silicone FIP material with lower

hardness (Shore A 25) and excellent compression set (21%).

ParPHorm S1945 is especially designed for low closure

force applications and those requiring exceptional adhesion

properties. Due to its minimal hardness, S1945, is one of the

most widely used ParPHorm materials and thus has extensive

application in many areas. The compound adheres well to

aluminum, phenolic resins, copper, stainless steel, glass,

rigid PVC, most ceramics, and various plastics. ParPHorm

S1945 is compatible with air below 400

F, ethylene glycol,

nitrogen, sea (salt) water, magnesium sulﬁte and sulfate,

citric acid, methanol, ozone, soap solutions, zinc salts and

zinc sulfates, potassium chloride/nitrate, barium chloride/

hydroxide/salts, sodium chloride/salts/sulfates, and glycols.

ParPHorm L1938

ParPHorm L1938 is a ﬂuorosilicone FIP elastomer with

Shore A hardness of 45 and compression set rating of 14%.

This ﬂuorosilicone material offers additional ��uid resistance

capabilities above and beyond the capabilities of S1945.

FEATURES

• One component moisture cure material

• Excellent resistance to a wide variety of ﬂuids

• Excellent adhesion to a wide variety of substrates

• Low material and installation costs

HANDLING AND CURING OF MATERIAL

ParPHorm S1945, and L1938 are one component, thermal

cure materials. Recommended cure temperature is 284

F (140

C) for 30 minutes. The full cure cycle of 30 minutes

allows for immediate handling, and performance of necessary

QC tests. The use of this thermal cure, form-in-place material

reduces the need for dispensed parts storage space. This

also allows for immediate packaging and shipment of parts

to their ﬁnal destination for subsequent integration into the

equipment assembly process.

HANDLING AND CURING OF MATERIAL

ParPHorm 1800 is a one component, moisture cure material.

Recommended cure condition is 22

C , 50% RH for 24 hours.

For these same temperature and humidity conditions the tack

free time is approximately 18 minutes and handling time is 4

hours.

CHOFORM and ParPHorm Form-In-Place Sealing Compounds

DESIGN AND PROTOTYPING

Application and design assistance is available to prospective customers. The speciﬁc focus of the assistance is on the

examination/identiﬁcation of design issues with regard to the substrate. These design issues include: enclosure material and

surface ﬁnish, available gasket placement area, material selection, part ﬂatness, transitions in the layout of the dispensed

bead, obstructions in the design of the enclosure to the unimpeded travel of the dispense needle, and z direction dispense

needs. Prototype dispensing is available on sample parts or sample coupons for customer evaluation.

MATERIAL DISPENSING

CHOFORM and ParPHorm are easily dispensed from a variety of commercially available gasket dispense systems. In addition

to Parker Chomerics existing worldwide network of CHOFORM applicators, our CHOFORM applications engineering group

can provide support for material dispense needs worldwide for customers wishing to utilize their own or other dispense

equipment.

Table 1b - ParPHorm Ordering Information

Material

Part Number Material Weight Packaging Type = Size

1800 19-26-1800-0345 345 grams 12 ﬂ. oz. Aluminum Cartridge

1938 19-26-1938-0200 200 grams 6 ﬂ. oz. SEMCO Tube

1945 19-26-1945-0250 250 grams 12 ﬂ. oz. SEMCO Tube

Samples typically provided in 30cc syringes

SEMCO is a registered trademark of PRC-DeSoto, Inc.

Table 1a - CHOFORM Ordering Information

Material Part Number Material Weight Packaging Type Size

5575

19-26-5575-0240

19-26-5575-0500

240 grams

500 grams

6oz SEMCO Tube

12 ﬂ. oz. Aluminum Cartridge

5513 19-26-5513-0850

Part A 450 grams

Part B 475 grams

12 ﬂ. oz. SEMCO Tube

5526 19-26-5526-0850 850 grams 12 ﬂ. oz. Aluminum Cartridge

5528 19-26-5528-0850 850 grams 12 ﬂ. oz. Aluminum Cartridge

5538 19-26-5538-0650 650 grams 12 ﬂ. oz. Aluminum Cartridge

5541 19-26-5541-0650 650 grams 12 ﬂ. oz. Aluminum Cartridge

5550 19-26-5550-0575 575 grams 12 ﬂ. oz. Aluminum Cartridge

5560 19-26-5560-0500 500 grams 12 ﬂ. oz. Aluminum Cartridge