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Introduction
Encapsulation Shells are compression molded
or injection molded using thermoset plastic (Diallyl
Phthalate) and are used to encapsulate
or enclose electronic circuitry and components.
Special Features
A) Holes in the bottom, flashed over on the outside.
B) Standoff feet on the outside bottom.
C) Header step at the inside open end.
D) Other special feature; Call for details.
Header Step - Mechanical
Drawing
An optional feature molded into a round, square or oblong shell to provide a locating ledge in which to insert a header in order to close off the open end of the shell.
Tolerances
& Materials
Encapsulation Shells produced by Robison Electronics,
Inc. are molded only of certified materials. Standard
material is flame-resistant glass-fibre filled Diallyl
Phthalate conforming to ASTM D5948, Type SDG-F.
Diallyl Phthalate Properties
Mechanical
Compressive Strength. . . . . . . . . . . . . 25,000 psi
Flexural Strength. . . . . . . . . . . . . . . . .11,000 psi
Flexural Modulus. . . . . . . . . . . . . . . . .1.4 x 106 psi
Izod Impact Strength. . . . . . . . . . . . . . 0.85 ft. lb./in.
Tensile Strength. . . . . . . . . . . . . . . . . 8,500 psi
Heat Distortion. . . . . . . . . . . . . . . . . . 365°F (185°C)
Heat Resistance, Continuous. . . . . . . .400-450°F (204-232°C)
Thermal Expansion
Linear Coefficient per Degree
Centigrade (25° to 70°C). . . . . . . . . . . 34 x 10-6
Thermal Conductivity,
Cal/sec/cm2/cm/°C. . . . . . . . . . . . . . .6.9 x 10-4
Specific Gravity. . . . . . . . . . . . . . . . . .1.84 to 1.91
Water Absorption,
48 hrs @ 50°C. . . . . . . . . . . . . . . . . . . 0.35%
Flame Resistance,
Heated coil. . . . . . . . . . . . . . . . . . . . . (FTMS-406,2023.2)
Ignition time. . . . . . . . . . . . . . . . . . . . .>90 seconds
Burning time. . . . . . . . . . . . . . . . . . . . <90 seconds
UL Listing. . . . . . . . . . . . . . . . . . . . . . 94 V0
(Note: UL Listed rating may be affected
by variation in part dimension.)
Electrical
Arc Resistance. . . . . . . . . . . . . . . . . . .130 sec.
Dielectric Strength . . . . . . . . . . . . . . . . 350V/MIL
Dielectric Constant. . . . . . . . . . . . . . . . 3.8 @ 1 MHz
Dissipation Factor. . . . . . . . . . . . . . . . . 0.012 @ 1MHz
Volume Resistance,
Megohms. . . . . . . . . . . . . . . . . . . . . . . as is 107 plus
30 days @ 100% R.H.
@ 70°C. . . . . . . . . . . . . . . . . . . . . . . . .40,000
Surface Resistance,
Megohms. . . . . . . . . . . . . . . . . . . . . . . as is 107 plus
30 days @ 100% R.H.
@ 70°C. . . . . . . . . . . . . . . . . . . . . . . . .150,000
Design Considerations
To ensure that maximum packaging density can be accomplished, the design of Robison Electronics' shells incorporated the following features:
Draft
Draft required to ensure proper molding and release of the molded shell from the mold is incorporated into the wall thickness tolerances for any given shell; this draft is evident only on the inside of the shell with the outside of the shell showing no draft.
Wall Thickness
Wall thicknesses shown in these tabulations are nominal thicknesses and are for reference only. Generally speaking, the following tolerances can be considered as maximum:
a. Up to .500 high, a tolerance of ±.005.
b. Between .500 and 1.00 inch high, a tolerance of ±.010.
c. Higher than 1.00 inch, a tolerance of ±.015.
Radii
The external radii on all shells tabulated are maintained at .015 maximum. Internal radii on shells varies from 1/64 to 1/16 inch depending on size.
Tolerances
Tolerances on external dimensions are generally specified to allow economical production.
In addition to the above features, and where production quantities warrant, shells can be produced incorporating cored holes for lead breakout and step design in the open end for headers, locating ribs, standoff feet, etc.
Dimensions
Dimensions shown in these tabulations describe the outside configuration of the encapsulation shell; they are nominal dimensions for reference only since tolerances vary from shell to shell. Generally speaking, the following tolerances can be considered as maximum:
1. On any diameter, width, length or height dimension under 1.00 inch, tolerances of ±.010.
2. On any diameter, width, length or height dimension between 1.00 inch and 3.00 inches, tolerances of ±.015.
3. On any diameter, width, length or height dimension exceeding 3.00 inches, tolerances of ±.020.
Standard Colors
Black is the standard color utilized in our production. Other colors are available on special order when production quantities permit economical production.
Secondary Operations
Robison Electronics, Inc. is equipped to provide secondary operations, such as silk screening, drilling of holes, installation of terminals and inserts, and on larger shells, sandblasting of the interior surface. Shells which require secondary operations will be quoted based on specific request.
Tooling of New Sizes
Since all tooling is produced in our own modern tool room, new shells can be made available with a normal lead time of eight (8) weeks after receipt of order (this lead time can be reduced in some cases, if required).
Part Numbering System
The three letters preceding the hyphen designate the type of shell, i.e. PMS designates Precision Module Shells, POS designates Precision Oblong Shells, PRS designates Precision Round Shells, and PSS designates Precision Square Shells.
The numbers following the hyphen indicate: in the case of Module Shells (PMS) and Oblong Shells (POS), the first several numbers are size identifiers and indicate the shell width, and the second group of several numbers indicates the shell length; with Square Shells (PSS), the first several numbers indicate the length and the width of the shell while the second series of numbers identify the height of the shell; with Round Shells (PRS), the first several numbers identify the shell diameter, the second series of numbers identify the shell height.
Letters and numbers (i.e. S2, S6, etc.) that follow the size identifiers are used internally to identify minor differences between shells that share the same size identifiers.
The height of standoff feet is included in the overall height of the shell.
Examples:
POS-25602960S1
POS: Precision Oblong Shell
2560: The shell is 2.560 inches wide
2960: The shell is 2.960 inches long
S1: An internal designation code
PSS-355395S27
PSS: Precision Square Shell
355: The shell is .355 inches square
395: The shell is .395 inches in height
S27: An internal designation code
PRS-400290S3
PRS: Precision Round Shell
400: The shell has a diameter of .400 inches
290: The shell is .290 inches in height
S3: An internal designation code
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