Semiconductor Junction Coating

Silicone Elastomer Systems for Protection and Passivation of Semiconductor Junctions

Translastic Semiconductor Junction Coatings, Types 3811 and 3812, are high purity, 100% solids, siloxane systems designed for passivation coating transistor, diode and rectifier junctions. Demanding production procedures and rigid quality control requirements guarantee ionic purity levels of 1 ppm (maximum). Typical applications include conformal coatings to provide mechanical and electrical insulation prior to plastic molding; protective coatings over hybrid integrated circuits to prevent chip damage during potting; and other ultra-pure, hermetic-type passivations.

Type 3811 and 3812 Junction Coatings will prevent electrical breakdown, minimize junction surface leakage, stabilize peak inverse voltage, and provide environmental protection for high temperature performance and thermal cycling.

PROPERTIES TYPE 3811 TYPE 3812
System One-Part Two-part
Solids 100% 100%
Appearance Clear Clear
Viscosity 7,500 cps 5,000 cps
Shelf Life 3 months 12 months
Storage Temperature 40 °F or below Room Temperature
Specific Gravity 1.03 1.03
Mix Ratio —— 10 to 1
Pot Life —— > 48 hours
Durometer (shore A) 30 30
Tensile Strength (psi) 400 350
Elongation (%) 130 140
Dielectric Strength (V/mil) > 450 > 450
Dielectric Constant @ 106 Hz 3.50 3.50
Volume Resistivity ohm/cm 1015 1015
Dissipation Factor @ Imc 0.001 0.001

METALLIC IMPURITY (by spectographic analysis)

Metal ppm Max. Metal ppm Max.
Aluminum (Al) 1.0 Lead (Pb) 1.0
Antimony (Sb) 1.0 Magnesium (Mg) 1.0
Chromium (Cr) 1.0 Nickel (Ni) 1.0
Copper (Cu) 1.0 Potassium (K) 1.0
Iron (Fe) 1.0 Sodium (Na) 1.0

CURE:
Electrical performance of junctions coated with these elastomers is influenced by both temperature and duration of cure. Longer post-cures and higher temperatures generally improve device characteristics.

CURE SCHEDULE:
1/2 hour @ 80 °C + (optional)
1 hour @ 135 °- 150 °C (cure)
2 hours @ 200 °-225 °C (post cure-minimum)

Semiconductor Junction Coating – Type I

Low cost, heat stable, moisture resistant, high purity silicone resin for semiconductor applications. Designed specifically for environmental protection of transistors, diodes and rectifiers.

PHYSICAL PROPERTIES:

System One-part; rigid
Base Silicone resins
Appearance Light amber
Specific Gravity 1.03
Viscosity 350 cps
Flash Point 90°F
Thinner Xylene
Solids 50%
Shelf Life 5 months @ 25°C
Thermal Life 250°C > 10,000 hours

CHEMICAL SPECIFICATIONS:

Sodium < 1 ppm
Potassium < 1 ppm

ELECTRICAL:

Dielectric Strength > 2500 (v/mil)
Dielectric Constant 2.75 (1 mc)
Volume Resistivity > 1016 ohm-cm
Dissipation Factor 0.001 (1 mc)

APPLICATION:

Dip, paint, spray or transfer.

CURE:

Air dry for 20 minutes. Bake at 65°C for 20 minutes, then at 125° for 1/2 hour. Postcure at 225°C for 1/2 hour, or at 200°C for 5 hours.