Technical Information
Kemlon manufactures a wide variety of glass to metal seals for use as electriocal connectors. The Kemlon glass sealed feedthrus are single pin seals designed to operate under pressure or vacuum. The glass serves the dual purpose of bonding the pin and body heremetically as well as insulating them electrically. Only high quality, high insulation glasses are used on Kemlon feedthrus for low dielectric loss. In some cases high alimina ceramic is used to reinforce the glass. It also serves as an extention of the insulation for designs that require longer body shells or arc paths. Both the design and the manufacturnig techniques of using ceramic to reinforce glass in high pressure electrical connectors are patented Kemlon processes.
Construction
The standard construction of Kemlon glass sealed feedthrus is 300 series stainless steel bodies, high temperature glass, and 52% nickel alloy pin. Other materials are available upon request. A represenative list of materials in which seals are available is shown in Table 1.
| Body or Shell | Pin Contact |
|---|---|
| 303 or 304 S.S. | 52% Nickel Alloy |
| 316 S.S | Kovar |
| Hast C | Molybdenum |
| Inconel | 446 S.S. |
| Titanium | Tantalum |
| Kovar | Hast C |
| Carbon Steel | Tantalum |
Current Capacity
The standard carrying capacity of Kemlon glass sealed feedthrus is a function of three conditions.
- The diameter of the pin
- The pin material type
- The operating temperature
In a glass seal the current passing through the pin
causes some resistive heating. Glass seals are not
easily damaged by this heating doe to the high
temperature proprities of the glass. Therefore, the
current carrying capacity depends upon how much
"warming" is acceptable. Kemlon has set
its current capacities for a maximum of 50 deg F
temperature rise.
| Pin Diameter | Service Temperature | ||
|---|---|---|---|
| Inches | mm | 25 °C / 77 °F | 175 °C / 374 °F |
| 0.030 | .076 | 3.8 | 2.6 |
| 0.040 | 1.02 | 5.9 | 4.1 |
| 0.062 | 1.57 | 10.0 | 6.9 |
| 0.093 | 2.36 | 16.6 | 11.5 |
| 0.125 | 3.18 | 24.5 | 17.0 |
| 0.187 | 4.75 | 40.5 | 28.0 |
In nonstandard materials of construction are used,
then a multiplier should be applied to these current
capacities shown in Table 2. At 78 deg F the
specific resistivity of various materials is shown in
Table 3. The multiplier is simply the square of the
ratio of the specific resistivity of the 52% Nickel alloy
to the specific resistivity of the pin material chosen.
| Material | Ohms per Circular Mil Foot | Micro Ohm Centimeter | Current Multiplier |
|---|---|---|---|
| 52% Nickel Alloy | 260 | 43.0 | 1.0 |
| Kovar/Rodar | 294 | 48.0 | 0.9 |
| 446 S.S. | 402 | 66.8 | 0.8 |
| Tantulum | 81 | 13.5 | 1.8 |
| Molybdenum | 34 | 5.7 | 2.8 |
| Inconel X-750 | 731 | 121.0 | 0.6 |
Pin Arrangement
Standard on all Kemlon seals is straight pin arrangement. Hovever, eyelets and tubular ends are available on request. Each eyelet lengthenes the pin .015 inch.
Plating
All Kemlon glass sealed feedthrus have tin plated conductors for ease of soldering. Gold plating is also available if required by special request.
Helium Leakage
Kemlon seals are designed to meet or exceed Helium leak test of 0.00000001 cc/sec. Represenative samples are inspected using a mass spectrometer leak detector to insure product integrity. In extreme circumstances 100% batch inspection can be preformed for an additional charge.