PS302J2 US Sensor, PS302J2 Datasheet - Page 6

• Manufacturer Part Number: PS302J2
• Description: THERMISTOR 3K OHM +/-0.10 C
• Manufacturer: US Sensor
• Series: PSr

Specifications of PS302J2

• Resistance In Ohms @ 25°c: 3K
• B0/50: 3890K
• Operating Temperature: -80°C ~ 150°C
• Lead Length: 1.50" (38.00mm)
• Mounting Type: Free Hanging
• Package / Case: Bead
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Resistance Tolerance: -
• B Value Tolerance: -
• B25/50: -
• B25/75: -
• B25/85: -
• B25/100: -
• Power - Max: -
• Other names: 615-1001

Chips
Precision interchangeable thermistors used for temperature measurement and
control as well as glass encapsulated and surface mount devices typically
utilize a small chip thermistor sensing element. A slurry, consisting of the
metal oxide compounds and special organic binders, is “cast” onto a flat sur-
face to exacting dimensions. The thickness of the “cast tape” can be as thin as
0.001" or as thick as 0.050" depending upon the application. The “cast tape”
ware is “blanked” into wafers or substrates of a suitable size. The “green”
wafers are sintered at high temperature and electroded with silver or other
electrode materials.
The electroded wafers are diced into the exact size dictated by the particular application. A typical
wafer will yield from 2,000 to 20,000 devices depending upon the size of the chips required.
The chips are tested electrically, lead wires are attached, resistance trimming is performed if neces-
sary and an encapsulant is applied. In some applications the “unleaded” bare chip can be used “as
is”. Chips can also be encapsulated in a hermetically sealed (DO-35 or DO-41) style leaded glass
package or into a “MELF” style surface mount package.
Discs
For production of large disc thermistors as well as power thermistors, those devices used
primarily for inrush current limiting in switching mode power supplies, discs ranging in size
from 0.200" diameter to over 1.000" diameter are formed from the oxide/binder formulation
using a tableting press. Precise quantities of powder are automatically metered into a die cavity
and compacted into a shape which conforms to the specified dimensional characteristics. This
process results in uniform density throughout the device as well as uniform electrical characteris-
tics throughout the production run. The “green” discs are then subjected to a high temperature
sintering process which will result in the device achieving the desired resistance versus tempera-
ture characteristics. The “sintered” discs are then metallized. A thick film silver electrode materi-
al is applied to the “flats” of the discs and fired to allow for subsequent electrical contact to the
device. Testing of the thermistor’s electrical characteristics is performed to confirm that the
devices conform to the desired resistance versus temperature characteristic. Lead wires are
attached using specially formulated solder and an encapsulant of epoxy or silicone resin is usually
applied to the device for environmental protection.
Silicon PTC Manufacturing Processes
Silicon PTC thermistors are manufactured using the positive temperature coefficient of
specially doped single crystal silicon. The ingot is grown and doped to precise specifications
and sliced into thin wafers. An electrode is applied to the flat surfaces of the wafers which are
subsequently diced into small chips. The chips are then sealed in DO-35 (Diode Style) or
LL-34 (Surface Mount) packages and electrically tested to confirm that they meet their
specified resistance temperature characteristics.
Probes And Assemblies
Most of the standard thermistors and RTD’s listed in the U.S. Sensor catalog are available
mounted in special probe housings designed for sensing temperature under the most demand-
ing environmental conditions. U.S. Sensor’s standard probe housings range in size from less
than 0.020" diameter to over 0.375" diameter and are constructed from various materials
including stainless steel, aluminum, epoxy, polyimide and PVC, just to name a few. Detailed
descriptions of some of U.S. Sensor’s standard probe housings are presented in this catalog.
5
1832 West Collins Avenue, Orange, CA 92867 • Tel. [phone] • Fax [phone] • www.ussensor.com