Chip Resistors

Pulse Withstanding Chip Resistors (PWR) Application & Soldering Notes

Today's electronic devices are becoming smaller and smaller. The requirement, in particular, for pulse withstand capability is growing due to the need to protect sensitive modern electronic systems.

To meet this demand Token Electronics have designed a Pulse Withstanding Chip Resistor (PWR Series). The enhanced performance of the chips is made possible by the precise use of the best resistance inks and a closely controlled production process.

Application Notes:

1. Applications vary from line protection for telecommunications to surge withstanding resistors for use in circuit breakers. Details of a typical telecomm and power supply application are given below.
2. Telephone lines can be subjected to a large range of voltage disturbances, many of which can damage switching equipment. This has led to the need for circuit protection against both high voltage transients, usually of short duration caused by lighting strikes and overloads of longer duration, due to direct connection to mains power lines.
3. These two faults are separated into primary and secondary protection.
   1. Primary protection handles the high voltage transients, and is usually located within the exchange.
   2. Secondary protection is usually built into the equipment to be protected, and deals with both current and voltage limiting.
4. Voltage limiting prevents damage to the equipment and shock hazards, and current limiting prevents damage to wiring.
5. To determine the suitability of a PWC series chip resistors for your application refer to the pulse withstanding data as given lighting surge performance using both 1.2/50μs and 10/700μs pulse shapes.

Soldering Notes:

1. Electrical connection to a ceramic substrate or to a printed circuit board can be made by
   reflow or wave soldering of wrap-around terminations.
2. Wrap-around terminations provide good leach properties and ensure reliable contact.
3. Due to the robust construction, the PWR can be immersed in the solder bath for 30 seconds at 260°C.
4. This enables the resistor to be mounted on one side of a printed circuit board and wire-leaded components applied on the other side.
5. PWR resistors themselves can operate at a maximum temperature of 155°C.
6. For soldered resistors, the joint temperature should not exceed 110°C.
7. This condition is met when the stated power levels at 70°C and recommended pad and trace areas are used.
8. Allowance should be made if smaller areas of copper are used.

Environmental Characteristics (PWR)

Power Derating Curve (PWR)
Test Item	Specification	Test Method
Short Time Overload	±0.5%	JIS-C-5202-5.5 RCWV*2.5 or Max Overloading Voltage, 5 seconds
Thermal Shock	±0.5%	MIL-STD-202F Method 107G -55°C~150°C, 100 cycles
Temperature Coefficient of Resistance	As Spec.	MIL-STD-202F Method 304 +25/-55/+25/+125/+25°C
Load Life	±1%	MIL-STD-202F Method 108A RCWV, 70°C, 1.5 hours ON, 0.5 hours OFF, total 1000~1048 hours
Humidity (Steady State)	±0.5%	MIL-STD-202F Method 103B 40°C, 90~95%RH, RCWV 1.5 hours ON, 0.5 hours OFF, total 1000~1048 hours
Resistance to Dry Heat	±0.5%	JIS-C-5202-7.2 96 hours @ +155°C without load
Low Temperature Operation	±0.5%	JIS-C-5202-7.1 1hour,-65°C followed by 45 minutes of RCWV
Bending Strength	As Spec.	JIS-C-5202-6.1.4 Bending Amplitude 3mm for 10 seconds
Resistance to Soldering Heat	±0.5%	MIL-STD-202F Method 210E 260±5°C, 10±1seconds
Solderability	95% min coverage	MIL-STD-202F Method 208H 245°C±5°C, 3±0.5(sec)
Dielectric Withstand Voltage	As Spec.	MIL-STD-202F Method 301 Apply Max Overload Voltage for l minute
Insulation Resistance	>1000MΩ	MIL-STD-202F Method 302 Apply 100VDC for 1minute

Note: Storage Temperature: 25±3°C; Humidity: <80%RH

Lightning Surge Resistor (PWR)

10/700μs Lightning Surge Surface Mount Resistor (PWR) 1.2/50μs Lightning Surge Surface Mount Resistor (PWR)
Note:	Lightning Surge Resistors are tested in accordance with IEC 60 115-1 using both 10/700μs and 1.2/50μs pulse shapes. The limit of acceptance is a shift in resistance of less than 1% from the initial value.

Order Codes (PWR)

Specification Download (PWR)

Download Complete SMD Resistor (PWR) Series Specification PDF (430KB) Surface Mount Pulse Withstanding Chip Resistors.