One. Rationale
PPTC device is a polymer temperature
PPTC polymer is filled by an internal toner and other material made; when the temperature rises when the polymers swell, causing a conductive filler material from the inside becomes large, the impedance becomes large to form a circuit block, when the temperature drops when restitution;
When current flows after, the PPTC will heat generated at this time based on the protective effect of the temperature characteristic of the above
• Special attention for so PPTC need three things: ambient temperature voltage current (voltage and current determine the internal temperature)
Meanwhile ornaments when the need to focus on the heat issue
two. PPTC production process Introduction
I PPTC material: polymer is a petroleum byproduct, the toner can be synthesized
These two kinds of material and other materials on a specific mixer mixing vessel, will be the same as a particulate material, the base material of the PPTC
(Ii) heating the granules to melt the raw material, and a thin layer of conductive material on both sides of the press, a sheet made of similar paper looks like -----
(Ii) the time when you need to make plug-in
Cut directly on the machine, then add pin, while completing welding, coating, testing on an automated assembly line
When you need to make a patch
The second portion is mailed to the PCB material mill, according to the requirements PPTC manufacturer, two layers of material in the upper and lower layer of the PCB are pressed, both ends of the PCB will reserve pin placement, and the plating of different materials, such as gold-plated
Then the entire PCB material, sent to PPTC factory, to do the cutting and automated testing and screening on it
three. PPTC important parameters introduced
Shown above: Note that the above data are the test results at room temperature
Ihold: PPTC below this current is stable, there will be no action
Itrip: operating current, when the current is larger than this current, the impedance will be in a very short period of time to change greatly, the interrupt circuit is formed, and the larger the current, the faster the operation time
Vmax: PPTC ends after the operation, can withstand the maximum voltage
Imax: PPTC by the maximum current, the current is directly burn over
Pd: internal resistance of the normal working time
Time To Trip: operating time, the operating current at a specific time from small to great impedance PPTC time
NOTE: When the current is greater than Ihold less than Itrip, a state is uncertain at this time, may be part of a PPTC operation, an operation portion not PPTC; may be considered the minimum value is Ihold Itrip;
four. PPTC specific test procedures
To test for the first PPTC test to note two resistance R0 and R1; R0 is the initial resistance value of the product size, the size of the resistance R1 is welded products, (Note: Try to an electric iron when Los welding tinning, welding as far as possible to quickly and can not be used for a long time PPTC heated air gun.)
Test link as follows:
1: Impact Test
Hardware connection diagram:
As shown, the DC load test PPTC series RL1, RL1 resistance is calculated taking appropriate, to ensure that the operation has not yet PPTC time, Imax of the current flowing to; the voltage across the circuit Vtest = Vmax
(The method of calculating the DC load resistance RL1 size: the first PPTC measuring impedance, then the Vmax / Imax-Rd, Rd is an internal resistance PPTC)
Test Method: PPTC and the DC load to the entire series circuit composed of electrically 6S, and is powered 60S, 100 continue
Test Data: initial resistance value R0 products
R1 resistance after welding products
R25 product testing resistance after 25 times
R50 product testing resistance after 50 times
R100 product testing resistance after 100 times
Rationale: a current power-on instant of Imax of the current flowing through, this time PPTC starts operating voltage PPTC impedance becomes large after the operation, since the RL1 resistance is small, the partial pressure, the voltage Vmax main the PPTC points; test 6S, this is equivalent to the Imax and Vmax tested; and then cooled off 60s, the number 100 shocks
2: Pressure test
Hardware connection diagram:
As shown, the test series PPTC and DC load RL2, RL2 calculated taking appropriate resistance, to ensure that the operation has not yet PPTC when flowing Itrip <current I <Imax; across-circuit voltage Vtest = Vmax
(DC method also calculates the size of the load resistor RL2: PPTC the first measured impedance, then the Vmax / I-Rd, Rd is an internal resistance PPTC)
Test Method: PPTC and the DC load to the entire series circuit composed of a voltage Vmax,
Test Data: initial resistance value R0 products
R1 resistance after welding products
R2 After two hours the product continued energization resistance
3: No action characteristic test
Test Method: continuous supply of power in the state 1h Ihold
Test Data: initial resistance value R0 products
R1 resistance after welding products
R2 product continuously energized after one hour resistance
4: Action Time Test
Test Method: selecting a current value I (and Imax of between Itrip, spec will generally recommended), to test the length of the current at this time PPTC operation.
Test Data: initial resistance value R0 products
R1 resistance after welding products
The length of the operation time T (for which a current probe current decay time test)
R2 product after testing resistance
About this time the action test, the test may be recommended when the multi-SPEC test action time and do some comparison under several different sets of current: see below
