Procedure of checking electrical parameters of low voltage foils.
Test procedure:
- Forming of etched foil specimens
- Measurement of forming voltage
- Capacitance measurement
- Oxide layer stability control
1.
Forming of etched foil specimens
Testing equipment
-
DC power supply
- Ripples ≤ 1%
- Voltage stability ± 3% - DC voltmeter — Accuracy ± 0.5%
- DC ammeter — Accuracy ± 1.0%
- Stainless steel tank, temperature control
Specimen size
Specimen length (L) is set by equipment.
The edges of the specimen must be perfectly cut without tears and burrs.
Forming electrolyte
- Ammonium adipate — 150 g
- De-mineralized water (≤ 0.1 µS/cm) — 1000 ml
- Electrolyte resistance, at +70°С — 5.0 … 8.5 Ω×cm
- рН, at + 50°С — 5.2 … 7.2
Forming conditions
- Forming current — 0.3 А/specimen
- Electrolyte temperature — 70 ± 2°С
Forming
The specimen is put in the electrolyte so that the upper part of the specimen is 10 … 15 mm below the solution surface.
Forming procedure
- Forming cycle (F1; F2; F3; F4) — 6 minutes
- Interval between forming cycles (I1; I2) — 1 minute
- Annealing 530°С (A) — 1 minute
Rinsing
Specimens shall be rinsed in de-mineralized water at room temperature.
Drying
Specimens shall be dried at the temperature < 100°C.
2.
Forming voltage measurement
Testing equipment
-
DC power supply
- Ripples ≤ 1%
- Voltage stability ± 3% - DC voltmeter — Accuracy ± 0.5%
- DC ammeter — Accuracy ± 1.0%
- Stainless steel tank, temperature control
Electrolyte for measuring the voltage
- Ammonium adipate — 150 g
- De-mineralized water (≤ 0.1 µS/cm) — 1000 ml
- Electrolyte resistance, at + 70°С — 5.0 … 8.5 Ω×cm
- рН, at + 50°С — 5.2 … 7.2
Electrolyte parameters
- Control current — 2.0 ± 0.2 mA/specimen
- Electrolyte temperature — 70 ± 2°С
Voltage measurement
The specimen is put in the electrolyte so that the upper part of the specimen is below the solution surface.
Voltage scheme
To check time to reach 0.9×UF and maximal voltage (UM) in 180 seconds after TR0.9×UF
3.
Capacitance measurement
Testing equipment
- Capacitance meter — accuracy ± 1%
- Measurement frequency — 100 Hz ± 5% (acceptable 50 Hz)
- Cell from inert materials
- Counter electrode - etched thermo-oxidized foil with capacitance of ≥ 400 µF/cm²
Electrolyte for measuring the voltage
- Electrolyte Ammonium adipate — 150g
- De-mineralized water (≤ 0.1 µS/cm) — 1000 ml
- Electrolyte resistance, at +70°С — 5.0 … 8.5 Ω×cm
- Electrolyte temperature — 20 … 25°С
Capacitance measurement
- formed foil specimen is to be put in a measurement cell with electrolyte so that in electrolyte solution was only the working part of the specimen (without leads)
- keep the specimen in for one minute, then capacitance should be measured
- to get specific capacitance value (µF/cm²) divide the value received from the meter by 10
4.
Oxide layer stability control
Test specimen
Formed foil specimen passed tests according to p. 2 and 3
Hydration
- Time: 60 ± 1 minutes
- Temperature: ≥ 95°С
- Number of specimens: ≤ 6
- Replacement of de- mineralized water: after each process of hydration
Electrolyte for measuring the voltage
- Ammonium adipate — 150 g
- De-mineralized water (≤ 0.1 µS/cm) — 1000 ml
- Electrolyte resistance, at + 70°С — 5.0 … 8.5 Ω×cm
Electrolyte parameters
- Control current — 2.0 ± 0.2 mA/specimen
- Electrolyte temperature — 85 ± 2°C
Voltage measurement
- Put the test specimen into electrolyte so that the top edge (is to be measured) was on the surface
- >Measure the time to reach 0.9UF
Procedure of checking electrical parameters of high voltage foils.
Test procedure:
- Forming of etched foil specimens
- Measurement of forming voltage
- Capacitance measurement
- Oxide layer stability test