Health Hazards
"The limited energy in capacitors (E = (1/2) C V²) restricts the duration of the shock, even if there are no circuit breakers to trip. The shock current will be limited by the body resistance, and the duration of the shock will be characterized by the time constant (τ = R C). Therefore, the total energy will be dissipated quicker when the body resistance is low, and slower when the body resistance is high. Additionally, increasing the capacitance will just extend the discharge time."[1]
E is energy in joules, C is capacitance in farads, V is voltage in volts, τ (tau) is the RC time constant in seconds, and R is resistance in ohms. A good reason why it says "do not open" on the chassis of some electronic equipment is that AC mains, capacitors or batteries can cause electric shock, and capacitors and batteries can store a dangerous charge after AC mains is disconnected. Digi-Key Electronics has calculators for safely discharging capacitors with a resistor that has the required wattage.[2][3][4] Digi-Key Electronics recommends not using a screwdriver to discharge capacitors, which implies that suitable resistors provide a safe RC time constant.[5] Converting the capacitance and voltage of a capacitor to joules is useful for knowing whether there is a risk of electric shock. 0.5 J to 10 J can be unpleasant to very painful. A safe threshold for when DC surge discharges can cause ventricular fibrillation, like disconnected capacitors can deliver, is 27 J = 27 W s (watt-seconds), and mains frequency impulse current with 13.5 J = 13.5 W s.
Reflex movements from an impulse shock of less than 13.5 W s can result in unexpected injuries. Injuries vary with contact resistance. DC might cause a single muscle contraction that prevents the hand from letting go of the circuit, but DC can jolt the hand away when the contact resistance is high. The 50 Hz or 60 Hz cycle of AC mains might give a chance to repel the hand away from the current, but the cyclical muscle contractions can be severely damaging. Currents around the let-go threshold are very painful and will help an individual with moving the hand or other inflicted body part away immediately. A safe 60 Hz RMS AC sine wave threshold for when muscle contractions become inextricable is 16 mA for men, and 10.5 mA for women. For men, this let-go threshold is 24 mA at 1 kHz, 32 mA at 2 kHz, 45 mA at 4 kHz, and 56 mA at 6 kHz. The corresponding milliamperes for women are approximately two thirds. An equivalent DC threshold is 76 mA for men, and 51 mA for women. These values are medians, so there is wide variation in how people react.[6]
Aluminum electrolytic capacitors will lose their electric charge with time, but there is dielectric absorption that brings up to 10% of the previous charge back. Charging electrolytic capacitors regularly, at least once every six months or so helps to maintain their breakdown voltage because of electrochemical reactions. This can be done by using the equipment they are installed in. High temperature or humidity where capacitors are stored, such as direct sunlight can be bad for their durability. The electrolyte in capacitors can be toxic or caustic, and becomes gas when excessive ripple current boils electrolyte that forces the pressure relief vent to open. Inhalation of lead from soldering fumes is not a considerable problem at the optimal temperature for hand soldering, but ingestion is prevented with hand hygiene. Rosin flux from soldering fumes should not be inhaled or come in contact with the skin, due to asthma and dermatitis. Recommended precautions from dross and flux in soldering fumes include ventilation, safety glasses, respirators, ESD gloves and ESD lab coats.[7][8] Computer fans can be modified by soldering them to a regulated 12 VDC adapter that has a suitable current rating. The temperature of soldering fumes is bad for the durability of a computer fan, but intake airflow can be used and computer fans are often not made for static pressure. Electrolytic capacitors, lead solder, used lead solder sponges and contaminated fume extractor filters are disposed as hazardous waste in accordance with regulations, such as the Waste Framework Directive of the European Union.[9][10][11]
Practical Calculations
"The reader is cautioned against interpreting the differences between the voltage values as a true index of the relative hazard between alternating current and direct current. Current is the proper criterion of electric shock intensity, and the hazard from the proposed reasonably safe voltages would be greatly increased if contact occurred at locations where the skin was lacerated or if local high current densities produced material breakdown of the skin. Currents of the let-go level are more than sufficient to produce very serious burns."
A safety limit for a mains frequency AC sine wave is 24 V RMS if there would otherwise be a risk of electric shock on skin that is not lacerated, and approximately 10–21 V RMS when there is conductive fluid on the skin, since there is a difference in contact area and dielectric strength of the epidermis. This limit is 12 V RMS when there is no GFCI (ground fault circuit interrupter). An equivalent safety limit for DC is 50 V, also on wet skin. These safety limits are set to half of what could generally cause electric shock in a worst-case scenario. Static electricity is safe for the skin, but the current and contact resistances can usually not be determined with accuracy when there was an injury from electricity. Therefore, voltage is used for safety limits. A multimeter can check whether the voltage in a device is safe, and a multimeter with a low-impedance mode can discharge capacitors. The effective resistivity inside the body, for electric power that can break the dielectric strength of healthy skin, is approximately 100 Ω cm (ohm-centimeters), which correlates with the electrical resistivity of intercellular fluid and the blood circulatory system.[12][13][14]
Here is the minimum dangerous capacitance for a capacitor with the minimum DC voltage, where ventricular fibrillation or respiratory paralysis can possibly occur under abnormal conditions, such as touching a set of the capacitor terminals with the tongue: 27 J = (1/2) C (50 V)² = 1,250 V C => 27 J/1,250 V = C = 0.0216 F = 21.6 mF. People normally use the milli, micro, nano and pico prefixes, so mF (1,000 times more), µF (often written uF and is 1,000,000 times more than F), nF (1,000,000,000 times more) and pF (1,000,000,000,000 times more). The minimum dangerous capacitance will naturally be lower when the voltage is higher. I have a Yamaha A-700 power amplifier with the original power supply capacitors. They are potentially deadly at the rated charge, since each is rated for (1/2) (22,000 µF/1,000,000) (69 V)² = 52.371 J. Watt-seconds are actually why electricity causes injuries as current and voltage are described in Ohm's law. The two capacitors are about 40 years old and should be measured or just replaced, since 15 years after the manufacturing date is where the end seals of electrolytic capacitors can stop working, which makes the electrolyte evaporate with time.[15][16] Touching and causing vibration on capacitors if they are soldered to a circuit board can cause deterioration of their lead seals. Film capacitors can work for 50 years or more, but they are generally too expensive at high values of capacitance, and their lower ESR can create some problems for designs that were made with electrolytic capacitors.[17]
Technical Specifications of Capacitors
"For aluminum electrolytic capacitors, the capacitance is measured under the standard measuring conditions of 20°C and a 120Hz AC signal of about 0.5V. Generally, as the temperature rises, the capacitance increases; as the temperature decreases, the capacitance decreases (Fig. 7). With a higher frequency, the capacitance is smaller; with a lower frequency, the capacitance is larger (Fig. 8)."[18]
Capacitance, dissipation factor and leakage current are used for finding out whether a capacitor is working.[19][20] An AC test voltage must be under 1.5 volts for polarized electrolytic capacitors, because they have an anodized dielectric with that breakdown voltage. Even non-polarized electrolytic capacitors are not suitable for an AC voltage application with considerable ripple current, since electric power can make the electrolyte evaporate. The anodized dielectric degrades continually if no voltage is applied. If the rated voltage (also called the working voltage) has not been applied to the electrolytic capacitor for a couple of years, then the leakage current will increase and reforming will be necessary for restoring the dielectric strength. However, the dielectric strength will not be the same as originally and the breakdown voltage will be reformed at the applied voltage.[21] This deterioration of the oxide layer can also interfere with accurate measurements, so it might be more desirable to skip measurements of electrolytic capacitors and just replace them around 30 years after the manufacturing date.
The IEC 60384-1 and IEC 60384-4 standards for aluminum electrolytic capacitors are a measurement frequency of 100 Hz or 120 Hz for capacitance and dissipation factor, at a temperature of 20 °C.[22] The IEC 60068-1:2013 standard for film capacitors is a measurement frequency of 1 kHz for capacitance and dissipation factor. MKT, MFP and MKP film capacitors with a rated capacitance ≤ 1 μF have additional measurement frequencies of 10 kHz or 100 kHz for dissipation factor.[23] The capacitance (IEC 60062) should normally be the same and the voltage can be higher, but not lower than the capacitor that is being replaced.[24] This also depends on finding the right physical dimensions, including lead spacing for the replacement. LCR meters or a program called Room EQ Wizard use an AC test signal. The dissipation factor also called tan(δ) is needed for testing the condition of capacitors accurately. Accurate measurements also provide an impression of authenticity if an authorized distributor was not used. However, there can still be defects because of the acceptance quality limit (ISO 2859-1, IEC 60410 and JIS Z 9015-1).[25] A multimeter can check for an internal short circuit or open circuit in a capacitor, which are failure modes.[26] A resistance reading that stays low is a short circuit, and one that starts and stays high is an open circuit. A working capacitor that is discharged will have a resistance reading that starts low and rises to infinity. Multimeters can give cursory measurements if they use a pulsed DC test signal for capacitance. ESR = tan(δ)/(2 π f C), where f is the measurement frequency in Hz.
Figure 1: "A capacitor’s total complex impedance is represented on a real-complex plane as the vector sum of a real component, (the ESR) and a complex (reactive) component representing the ‘ideal’ capacitor that things like ESR mess up in all actual components. The angle between the total impedance and its complex component is called the ‘loss angle,’ and is a figure used to summarize the ratio between the ideal and non-ideal components of a capacitor’s overall impedance."[27]
Replacement of Capacitors and Related Components
"The expected life time shall be about fifteen years at maximum as a guide in terms of deterioration of the sealant."[28]
Rosin or resin flux that is halide-free, respectively called ROL0 or REL0 (IPC J-STD-004) is used because of chemical reactions of halides or other fluxes that are harmful for aluminum electrolytic capacitors or other electronic components. Eutectic Sn63/Pb37 solder is optimal for restoration of vintage electronic equipment, since the RoHS Directive of the European Union only came into effect for products that were originally marketed on July 1, 2006 or later. RoHS means lead-free in this context. The soldering iron tip should always be tinned in order to prevent oxidation. Polarized electrolytic capacitors should be installed with the correct polarity, because reverse polarity can cause a catastrophic failure and open the pressure relief vent. Applying pressure during soldering can cause excessive wear on solder pads and the weight from gravity is enough. Movement of the parts to be soldered during solidification does not ensure the necessary solderability.
ELNA states that the sleeves of aluminum electrolytic capacitors should not be considered as an insulation, and that the aluminum case is connected to the cathode terminal through the electrolyte, which has uncertain resistance.[29] PCBs (printed circuit boards) should be horizontal during soldering, so that gravity provides adhesion and concave solder joints along the periphery of through holes. The optimal dwell time is less than 3 seconds.[30] Jim Smith recommends preapplying separate flux on areas to be soldered, since oxidation prevents intermetallic bonding.[31] 30 °C to 50 °C more than the liquidus temperature of the solder is recommended, in order to ensure that enough heat energy is available for the metallurgical bond.[32] Nichicon states that film capacitors must not be used if there are more than two directly connected in series, and recommends using isopropyl alcohol for cleaning PCBs.[33]
References
[1] Scott, Mark A. "Working Safely with Hazardous Capacitors". IEEE Industry Applications Magazine (Volume 25, Issue 3, May–June 2019).
https://ieeexplore.ieee.org/ielaam/2943/8685745/8661497-aam.pdf
[2] Sculley, D. RC Time Constant. Tufts University.
https://www.eecs.tufts.edu/~dsculley/tutorial/rc/rc3.html
[3] Digi-Key Electronics. Capacitor Safety Discharge Calculator.
https://www.digikey.dk/en/resources...version-calculator-capacitor-safety-discharge
[4] Digi-Key Electronics. Time Constant Calculator.
https://www.digikey.dk/en/resources/conversion-calculators/conversion-calculator-time-constant
[5] Awalt, Ashley. How to Safely Discharge a Capacitor. Digi-Key Electronics.
https://www.digikey.com/en/blog/how-to-safely-discharge-a-capacitor
[6] Dalziel, Charles F. "Effects of Electric Shock on Man". IRE Transactions on Medical Electronics (PGME-5, July 1956).
[7] Lawrence Berkeley National Laboratory. Safe Soldering Work Practices.
https://eta-safety.lbl.gov/sites/default/files/Soldering Guidelines.pdf
[8] Massachusetts Institute of Technology. Soldering Safety and Health Guidelines.
https://ehs.mit.edu/wp-content/uploads/EHS-0167.pdf
[9] Nippon Chemi-Con. Precaution of Capacitor Disposal.
https://www.chemi-con.co.jp/en/faq/detail.php?id=29BFLER
[10] University of Cambridge. Soldering Safety.
https://safety.eng.cam.ac.uk/safe-working/copy_of_soldering-safety
[11] Farnell. Managing Solder Fume Extraction.
https://uk.farnell.com/essential-considerations-for-managing-soldering-fume-extraction-p2
[12] Dalziel, C. F. & Massoglia, F. P. "Let-Go Currents and Voltages". Transactions of the American Institute of Electrical Engineers, Part II: Applications and Industry (Volume 75, Issue 2, May 1956).
[13] Schwan, Herman P. & Kay, Calvin F. "Specific Resistance of Body Tissues". Circulation Research (Volume 4, No. 6, November 1956).
https://www.ahajournals.org/doi/pdf/10.1161/01.RES.4.6.664?download=true
[14] Rush, Stanley, Abildskov, J. A. & McFee, Richard. "Resistivity of Body Tissues at Low Frequencies". Circulation Research (Volume 12, No. 1, January 1963).
https://www.ahajournals.org/doi/pdf/10.1161/01.RES.12.1.40?download=true
[15] Nichicon. Application Guidelines for Aluminum Electrolytic Capacitors.
https://www.nichicon.co.jp/english/products/pdf/aluminum-e.pdf
[16] Parler, Sam G., Jr. Reliability of CDE Aluminum Electrolytic Capacitors. Cornell Dubilier.
https://www.cde.com/resources/technical-papers/reliability.pdf
[17] Cornell Dubilier. AC Capacitor Application Guide.
https://www.cde.com/resources/technical-papers/ACappGUIDE.pdf
[18] Nippon Chemi-Con. Judicious Use of Aluminum Electrolytic Capacitors.
https://www.chemi-con.co.jp/products/relatedfiles/capacitor/catalog/al-technote-e.pdf
[19] Parler, Sam G., Jr. Selecting and Applying Aluminum Electrolytic Capacitors for Inverter Applications. Cornell Dubilier.
https://www.cde.com/resources/technical-papers/selectinvcap.pdf
[20] Parler, Sam G., Jr. & Macomber, Laird L. Predicting Operating Temperature and Expected Lifetime of Aluminum-Electrolytic Bus Capacitors with Thermal Modeling. Cornell Dubilier.
https://www.cde.com/resources/techn...erating-Temperature-and-Expected-Lifetime.pdf
[21] Würth Elektronik. Afraid of Aging? The Effects of Time on Electrolytic Capacitors.
https://www.we-online.com/catalog/media/o467325v410 SN019_EN_d.pdf
[22] TDK Electronics AG. Aluminum Electrolytic Capacitors: General Technical Information.
https://www.tdk-electronics.tdk.com...2da2adf2b/pdf-generaltechnicalinformation.pdf
[23] TDK Electronics AG. Film Capacitors: General Technical Information.
https://www.tdk-electronics.tdk.com...1513474ba/pdf-generaltechnicalinformation.pdf
[24] TDK Electronics AG. Film Capacitors: Marking and Ordering Code System.
https://www.tdk-electronics.tdk.com...53733752/pdf-markingandorderingcodesystem.pdf
[25] TDK Electronics AG. Aluminum Electrolytic Capacitors: Quality and Environment.
https://www.tdk-electronics.tdk.com...1ab2a2d36b44f51/pdf-qualityandenvironment.pdf
[26] United Chemi-Con. Failure Modes.
https://chemi-con.com/failure-modes/
[27] Digi-Key Electronics. Calculating Capacitor ESR from tan(δ).
https://forum.digikey.com/t/calculating-capacitor-esr-from-tan/2633
[28] ELNA. Aluminum Electrolytic Capacitors.
https://www.elna.co.jp/en/capacitor/alumi/catalog/pdf/0-tech-note_AL_e.pdf
[29] ELNA. Cautions for Using Aluminum Electrolytic Capacitors.
https://www.elna.co.jp/en/capacitor/alumi/catalog/pdf/al_caution_e.pdf
[30] ELNA. Soldering Conditions.
https://www.elna.co.jp/en/capacitor/alumi/catalog/pdf/al_handa_e.pdf
[31] Smith, Jim. A Practical Guide to Soldering Flux. Sierra Circuits.
https://www.protoexpress.com/blog/guide-soldering-flux/
[32] Indium Corporation. Soldering 101 — A Basic Overview.
https://www.indium.com/technical-documents/application-notes/download/27/
[33] Nichicon. Plastic Film Capacitors.
https://www.nichicon.co.jp/english/products/pdf_x/Plastic_Film_Capacitors_E.pdf
"The limited energy in capacitors (E = (1/2) C V²) restricts the duration of the shock, even if there are no circuit breakers to trip. The shock current will be limited by the body resistance, and the duration of the shock will be characterized by the time constant (τ = R C). Therefore, the total energy will be dissipated quicker when the body resistance is low, and slower when the body resistance is high. Additionally, increasing the capacitance will just extend the discharge time."[1]
E is energy in joules, C is capacitance in farads, V is voltage in volts, τ (tau) is the RC time constant in seconds, and R is resistance in ohms. A good reason why it says "do not open" on the chassis of some electronic equipment is that AC mains, capacitors or batteries can cause electric shock, and capacitors and batteries can store a dangerous charge after AC mains is disconnected. Digi-Key Electronics has calculators for safely discharging capacitors with a resistor that has the required wattage.[2][3][4] Digi-Key Electronics recommends not using a screwdriver to discharge capacitors, which implies that suitable resistors provide a safe RC time constant.[5] Converting the capacitance and voltage of a capacitor to joules is useful for knowing whether there is a risk of electric shock. 0.5 J to 10 J can be unpleasant to very painful. A safe threshold for when DC surge discharges can cause ventricular fibrillation, like disconnected capacitors can deliver, is 27 J = 27 W s (watt-seconds), and mains frequency impulse current with 13.5 J = 13.5 W s.
Reflex movements from an impulse shock of less than 13.5 W s can result in unexpected injuries. Injuries vary with contact resistance. DC might cause a single muscle contraction that prevents the hand from letting go of the circuit, but DC can jolt the hand away when the contact resistance is high. The 50 Hz or 60 Hz cycle of AC mains might give a chance to repel the hand away from the current, but the cyclical muscle contractions can be severely damaging. Currents around the let-go threshold are very painful and will help an individual with moving the hand or other inflicted body part away immediately. A safe 60 Hz RMS AC sine wave threshold for when muscle contractions become inextricable is 16 mA for men, and 10.5 mA for women. For men, this let-go threshold is 24 mA at 1 kHz, 32 mA at 2 kHz, 45 mA at 4 kHz, and 56 mA at 6 kHz. The corresponding milliamperes for women are approximately two thirds. An equivalent DC threshold is 76 mA for men, and 51 mA for women. These values are medians, so there is wide variation in how people react.[6]
Aluminum electrolytic capacitors will lose their electric charge with time, but there is dielectric absorption that brings up to 10% of the previous charge back. Charging electrolytic capacitors regularly, at least once every six months or so helps to maintain their breakdown voltage because of electrochemical reactions. This can be done by using the equipment they are installed in. High temperature or humidity where capacitors are stored, such as direct sunlight can be bad for their durability. The electrolyte in capacitors can be toxic or caustic, and becomes gas when excessive ripple current boils electrolyte that forces the pressure relief vent to open. Inhalation of lead from soldering fumes is not a considerable problem at the optimal temperature for hand soldering, but ingestion is prevented with hand hygiene. Rosin flux from soldering fumes should not be inhaled or come in contact with the skin, due to asthma and dermatitis. Recommended precautions from dross and flux in soldering fumes include ventilation, safety glasses, respirators, ESD gloves and ESD lab coats.[7][8] Computer fans can be modified by soldering them to a regulated 12 VDC adapter that has a suitable current rating. The temperature of soldering fumes is bad for the durability of a computer fan, but intake airflow can be used and computer fans are often not made for static pressure. Electrolytic capacitors, lead solder, used lead solder sponges and contaminated fume extractor filters are disposed as hazardous waste in accordance with regulations, such as the Waste Framework Directive of the European Union.[9][10][11]
Practical Calculations
"The reader is cautioned against interpreting the differences between the voltage values as a true index of the relative hazard between alternating current and direct current. Current is the proper criterion of electric shock intensity, and the hazard from the proposed reasonably safe voltages would be greatly increased if contact occurred at locations where the skin was lacerated or if local high current densities produced material breakdown of the skin. Currents of the let-go level are more than sufficient to produce very serious burns."
A safety limit for a mains frequency AC sine wave is 24 V RMS if there would otherwise be a risk of electric shock on skin that is not lacerated, and approximately 10–21 V RMS when there is conductive fluid on the skin, since there is a difference in contact area and dielectric strength of the epidermis. This limit is 12 V RMS when there is no GFCI (ground fault circuit interrupter). An equivalent safety limit for DC is 50 V, also on wet skin. These safety limits are set to half of what could generally cause electric shock in a worst-case scenario. Static electricity is safe for the skin, but the current and contact resistances can usually not be determined with accuracy when there was an injury from electricity. Therefore, voltage is used for safety limits. A multimeter can check whether the voltage in a device is safe, and a multimeter with a low-impedance mode can discharge capacitors. The effective resistivity inside the body, for electric power that can break the dielectric strength of healthy skin, is approximately 100 Ω cm (ohm-centimeters), which correlates with the electrical resistivity of intercellular fluid and the blood circulatory system.[12][13][14]
Here is the minimum dangerous capacitance for a capacitor with the minimum DC voltage, where ventricular fibrillation or respiratory paralysis can possibly occur under abnormal conditions, such as touching a set of the capacitor terminals with the tongue: 27 J = (1/2) C (50 V)² = 1,250 V C => 27 J/1,250 V = C = 0.0216 F = 21.6 mF. People normally use the milli, micro, nano and pico prefixes, so mF (1,000 times more), µF (often written uF and is 1,000,000 times more than F), nF (1,000,000,000 times more) and pF (1,000,000,000,000 times more). The minimum dangerous capacitance will naturally be lower when the voltage is higher. I have a Yamaha A-700 power amplifier with the original power supply capacitors. They are potentially deadly at the rated charge, since each is rated for (1/2) (22,000 µF/1,000,000) (69 V)² = 52.371 J. Watt-seconds are actually why electricity causes injuries as current and voltage are described in Ohm's law. The two capacitors are about 40 years old and should be measured or just replaced, since 15 years after the manufacturing date is where the end seals of electrolytic capacitors can stop working, which makes the electrolyte evaporate with time.[15][16] Touching and causing vibration on capacitors if they are soldered to a circuit board can cause deterioration of their lead seals. Film capacitors can work for 50 years or more, but they are generally too expensive at high values of capacitance, and their lower ESR can create some problems for designs that were made with electrolytic capacitors.[17]
Technical Specifications of Capacitors
"For aluminum electrolytic capacitors, the capacitance is measured under the standard measuring conditions of 20°C and a 120Hz AC signal of about 0.5V. Generally, as the temperature rises, the capacitance increases; as the temperature decreases, the capacitance decreases (Fig. 7). With a higher frequency, the capacitance is smaller; with a lower frequency, the capacitance is larger (Fig. 8)."[18]
Capacitance, dissipation factor and leakage current are used for finding out whether a capacitor is working.[19][20] An AC test voltage must be under 1.5 volts for polarized electrolytic capacitors, because they have an anodized dielectric with that breakdown voltage. Even non-polarized electrolytic capacitors are not suitable for an AC voltage application with considerable ripple current, since electric power can make the electrolyte evaporate. The anodized dielectric degrades continually if no voltage is applied. If the rated voltage (also called the working voltage) has not been applied to the electrolytic capacitor for a couple of years, then the leakage current will increase and reforming will be necessary for restoring the dielectric strength. However, the dielectric strength will not be the same as originally and the breakdown voltage will be reformed at the applied voltage.[21] This deterioration of the oxide layer can also interfere with accurate measurements, so it might be more desirable to skip measurements of electrolytic capacitors and just replace them around 30 years after the manufacturing date.
The IEC 60384-1 and IEC 60384-4 standards for aluminum electrolytic capacitors are a measurement frequency of 100 Hz or 120 Hz for capacitance and dissipation factor, at a temperature of 20 °C.[22] The IEC 60068-1:2013 standard for film capacitors is a measurement frequency of 1 kHz for capacitance and dissipation factor. MKT, MFP and MKP film capacitors with a rated capacitance ≤ 1 μF have additional measurement frequencies of 10 kHz or 100 kHz for dissipation factor.[23] The capacitance (IEC 60062) should normally be the same and the voltage can be higher, but not lower than the capacitor that is being replaced.[24] This also depends on finding the right physical dimensions, including lead spacing for the replacement. LCR meters or a program called Room EQ Wizard use an AC test signal. The dissipation factor also called tan(δ) is needed for testing the condition of capacitors accurately. Accurate measurements also provide an impression of authenticity if an authorized distributor was not used. However, there can still be defects because of the acceptance quality limit (ISO 2859-1, IEC 60410 and JIS Z 9015-1).[25] A multimeter can check for an internal short circuit or open circuit in a capacitor, which are failure modes.[26] A resistance reading that stays low is a short circuit, and one that starts and stays high is an open circuit. A working capacitor that is discharged will have a resistance reading that starts low and rises to infinity. Multimeters can give cursory measurements if they use a pulsed DC test signal for capacitance. ESR = tan(δ)/(2 π f C), where f is the measurement frequency in Hz.
Figure 1: "A capacitor’s total complex impedance is represented on a real-complex plane as the vector sum of a real component, (the ESR) and a complex (reactive) component representing the ‘ideal’ capacitor that things like ESR mess up in all actual components. The angle between the total impedance and its complex component is called the ‘loss angle,’ and is a figure used to summarize the ratio between the ideal and non-ideal components of a capacitor’s overall impedance."[27]
Replacement of Capacitors and Related Components
"The expected life time shall be about fifteen years at maximum as a guide in terms of deterioration of the sealant."[28]
Rosin or resin flux that is halide-free, respectively called ROL0 or REL0 (IPC J-STD-004) is used because of chemical reactions of halides or other fluxes that are harmful for aluminum electrolytic capacitors or other electronic components. Eutectic Sn63/Pb37 solder is optimal for restoration of vintage electronic equipment, since the RoHS Directive of the European Union only came into effect for products that were originally marketed on July 1, 2006 or later. RoHS means lead-free in this context. The soldering iron tip should always be tinned in order to prevent oxidation. Polarized electrolytic capacitors should be installed with the correct polarity, because reverse polarity can cause a catastrophic failure and open the pressure relief vent. Applying pressure during soldering can cause excessive wear on solder pads and the weight from gravity is enough. Movement of the parts to be soldered during solidification does not ensure the necessary solderability.
ELNA states that the sleeves of aluminum electrolytic capacitors should not be considered as an insulation, and that the aluminum case is connected to the cathode terminal through the electrolyte, which has uncertain resistance.[29] PCBs (printed circuit boards) should be horizontal during soldering, so that gravity provides adhesion and concave solder joints along the periphery of through holes. The optimal dwell time is less than 3 seconds.[30] Jim Smith recommends preapplying separate flux on areas to be soldered, since oxidation prevents intermetallic bonding.[31] 30 °C to 50 °C more than the liquidus temperature of the solder is recommended, in order to ensure that enough heat energy is available for the metallurgical bond.[32] Nichicon states that film capacitors must not be used if there are more than two directly connected in series, and recommends using isopropyl alcohol for cleaning PCBs.[33]
References
[1] Scott, Mark A. "Working Safely with Hazardous Capacitors". IEEE Industry Applications Magazine (Volume 25, Issue 3, May–June 2019).
https://ieeexplore.ieee.org/ielaam/2943/8685745/8661497-aam.pdf
[2] Sculley, D. RC Time Constant. Tufts University.
https://www.eecs.tufts.edu/~dsculley/tutorial/rc/rc3.html
[3] Digi-Key Electronics. Capacitor Safety Discharge Calculator.
https://www.digikey.dk/en/resources...version-calculator-capacitor-safety-discharge
[4] Digi-Key Electronics. Time Constant Calculator.
https://www.digikey.dk/en/resources/conversion-calculators/conversion-calculator-time-constant
[5] Awalt, Ashley. How to Safely Discharge a Capacitor. Digi-Key Electronics.
https://www.digikey.com/en/blog/how-to-safely-discharge-a-capacitor
[6] Dalziel, Charles F. "Effects of Electric Shock on Man". IRE Transactions on Medical Electronics (PGME-5, July 1956).
[7] Lawrence Berkeley National Laboratory. Safe Soldering Work Practices.
https://eta-safety.lbl.gov/sites/default/files/Soldering Guidelines.pdf
[8] Massachusetts Institute of Technology. Soldering Safety and Health Guidelines.
https://ehs.mit.edu/wp-content/uploads/EHS-0167.pdf
[9] Nippon Chemi-Con. Precaution of Capacitor Disposal.
https://www.chemi-con.co.jp/en/faq/detail.php?id=29BFLER
[10] University of Cambridge. Soldering Safety.
https://safety.eng.cam.ac.uk/safe-working/copy_of_soldering-safety
[11] Farnell. Managing Solder Fume Extraction.
https://uk.farnell.com/essential-considerations-for-managing-soldering-fume-extraction-p2
[12] Dalziel, C. F. & Massoglia, F. P. "Let-Go Currents and Voltages". Transactions of the American Institute of Electrical Engineers, Part II: Applications and Industry (Volume 75, Issue 2, May 1956).
[13] Schwan, Herman P. & Kay, Calvin F. "Specific Resistance of Body Tissues". Circulation Research (Volume 4, No. 6, November 1956).
https://www.ahajournals.org/doi/pdf/10.1161/01.RES.4.6.664?download=true
[14] Rush, Stanley, Abildskov, J. A. & McFee, Richard. "Resistivity of Body Tissues at Low Frequencies". Circulation Research (Volume 12, No. 1, January 1963).
https://www.ahajournals.org/doi/pdf/10.1161/01.RES.12.1.40?download=true
[15] Nichicon. Application Guidelines for Aluminum Electrolytic Capacitors.
https://www.nichicon.co.jp/english/products/pdf/aluminum-e.pdf
[16] Parler, Sam G., Jr. Reliability of CDE Aluminum Electrolytic Capacitors. Cornell Dubilier.
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[17] Cornell Dubilier. AC Capacitor Application Guide.
https://www.cde.com/resources/technical-papers/ACappGUIDE.pdf
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[19] Parler, Sam G., Jr. Selecting and Applying Aluminum Electrolytic Capacitors for Inverter Applications. Cornell Dubilier.
https://www.cde.com/resources/technical-papers/selectinvcap.pdf
[20] Parler, Sam G., Jr. & Macomber, Laird L. Predicting Operating Temperature and Expected Lifetime of Aluminum-Electrolytic Bus Capacitors with Thermal Modeling. Cornell Dubilier.
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[21] Würth Elektronik. Afraid of Aging? The Effects of Time on Electrolytic Capacitors.
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[23] TDK Electronics AG. Film Capacitors: General Technical Information.
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[24] TDK Electronics AG. Film Capacitors: Marking and Ordering Code System.
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[25] TDK Electronics AG. Aluminum Electrolytic Capacitors: Quality and Environment.
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[26] United Chemi-Con. Failure Modes.
https://chemi-con.com/failure-modes/
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[30] ELNA. Soldering Conditions.
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[31] Smith, Jim. A Practical Guide to Soldering Flux. Sierra Circuits.
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[33] Nichicon. Plastic Film Capacitors.
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