Abstract: In recent years, with the shift from CRT to LCD (liquid crystal television) in the color TV industry, the demand for foil capacitors has been decreasing year by year. Meanwhile, since China's accession to the WTO, energy-saving lamps have gained popularity due to their advantages such as brightness, easy start-up, flicker-free operation, high power factor, and energy saving. Domestic and international demand has been increasing year by year. Therefore, the performance requirements for film capacitors are becoming increasingly stringent, especially the need to improve their withstand high temperature and high pressure. Keywords: Energy-saving lamp, foil capacitor, capacitor, temperature, voltage, dielectric, discharge path (surface allowance) Introduction 1. Operating temperature of capacitors in energy-saving lamps: Because the lamp tube and electronic ballast are integrated, the temperature of the lamp tube is above 100℃ when the lamp is normally lit. Due to the close contact between the lamp tube and the sealed plastic shell of the electronic ballast, some heat dissipates into the space, while the rest is conducted to the electronic ballast. Combined with the heating of components inside the plastic shell, the temperature inside the plastic shell can reach approximately 105℃. In other words, the capacitor needs to operate at an ambient temperature of approximately 105℃. 2. Rated Voltage of Capacitors in Energy-Saving Lamps: In electronic energy-saving lamp circuits, the highest rated voltage of capacitors is generally above 1000V, requiring high withstand voltage. For example, in oscillating circuits, due to the high oscillation frequency, the resulting reverse peak voltage (or transient overvoltage) can easily cause capacitor breakdown. Source: http://tede.cn I. Analysis of Capacitor Failure Mechanisms under High Temperature and High Pressure Capacitor breakdown largely depends on its macroscopic structure and manufacturing process, as well as the resulting non-uniform electric field and non-uniform dielectric. Capacitor breakdown often occurs at these weak points. The following are the main influencing factors analyzed: 1. Influence of Dielectric on Capacitor Breakdown: i. If the dielectric breakdown voltage is close to the operating voltage during product design, the capacitor is prone to early failure under high temperature and high pressure. ii. Under a uniform electric field, the microscopic nature of the dielectric and poor dielectric quality, such as surface roughness, pores, wrinkles, and cracks, will reduce the dielectric's ability to withstand electric field strength, leading to dielectric breakdown. The mechanism is that free electrons in the capacitor dielectric collide with neutral molecules under the action of a strong electric field, causing them to ionize and generate positive ions and new free electrons. The rapid development of the ionization process forms an avalanche-like electron flow, leading to dielectric breakdown. This reduces the capacitor's withstand capability under high temperature and high pressure. 2. The effect of the plates (aluminum foil) on capacitor breakdown: When aluminum foil is cut, due to the lack of sharpness of the roller, the end face of the cut aluminum foil coil will have serrations, burrs, etc. Such coils are prone to puncturing the dielectric film during winding, reducing the withstand voltage. Severe burrs will also cause the capacitor to break down after voltage is applied. 3. The effect of discharge path (edge ​​allowance) on capacitor edge breakdown: Under the action of instantaneous overvoltage, the capacitor may not only break down through the dielectric, but also, when the electric field at the edge of the plate is significantly uneven or the discharge path (edge ​​allowance) is small, surface breakdown may also occur along the edge of the plate. As shown in the figure below, "△L" is the discharge path, "△b" is the edge allowance, and "d" is the dielectric thickness. As shown in the diagram above, if the aluminum foil deviates or the discharge path (margin allowance) is too small due to product design, it can easily lead to surface breakdown at the lead root. This is determined by the lead-out method of the capacitor. Under normal circumstances, the discharge path ΔL between the two poles at the lead root is Δb + d, while at the leadless end, the discharge path ΔL = 2Δb + d. If d << ΔL is negligible, the discharge path at the lead-out end is reduced by 1/2 compared to the leadless end. In addition, the width error of the aluminum foil during slitting or the "snake-like" deviation of the aluminum foil during winding can further reduce the discharge path (margin allowance) between one aluminum foil plate and the lead root of another aluminum foil at that position. Under pressure, especially at high temperature and high pressure, the capacitor is prone to surface breakdown. 4. The impact of lead spot welding on capacitor breakdown: During the winding process, the leads of the capacitor are directly spot welded to the aluminum foil. Therefore, improper adjustment of the pressure of the two electrode heads, the magnitude of the spot welding current, and the flatness of the spot welding platform during spot welding will cause burrs at the weld between the leads and the aluminum foil, which will damage the dielectric film, reduce the withstand voltage, and severe burrs will cause the capacitor to break down after being pressurized. 5. The impact of heat sealing of the outer film on capacitor breakdown: The outer film of the capacitor core winding is sealed by the heat of the heat sealer. If the heat of the heat sealer is not properly controlled, or the contact time between the heat sealer and the core is too long, the outer film is easily burned, affecting the withstand voltage of the capacitor, and in severe cases, it will cause the capacitor to break down after being pressurized. II. Control measures (I) Control of the impact of raw materials (dielectric, aluminum foil) on capacitor breakdown: 1. Establish a sound raw material management and inspection system to ensure that the quality of raw materials meets the requirements. 2. When designing products, the dielectric thickness should be correctly selected according to the working voltage of the capacitor so that it can work under a large electric field without breakdown. 3. Establish a sound management system and operating requirements for the equipment for slitting materials, especially the roller cutter, which should be inspected and replaced regularly to eliminate potential problems. (II) Control of capacitor edge breakdown: In order to prevent capacitor edge breakdown, the discharge path between the two plates should be increased when designing the capacitor. On the other hand, when the total discharge path of the capacitor core group is fixed, the discharge path at the end with the lead wire should be slightly larger than the discharge path at the end without the lead wire. This can effectively avoid capacitor edge breakdown. (III) Control of the impact of lead wire spot welding on capacitor breakdown: 1. Establish control documents for the lead wire welding process in the winding process, and clarify the welding status requirements of the lead wire and aluminum foil. For the welding quality of the capacitor core group, the operator must conduct regular self-inspection, such as the first piece inspection before starting the machine. Inspector's patrol inspection, special inspection, etc. Establish a sound quality assessment system to ensure that the lead wire welding status meets the requirements. 2. When welding leads, the pressure and welding current of the two electrode heads should be adjusted appropriately. The welding platform should be flat and free of grooves. The welding state of the lead and aluminum foil should be visually smooth on both sides, without burrs. At the same time, the welding of the lead and aluminum foil should be firm, and there should be no lead detachment or aluminum foil breakage. The flattening degree and flattening length of the lead must be appropriate. (IV) Control of the impact of heat sealing on capacitor breakdown: When heat sealing the outer film, the heat of the heat sealer and the contact time between the heat sealer and the core assembly must be adjusted to avoid damaging the aluminum foil. In addition, the length of the outer film should be appropriate. Too long will waste raw materials, and too short will easily burn the aluminum foil during heat sealing, causing the two plates to conduct and break down. III. Conclusion The above are only the main factors affecting the withstand capability of capacitors under high temperature and high pressure. Of course, many other factors will also affect the withstand capability of capacitors. This requires us to strengthen quality management and control in many aspects during the production process. We must continuously improve and enhance our products to meet the needs of the energy-saving lamp market.