2CL76 Fast Recovery High Voltage Diode 18KV 5mA 80nS

Product Overview

• 2CL76 is an axial leaded, epoxy molded rectifier built for high voltage stages. It blocks 18 kV of repetitive peak reverse voltage at a leakage current of 2.0 µA, carries 5 mA of average forward current and recovers in 80 nS — a set of ratings aimed at the multiplier and rectifier sections of imaging, inspection and high voltage test power supplies rather than at general purpose rectification.
• Both leads leave opposite ends of a small cylindrical body, so the part can bridge a gap on a board or sit inside an oil-filled or gas-filled assembly. A cathode band on the body sets the orientation, and the epoxy molding carries heat away from the chip while sealing the junction from its surroundings. That combination — sealed body, formed lead and insulating adhesive at the bend — is what lets a part this small hold 18 kV without tracking across its own surface.
• The rating table is reproduced below exactly as it appears in the data sheet, with the test condition attached to each figure: repetitive and working reverse voltage, average and surge forward current, recovery time, forward peak voltage, and reverse leakage at both 25 °C and 100 °C, alongside the operating and storage temperature limits. Read it against your design window before you fix a voltage step.
• As high voltage diode manufacturers, we publish the leakage at two temperatures rather than at room temperature alone, because the 100 °C figure is the one that decides whether a stack stays stable once the enclosure warms up.
• Axial leaded connection: the two leads exit opposite ends of the body, so the diode can bridge a gap on a board, sit inside a multiplier ladder, or hang between two terminations in an oil-filled can.
• High thermal conductivity epoxy compound molding: the molded body pulls heat out of the chip and seals the junction against moisture and surface contamination.
• Low internal resistance reduces energy loss: forward losses stay modest in continuous operation, which matters where the part sits in a sealed assembly with little airflow.
• Special passivation glue chip protection: the passivated chip surface holds reverse leakage steady at high voltage instead of drifting as surface charge builds.
• Excellent discharge characteristics: the part handles the pulse currents a multiplier or capacitor discharge stage presents, inside its 0.5 A surge rating.
• Fast 80 nS recovery: short reverse recovery keeps switching loss down in higher frequency rectifier stages and reduces the disturbance the diode injects into the surrounding circuit.
• Compact cylindrical body: several high voltage diodes fit into a stack in the space a larger package would need for one.
• Rated from -55 °C to +150 °C ambient, so the same part covers cold-start and hot-cabinet conditions without a separate variant.

Specifications

Voltage Step & Alternatives

• The 2CL7 range is laid out as a voltage ladder. The high voltage diodes in the family share one electrical profile — the same average forward current, the same recovery time and the same surge rating — and differ mainly in reverse voltage, so a change of step rarely forces a change anywhere else in the circuit. This part sits in the middle: 18 kV, one step above the 16 kV version and one below the 20 kV version.
• Moving up from 16 kV to 18 kV buys dielectric margin, and moving from 18 kV to 20 kV buys a little more. What it does not buy is a different forward behaviour: the 18 kV and 20 kV parts are both rated at a forward peak voltage of ≥ 43.0 V, so the step up costs nothing in forward drop. That makes 18 kV the sensible landing point for a rail that sits comfortably inside the upper teens and needs headroom for regulation and transients, while the 20 kV part is there for designs that genuinely work closer to the higher figure.
• The top of the family behaves differently. The 30 kV version keeps the same 5 mA average current and 80 nS recovery but rises to a forward peak voltage of ≥ 52.0 V, a step change worth accounting for when a stack runs continuously at the top of the range. If your design is heading for that territory, size the thermal path for the higher forward drop rather than assuming the electrical profile carries across unchanged.
• All four steps use the same axial leaded epoxy package and the same cathode band marking, so the mounting and insulation practice described on this product applies to the whole family. What changes is how much voltage the body has to hold off — and that is the figure to check against your own rail before you order.
• Two 2CL76 diodes in series are a normal way to reach a working voltage above 18 kV, and three take the nominal figure past 50 kV. Treat the total as a design target rather than a guarantee: the string only holds the sum of the ratings when the reverse voltage actually divides evenly across the devices.
• The division is set by reverse leakage, not by the part number. The device that leaks least carries the largest share of the reverse voltage, so a string of high voltage diodes is never automatically a balanced string. Work the numbers with the 100 °C figure of 20.0 µA rather than the 2.0 µA quoted at 25 °C — the spread between devices widens as they warm, which is exactly the condition a sealed module reaches after an hour of running.
• Add a balancing network across each diode — a resistor, or a resistor with a capacitor in parallel — sized so the current it passes is large compared with the worst-case leakage difference. Once the balancing current dominates, the division follows the network instead of batch spread. Send us your string length and working voltage and we will check the values with you.
• Keep derating on top of the balancing. A three-device string totals 54 kV on paper only; leave margin for regulation, transients and the uneven division that remains after balancing, so no single diode in the string sits at its own limit.
• Mount the string so every device runs at a similar temperature. A diode running hotter than its neighbours leaks more, and the imbalance shifts onto the cooler parts. Group the string away from heat sources, keep the spacing between bodies even, and run the whole assembly in oil or gas where the layout allows it.
• Insulate and clean every intermediate joint. At these voltages the surface path between two adjacent bodies matters as much as the chip inside them, and flux residue or a fingerprint across the gap can leak more than the diodes themselves.
• Check the finished string before it enters service: measure the reverse voltage across each device at working voltage and compare the readings. One device sitting noticeably higher than the rest is the first sign that sharing is uneven, and it is far cheaper to find on the bench than in the field.
• Stacking stops being the sensible answer once the total climbs well past a few steps. The 30 kV 2CL82 covers a large part of that ground in a single body, and above it the surface tracking around the package, not the silicon, becomes the limit.

Operating Environments

Insulation Adhesive Options

The adhesive around the lead bend decides how well that termination behaves at high voltage, and the four common chemistries that high voltage diode manufacturers work with behave differently. Silicone usually ends up as a transparent, elastic rubber after curing: it absorbs shock and rides out the severe stress of rapid temperature swings from -40 °C to 200 °C, which suits assemblies that cycle hard or see vibration. Acrylic cures to a transparent, hard coating with low moisture absorption, a fast cure time and excellent wear resistance and insulation — a practical match for a line that needs the part coated and moving on quickly. Urethane also cures hard and clear, with superior wear resistance and good moisture resistance; its performance is particularly stable in low temperature environments, but it is less resistant to high temperatures, so it suits cold-running assemblies rather than hot ones. Epoxy-based coatings are very sturdy and usually opaque, with good moisture resistance, very good resistance to chemical corrosion and wear, and good dielectric properties — the choice for rigid potted modules where the coating has to survive the environment rather than flex with it.

Pick by the situation the high voltage diode will actually see. Oil-filled and gas-filled assemblies generally tolerate a harder coating, while parts that will be handled, vibrated or thermally cycled benefit from the elastic behaviour of silicone. Whatever the choice, clean the surface first: an adhesive applied over flux residue seals the contamination in, and the leakage problem simply moves under the coating.

Installation Guide

1. Check the cathode band against the board or stack marking before you form anything. Once a lead is bent, correcting the orientation means scrapping the part.
2. Form each lead over a support so the bend starts well away from the epoxy body. Bending flush against the body puts stress straight on the seal.
3. Set the lead length from the package drawing in the data sheet so the body clears the board surface and any nearby traces.
4. Solder quickly and keep heat away from the body. If your process runs hot, clamp or heat-sink the lead between the joint and the epoxy.
5. Clean flux residue from the body and from the lead exit points, then dry the part. At 18 kV a contaminated surface leaks far more than the chip does.
6. Where the part runs in air, fit insulated electrodes at both ends and hold clearance to earthed hardware on every side of the body.
7. Apply the insulating adhesive around the lead bend after cleaning, and let it cure fully before the assembly is potted or energised.
8. Measure reverse leakage at working voltage on the finished assembly before the equipment goes into service, so a surface problem is caught before it becomes a field failure.

Ordering & Delivery

• Shipping: orders are dispatched by international express.
• Minimum order quantity, unit price and current lead time are confirmed by your sales contact for the specific rating and quantity you need.
• Packing: axial diodes are usually supplied in taped or bulk packs for assembly; tell us which format your line uses and we will confirm what is available.
• Documents: ask for the data sheet and the package drawing if your incoming inspection file needs them.
• Payment terms and the paperwork for a first cross-border order are confirmed with your sales contact before the order is placed.
• Second sourcing: if you are comparing high voltage diode manufacturers against a part already in production, send the ratings your circuit actually sees and we will tell you which step in the family matches them.
• Keep one voltage step per line item. Mixing the 16 kV, 18 kV and 20 kV parts in a single bin is the most common way a stack ends up with the wrong diode in it.

Technical Support & Model Matching

Selection starts with your circuit, not a catalogue number: tell us the working voltage, load current, switching frequency and ambient cooling conditions, and our engineers will match a model from our range and explain the margin left in the design. Each model ships with its datasheet, package drawing and installation guide, and we stay available for mounting and soldering questions, start-up checks and fault finding when an existing part runs hot or fails early. Orders run from about 7 days to 6 months depending on quantity, usually by international express.

FAQ