Schottky diodes are widely used in power rectification, freewheeling, protection, RF detection, and other applications due to their low forward voltage drop and high-speed switching characteristics. Its packaging forms are diverse, mainly selected based on power consumption (current), heat dissipation requirements, space limitations, and installation methods (via or patch). Here are some of the most commonly used and representative types of packaging:
DO-41/DO-15/DO-201AD (Axial Lead Packaging)
Characteristics: The most traditional and cost-effective packaging form. A cylindrical glass or plastic body with metal leads at both ends.
Advantages: Simple structure, sturdy, and low cost. Suitable for through-hole insertion (THT).
Disadvantages: Relatively large size, occupying a lot of PCB space, not suitable for high-density installation. The heat dissipation ability is average.
Application: Design for general rectification, protection, and other applications with low space requirements for small and medium power (common below 1A).
SMA/SMB/SMC (Surface Mount - JEDEC DO-214 Series)
Features: This is currently the most widely used surface mount Schottky diode packaging family. The sizes of the three increase in sequence (SMA is the smallest, SMC is the largest).
Structure: Plastic molded rectangular package with metal solder terminals (gull wing or internally bent) at both ends.
Advantages:
Miniaturization: significantly saves PCB space and supports high-density SMT assembly.
Performance: Provides good electrical performance and certain heat dissipation capability (through PCB copper foil heat dissipation).
Universality: Extremely common, with sufficient material supply and competitive cost.
Typical current range: SMA (below 1A - commonly 1A), SMB (1A -3A), SMC (3A -5A or higher). It depends on the chip design and heat dissipation conditions.
Applications: Input/output rectification, freewheeling diodes, reverse polarity protection, signal clamping, etc. of power converters (DC-DC, AC-DC), covering almost all modern electronic devices.
TO-220/TO-220F (direct insertion power package)
Features: Classic through-hole power semiconductor packaging. Usually comes with a metal heat sink (TO-220) or fully plastic sealed (TO-220F/FullPak).
Advantages:
Heat dissipation capability: The metal sheet of TO-220 can easily install heat sinks, providing excellent heat dissipation performance and suitable for medium to high power applications.
Current capacity: capable of carrying higher currents (usually 5A, 10A, 15A, 20A or even higher).
Easy to manually weld/repair.
Disadvantages: Large size, requiring through-hole installation, not suitable for compact design. The heat dissipation capability of TO-220F is weaker than that of TO-220 with metal plates.
Application: PFC rectification, output rectification, motor drive freewheeling, inverters, and other applications that require handling large currents and power in switch mode power supplies (SMPS).
TO-263/D ² PAK (Surface Mount Power Package)
Features: Surface mount version of TO-220. The size is smaller than TO-220, but there is a large metal backplate (heat sink) directly soldered onto the copper foil heat dissipation pads on the PCB.
Advantages:
High power density: combines the advantages of surface mount technology with powerful heat dissipation capabilities (through PCB heat dissipation).
Current capacity: The current carrying capacity is equivalent to TO-220 (5A, 10A, 15A, 20A+).
Disadvantages: PCB design requires a sufficiently large copper foil heat dissipation area, and the soldering process (reflow soldering) requires high standards.
Application: Similar to TO-220, it is mainly used for medium to high power switching power supplies, DC-DC converters, etc., and is the mainstream choice to replace TO-220 for SMT automation.
DFN/WDFN/LFPAK (ultra-thin/leadless surface mount packaging)
Features: Extremely compact and ultra-thin surface mount packaging. There are large exposed pads at the bottom and small electrical connection pads (DFN-2, DFN-3, DFN-5/6, etc.) around.
Advantages:
Ultimate miniaturization: occupying minimal PCB area and height, suitable for ultra-thin portable devices.
Heat dissipation: The bottom thermal pad provides a good heat dissipation path to the PCB (better than the same sized lead package).
Electrical performance: Low parasitic inductance, beneficial for high-frequency applications.
Disadvantages: After welding inspection (X-Ray) and repair are relatively difficult, requiring high PCB design and welding process requirements.
Applications: Portable devices with extremely limited space (mobile phones, tablets, wearable devices), high-performance DC-DC converters, high-frequency circuits, onboard POL (Point of Load) power supplies, etc.
Summary and selection key points:
Power consumption (current) is the primary factor: for small currents (<1A), DO-41 or SMA/SOD series can be selected; Medium current (1A-5A) SMB/SMC or DFN is the main force; For high currents (>5A), TO-220, TO-263 or larger packages are required.
Cooling requirements: The higher the power consumption, the higher the demand for packaging cooling capability. TO-220 (with heat sink), TO-263 (dependent on PCB heat dissipation), and DFN (dependent on PCB heat dissipation) are key packaging solutions for heat dissipation.
Space limitations: Modern electronic devices generally pursue miniaturization, and SMT packaging such as SMA/SMB/SMC/DFN is absolutely mainstream. Axial and TO packaging are gradually decreasing in space constrained designs.
Installation method: THT (DO, TO-220) vs SMT (most others). SMT is an industry standard.
Cost: Axial and standard SMT (SMA/SMB) typically have lower costs, while power packaging and ultra-thin packaging have higher costs.
Therefore, when choosing Schottky diode packaging, it is necessary to comprehensively consider the specific current and voltage specifications, heat dissipation conditions, available PCB space, production processes (SMT vs THT), and cost budget. SMA/SMB/SMC and TO-263 (D ² PAK) are currently the most widely used packaging forms in the market.