SMD diodes — the surface-mount range by package

Shenzhen Haiben Electronic Technology Co., Ltd. has supplied electronic components to electronics manufacturers since 2013, and through our wholly-owned subsidiary we operate the Weforsemi line of own-brand semiconductors. This page covers the surface-mount diode families we stock and the practical questions purchasing staff and hardware engineers ask when moving a design from through-hole to SMD. It is written for BOM work: which package suits which family, which parameters matter, and what to confirm before release to production.

Why production moved to SMD diodes

Through-hole diodes such as the 1N5400 through 1N5408 series in DO-27 still have a place in high-power rectification. For most new boards, though, the SMD diode has displaced them. The reasons are structural rather than fashionable: surface-mount parts have no lead holes to drill, so board area shrinks; they can be placed by standard pick-and-place equipment and reflowed with the rest of the board; and they sit closer to the pins they protect, which shortens the loop that transient current must travel.

For a purchasing team, the practical consequence is that the BOM line changes character. You are no longer specifying a leaded part with a long history and a datasheet in a drawer; you are specifying a package code, a reel, and a set of ratings that must match the circuit. The sections below map the packages we hold in the Weforsemi line to the families they carry.

The package map: SOD and DFN formats

Two package families dominate the range. The SOD family is a two-terminal leaded surface-mount format, scaled from the relatively generous SOD-123 down to the SOD-523 and SOD-882. The DFN family is leadless, with the terminals underneath the body, which gives a smaller footprint for a given die size and shortens internal paths.

From the stocked range, the mapping runs as follows:

• SOD-123 and SOD-123FL: the VC1N4148WB switching diode and the VCDS24WZ Schottky
• SOD-523: the VCRB520S-30B and VC5819THX Schottky diodes, and the VC1N4148WTB switching diode
• SOD-323: the VC103AWSB Schottky and VCLT550-YW TVS
• SOD-882: the VC520S8-30F Schottky
• DFN0603-2L and DFN1610-2L: the TVS/ESD family, including the VCTB3V32515LC and VCTU7V550F3S
• DFNWB0603-2L: the VC521S6-30X Schottky barrier diode

When choosing between them, treat the package as a constraint on both layout and assembly. Smaller bodies reduce board area but tighten the process window for paste volume and placement accuracy; confirm the footprint with your assembly partner rather than assuming the footprint library is correct.

Surface-mount Schottky and Zener diodes

Schottky diodes are chosen where forward drop and switching speed matter more than reverse leakage. In the Weforsemi line the ratings span a wide practical range. The VCDS24WZ is a 40 V, 2 A part in SOD-123FL. The VC5819THX in SOD-523 is rated 350 mA at 150 mW, with low forward voltage drop, guard-ring construction for transient protection, low reverse recovery time and low reverse capacitance. Smaller-current options include the VCRB520S-30B (30 V, 200 mA, SOD-523), the VC103AWSB (200 mW, low forward voltage, marking S4, SOD-323) and the VC520S8-30F (150 mW, low Vf, SOD-882). The VC521S6-30X in DFNWB0603-2L is a 100 mA-class versatile barrier diode with IFSM 0.5 A.

Zener references and clamps follow the same selection logic: pick the working voltage with margin, then check the power the package can dissipate at the ambient your enclosure will see. Do not size a Zener from its nominal voltage alone.

Our Schottky diodes and TVS diodes pages carry the full portfolio; the switching diodes page covers the 4148-type parts discussed below.

Specifying SMD diodes for a production BOM

For switching duties, the VC1N4148WB in SOD-123 is rated IF(AV) 150 mA with IR 1 uA and fast switching in a plastic surface-mounted package with 2 leads; a platform listing classes it at Vr 75 V. The VC1N4148WTB in SOD-523 is a 100 V fast switching diode in an ultra-small surface-mount package with high conductance, intended for general-purpose switching. The VC4148K in LL-34 is a glass-sealed epitaxial silicon switching diode with a planar structure.

For protection, the details that decide a part are the standard and the clamping behaviour, not the headline number alone. The VCTB3V32515LC in DFN0603-2L is bidirectional, 3.3 V working voltage, 80 W peak pulse power, 8 A peak pulse current, compliant with IEC 61000-4-2 (ESD) at +/-30 kV air and +/-30 kV contact, in a 0.6x0.3x0.3 mm package, with very low capacitance and ultra-low leakage at nA level, protecting one data or power line. The VCTU7V550F3S in DFN1610-2L (1.6x1.0x0.5 mm) is a 7 V part with 1600 W peak pulse power and 80 A peak pulse current for one data or power line. The VCLT550-YW in SOD-323 offers 350 W (8/20 us) peak pulse power, low clamping voltage and a Pb-free matte tin finish.

On the checklist: confirm the reverse voltage margin against the rail with derating applied; check leakage against the circuit's sensitivity; match capacitance to the signal bandwidth; and record the marking code so incoming inspection can verify the reel. If you need rectifier parts for the same board, the 1N5400–1N5408 series in DO-27 covers 3 A with grades from 50 V to 1000 V.

Frequently asked questions

Can you supply both the SMD part and the equivalent through-hole rectifier for the same build?

Yes. The stocked range includes surface-mount families and leaded rectifiers such as the 1N5400 through 1N5408 series in DO-27, so a single purchase order can cover a mixed board.

How do I choose between SOD-523 and SOD-882 for a small Schottky?

Compare the current and power ratings first, then the assembly process. The VC520S8-30F in SOD-882 is a 150 mW part, while SOD-523 carries the VCRB520S-30B at 200 mA and the VC5819THX at 350 mA. Where the rating allows, the smaller body saves area.

Are the TVS parts specified against a standard I can put in my qualification report?

The VCTB3V32515LC is stated as compliant with IEC 61000-4-2 at +/-30 kV air and contact. For other models, request the datasheet so the test conditions and clamping figures can be quoted directly rather than inferred.