Key Takeaways

• DO-35 = DO-204AH = SOD27 = SC-40. All four names designate the same JEDEC-registered package.
• Body: ≈ 3.5 mm long × ø 1.5 mm typical. Leads: ≥ 25.4 mm, ≤ 0.55 mm diameter (Vishay 1N4148 datasheet, Rev. 1.6, Nov. 2024).
• Power limit is 500 mW at 25 °C (4 mm lead length, TL ≤ 25 °C); derate above that temperature.
• The direct surface-mount form-factor equivalent is the LL-34 (MiniMELF / SOD-80C). For plastic SMD, use SOD-123 or SOD-323 depending on power budget.

[IMAGE 1: DO-35 package outline drawing showing body length, body diameter, lead diameter, and cathode marking band | alt: “DO-35 DO-204AH glass axial diode package outline dimensions diagram”]

Standard Names and JEDEC Registration

The DO-35 designation predates the current JEDEC numbering system. JEDEC later archived it under the unified DO-204 family as variant AH (DO-204AH), which is the preferred name in new design documentation. Three additional synonyms appear in datasheets and CAD libraries:

• SOD27 — JEITA (formerly EIAJ) designation; common on European and Asian datasheets
• SC-40 — EIAJ package code
• DO-35 — legacy name that remains dominant in distributor databases and EDA footprint libraries

When searching Digi-Key, Mouser, or JLCPCB, the legacy “DO-35” string returns the widest result set. When filing official design documentation, use “DO-204AH” to align with current JEDEC Publication No. 95 (Diode Outlines index).

Package Dimensions and Construction

Body and Lead Dimensions

The table below consolidates dimensions from the Vishay 1N4148 package drawing (Doc. 81857, Rev. 1.6, Nov. 2024) and the Diodes Inc. DO-35 package specification (Rev. 2017-05-15).

Dimension	Symbol	Min	Max	Source
Lead length	A	25.40 mm	—	Diodes Inc. / Vishay
Body length	B	—	3.40 mm (Vishay) / 4.00 mm (Diodes Inc.)	See note
Lead diameter	C / E	—	0.55 mm (Vishay) / 0.60 mm (Diodes Inc.)	Vishay / Diodes Inc.
Body diameter	D	—	1.75 mm (Vishay) / 2.00 mm (Diodes Inc.)	Vishay / Diodes Inc.
Weight	—	—	≈ 105 mg (Vishay) / 0.13 g (Diodes Inc.)	Respective datasheet

Note on body length divergence: Vishay quotes 3.4 mm max for the glass-encapsulated body; Diodes Inc. quotes 4.0 mm max. The difference reflects glass (Vishay) versus other body materials. For PCB footprint design, the 3.4 mm glass body is the dominant form in signal and zener diode applications.

Cathode identification: A band printed or fired onto the body near the cathode lead. On Vishay parts, the cathode band color is black. On tape-and-reel reels, the cathode end faces the colored tape and the anode end faces the white or light-beige tape (Diodes Inc. package specification Rev. 2017-05-15 — a detail critical for automated insertion machine setup).

Glass-to-Metal Seal Construction

The glass body is formed by threading two Dumet (copper-clad nickel-iron) stud leads through a borosilicate glass sleeve, then heating the assembly to approximately 700 °C to achieve the hermetic glass-to-metal seal (per US Patent 3,961,350). As the assembly cools, differential thermal contraction places the glass in compression against the leads, producing a seal that passes moisture resistance testing per MIL-STD-202 Method 106.

This construction gives the DO-35 a key advantage over plastic-bodied packages: hermetic encapsulation. No moisture penetrates the sealed junction, which is why the DO-35 remains specified in aerospace, mil-spec, and long-life industrial designs decades after plastic SMD alternatives became available.

DO-35 Parametric Comparison Table

The table below compares the DO-35 with its closest relatives across four package families.

Parameter	DO-35 (DO-204AH)	DO-41 (DO-204AL)	LL-34 (SOD-80C)	SOD-123	SOD-323
Mount type	Through-hole	Through-hole	Surface-mount	Surface-mount	Surface-mount
Body construction	Glass hermetic	Glass / plastic	Glass hermetic (MELF)	Plastic	Plastic
Body length (typ.)	3.5 mm	4.6 mm	3.5 mm	3.85 mm	2.85 mm
Body dia. / height (typ.)	ø 1.5 mm	ø 2.4 mm	ø 1.5 mm	1.35 mm	1.15 mm
Max power (25 °C)	500 mW	1,000–1,300 mW	500 mW	350–410 mW	200 mW
Typical max current	200–300 mA	1,000 mA	200–300 mA	200–300 mA	100–200 mA
Max Tj	175 °C	175 °C	175 °C	150 °C	150 °C
Tape pitch	5.0 mm	5.0 mm	N/A (reel)	4.0 mm	4.0 mm
Auto insertion	Yes (axial)	Yes (axial)	Reflow only	Reflow only	Reflow only
Typical uses	Signal, zener, Schottky	Rectifier, zener	Signal, zener (SMD)	Signal, zener (SMD)	Signal (SMD, small)

The LL-34 (MiniMELF, SOD-80C) is the closest form-factor successor to the DO-35: identical glass body construction, identical power rating, and an identical electrical die. Part numbers follow a direct mapping: 1N4148 (DO-35) ↔ LL4148 (LL-34); BZX55 (DO-35) ↔ BZX84 series (SOT-23, plastic, different form factor).

Common Part Families in the DO-35 Package

Part family	Type	Key ratings	Manufacturers
1N4148 / 1N914	Fast switching	VR = 75 V, IF = 300 mA, trr = 4–8 ns, CD = 4 pF (0 V, 1 MHz)	Vishay, onsemi, Nexperia, Diodes Inc.
BZX55 series	Zener	VZ = 2.4–75 V, Ptot = 500 mW	Vishay, Nexperia
BZX79 series	Zener	VZ = 2.4–75 V, Ptot = 500 mW	Vishay, NXP
BAT42 / BAT43	Schottky signal	VR = 30 V, IF = 100 mA, VF < 400 mV @ 10 mA	STMicroelectronics, Vishay
BAV21	High-voltage signal	VR = 200 V, IF = 200 mA, trr = 50 ns	onsemi, Vishay
1N4150	Fast switching	VR = 50 V, IF = 300 mA, trr = 4 ns	Vishay

1N4148 detailed parameters (Vishay Doc. 81857, Rev. 1.6, 07-Nov-2024, Tamb = 25 °C):

• Forward voltage VF: 1 V max at IF = 10 mA
• Reverse current IR: 25 nA max at VR = 20 V; 5 µA max at VR = 75 V
• Reverse recovery time trr: **4 ns** (IF = 10 mA, VR = 6 V, iR = 0.1 × IR, RL = 100 Ω); 8 ns under the standard test condition (IF = IR = 10 mA, iR = 1 mA)
• Diode capacitance CD: **4 pF** at VR = 0 V, f = 1 MHz
• Rectification efficiency: 45% at 100 MHz, VHF = 2 V
• Thermal resistance junction-to-ambient RthJA: **350 K/W** (l = 4 mm, TL = constant)
• Maximum junction temperature Tj: 175 °C; storage: −65 °C to +150 °C
• Power dissipation Ptot: **500 mW** (l = 4 mm, TL ≤ 25 °C); 440 mW at TL = 45 °C

The thermal resistance of 350 K/W is high by modern standards. A 1N4148 dissipating its full 500 mW reaches 175 °C junction temperature with only a 25 °C ambient. Real designs should budget no more than 200–250 mW continuous to maintain a meaningful thermal margin.

PCB Footprint and Assembly

[IMAGE 2: DO-35 horizontal mounting on PCB showing lead forming dimensions and minimum bend radius | alt: “DO-35 diode PCB footprint horizontal mounting with lead forming”]

Horizontal mounting (standard): Bend leads at 90° to place the body flat on the board. Standard through-hole land pattern centers pads at 10.16 mm (400 mil) or 12.7 mm (500 mil) pitch. Use a minimum bend radius of 1 × lead diameter (≥ 0.55 mm) and keep the bend at least 2 mm from the glass-to-metal seal to avoid cracking the hermetic seal — a common assembly defect causing long-term moisture ingress failures.

Vertical mounting: One lead inserts straight down; the other is looped back under the body. Requires 2.54 mm (100 mil) pad pitch. Saves board area when density is high.

Soldering: Wave solder per JEDEC J-STD-020. Maximum soldering temperature: 260 °C for 30 seconds (Diodes Inc. package specification). Hand-solder time should be limited to ≤ 3 seconds at 350 °C tip temperature.

Tape-and-reel packaging (Diodes Inc. DO-35 package specification Rev. 2017-05-15):

• Component pitch on tape: 5.0 mm ± 0.5 mm
• Tape width: 6.0 mm ± 0.4 mm
• Reel diameter: 345.0 mm ± 15.0 mm (13″ standard); alternate 260 mm ± 15.0 mm
• Polarity: **cathode tape is colored; anode tape is white or light beige.** Anode end must face the label side of the reel.
• Standard quantities: 10,000 per reel; 5,000 or 10,000 per ammo pack; 500 bulk per box

When to Stay DO-35, When to Switch

Use the DO-35 when:

• **Prototyping or breadboarding** — through-hole leads make manual placement and rework trivial.
• **Harsh environment or long-life design** — the hermetic glass seal withstands humidity, condensation, and corrosive atmospheres that degrade plastic SMD packages over time.
• **High Tj designs** — DO-35 is rated for Tj = 175 °C; many plastic SOD packages derate at 150 °C.
• **Repair / legacy board compatibility** — DO-35 remains the replacement package for decades-old military and industrial equipment.

Switch to a surface-mount alternative when:

• **Volume PCB assembly** — SMD (SOD-123, SOD-323, LL-34) eliminates axial insertion cost and supports full reflow processes.
• **Board density** — even a vertically mounted DO-35 occupies 3× the footprint of a SOD-323.
• **Wave-solder-free lines** — modern lead-free SMT-only lines cannot economically run through-hole axial parts.

Direct migration paths:

• 1N4148 (DO-35) → LL4148 (LL-34): identical die, glass hermetic, surface-mount footprint
• 1N4148 (DO-35) → 1N4148W (SOD-123): plastic, smaller, 3× lower power limit
• BZX55 series (DO-35) → BZX84 series (SOT-23): plastic, lower power, pin 3 unused
• BAT42/43 (DO-35) → BAT43W (SOD-123): Schottky characteristics preserved, smaller footprint

FAQ

What is the DO-35 package?

The DO-35 is a two-terminal, axial through-hole diode package with a hermetically sealed glass body approximately 3.5 mm long and 1.5 mm in diameter. It is registered with JEDEC as DO-204AH and is also known as SOD27. Common uses include signal switching, zener voltage regulation, and Schottky rectification at power levels up to 500 mW.

Is DO-35 the same as DO-204AH?

Yes. DO-35 is the legacy name; DO-204AH is the current JEDEC designation from Publication No. 95. Both names refer to the identical package. SOD27 (JEITA) and SC-40 (EIAJ) are further synonyms. All four names will yield the same package in distributor parametric searches.

What diodes use the DO-35 package?

The three main families are: fast switching diodes (1N4148, 1N914, 1N4150), zener voltage regulators (BZX55 series, BZX79 series, 2.4 V to 75 V), and Schottky signal diodes (BAT42, BAT43, BAT85). High-voltage signal diodes such as the BAV21 (200 V, 200 mA) also use the DO-35. All are rated ≤ 500 mW and ≤ 200–300 mA continuous forward current at 25 °C.

What is the SMD equivalent of DO-35?

The LL-34 (MiniMELF, SOD-80C) is the closest equivalent — same glass body construction, same 3.5 mm × ø 1.5 mm geometry, same 500 mW rating, surface-mount end-cap contacts. For plastic-body SMD: SOD-123 matches power (350–410 mW), SOD-323 is smaller but limited to ~200 mW. For dual-diode integration, the SOT-23 (e.g., BAV99) replaces two DO-35 Schottkys in a single three-pin package.

What is the difference between DO-35 and DO-41?

The DO-41 (DO-204AL) is physically larger — body approximately 4.6 mm × ø 2.4 mm versus DO-35’s 3.5 mm × ø 1.5 mm. The DO-41 handles up to 1,000–1,300 mW and 1,000 mA continuous forward current, making it the standard package for general-purpose rectifiers like the 1N400x series. The DO-35 is for signal and low-power applications (≤ 500 mW, ≤ 300 mA). Both are through-hole, axial, wave-solderable, and on 5.0 mm tape pitch.

Closing decision: Use the DO-35 when the combination of hermetic glass sealing, Tj = 175 °C rating, and through-hole accessibility outweighs the PCB area cost. For new SMT-only designs with standard ambient conditions, transition to the LL-34 (glass hermetic) or SOD-123 (plastic, lower cost) and verify the die power budget — plastic packages cap out 100–150 mW lower than the DO-35.