The DO-204AL package is JEDEC’s current name for the axial plastic body every engineer still calls DO-41 — the 1N4001 body. It holds a 2.0 mm to 2.7 mm diameter case with 25.4 mm leads, and it carries anything from a 1 A general-purpose rectifier to a 40 V Schottky. The mechanical outline is trivial. The rating conditions printed against it are not, and that is where designs go wrong.

Key takeaways

• DO-204AL and DO-41 are the same package. DO-41 is the archived designation; NXP also calls it SOD66.
• Body: 2.0 mm to 2.7 mm diameter, 4.1 mm to 5.2 mm long, leads 25.4 mm minimum each end at 0.71 mm to 0.86 mm diameter (Vishay drawing in document 88503, rev. 29-Apr-2020).
• Vishay’s “E”-suffix part numbers use a thinner lead: 0.58 mm to 0.66 mm. That changes your drill size and your thermal path.
• Current ratings in this package are quoted at different reference conditions. The 1N4001 is rated at 9.5 mm lead length and 75 °C ambient; the 1N5391 at 12.7 mm lead length and 70 °C lead temperature.
• Typical R(thJA) is 50 °C/W for the 1N400x and 55 °C/W for the 1N539x. Junction-to-lead is 25 °C/W for both — the leads, not the body, are the heat path.
• The same generic number can ship in two different outlines. Good-Ark builds 1N5391 in DO-15; Vishay builds it in DO-41.

What the DO-204AL outline specifies

DO-204 is the JEDEC family for lead-mounted axial diodes with round leads. Variant AL is the archived DO-41 outline, and it is the physically largest of the common plastic axial bodies below DO-15. A painted band marks the cathode end. Nothing in the registration constrains voltage, current or recovery time — only the envelope.

Vishay prints the outline in document 88503. Every dimension in the table below is taken from that drawing, and they are the numbers a footprint or a pick-and-place profile should be built against.

Feature	Dimension (mm)	Dimension (in)
Body diameter	2.0 to 2.7	0.080 to 0.107
Body length	4.1 to 5.2	0.160 to 0.205
Lead diameter, standard	0.71 to 0.86	0.028 to 0.034
Lead diameter, “E” suffix parts	0.58 to 0.66	0.023 to 0.026
Lead length, each end	25.4 minimum	1.0 minimum
Unit weight, 1N4004-E3/54	0.33 g	—
Unit weight, 1N5391-E3/54	0.336 g	—

The lead-diameter note is the one that bites. A 0.86 mm lead needs roughly a 1.0 mm finished hole; a 0.66 mm “E”-suffix lead rattles in it. If your board was drilled for the thicker lead and you second-source to an E-suffix part, expect wicking problems and marginal barrel fill on a wave line.

The rating-condition trap: 9.5 mm versus 12.7 mm lead length

This is the single most useful thing to know about DO-204AL, and no package-overview page states it. An axial diode dumps most of its heat out through the leads into the copper. So the current rating is meaningless without the lead length it was measured at.

Vishay rates the 1N4001 series at 1.0 A with 0.375 in (9.5 mm) lead length at TA = 75 °C. It rates the 1N5391 series — same DO-41 body, same document family — at 1.5 A with 0.500 in (12.7 mm) lead length at TL = 70 °C. The reference is not just a different number; it is a different quantity. One derating curve is plotted against ambient temperature, the other against lead temperature.

The ultrafast UF4001 series shifts the reference again: 1.0 A at 9.5 mm lead length, but at TA = 55 °C. That is a 20 °C penalty against the 1N4001 in an identical body, and it is easy to miss when a BOM swap is justified as “same package, same current.”

Vishay also qualifies the 1N400x derating curve for a board with 5.0 mm × 5.0 mm copper pads. Its 3 A DO-201AD sibling, the 1N5400 series, quotes thermal resistance against 20 mm × 20 mm copper heatsinks. Copy the copper, or the curve does not apply.

Worked example: a 1N4007 in a 55 °C enclosure

Assume a half-wave 60 Hz rectifier passing 0.6 A average, mounted with 9.5 mm leads on 5.0 mm × 5.0 mm pads. Maximum forward voltage is 1.1 V at 1.0 A, so conduction loss is roughly 0.7 W once the peak-to-average form factor is allowed for. At R(thJA) = 50 °C/W that is a 35 °C rise, putting the junction near 90 °C in a 55 °C enclosure — against a 150 °C limit.

Now trim the leads to 4 mm to fit a tight board. Junction-to-lead is 25 °C/W, so half the thermal path is inside the part and unaffected; the external half roughly doubles. The junction lands closer to 120 °C. Nothing on the schematic changed, but half the thermal margin is gone.

Choosing a die inside the same body

DO-204AL is a body, not a product. Four families dominate it, and the trade is forward drop against recovery and blocking voltage.

Series	Type	I(FAV) and condition	V(RRM)	V(F) max	Recovery
1N4001-1N4007	Standard	1.0 A, 9.5 mm lead, TA = 75 °C	50 V to 1000 V	1.1 V at 1.0 A	Standard
1N5391-1N5399	Standard	1.5 A, 12.7 mm lead, TL = 70 °C	50 V to 1000 V	1.4 V at 1.5 A	t(rr) 2.0 µs typ.
UF4001-UF4007	Ultrafast	1.0 A, 9.5 mm lead, TA = 55 °C	50 V to 1000 V	1.0 V / 1.7 V	t(rr) 50 ns / 75 ns
1N5817-1N5819	Schottky	1.0 A	20 V / 30 V / 40 V	0.45 V at 1.0 A (1N5817)	Fast

Two conditions to carry forward. The Schottky parts stop at 125 °C junction, not 150 °C, and the 1N5817 shows 125 pF of junction capacitance at 4 V and 1 MHz — enough to matter in a high-frequency freewheeling position. The 1N400x, by contrast, carries a fusing rating of 3.7 A²s for t under 8.3 ms, which is the figure you need to coordinate an upstream fuse and which almost no summary page quotes.

When to leave DO-204AL

Two steps up keep the axial form factor. DO-204AC (DO-15) is the intermediate body. DO-201AD is the 3 A body: 4.8 mm to 5.3 mm diameter, 7.2 mm to 9.5 mm long, with a 1.22 mm to 1.32 mm lead, per Vishay document 88516 rev. 19-Dec-2025. That lead is roughly 1.5 times the diameter of a DO-41 lead, which is most of where the extra current capability comes from.

Move up when average current exceeds about 1.5 A, when surge duty exceeds the 30 A to 50 A that DO-41 dice allow, or when enclosure ambient sits above about 70 °C. Move to SMA, SMB or SMC instead if the board is machine-assembled.

Sourcing and lifecycle reality

DO-204AL is not going away. DigiKey’s axial DO-204AL filter returned 2,607 line items in July 2026, and RS listed 13,940 units of the Vishay 1N4001-E3/54 in stock, priced down to a fraction of a cent each in reel quantities. Specific part numbers are a different matter: RS marked 1N4007-E3/54 as no longer stocked and 1N5395-E3/54 as discontinued by the manufacturer.

• Schottky parts move slower than the silicon ones. DigiKey showed a 15-week manufacturer lead time on 1N5817-E3/54 and 1N5819-E3/73, and RS showed 1N5818-E3/54 out of stock with a May 2026 restock date.
• Check the package field, not just the part number. DigiKey’s listing for the Diotec 1N4007 carries the package attribute “DO-204AC (DO-41)” — two mutually exclusive outlines in one field.
• The 1N5391 series is genuinely dual-outline. Good-Ark rev. B builds it in DO-15 (DO-204AC) and DO-41 (DO-204AL); Vishay 88514 builds it only in DO-41.
• Automotive work needs an explicit qualification. Vishay states plainly that the 1N4001 and 1N5400 series are not AEC-Q101 qualified. Taiwan Semiconductor sells an AEC-Q101 UF400x under an “H” ordering suffix in the same DO-204AL body.
• For high-reliability builds, Digitron offers UF4001-UF4007 screened to MIL-PRF-19500 JANTX level under an “HR” suffix.
• Counterfeit exposure is real here because the part is cheap and visually generic. Buy franchised and check the body marking against the manufacturer photo.

Design mistakes that cause returns

• Trimming leads short without re-deriving the thermal budget. The datasheet current assumes a specific lead length. Shorter leads mean less copper, and the rating no longer holds.
• Bending the lead at the body. Support the lead between the bend and the case, or the glass-to-lead or epoxy-to-lead interface takes the strain.
• Assuming 150 °C junction across the package. The 1N5817 through 1N5819 Schottky parts are limited to 125 °C.
• Substituting UF400x for 1N400x on “same package, same current”. The ultrafast part is rated at 55 °C ambient, not 75 °C.
• Ignoring the E-suffix lead diameter. A 0.58 mm lead in a hole drilled for 0.86 mm gives poor barrel fill.
• Exceeding the solder window. Vishay specifies solder dip at 275 °C maximum for 10 s per JESD 22-B106. Good-Ark quotes 260 °C for 10 s. Use the lower of the two if you dual-source.

Frequently asked questions

What is a DO-204AL package?

DO-204AL is the JEDEC outline for a molded plastic axial diode with round leads, formerly registered as DO-41. The body is 2.0 mm to 2.7 mm in diameter and 4.1 mm to 5.2 mm long, with leads at least 25.4 mm on each end. A painted band marks the cathode.

Is DO-204AL the same as DO-41?

Yes. DO-41 is the older designation and DO-204AL is the current JEDEC variant name within the DO-204 axial family. The physical part is unchanged. Datasheets print both, usually as “DO-41 (DO-204AL)”. NXP publishes the same outline under its own SOD66 name.

What are the dimensions of a DO-41 diode?

Per the Vishay outline drawing in document 88503, the body measures 2.0 mm to 2.7 mm in diameter and 4.1 mm to 5.2 mm in length. Leads are 0.71 mm to 0.86 mm in diameter and at least 25.4 mm long on each end. E-suffix parts use a thinner 0.58 mm to 0.66 mm lead.

What lead spacing should I use for a DO-204AL footprint?

Lead pitch is set by you, not by the package, because the leads are long and straight. A 10.16 mm (0.4 in) horizontal pitch is common and leaves room to bend without stressing the body. Whatever you pick, keep at least the datasheet lead length between body and pad or the current rating stops applying.

How much current can a DO-204AL diode handle?

Between 1.0 A and 1.5 A average, depending on the die and the stated reference condition. The 1N4001 series is 1.0 A at 9.5 mm lead length and 75 °C ambient; the 1N5391 series is 1.5 A at 12.7 mm lead length and 70 °C lead temperature. Surge ratings run 30 A to 50 A for an 8.3 ms half sine.

What is the difference between DO-41 and DO-15?

DO-15 (DO-204AC) is the larger axial body, with a thicker lead and more surface area, so it dissipates more. Both are axial plastic packages and both are used for 1.5 A parts, which is why the same generic 1N5391 number ships in DO-15 from one supplier and DO-41 from another. Always check the outline on the specific datasheet.

What to do next

If your average current is at or below 1.0 A and your ambient stays under 75 °C, specify a 1N400x in DO-204AL and lay out for 9.5 mm leads on 5 mm copper pads. If you need 1.5 A, use a 1N539x and budget for 12.7 mm leads and a lead-temperature derating curve. If you are switching above a few kilohertz, take the UF400x and accept its 55 °C reference. Above 1.5 A, or above 70 °C ambient, stop specifying DO-204AL and open the DO-201AD datasheet.

External references

• Vishay 88503, 1N4001 thru 1N4007: https://www.vishay.com/docs/88503/1n4001.pdf
• Vishay 88514, 1N5391 thru 1N5399: https://www.vishay.com/docs/88514/1n5391.pdf
• Vishay 88516, 1N5400 thru 1N5408: https://www.vishay.com/docs/88516/1n5400.pdf
• JEDEC DO-204 family index and variant table: https://en.wikipedia.org/wiki/DO-204
• Taiwan Semiconductor UF4001 series (AEC-Q101 “H” codes): https://services.taiwansemi.com/storage/resources/datasheet/UF4001%20SERIES_P2104.pdf
• Good-Ark 1N5391 thru 1N5399 (dual DO-15 / DO-41 outline): https://www.goodark.com/specification/1N5391%20thru%201N5399.pdf

Image placeholders

• IMAGE 1: Macro photograph of a 1N4007 with a scale rule, cathode band clearly visible. Alt: “DO-204AL package axial diode outline showing 2.7 mm body and cathode band on a 1N4007”
• IMAGE 2: Annotated mechanical drawing with body diameter, body length, lead diameter and 25.4 mm lead length called out. Alt: “DO-204AL (DO-41) axial diode dimensions including 2.0 to 2.7 mm body and 0.71 to 0.86 mm leads”
• IMAGE 3: Two boards side by side, one with 9.5 mm leads on 5 mm copper pads, one with trimmed 4 mm leads, with a thermal overlay. Alt: “Effect of lead length on DO-204AL diode junction temperature at 9.5 mm versus 4 mm”
• IMAGE 4: Size comparison of DO-204AL, DO-204AC (DO-15) and DO-201AD bodies against a common rule. Alt: “Axial diode package size comparison of DO-204AL, DO-15 and DO-201AD”

Internal link placements (fpga.io)

• INTERNAL LINK: “DO-201AD package” -> DO-201AD axial rectifier outline and 3 A derating
• INTERNAL LINK: “junction-to-ambient thermal resistance” -> how R(thJA) is measured and why board copper changes it
• INTERNAL LINK: “reverse recovery time” -> choosing standard, fast and ultrafast rectifiers
• INTERNAL LINK: “AEC-Q101 qualification” -> what AEC-Q101 covers and when you actually need it
• INTERNAL LINK: “through-hole footprint design” -> hole sizing and annular ring rules for axial parts