An SDIP (shrink dual in-line package) is a through-hole DIP with a finer lead pitch than the standard part: 1.778 mm (0.070 in) instead of 2.54 mm (0.100 in). The tighter pitch packs more pins into a shorter body, which is why 1980s–90s memory, microcontroller, and video ICs used it. This guide gives the exact pitch, the row-spacing and pin-count options, the naming traps, and how to socket and source one today.

Key takeaways

• An SDIP (shrink DIP) uses a 1.778 mm (0.070 in) lead pitch, versus 2.54 mm (0.100 in) on a standard DIP.
• The finer pitch fits more pins in less length; a 64-pin shrink DIP is about 56 mm long, versus roughly 79 mm for a hypothetical 0.100 in 64-pin part.
• Row (body) spacing runs 300 mil (7.62 mm), 600 mil (15.24 mm), or 750 mil (19.05 mm), rising with pin count; 64-pin shrink DIPs use 0.75 in rows (Harwin).
• Watch the naming: “shrink DIP” (fine pitch) is not a “skinny DIP” (narrow 0.3 in body at standard 0.100 in pitch), and SPDIP is through-hole, not the surface-mount SSOP.
• Shrink DIPs need 0.070 in sockets or footprints; standard 0.100 in DIP sockets do not fit.
• The package is legacy: pin counts top out near 64 and new designs use SMT, so treat SDIP parts as end-of-life and buy from traceable sources.

What is an SDIP (shrink DIP) package?

An SDIP is a dual in-line package whose two rows of leads sit on a 1.778 mm (0.070 in) pitch, finer than the 2.54 mm (0.100 in) pitch of an ordinary DIP (electrical-information; Mill-Max). Everything else is familiar: a rectangular plastic or ceramic body, leads bent down for through-hole insertion, and a pin-1 notch or dot at one end.

[IMAGE 1: an SDIP shrink DIP beside a standard DIP, with lead-pitch callouts (0.070 in vs 0.100 in) and a pin-1 notch | alt: “SDIP shrink dual in-line package beside a standard DIP with lead-pitch callouts”]

The point of the shrink is density. At 0.070 in, a given pin count fits in about 70% of the length, so a high-pin device stays a manageable size on the board and in a socket. Shrink DIP appeared when pin counts on memory and microcontrollers outgrew a practical 0.100 in DIP but surface mount was not yet standard (Mill-Max). The letters vary by vendor: “shrink DIP,” “shrink plastic DIP” (SPDIP), and Microchip’s “SP” body all mean the same 0.070 in pitch.

SDIP vs. DIP: the pitch and size difference

The only defining difference is pitch; that ripples into length, pin count, and tooling.

Attribute	SDIP (shrink DIP)	Standard DIP
Lead pitch	1.778 mm (0.070 in)	2.54 mm (0.100 in)
Row (body) spacing	300 / 600 / 750 mil	300 / 400 / 600 mil
Typical pin range	24–64 (density-driven)	8–40 (mostly)
Body length, same pins	About 30% shorter	Baseline
Breadboard-friendly	No	Yes (0.1 in grid)
Socket / footprint	0.070 in only	0.100 in
Era / status	1980s–90s, legacy	Legacy, still stocked

A standard DIP maps onto the 0.100 in breadboard grid; a shrink DIP does not, so it needs its own socket or a custom footprint. That single fact causes most shrink-DIP surprises.

SDIP dimensions: pitch, row spacing, and pin counts

Pitch is fixed at 1.778 mm. Row spacing (the center-to-center distance across the two rows, the “body width”) steps with pin count, and it sets which socket fits. Common shrink-DIP bodies, using Microchip’s package-spec designators:

[IMAGE 2: a labeled shrink-DIP dimension drawing showing lead pitch, row spacing, and lead-row length | alt: “Shrink DIP dimensions: 1.778 mm lead pitch, row spacing, and lead-row length”]

Pin count	Row (body) spacing	Vendor designator (example)
24	300 mil (7.62 mm)	SPDIP “SP” 300 mil (Microchip)
28	300 mil (7.62 mm)	SPDIP “SP” 300 mil (Microchip)
42	600 mil (15.24 mm)	shrink DIP 600 mil
52	600–750 mil	shrink DIP
64	750 mil (19.05 mm)	shrink DIP “SP/SS” 750 mil (Microchip); socket 0.75 in (Harwin)

Body length follows from the pitch: with N pins there are N/2 per row, so the pin-1-to-last span is (N/2 − 1) × 1.778 mm. A 28-pin SPDIP spans 13 × 1.778 = 23.1 mm; a 64-pin shrink DIP spans 31 × 1.778 = 55.1 mm, which is why a “DIP-64” measures about 56 mm long (PCBSync) rather than the roughly 79 mm a 0.100 in 64-pin part would need. Lead width and standoff follow ordinary DIP practice; a shrink-DIP socket contact accepts a Ø0.38–0.63 mm lead (Mill-Max).

A naming trap: shrink DIP vs. skinny DIP vs. SPDIP vs. SSOP

“SDIP” is overloaded, and the wrong reading picks the wrong socket.

• Shrink DIP / SPDIP: 0.070 in pitch, through-hole. This is the package this article covers. Microchip labels its 24- and 28-lead parts “Skinny Plastic (SP)” and its 64-lead part “Shrink Plastic,” both at 0.070 in.
• Skinny DIP: a standard 0.100 in-pitch DIP in a narrow 0.300 in (7.62 mm) body, versus the wide 0.600 in body. Same pitch as a normal DIP, just narrower; not a shrink part (electrical-information).
• SSOP (shrink small outline package): a surface-mount shrink package, not through-hole. Some pages wrongly expand SPDIP as “shrink small outline”; that conflates a through-hole DIP with an SMD part, which is a different footprint entirely.

Because vendors mislabel these, distributor listings sometimes tag a 0.070 in part as “PDIP.” Confirm the pitch from the mechanical drawing, not the marketing name (element14 community).

Sockets, footprint, and mounting

A shrink DIP needs 0.070 in hardware end to end.

• Sockets. Use a 0.070 in shrink-DIP socket; a 0.100 in DIP socket will not align. Machined sockets from Mill-Max and Harwin cover 24–64 pins; the Harwin D8864-42 is a 64-way shrink-DIP socket on 0.75 in rows and 0.070 in pitch, taking a Ø0.40–0.56 mm pin, and Mill-Max’s contacts carry 3 A (Harwin; Mill-Max).
• PCB footprint. Place the holes on a 1.778 mm pitch and the correct row spacing, then size the hole from the lead: per IPC-2222, hole = maximum lead diameter + 0.15 to 0.25 mm by producibility level. Watch copper-to-copper clearance, because 0.070 in leaves less room between adjacent pads than 0.100 in.
• Hand assembly. Shrink DIPs still hand-solder, but the tighter pitch bridges more easily; use a fine tip and inspect between pins. Socketing a scarce shrink-DIP part protects it during rework.

Where SDIP was used, and sourcing today

Shrink DIP was a density stopgap for through-hole memory, microcontrollers, video and audio controllers, and some automotive ICs of the 1980s and 1990s (Mill-Max). Once surface mount matured, new devices moved to SOIC, SSOP, QFP, and BGA, and pin counts above roughly 64 went to PGA or QFP; a DIP-64 is already large (PCBSync).

Treat shrink-DIP silicon as end-of-life. It survives in the repair and retro-computing channel, where remarked and mislabeled parts are common; verify the pitch and markings, and buy from traceable sources. For a new design that must stay through-hole, prefer a standard 0.100 in DIP if the pin count allows, or move to SMT; reach for shrink DIP only to match an existing socket or footprint.

Design and handling mistakes

• Assuming 0.100 in. The most common error: ordering a 0.100 in socket or laying a 0.100 in footprint for a 0.070 in part. Check the drawing.
• Breadboarding a shrink DIP. It will not seat on a 0.1 in breadboard; use a 0.070 in-to-0.100 in adapter.
• Trusting the marketing name. “PDIP” on a listing can hide an SPDIP; confirm pitch and row spacing.
• Tight pad spacing. At 0.070 in, annular ring and clearance shrink; follow the IPC hole rule and check the fab’s minimum.
• Bridging on hand-solder. Finer pitch solders closer; inspect between pins.

Frequently asked questions

What does SDIP stand for?

SDIP stands for shrink dual in-line package, a through-hole DIP with a finer lead pitch than standard. It uses 1.778 mm (0.070 in) between pins instead of the usual 2.54 mm (0.100 in), which fits more pins in a shorter body. It is also written SPDIP (shrink plastic DIP).

What is the pin pitch of an SDIP package?

An SDIP has a 1.778 mm (0.070 in) lead pitch, measured center to center between adjacent pins. That is 70% of the 2.54 mm (0.100 in) pitch of a standard DIP. Row (body) spacing is separate and runs 300, 600, or 750 mil depending on pin count.

Is SDIP the same as skinny DIP?

No. Shrink DIP (SDIP/SPDIP) has a finer 0.070 in pitch. A skinny DIP is a standard 0.100 in-pitch DIP in a narrow 0.300 in body, versus the wide 0.600 in body. The names are often confused, so check the pitch on the datasheet drawing before choosing a socket.

Can I put an SDIP chip in a normal DIP socket?

No. A standard DIP socket is on 0.100 in pitch and will not align with the 0.070 in leads of a shrink DIP. Use a dedicated 0.070 in shrink-DIP socket, or a 0.070 in-to-0.100 in adapter if you need breadboard access.

How many pins does an SDIP package have?

Shrink DIPs typically run 24 to 64 pins. Low-count 24- and 28-pin parts use a 0.300 in body; high-count 64-pin parts use a 0.750 in body. Above about 64 pins the package becomes impractical, and designs move to PGA for through-hole or QFP and BGA for surface mount.

The bottom line

Before you socket or lay out an SDIP, confirm one number from the mechanical drawing: the 1.778 mm (0.070 in) pitch. Match the row spacing to the pin count (300 mil for 24–28 pins, up to 750 mil for 64), buy a 0.070 in shrink-DIP socket rather than a standard one, and size the footprint holes from the lead diameter with the IPC-2222 rule. Do not trust a “PDIP” label on a listing; a shrink part hides behind it often enough to matter. For anything new, use a standard DIP if the pin count fits or go surface-mount, and keep shrink DIP for matching legacy hardware.