SD Card Socket Types: SD and microSD (TF) Sizes, Contacts and Mechanisms

An SD card connection is a row of flat pads on the card and a matching row of spring contacts in the socket on your board. The card is the standard part; the socket is what you have to choose. Card dimensions and contact counts on this page come from the SD Association SD Physical Layer specification. Every KINGCONN figure comes from the engineering drawing published on the part page.

SD, miniSD and microSD: the card sizes

The SD Association defines these form factors, and they are not interchangeable in a socket:

• SD — 32.0 × 24.0 × 2.1 mm, the full-size card with the write-protect slider.
• miniSD — 21.5 × 20.0 × 1.4 mm. Obsolete in new designs; you still meet it in legacy equipment.
• microSD — 15.0 × 11.0 × 1.0 mm, the card most modules use today.

An adapter shell lets a microSD card sit in an SD socket. That is a mechanical adapter only: it re-routes the pads, it does not change what the card can do.

Why "TF card" and microSD mean the same slot

TF (TransFlash) was the original name of the format before the SD Association adopted it. A part described as a TF card socket, a TF port or a T-Flash connector accepts a microSD card — KINGCONN uses either name inside the same series, for example 7TFCN-F0-0018 and 7MSDP-F0-0028. If a datasheet says TF, read microSD.

How many contacts an SD card socket has

A full-size SD card carries 9 contacts, miniSD carries 11, and microSD carries 8. UHS-II cards add a further row of pads behind the original row, which takes a full-size SD card to 17 contacts in total; a UHS-II socket needs that added row and a layout that treats the pairs as a high-speed channel.

Socket contact counts do not always match the card. Published counts across the KINGCONN microSD family run from 8 to 11 positions: versions that bring out a card-detect switch have terminals the card itself never touches. 7TFCN-F0-0126 is published at 9 positions, 7MSDP-F0-0037 at 11. Firmware that can tell "no card" from "card failed" needs that switch, so decide it before layout, not after.

Push-push, push-pull and hinge: the socket mechanism

The mechanism decides how the user gets the card back out, and it is the part of the selection that the card standard says nothing about.

• Push-push — insert to latch, push again to eject. No lever clearance, positive tactile latch. 7MSDP-B0-2210 is the push-push part rendered on our homepage.
• Push-pull (normal / no-push) — the card is pulled straight out. Fewer moving parts, shorter body, and the card cannot be launched out by a knock. 7TFCN-F0-0126 is a no-push socket at 1.15 mm profile.
• Hinge (flip / top-mount) — a lid folds down over the card. Used where the card is fitted at assembly and rarely swapped, such as 7MSDH-F0-1012.

The 3 numbers to read off the drawing

Profile height is usually the binding constraint: the KINGCONN microSD family publishes 1.15, 1.28, 1.45, 1.5 and 1.68 mm, and the full-size SD family 2.85 and 2.95 mm. Durability is published at 3,000, 5,000 or 10,000 insertion cycles depending on the model — specify the high class when the card is a user-replaceable medium (dashcam, data logger, POS), not a factory-fitted card. Contact and housing material: contacts are copper alloy or phosphor bronze, housings LCP rated UL94V-0, RoHS compliant.

KINGCONN SD and microSD sockets

The catalog lists 15 full-size SD sockets and 19 microSD (T-Flash) sockets, plus SD 4.0 (UHS-II) dual-row parts. For the selection question rather than the format question, read the SD card connector selection guide or the microSD connector selection guide; for the newer media, microSD generations and combo sockets. Send your height limit, mechanism and duty cycle to service@kingconn.com.tw and the Taoyuan R&D team will shortlist against the drawings.

Standards referenced:

• SD Association SD Physical Layer specification (card sizes and contact counts)