# SMD crystal

A surface-mount quartz crystal. Most series are ceramic packages: the ceramic base with its pads underneath and the lid on top. Epson MA-406 and MA-505 are moulded, with four leads bent under the body. The part is centred on the origin and seated on the XY plane, with the long side along X. Seen from above, pad or lead 1 is at -X -Y and they count counter-clockwise (2 at +X -Y, 3 at +X +Y, 4 at -X +Y). The two-pad TXC AX has pad 1 at -X and pad 2 at +X.

| Series | Maker | Length | Width | Height | Pads | Pad (X x Y) | Gaps between pads (X, Y) | Chamfered pad | Lid |
|---|---|---|---|---|---|---|---|---|---|
| FA-238 | Epson | 3.2 | 2.5 | 0.7 max | 4 | 0.9 x 0.8 | 1.2, 0.7 | none | metal |
| FA-238V | Epson | 3.2 | 2.5 | 0.7 max | 4 | 0.9 x 0.8 | 1.2, 0.7 | 1 | metal |
| TSX-3225 | Epson | 3.2 | 2.5 | 0.6 max | 4 | 1.0 x 0.8 | 1.0, 0.7 | 2, C 0.3 | metal |
| 7M | TXC | 3.20 | 2.50 | 0.70 | 4 | (0.9 x 0.8) | 1.2, 0.7 | 1 | metal |
| AX | TXC | 8.0 | 4.5 | 1.50 max | 2 | (1.5) x 2.0 | 5.0 | 2 | ceramic |
| ABM8G | Abracon | 3.2 | 2.5 | 1.0 max | 4 | (0.9 x 0.7) | 1.2 ref, 0.9 ref | 1 | ceramic |
| ABM3B | Abracon | 5.00 | 3.20 | 1.1 max | 4 | 1.20 x 0.80 | 2.60, 1.40 | 1 | metal |
| MT | EuroQuartz | 3.2 | 2.5 | 0.7 | 4 | 1.0 x 0.75 | 1.2, 1.0 | not drawn | metal |

Values in brackets follow from the drawing's gaps and the proportions below.

| Series | Body length | Body width | Body height | Overall height | Leads | Lead width | Lead positions | Feet |
|---|---|---|---|---|---|---|---|---|
| MA-406 | 11.7 max | 4.0 | 3.5 | 3.7 max | 4, on the long sides | 0.7 | 9.6 apart along the length | (1.2) ref, 2.1 between them |
| MA-505 | 12.70 | 5.08 max | 4.19 | 4.6 max | 4, on the ends | 1.09 | centre lines 3.3 apart across the body; 13.46 max over the ends | 2.54 long |

Every frequency of a series has the same package.

## Source

Each maker's data sheet, downloaded from the maker's own site except TXC AX:

- Epson, "Crystal unit" sheet for FA-238V, FA-238 and TSX-3225 (© Seiko Epson Corporation 2025), from <https://download.epsondevice.com/td/pdf/brief/FA-238_en.pdf>, linked from the FA-238 product page. "External dimensions": the body 3.2 ±0.1 x 2.5 ±0.1 (TSX-3225 ±0.15), 0.7 max (TSX-3225 0.6 max); FA-238 and FA-238V pads 0.9 x 0.8 with 1.2 and 0.7 between them, FA-238V's pad #1 chamfered; TSX-3225 pads 1.0 x 0.8 with 1.0 and 0.7 between them, pad #2 chamfered "C 0.3 Min.". "#2 and #4 are connected to the cover", so the cover is metal.
- TXC, "7M MHz Crystal", Rev. 1.09, from <https://www.txccrystal.com/images/pdf/7m-accuracy.pdf>. Page 2, "Dimensions": 3.20 ±0.1 x 2.50 ±0.1, 0.70 ±0.1; the bottom view gives the gaps between pads, 1.2 and 0.7, with pad 1 chamfered. Page 1: "Ceramic SMD package", "Seam sealing".
- TXC, catalogue page 22, "SMD Glass Sealing Crystals 8.0 x 4.5 x 1.5 mm AX Series", the copy LCSC hosts for part C7078706 (<https://datasheet.lcsc.com/datasheet/pdf/9b110e8e7e14b36ea63b1aaa26210cde.pdf>), since TXC's site has no AX file we could find. "Dimensions": 8.0 ±0.15 x 4.5 ±0.15, 1.50 max; two pads 2.0 wide with 5.0 between them, one chamfered.
- Abracon, "ABM8G", revised 08.13.15, from <https://abracon.com/Resonators/ABM8G.pdf>. Page 2, "Outline drawing": 3.2 ±0.1 x 2.5 ±0.1, 1.0 max; pads 1.2 ref apart along X and 0.9 ref apart along Y, 0.1 ref in from the ends; pad 1 chamfered; "ceramic glass sealed".
- Abracon, "ABM3B series", Revision U, 8/27/2024, from <https://abracon.com/Resonators/ABM3B.pdf>. Page 3, "Mechanical Dimensions": 5.00 ±0.10 x 3.20 ±0.10, 1.1 max for ABM3B (ABM3B1, 0.8 max, isn't modelled); pads 1.20 ±0.15 x 0.80 ±0.15 with 2.60 and 1.40 between them; pad 1 chamfered; "Seam Sealing".
- Epson, "Crystal unit" sheet for MA-406, MA-505 and MA-506 (© Seiko Epson Corporation 2020, marked discontinued), from <https://download.epsondevice.com/td/pdf/brief/MA-406_en.pdf> (`MA-505_en.pdf` is the same sheet). Page 1, "External dimensions". MA-406: body 11.7 max x 4.0, 3.5 high and 3.7 max overall, 4.8 max across the leads; leads 0.7 wide, 9.6 apart, wrapped under the body with feet (1.2) ref and 2.1 between them. MA-505: body 12.70 x 5.08 max, 4.19 high and 4.6 max overall, 0.2 min under the body, 13.46 max over the leads; leads 1.09 wide, wrapped round the ends with feet 2.54 long, their centre lines (the chain lines the 3.3 dimension runs to) 3.3 apart. MA-505's internal connection joins #1 to #4 and #2 to #3, so the old catalogue calls it 2-pin.
- EuroQuartz, "MT Crystals", from <https://www.euroquartz.co.uk/media/1904/mt.pdf>. "Outline & dimensions": 3.2 x 2.5 x 0.7; pads 1.0 x 0.75 with 1.2 and 1.0 between them; "metal lid". The sheet's note says the chamfered pad's position varies, so no pad is chamfered here.

**Proportions, for looks only.** The drawings show these but don't dimension them:

- Where a sheet gives only the gaps, the pads run from the gap to 0.1 inside the body's edge: TXC 7M both ways, and ABM8G along Y, where the drawing gives the 0.1 ref only at the ends. AX's pads run to the ends, as drawn.
- An undimensioned pad chamfer is 0.35 x the pad's smaller side. The bottom views are drawn turned over about the X axis, as the sheets that number their pads show, so AX's chamfer is on pad 2's corner at the gap, on the +Y side seen from above.
- The lid is 0.2 x the height thick, and AX's ceramic lid 0.4 x, as its side view draws it. It's set in from the base's edge by 0.04 x the width.
- The base's corners have castellation notches of radius 0.06 x the width.
- The pads are 0.05 thick, let into the base's underside.
- MA-406 and MA-505: the leads are 0.2 thick and run up the body's side or end to 0.4 x the overall height, as the side views draw them. Above 0.4 x its height the moulding's top tapers to 0.85 x its width, as the end views draw it. MA-406's pin-1 mark is a half-round notch at the -X end, radius 0.2 x the width and 0.1 deep. MA-505's -X top edge is bevelled by 0.08 x the length. MA-406's feet start 0.05 outside the body's sides, because (1.2) + 2.1 + (1.2) is 4.5 against the body's 4.0.
- Materials are for looks and a rough mass. The base is alumina. A metal lid is a Fe-Ni-Co alloy (Kovar, density about 8.4), and invar, the Fe-Ni alloy in the material list (8.05), stands in for it. A ceramic lid is alumina. The pads are gold-plated tungsten metallisation, so gold (19.3, about tungsten's density). MA-406's and MA-505's moulding is epoxy compound, mostly silica filler (density about 1.9 to 2.0) round the crystal's metal can, and ptfe (2.2) is the nearest in the material list. Their leads are tinned copper alloy, so copper.

## Catalogue models

The old catalogue's models for the ceramic packages were placeholder blocks without pads, so each name maps to the part it names, built from the maker's drawing. Measured on the reference models:

- Every 3.2 x 2.5 one, `Crystal_SMD_SeikoEpson_FA238`, `FA238V` and `TSX3225`, `Crystal_SMD_TXC_7M`, `Crystal_SMD_Abracon_ABM8G` and `Crystal_SMD_EuroQuartz_MT`, each with its `_HandSoldering` footprint variant, is the same block, 3.2 x 2.5 x 0.64, with a step on top and no pads. ABM8G is 1.0 max on Abracon's sheet and TSX-3225 0.6 max on Epson's.
- `Crystal_SMD_Abracon_ABM3B-4Pin_5.0x3.2mm` is a block 5.0 x 3.2 x 1.1 with no pads.
- `Crystal_SMD_TXC_AX_8045-2Pin_8.0x4.5mm` is a block 8.0 x 4.5 x 1.45 with no pads.

Epson MA-406 and MA-505's old models have leads, but not the leads on Epson's drawing, so they map to the parts built from the drawing:

- MA-406: the old model's leads are gull-wing feet 0.6 long, 3.6 apart at the board. The drawing wraps the leads under the body, with feet (1.2) ref and 2.1 between them.
- MA-505: the old model's end leads are 0.8 wide, with feet 1.73 long, centres 3.84 apart. The drawing gives 1.09 wide, 2.54 long and 3.3 apart.