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8 mm vs 12 mm Feeder Tape: What Forces the Wider One

A build of nothing but 0603 passives and SOT-23 transistors will run for a year on 8 mm feeders. One narrow-body SOIC, one SMD electrolytic, or one 5 mm inductor changes that, and the tape decides it rather than the machine. A part wider than the pocket, or one that cannot sit on the available pocket pitch, will mis-pick at every feed position no matter how the feeder is tuned.

EIA-481-D is the standard that defines carrier tape dimensions. Three of its numbers set the minimum tape width for a given component: the outside pocket width (B1), the cavity pitch (P1) and the cavity depth (T2). The table below takes Table 2 of that standard, embossed carrier, and keeps the four widths a desktop machine uses.

Tape widthMax outside pocket width (B1)Cavity pitch options (P1)Max cavity depth (T2)
8 mm4.35 mm2.0 or 4.0 mm2.5 mm
12 mm8.2 mm2.0, 4.0 or 8.0 mm6.5 mm
16 mm12.1 mm4.0, 8.0 or 12.0 mm8.0 mm
24 mm20.1 mm4.0 to 20.0 mm in 4.0 mm steps12.0 mm

Chart of the EIA-481-D pocket width, pitch and depth ceilings for 8, 12, 16 and 24 mm carrier tape, with the slot cost of each width

Pocket width turns away every SOIC-8​

B1 is the outside width of the pocket, so it has to clear the widest part of the component. On a leaded part that measurement is the lead span, not the plastic body. A narrow-body SOIC-8 comes in at 6.00 mm across the leads (Analog Devices R-8 drawing: 5.80 mm to 6.20 mm), well past the 4.35 mm ceiling on 8 mm tape. Every 8-lead SOIC you buy arrives on 12 mm tape, and Renesas lists the 8-lead narrow SOIC on 12 mm in its own tape and reel specification (TB347). Vishay lists SO-14 and SO-16 on 16 mm tape and SOT-223 on 12 mm, while SOT-23 stays on 8 mm.

Passives sit a long way inside the 8 mm limit. An 0805 chip is 2.0 mm wide, so a 4.35 mm pocket leaves room to spare. The standard's own problem list is tighter than the table: B1 above 4.2 mm on 8 mm embossed tape is flagged in section 4.3(a) as a source of feeding trouble, which leaves 0.15 mm between that flag and the table maximum.

Pocket pitch keeps long parts off 8 mm tape​

Pocket pitch is the distance between pocket centres, and the longest dimension of a component runs along the tape. In 8 mm tape the only pitches are 2.0 mm and 4.0 mm, so a part longer than roughly 4 mm cannot be packed on it at all. That one rule pushes a lot of parts onto 12 mm tape. An SMD electrolytic measuring 5.4 mm by 4.3 mm needs 8.0 mm pitch, and 8.0 mm pitch starts at 12 mm tape. A 10 mm long inductor needs 12.0 mm pitch, which puts it on 16 mm tape or wider even though its width would fit inside a 12 mm pocket.

Pitch appears twice more in the standard's problem list, where 2.0 mm pitch on 8 mm and 12 mm embossed tape is flagged in section 4.3(a). Where the same component is offered on both a 2.0 mm and a 4.0 mm pitch reel, the 4.0 mm reel is the easier one to feed.

Punched tape stops at 12 mm and its pockets stay shallow​

EIA-481-D defines two carrier styles. Punched carrier exists in 8 mm and 12 mm only (Table 1), while embossed carrier runs from 8 mm to 200 mm (Table 2). The 0603 and 0805 reels in a parts bin are normally punched paper. Table 1 caps the punched cavity at 1.1 mm for paper base tape and 1.6 mm for non-paper base, and section 4.3(a) flags a punched cavity above 1.1 mm on both 8 mm and 12 mm tape. A part thicker than about 1 mm therefore ships on embossed plastic.

For embossed tape the depth ceilings are 2.5 mm at 8 mm, 6.5 mm at 12 mm, 8.0 mm at 16 mm and 12.0 mm at 24 mm, with tighter flagged values of 4.5 mm at 12 mm and 6.5 mm at 16 and 24 mm. A 5 mm tall part sits inside the 12 mm table limit but above the standard's 4.5 mm flag, while at 16 mm that flag does not bite until 6.5 mm. When a part fills its pocket, the taller tape is the safer order.

Cover tape seal depends on S1​

Table 2 sets a minimum S1 of 0.6 mm, the seal area between the pocket and the tape edge, and section 4.3(b) warns that below 1.0 mm there may not be enough area for the cover tape to seal. A part that fills the pocket width leaves less of that area, so a reel can sit inside every table dimension and still peel badly. Peel strength is specified in section 4.11 as 0.1 N to 1.0 N (10 g to 100 g) for 8 mm tape and 0.1 N to 1.3 N (10 g to 130 g) for 12 mm to 56 mm tape, pulled at 300 mm/min with the cover tape held between 165 and 180 degrees to the carrier.

Part movement gets looser above 12 mm​

Rotation inside the cavity is capped at 20 degrees on 8 mm and 12 mm tape and at 10 degrees on 16 mm and 24 mm tape. Lateral movement is capped at 0.5 mm on 8 mm and 12 mm tape and at 1.0 mm on 16 mm and 24 mm tape (Table 2, notes c and d). A part sitting 1.0 mm off centre in a 16 mm pocket is within specification, so a pick coordinate copied from one pocket does not hold for the next one. That offset is what bottom camera calibration measures, per pocket, instead of trusting the tape.

What the wider tape costs on a Vertex 4​

Slot cost separates 16 mm and 24 mm feeders from 8 mm and 12 mm ones. A Vertex 4 has 50 slots: 8 mm and 12 mm feeders take one slot each, while 16 mm and 24 mm feeders take two. Powered feeder four-packs are $299 in 8 mm and 12 mm, $319 in 16 mm and $329 in 24 mm, and the AS2 servo four-packs are $199 in every width, so on the AS2 line the extra cost of a wide feeder is the slot rather than the price.

Spool handling differs as well. Most 12 mm reels are wider than the feeder, which is why the mounting procedure runs them from a floor spool over a ramp (see mounting feeders). The 16 mm and 24 mm feeders reach farther forward to suit the tape exit path, so staging plates move back 5 mm and OpenPnP calibration gets redone on that rail. The standard adds its own warning in section 4.2(e) that a heavy reel may not work on every feeder.

Slot arithmetic bites as soon as a build mixes widths. Take a job with 34 eight-millimetre parts, 8 parts on 12 mm tape, 3 on 16 mm and 2 on 24 mm: 34 + 8 + 6 + 4 = 52 slots, two over the limit. Running 32 eight-millimetre feeders brings it to exactly 50 and leaves nothing spare, so the workable version is 30 eight-millimetre feeders with two slots held open. Counting feeders from a BOM is the other half of this arithmetic, covered in how to choose a feeder.

Checking a part before you order tape or a feeder​

  1. Measure the widest dimension. On a leaded part use the lead span, then find the smallest pocket width that clears it.
  2. Find the longest dimension that runs along the tape, then pick a width whose pitch options go above it. The practical ceilings are 4.0 mm at 8 mm tape, 8.0 mm at 12 mm and 12.0 mm at 16 mm.
  3. Compare the thickness against the depth ceilings: 1.1 mm on punched paper, 2.5 mm at 8 mm embossed, 6.5 mm at 12 mm embossed, 8.0 mm at 16 mm embossed and 12.0 mm at 24 mm embossed, keeping the 4.5 mm and 6.5 mm flagged values in mind.
  4. Take the widest answer from the three steps. If it lands on 16 mm or 24 mm, check the slot budget before ordering, and budget for two slots and a recalibration rather than one.

Most boards we see need 12 mm for one or two part numbers and nothing wider, so the first 12 mm feeder usually arrives with the first board that carries a SOIC. Nozzle choice follows the parts on the tape, so a 12 mm reel of SOICs and a 12 mm reel of electrolytics do not call for the same tip (Juki nozzle compatibility).

Further reading​