Reel Splicing and Tape Joint Rules
Splicing joins the end of an almost empty carrier tape to the start of a full reel so that the feeder never has to be reloaded during a run. It is a small operation with a disproportionate effect: a splice that is too thick, offset by a fraction of a millimetre or made with the wrong tape will cause a feeder jam at 3 am, and the resulting stop costs far more than the parts involved. The rules that make a splice reliable are simple, and they are worth writing down because the operation is usually done by whoever is nearest.
Why Reel Splicing Is Used and Where It Fails
Reloading a feeder mid-run requires stopping the machine, removing the empty reel, threading the new tape and re-establishing the pick position. Each of those steps is a chance to make a mistake and a loss of output on a line that may be moving several thousand parts an hour. Splicing lets the change happen while the line runs, and the feeder simply picks up the new reel when it reaches the joint.
The failure modes are concentrated at the joint. A splice that is thicker than the tape will not pass through the feeder’s guides. One that is misaligned will shift the pockets sideways, so the nozzle picks from the edge of the pocket rather than the centre. One made with the wrong tape will lose adhesion at the joint and separate inside the feeder. Every one of those outcomes traces back to how the splice was made, not to the feeder.
Splice Tape Types and Their Selection
Splice tape is supplied in two broad types: a single-sided tape that is applied over the top of the carrier tape, and a double-sided tape that is placed between the two tape ends. The single-sided type is faster and is used where the carrier tape is thin and the pockets are shallow; the double-sided type gives a flatter joint and is used where the tape is thick or where the tape passes through a narrow channel.
The tape has to suit the carrier material. Paper carrier tape accepts a paper splice tape, while a polystyrene or polycarbonate carrier needs a tape whose adhesive does not attack the polymer. Where the splice tape is too wide, it overhangs the carrier and catches in the guide; where it is too narrow, it does not cover the joint and the two ends separate. The correct width matches the carrier tape width, and the correct length gives about 15 mm of overlap on each side of the joint.
The Cut: Position and Angle
The cut should be made between pockets, in the flat web where there is no component and no pocket edge. Cutting through a pocket leaves a ragged edge and a piece of the pocket wall that can catch in the feeder, and it also exposes the component at the end of the tape. The cut itself should be square to the tape axis, because an angled cut produces a joint that is wider on one side and misaligns the pockets at the joint.
A clean cut needs a sharp tool made for carrier tape. Scissors used for other purposes leave a curled edge and a burr, and they also compress the tape where they cut. A dedicated cutter that shears rather than crushes gives a flat end, and the ends should be inspected before the splice is made. Where the tape has been crushed or deformed, cutting back to a clean section and losing a few pockets is cheaper than fighting a splice that has been made on a damaged end.
Tape Alignment and Pocket Registration
The two ends must be aligned so that the pocket pitch is continuous across the joint. If one end is shifted by half a pitch, the feeder’s sprocket will engage the holes of one section and the pockets of the other, and the nozzle will pick from the wrong position for every component until the joint passes. The alignment is checked by holding the two ends on a flat surface and looking along the tape, or by using a splice block that has a channel to hold both ends in line.
The sprocket holes are the reference, not the pocket edges, because the feeder indexes on the holes. Aligning the holes gives the correct pick position even where the pocket edges are slightly out of register, which happens with older tape. A splice block with pins that engage the sprocket holes is the most reliable method and takes only a few seconds more than doing it by eye.
Cover Tape and Peel Force at the Joint
The cover tape is peeled back by the feeder before the pick position, and the peel force has to stay within the range the feeder expects. A splice that adds thickness under the cover tape increases the peel force at the joint, and a feeder set close to its limit will stall there. Where the splice tape is placed over the cover tape rather than under it, the joint is thicker and the peel force change is larger.
The cover tape of the new reel also has to continue from where the old one ended, without a gap that lets a component fall out and without an overlap that doubles the thickness. Some splicing practice joins the cover tapes with a short piece of splice tape on the underside, which keeps the joint within the pocket depth. The joint should be checked by pulling the cover tape across it by hand and feeling for a step, which is a quicker check than measuring the peel force.
Feeder Behaviour and Pick Position
The feeder indexes the tape by a fixed number of sprocket holes per step, so a joint that changes the effective pitch will shift the pick position slightly and then restore it after the joint. Most machines correct for this by re-teaching after a splice or by using a vision check on each pick, but a machine without that correction will produce a small number of offset placements after each splice. Knowing whether the machine has that correction decides how much the splice alignment matters.
Feeder condition amplifies the problem. A feeder whose sprocket is worn, or whose spring tension is low, will skip or slip at a splice where a good feeder would pass it. This is why spliced reels that run perfectly on one machine jam on another: the splice is the same, and the feeder is not. The feeder maintenance schedule should therefore include a splice test on a sample tape, which is a quick check that catches a worn sprocket before a production run.
Orientation and Polarity Checks
The most damaging splicing error is a polarity reversal. If the new reel is joined with the pockets facing the other way, every component after the joint is placed in the wrong orientation, and the error may not be noticed until the board is tested. The check is simple: before the splice, confirm that the sprocket holes are on the same side of the tape on both reels and that the component orientation within the pocket matches the drawing.
The check should cover the cover tape as well. Some tapes are loaded with the cover tape on the opposite face, and joining a reel loaded one way to a reel loaded the other way produces a twisted section in the feeder. Where a splice is made by an operator who did not load the original reel, the drawing for the part should be consulted rather than the appearance of the tape. Recording the operator and the part number against the splice is a small discipline that makes a polarity escape traceable to its source. The preventive maintenance and handling procedures cover the same theme from the equipment side, and both should be reviewed together.
Records, Training and Acceptance
A splice does not need a detailed record, but the shop should know who is qualified to make one and what a good one looks like. A short acceptance list works well: the cut is square, the pockets are in register, the tape is the correct width, the joint is no thicker than the carrier plus the splice tape, the cover tape runs continuously, and the orientation has been checked against the drawing.
Training should include doing the splice on a scrap tape and running it through a feeder, because the physical feel of a correct joint is easier to teach than a description of one. New operators should have their first few splices inspected, and the acceptance list should be posted at the machine rather than kept in a manual. Because a faulty splice usually shows up as a placement defect rather than as a feeder alarm, the first pass yield data for the period after a splice is the best evidence that the discipline is working.
FAQ
Can any two reels be spliced? No. The tape width, the material, the pocket pitch and the loading orientation all have to match, and the part number on both reels should be the same revision. Mixing two revisions of the same part is a change-control question rather than a splicing one, and it should be raised before the splice is made.
How many components are lost at a splice? Usually none if the splice is made between pockets with the correct overlap. Where a pocket is cut through, the component in it is lost, which is why the cut should be placed in the flat web between pockets rather than through one.
Does the splice affect the moisture exposure of the parts? A well-made splice leaves the pockets sealed. Where the cover tape is lifted across the joint, the parts in the affected pockets are exposed to the room, and the exposure time should be counted against the floor life for a moisture-sensitive part.
