Choosing carrier and cover tapes for tape-and-reel packaging is often an afterthought. Electronic component manufacturers may not view feeder packaging as adding value to their product. Carrier and cover tape are considered as pure cost, so the cheaper, the better.
However, proper carrier and cover tape selection will minimize part migration, flipping and sticking during transportation, and mis-picks during the pick-and-place process, preventing product and productivity losses during SMT assembly. Carrier and cover tapes can also protect sensitive devices against damage due to electrostatic discharge (ESD). Putting some thought into choosing the right carrier and cover tapes can help manufacturers balance the need for product quality with the desire to control cost.
Larger devices and those that require ESD protection are better served by a plastic carrier tape with embossed pockets. Plastic carrier tapes are constructed from a variety of polymers, but polystyrene and polycarbonate are the most common.
Polystyrene, the next level up from paper, can deliver a sufficient amount of protection and support at a cost-effective price for many components. A deeper, more rigid pocket than is possible with paper makes polystyrene carrier tape a good choice for some thicker components.
Moreover, polystyrene carrier tapes are available in dissipative and conductive versions to protect ESD-sensitive parts.
While polystyrene is a good solution for a large number of component packing applications, it does have some drawbacks.
Camber occurs when the carrier tape curves in the X/Y plane, increasing the risk of rough feeding into SMT equipment and errors during the pick-and-place operation. Industry standards such as EIA-481 and IEC 60286-3 dictate a maximum allowable camber of 1 mm over a 250-mm section of tape. Polystyrene tapes can exhibit a higher degree of camber than tapes produced from engineered plastics.
Choosing the right carrier tape for your device is only half the battle. Selecting the proper cover tape is also important to protect components, minimize product loss, and ensure a smooth ride through the pick-and-place process.
Heat-activated adhesive (HAA) cover tapes are the most widely used in the electronic component industry. Historically, they have been the least expensive and most readily available cover tapes on the market and work well in many cases. In the taping process, a heated sealing shoe presses the tape onto the edges of the carrier tape on both sides of each device, sealing the cover tape to the carrier tape while leaving the component free from active adhesive. In the HAA taping process, time, heat, and pressure must be carefully controlled to achieve optimum adhesion.
For smaller devices, a pressure-sensitive adhesive (PSA) cover tape may offer a better alternative to HAA tape. As the name implies, PSA tape adheres when pressure is applied; heat is not required to activate the bond. PSA tapes are designed to provide a smoother peel force.
In choosing carrier and cover tapes for tape-and-reel packaging, electronic component manufacturers must balance performance with cost-effectiveness. In selecting a carrier tape, manufacturers must weight the benefits and drawbacks of paper, polystyrene, and polycarbonate products for the component size and sensitivities that must be accommodated.
Cover tapes are available with heat- and pressure-activated adhesives.
A third alternative, universal cover tape, works well in a variety of applications with virtually any carrier tape.
Finally, manufacturers should weigh design capability, global reach, and technical service support when choosing a carrier and cover tape supplier. Technical support should be available to tape purchasers as well as end users in SMT assembly.
