It has become a norm to automate most, if not all of the process steps involved in the packaging of semiconductor components. Such automated assembly lines are also commonly referred to as in-line packaging equipment. With increased automation, the need to manage semiconductor components in an in-line system is becoming more important. An efficient transportation system is thus required to take into account varying processing speeds on different equipment in the in-line assembly system and reduce idling time when waiting to proceed to the next process.
In a typical in-line transporter for semiconductor assembly equipment, the work flow of the in-line transportation mechanism of the semiconductor components such as leadframes and other substrates into a work-holder is unidirectional. Being unidirectional makes the transportation process easier to handle. However, with increased sophistication in semiconductor packaging equipment, the ability of in-line transportation mechanisms to manage bi-directional movement becomes an advantage. An example of this is in the case of a wire-bonding machine with dual bond heads which can simultaneously perform wire-bonding on two separate leadframes. In a conventional wire-bonding machine with a single bond-head, unidirectional transportation has proven generally adequate. However, dual bond-head wire bonders have been configured to allow bi-directional flow of the leadframes into the work-holders of the wire-bonding machine for bonding and out of the work-holder after bonding.
Bi-directional transportation can be useful in the event that one of the transportation mechanisms or one of the bond heads on the wire-bonding machine is not functioning. Therefore, an operator may have to avoid routing leadframes through the non-functioning transportation machine or bond head. Since this might mean leadframes being transported in two directions along the same travel paths (as will be explained in greater detail below), there needs to be a system in place to avoid congestions or bottlenecks along the transportation paths.