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Browse Prior Art Database

Process Monitor for Electrical Microweld

IP.com Disclosure Number: IPCOM000062456D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Arjavalingam, G: AUTHOR [+2]

Abstract

Disclosed is an in-situ monitor which is arranged to directly monitor a key physical parameter governing an electrical microweld bonding process. Ordinarily the process is driven by a controlled voltage source and the process is monitored by measuring the current flowing through the bonding tip. The circuit diagram representing the conventional setup is shown in Fig. 1, where Ri, Rs and Rc are respectively the internal resistance of the voltage source, the standard resistance used to measure the current and the resistance of the tip. R(t) is the resistance of the melt zone and the contact resistance between the bonding tip and the wire represented by a single time-varying resistance. Since all the energy deposited into the wire is governed by R(t), it is the key physical parameter of the process.

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Process Monitor for Electrical Microweld

Disclosed is an in-situ monitor which is arranged to directly monitor a key physical parameter governing an electrical microweld bonding process. Ordinarily the process is driven by a controlled voltage source and the process is monitored by measuring the current flowing through the bonding tip. The circuit diagram representing the conventional setup is shown in Fig. 1, where Ri, Rs and Rc are respectively the internal resistance of the voltage source, the standard resistance used to measure the current and the resistance of the tip. R(t) is the resistance of the melt zone and the contact resistance between the bonding tip and the wire represented by a single time-varying resistance. Since all the energy deposited into the wire is governed by R(t), it is the key physical parameter of the process. The conventional process monitor measures the current I(t) as follows: I(t) = Vo Ri + Rs + Rc + R(t) This gives only an indirect measure of R(t). In Fig. 2, there is shown an alternative setup for monitoring R(t) directly. The voltage across the tip close to the wire and the voltage across Rs are both fed into a log-ratio amplifier 12 via voltage-to- current converters 10. The output of the log-ratio amplifier 12 is then input into an anti-log unit 14 to produce R(t) in real time. This setup can be used with either a voltage source or a current source for bonding.

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