Alert: Export Control Check Required
Thank you for requesting a TWI Industrial Members Report.
To meet UK government requirements, your request will undergo an Export Control Check. This process reviews the technical content of the report, identifies the end user, and addresses any concerns.
Please submit your request to CRP@twi.co.uk including your name, member company that you work for and your location. We will contact you regarding the request within 2 working days and any additional information required to complete the necessary checks.
We look forward to receiving your request and processing it through our export control procedure.
Thank you,
TWI CRP Operations Team
This content is only available to Industrial Members, Find out how to become a Member of TWI.
TWI Industrial Member Report Summary 615/1997
R G Clements and N R Stockham
With the increase in interest in chip-on-board (COB) technology, wire bond interconnections are required to a wide range of printed circuit boards. This report demonstrates that successful bonds can be made to rigid, flexible and compliant boards, once optimised procedures are established.
Background
The use of chip-on-board (COB) technology in the electronics industry is increasing due to its low cost and the potential for increasing packing densities. The ultrasonic bonding of fine Au and Al wires (e.g. 25-33 µm diameter) on these organic based printed circuit boards has, in many cases, proved to be difficult. The relatively poor yields appear to be associated with the inherently soft and flexible nature of the material and the surface finish of the conductors.
TWI's many years experience in wire bonding has indicated that a high proportion of these problems could be overcome by establishing correct board clamping procedures and optimising bonding conditions (machine parameters and surface finish of tracks). This project aimed to establish the bondability of very thin (low cost) Au metallised Cu conductor tracks on FR4 (rigid), Kapton (flexible) and RT Duroid (soft) boards. This report deals with the techniques employed to establish satisfactory wire bonding to these substrates, discusses the issues involved and gives a best practice guide for wire bonding chip-on-board applications.
Objectives
To develop fine wire (25µm diameter) bonding techniques to enable interconnection to rigid, flexible and compliant boards with thin (0.3-0.9µm ) Au metallisation.