A Subminiature CCD Module Using a New Assembly Technique

You KONDOH  Masayuki SAITO  

IEICE TRANSACTIONS on Electronics   Vol.E74-C   No.8   pp.2355-2361
Publication Date: 1991/08/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Advanced Packaging Technology for Microelectronics Manufacturing)
Category: Interconnection

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Electronic video cameras have recently become both small and light. A CCD module is one of the principal devices in electronic video cameras, so it has been requested to become smaller and lighter. The authors have developed a subminiature CCD module. In this subminiature CCD module, a bare CCD chip is mounted directly on an optical glass substrate, and the outer circuit is connected to the surface of the glass substrate. This work needs two important assembly techniques. One is the COG wireless bonding technique, and the other is the glass outerconnecting technique. In the COG bonding technique, gold bumps are formed on aluminum pads of a CCD chip using the ball bonding method. A thick gold film wiring pattern and indium-alloy bumps are formed on the glass substrate. The CCD chip is pressed onto the glass substrate, and is heated. The CCD chip is connected electrically to the glass substrate. The glass outerconnecting technique is that of connecting an FPC (flexible printed circuit) to the glass substrate. The authors decided to use ACF (anisotropic conductive film) connection. An ACF is an adhesive film which has anisotropic conductivity. When it is placed between the glass substrates and FPC, pressed, and heated, the wiring pattern on the glass substrate is connected selectively to the corresponding electrode on the FPC. Four kinds of ACFs were examined and one of them was selected. The optimum conditions for COG wireless bonding and ACF connection using the above selected ACFs were respectively obtained. Four kinds of reliability tests, i.e., a high temperature test, low temperature test, high temperature and high humidity test, and thermal shock test, were carried out for COG bonding and ACF connection. Both COG bonding and ACF connection passed all the four reliability tests. The authors manufactured a subminiature CCD module using these new assembly technique on trial. The manufactured subminiature CCD module was small, one-fifth in volume, and light, one-tenth in weight, compared with the conventional types.