Koa Corp had a panel presentation at CEATEC JAPAN 2008 on an LTCC board on which wiring patterns are formed by combining photolithography, screen and inkjet printing and other methods.
Koa calls the new substrate the "LTCC Hybrid Wiring Board" because it is made by combining multiple wiring formation technologies. With the view of commercialization in fiscal 2009, the company reportedly succeeded in improving the technology to a level where samples can be produced.
The wiring patterning technologies can be selected and combined freely depending on the pattern size and width as well as whether the pattern is formed on the outer or inner layer of a multilayer board. The new method makes it possible to select the formation technique suitable for the wiring pattern, etc on each layer of a multilayer LTCC substrate.
For example, thin film formation technology and photolithography are applicable when the wiring width and pitch are sas mall as 20μm/20μm and the pattern is formed on the outer layer. When the pattern with a greater wiring width and pitch, like 60μm/60μm, is formed on the inner layer, conductive paste and screen printing can be used.
When the wiring width and the pitch are between the above values and the pattern is on the inner layer, metal ink with dispersed nanoscale particles and inkjet printing can be used.
Inkjet printing is applied only to the inner surface of the multilayer board because wiring patterns formed by ink-jetting may sometimes be removed, according to the company. The technique used for inkjet printing was developed in collaboration with Seiko Epson Corp.