Fine‐Line Applications of Ormet® Transient Liquid Phase Sintered Conductive Ink

Abstract

In recent years, electronic devices have increasingly employed printed circuits produced using electrically conductive adhesives, commonly known as polymer thick films. This method is much more cost‐effective and efficient than other methods of wiring, including those using chemical etching or plating. In the past, the use of metal‐filled polymers as conductors in printed circuit fabrication has suffered from several limitations such as poor solderability, conductivity and adhesion. A new electrically conductive metal‐filled polymer formulation has been developed which overcomes these problems inherent in typical polymer thick film inks. This new product is based on transient liquid‐phase sintering wherein the metallic components of the formulation sinter at a relatively low temperature, resulting in a highly conductive continuous metal network. The sintering is achieved through the interaction of several metallic components with an adhesive‐flux component. The final product is highly conductive, solderable and exhibits excellent adhesion to a wide range of substrate materials. A new process for manufacturing fine‐line printed circuit boards using this ink technology is under investigation. It promises potentially simpler processing and lower cost than plating. In this new process, traces (in the form of troughs in the dielectric) are imaged using conventional photoimageable dielectrics. Exposure and developing conditions depend upon the polymer system used. The transient liquid phase sinterable conductive ink is applied to fill the photo‐exposed conductor pattern. Next, another layer of photoimageable dielectric is applied over the traces and imaged with vias for interconnections with subsequent layers. The dielectric is then cured and the ink applied to fill the vias. These steps may be repeated several times to produce low‐profile fine‐line multilayer printed circuits. This process for producing multilayer circuits using conductive inks simplifies the manufacturing of printed circuits, reduces profile, eliminates most waste in manufacturing, and reduces cost compared with plating.

Citation

Gandhi, P. (1997), "Fine‐Line Applications of Ormet® Transient Liquid Phase Sintered Conductive Ink", Circuit World, Vol. 23 No. 1, pp. 43-46. https://doi.org/10.1108/03056129710800071