Browse Prior Art Database

Use of Amalgam Jetting Technology for Z-Axis Interconnection

IP.com Disclosure Number: IPCOM000005031D
Original Publication Date: 2001-Jul-23
Included in the Prior Art Database: 2001-Jul-23
Document File: 2 page(s) / 25K

Publishing Venue

Motorola

Related People

Jad Rasul: AUTHOR

Abstract

Use of Amalgam Jetting Technology for Z-Axis Interconnection

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Use of Amalgam Jetting Technology for

Z-Axis Interconnection

Jad Rasul

BACKGROUND

The continuing increase in printed wiring board density associated with smaller and lighter weight portable products has driven the PWB industry into new innovative manufacturing processes. High Density Interconnection (HDI) technology is a printed wiring board (PWB) technology that enables the fabrication of PWB's with fine lines and spaces (typically 100um) and small vias and pads 5 mil inner via diameter). Consistently forming small vias to establish the vertical (Z-Axis) interconnections is challenging. Via forming can be done using a number of technologies that can range from the mass production photovia technology to the more selective laser drilling technology.

PROBLEM

Recent developments in PWB Z-Axis interconnection technologies enables the formation of small via sizes. However, plating those high aspect ratio vias is very challenging. The reliability of the plated vias currently used is also a concern. Cracking of the thin via wall plating inhibits high density interconnection technology from repeatedly producing high quality PWB's. Moreover, unfilled vias consume a large area of substrate real estate which can otherwise be used for component assembly or building subsequent layers.

SOLUTION

This invention incorporates the use of material jetting technology to fill high aspect ratio vias with a conductive amalgam. This process eliminates the need for electroplating of small vias (<3mil). By filling drilled vias with the amalgam, valuable surface real estate can be utilized for subsequent PWB build up layers.

Figure 1. Cross section of HDI PWB with amalgam filled vias.

Figure 2. Amalgam jetting process flow.

This invention replaces via hole electroplating with via amalgam filling using high yield jetting technology (Figure. 1).

Amalgams are non-equilibrium, mechanically alloyed materials formed at or near room temperature between a liquid metal and a metal powder. Amalgams offer exceptional thermal stability and superior joint strength. They can be jetted into the created vias forming a conductive post.