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Release: September 20, 1999

NGK DEVELOPS GVP CORE SUBSTRATE FOR BUILD-UP WIRING BOARDS

NGK INSULATORS, LTD. (President: Masaharu Shibata, Head Office: Nagoya) has developed a core substrate for build-up wiring boards, "GVP (Grid Via Plate: Trade Mark pending)" based on a new concept. NGK also applied jointly with IBM Corporation (Headquarters: N.Y., U.S.A., Chairman: Louis V. Gerstner, Jr.) for a patent on the build-up wiring board using the GVP, which features high reliability and circuit density.

The term "build-up circuit board" refers to a high-density, multiple-layer printed wiring board consisting of alternate layers of insulating and conducting materials. The core substrate serves as base of the build-up wiring board. The newly developed GVP uses insulating material which combines silica-based ceramics with epoxy resin. It contains numerous embedded electrodes, called "through-via electrodes," which allow electric current flow through the substrate. Until now, manufacturers of build-up wiring boards have prepared through-via electrodes by drilling a large number of through holes in core substrates made of epoxy glass and then copper-plating the penetrations. The GVP is a general-purpose substrate with electrodes installed. It measures up to 500mm X 600mm and has approximately 170,000 embedded through-via electrodes with a diameter of 0.1mm which are configured in a grid pattern. As a result, the GVP does not require through-hole drilling and copper-plating. Use of GVPs enables manufacturers to produce build-up wiring boards with higher reliability and density.

Main Features of the GVP

  1. The GVP is equipped with grid-like through-via electrodes, eliminates through-hole processing, and achieves higher circuit densities.
    Since the GVP contains grid-like through-via electrodes, there is no need for the drilling and plating processes carried out by manufacturers of conventional wiring boards. The current standard pitch for through-via electrodes is 1.27mm; however, a narrower pitch of 0.5mm is now under development. Once developed, higher-density wiring boards will be available.
  2. The GVP can prevent barrel cracks.
    Since conventional epoxy glass substrates have large vertical direction thermal expansion, barrel cracks (cracks on the plated penetrations) occur when parts are soldered on the substrates. The GVP employs a compound insulating material made by diffusing ceramics throughout resin, thereby balancing thermal expansion in all directions; in addition, the compound applies the same thermal expansion coefficient as through-via electrodes. As a result, the GVP is free from deformation due to heat and prevents barrel cracks. The small number of irregularities on the through-via electrodes also helps increase the reliability of build-up layers.
  3. GVP eliminates copper migration within the substrate.
    A phenomenon known as "copper migration" occurs under high humidity conditions if copper from the anode melts out due to the electrical potential difference between conductors and if the melted copper travels and precipitates over the interface between the glass fiber and resin. This phenomenon occurs in conventional epoxy glass substrates because the melted copper travels along the continuous interface between the glass fiber and resin and deteriorates insulation between through holes made by drilling. On the contrary, the GVP does not contain glass fibers and the interface between silica-based ceramics and resin is noncontinuous. As a result, the GVP does not experience copper migration.
  4. The GVP provides a substrate which is low in permittivity and dielectric
    NGK has achieved the GVP's low permittivity and dielectric dissipation by combining ceramics and resin for its material. Compared with conventional epoxy glass substrates, the GVPs are superior in their high-frequency property.

This new product was developed as the result of soliciting development ideas for new products form NGK's employees. Initially, development was conducted as a project within the company's research laboratory but was subsequently transferred to "BIU" (the Buiness Incubation Unit) established in April 1994 to accelerate commercialization. NGK aims to reach sales of 10 billion yen within the next five years.

* Schematic diagram of the GVP core substrate for build-up wiring boards
Photo and schematic diagram of the GVP core substrate for build-up wiring boards

Photo and schematic diagram of the GVP core substrate for build-up wiring boards


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