Conductive Seed Layer for PCB and packaging electronics
Seed layer alternative for surface metal (either electroless process or vapor deposition)
Metallization are important processes for 3D IC chip packaging and printed circuit board (PCB) fabrication. For 3D IC chip packaging, interposer is an important bridge to vertically connect the stacked chip through redistribution lines (RDL). Regarding the materials of interposers, there are silicon, glass, resin and ceramic. To be an interposer, it has to have RDL and through hole as well. Through Silicon Via (TSV) and Through Glass Via (TGV) are often read.
For PCB with high density interconnection, microvia and Through Hole (TH) filling with copper deposit become more and more important, especially for smart phones. Both microvia and TH are composed of resin and glass fiber, which means that they are not conductors. Based on the above description, not only TMV but also microvia and TH need to be metallized before electroplating.
The metallization processes include dry and wet processes. Usually, dry processes, such as PVD, CVD and sputtering, are employed for the IC packaging fabrication whereas wet processes, such as electroless deposition and coating of conducting material, are employed for PCB fabrication. No matter dry or wet process, metal is the only material for sidewall metallization. A new metallization process proposed is using graphene as the seed layer for the subsequent metal electroplating.
Based on characteristics of graphene, direct plating process is developed, which used Graphene as both conducting and barrier layers for microvia and TSV. Also, plating TH (PTH) was achieved by using the Graphene process. Good throwing power of PTH was obtained, indicating that Graphene indeed is a good conductor to replace the traditional electroless copper deposition for microvia and PTH metallization and to replace the PVD or CVD copper seed layer for TSV metallization.
Seed layer – wet process alternative
PCB construction contains many layers to connect the circuits. The way to connect the layers is by through hole or blind microvia which are generally called interconnects. The dielectric layer of the interconnect has to be metallized to be conductive in order to make the electrical connection of different circuit layers. The traditional way to deposit a seed layer is by electroless copper process. This is the first step in the plating process with chemical deposition of a very thin layer of copper on the hole walls. Almost all PCBs with 2 or more circuit layers use plated through holes to connect the conductors between the layers. A good connection needs about 25 microns of copper on the walls of the holes. This thickness must be electroplated; however, the walls of the holes are non-conductive glass cloth and resin and the first step is to deposit a conductive layer over the hole walls. Currently, electroless copper is the most popular process for deposit chemically a layer of copper about 1 micron thick over the walls of the hole (and incidentally across the whole panel). The electroless copper is a multi-stage process including the pretreatment of hole wall, then seed the hole wall with micro-particles of palladium, and finally deposit the copper through a REDOX reaction.
Although electroless copper process was a historical proven technology for the PCB industry, there are several drawbacks of this traditional electroless process.
The demand for lower costs and more environmentally friendly processes has generated a need for alternatives to conventional electroless copper processing. We have a complete line of direct metallization solutions for substrates of all kinds. Graphene direct metallization is the choice for HDI and flex type constructions and allows for plating of complex through holes in a simple and easy to controll process Graphene Direct Metallization Process is a patented graphene based dispersion of conductive colloids used to make conductive for subsequent copper plating on various kinds of substrate materials. Most suitable for HDI and Flex PCB.
‧ Formaldehyde free and reduced water usage
‧ Superior Reliability
‧ Copper-to-copper direct bonding strength and good reliability
‧ No chelating agents and heavy metals
‧ Simple, easy to control process
‧ Compatible with exotic materials like PI, LCP, Rigid flex and Teflon
Insulation Coating
Graphene are impermeable under dry conditions. While exposed to water, they allow passage of molecules below certain sizes. The films consist of stacked few layers, leaving nano-sized cbetween them. Closing these nanocapillaries using chemical reduction creates films that are completely impermeable to gases, liquids or strong chemicals. Glassware or copper plates covered with such a Graphene coating can be used as containers for corrosive acids. Graphene-coated plastic films could be used in medical packaging to improve shelf life.
Flexible rechargeable battery electrode
Graphene has been demonstrated as a flexible free-standing battery anode material for room temperature lithium-ion and sodium-ion batteries. It is also being studied as a high surface area conducting agent in lithium-sulfur battery cathodes.
Optics
One of the most unique properties of Graphene oxide is that its electrical and optical properties can be tuned by manipulating the content of oxygen-containing groups through either chemical or physical reduction methods.
‧ Serve as promising solid state materials for nonlinear functional devices.
‧ Miniaturization of the conventional optical lenses for various applications such as communications, sensors, data storage and a wide range of other technology-driven and consumer-driven industries. Graphene oxide overcomes the challenges of current planar focusing devices. Lens thickness can be potentially reduced by more than ten times.
Water purification
Nano-filter – Water pass through but not for larger ions.
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