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Introducing Graphene into advanced printed circuit boards

Introducing Graphene into advanced printed circuit boards

 

A unique consortium has been formed between industry-leading companies and academic institutes to introduce Graphene into advanced printed circuit boards.

Graphene is a phenomenal 2D material made out of carbon hexagons. Despite its monoatomic thickness, it is extremely strong and has better electrical conductivity than that of metals. This attractive material can be deposited on copper, which is the metal of choice for PCBs, by chemical vapor deposition using methane as a precursor. Graphene/Cu stacks can then be integrated into standard PCB processing to form advanced circuits. Due to its 2D structure and high charge mobility, Graphene improves the circuit performance at high frequency, which is relevant for both RF systems - such as airborne and automotive radars, as well as for high-speed digital circuits used for 5G communication. Another exceptional property of Graphene is its thermal conductivity, which is 5 times higher than that of copper. This property enables significant improvements in heat dissipation, which is critical for an analog high-power devices such as amplifiers and transmitters. Graphene can be included in circuits not only as a layer – Graphene platelets can be mixed into hole-filling epoxy pastes thus improving the heat conduction of non-plated vias. A fine balance is needed in this case between Graphene and epoxy since a high percentage of the Graphene in the mix results in an electrically-conductive paste.

The challenge in working with Graphene is finding a way to include the material on Cu layers without harming its chemical nature by standard processing. As an example, Graphene is not resistant to strong oxidizing agents, such as those critical for surface preparation before drill-hole coating. Exposed Graphene can contaminate electrodeposition baths with carbon or lose its desired properties due to mechanical damage from handling.
So far we have managed to drill, press, and plate holes in Graphene-including circuits, which makes the next phase of Graphene patterning look promising. This work is done in close collaboration with Prof. Doron Naveh (Bar Ilan University), Prof. Oren Regev, and Prof. Gennady Ziskind (both from Ben-Gurion University).

PCB Technologies All-in-One approach has proved essential in this process providing decades of experience in using various raw materials and a wide array of engineering capabilities.

Our new CU fill (electroplated) machine enabling enhanced system performance

Our new CU fill (electroplated) machine enabling enhanced system performance

 

One of the main challenges facing the PCB industry is the need to reduce board footprint by creating vias with the minimum diameter and maximum depth (high aspect ratio) that will connect all layers of the printed circuit board. Mechanical drilling is not applicable for this purpose, as small diameter drill bits break easily and cannot penetrate multiple layers. The only way to achieve the desired aspect ratio is to vertically stack laser drills (micro-vias). To ensure that the drills are aligned with each other and are located at the correct depth (Z-Axis), the drills must be filled before the next pressing cycle.

Existing pre-filled epoxy-ceramic & Cu capped filling methods are not suitable for miniaturized PCBs in which the boards’ thickness is very small in size. Manufacturing a PCB with aligned laser drills requires CU fill (electroplated) of the micro-vias to assure, among others, no dimples are created which might result in reduced performance. This process allows optimal electrical conductivity between all stack-up layers.

PCB Technologies recently purchased a new CU fill (electroplated) machine (manufactured by #LSR), which was specially designed to meet this challenge. The machine is equipped with several agitation and spray systems to ensure uniform copper coating of the micro-vias.

This machine allows the filling of laser micro-vias with small diameters and aspect ratios as high as 1.1

Modified Semi Additive Process (mSAP) boosts High-Density Interconnect (HDI) PCB capabilities

Modified Semi Additive Process (mSAP) boosts High-Density Interconnect (HDI) PCB capabilities

 

For decades, the microelectronic industry has been engaged in shrinking electronic devices sizes for various applications (automotive, aerospace, medical industries, and others). At the same time, the demand for extended functionality and reliability, not to mention the competitive costs of the final product, has posed an additional challenge to the miniaturization technology. The solution dictated high density of conductor lines in the underlying PCB, thus allowing High-Density Interconnect (HDI) PCB capabilities.


PCB Technologies utilizes the Modified Semi Additive Process (mSAP) for that end. The process is based on a detailed flow:

1. Coating the substrate surface with a very thin Copper layer

2. Laminating the Copper with photoresist suited for high-resolution PCBs

3. Using Laser Direct Imaging to draw the PCB design on the inner layer pattern

4. Fine etching and stripping of the undesired Copper plating (quick etching).

This process leaves the Copper layer unimpaired on the one hand, and decreases its width on the other, thus allowing HDI on organic substrates which can then be used for capsulated dies (Systems in Package). The added value of the process is its high yields on large-format boards, enabling control of manufacturing costs on substrate-like panels.