Copper Pattern Plating


One of the most common applications of copper electrodeposition is the panel and pattern plating used for the production of printed circuit boards (PCB/PWB) and wafers in the semiconductor industry.

Due to the complexity of the pattern over the surface, the position and number of the panels in the plating cell, and the requirement for high speed mass production, the copper deposit thickness over the substrate becomes very non-uniform. Additionally the aspect ratio of the through holes continuously increases, thereby putting more emphasis on maintaining uniform process conditions on the entire panel and rack.

The Elsyca SmartPlate simulation software platform allow taking into account the pattern layout and hole aspect ratio for predicting the copper layer thickness distribution over the panel or wafer. Hence the impact of changes in the plating cell design, process parameters and pattern layout on the layer thickness distribution can be quantified accurately.

Elsyca Intellitool is a software controlled electroplating tooling concept that severely reduces the pattern dependence of the deposited copper layer thickness over a board, both over the tracks and in blind and through holes.

Copper Plating Challenges

The Printed Circuit Board (PCB/PWB) industry has to cope with ongoing miniaturisation, short delivery times and reduced margins. This means that more complex boards need to be produced at lower cost and improved quality. An important cost factor during production is the yield. One of the most critical processes that influence the yield is the electrodeposition of copper, both on the surface and in the through-holes/vias as shown in the picture below.

The plating process needs to deposit a minimum amount of copper in all through-holes, regardless of the aspect ratio, while on the other hand the surface of the board cannot be overplated. In many high-end applications both panel and pattern plating is used to achieve the required specifications.

Elsyca's engineering solutions

Elsyca developed the dedicated simulation tool SmartPlate to predict the plated deposit thickness on PCB / PWB's while taking all relevant phenomena into account. Using this software solution, manufacturers can change process parameters or PCB / PWB layout design to ensure maximum yield with increased throughput. SmartPlate calculates the copper deposition on the surface of the PCB / PWB based on the pattern layout of the board, the plating tank configuration and the process parameters. Using these simulations, an Elsyca in-house developed and patented approach enables predicting the plating thickness in the through-holes and vias. This allows PCB manufacturers optimizing their production process and reducing scrap by plating through-holes within specifications.

Additionally, Elsyca has developed a fully automated intelligent tooling and plating cell configuration (Elsyca IntelliTool) for optimising the layer thickness uniformity regardless of the PCB / PWB layout and aspect ratios of the through-holes. The Elsyca Intellitool solution for PCB marks a revolution in control of the deposit distribution on printed cicuit boards allowing designer and manufacturers to plate (almost) any pattern layout within specifications.

In micro-electronics the ongoing trend is to reduce the feature size (sub 20 nm), thereby electroplating the wafer starting from a very thin or even completely absent copper seed layer. Another trend is the increasing wafer size (300 mm). Both effects lead to significant ohmic drop between the contacts at the outer ring of the wafer and the centre of the wafer. This ohmic drop causes increased non-uniformity of the current density distribution and thus increased non-uniformity of the deposit thickness over a large, high-end wafer. Additionally, the ohmic drop in the contact layer is strongly influenced by the deposited copper on top of the seed layer, so a time dependence of the deposition distribution is observed (terminal effect). The Elsyca Intellitool solution has the capabilities to compensate for each of these effects. Elsyca has designed and tested state-of-the-art plating equipment that includes the Elsyca Intellitool approach in collaboration with leading manufacturers in the semiconductor industry.

On the other hand, Elsyca's Advanced Engineering Services team assists in analyzing and optimizing the complete copper electroplating process making use of the powerful combination of lab experiments for determining plating bath characteristics, engineering expertise and computational modeling technology.
On top of the range of advanced engineering services, Elsyca has substantial experience in process optimization, in particular for assisting manufacturers to implement and refine the use of pulse plating for many different PCB / PWB applications. To increase the deposition rate and improve the plating uniformity many PCB manufacturers investigate into pulse plating. However, no standard approach exists for determining the optimal pulse signal, depending on the pattern and aspect ratio of the through-holes. Additionally the stability and repeatability of the process can be cumbersome.

Some examples

The simulation and validation of the Elsyca SmartPlate software solution for predicting the copper deposition thickness on the surface and in the through holes of printed circuit boards is presented here.

The application of Elsyca's Intellitool concept for copper deposition on printed circuit boards is demonstrated here.

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