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44 The PCB Magazine • August 2014 by Dr. Khasha Ghaffarzadeh Idtechex f e a t u r e s h o r t Photovoltaic Market The photovoltaic market is a large, address- able market, which is growing again after sev- eral years of difficulty, when the prices crashed from $3.5/W in 2008 to $0.75/W in 2012. This period of overcapacity was characterised by many companies going bankrupt, closing, or selling. However, the market is showing signs of re- covery. Each crystalline silicon PV wafer carries 150–200 mg of screen-printed silver. This is mostly in the form of bus bars, but also fingers and back electrodes. Screen printing is a robust technology that is cost competitive. However, the high price of silver has compelled compa- nies to look for alternatives to silver as the high bill of materials can constitute up to 30% of the wafer cost. Plating is the main threat, although it is still at an experimental stage. Despite this, many in- dustry players expect to be phased-in in a sig- nificant way over the coming decade. A com- mon approach is to print a fine seed layer (i.e., inkjet print), plate nickel as a diffusion barrier and then thicken it with copper. Note that the silver nitride layer will have to be opened up to enable plating. In general, plating wins on re- ducing the bill of materials, but loses on high process costs as it is more complex than screen printing. IDTechEx estimates that plating will take approximately 20% market share by 2024. Touch Screen Market The touch screen market is booming. Con- ductive pastes are used to make the edge (or frame) electrodes, as shown in the image below. The edge electrodes can be made by sputtering followed by patterning or by printing. The for- mer method gives high resolution but can be expensive due to the subtractive nature and the number of steps involved. This method is most common in Korea. The latter method is lower cost but L/S resolution is typically 100/100. This method is most common in China and Taiwan. Our industry input confirms that 18–20 grams of conductive paste is consumed per one square meter of transparent conductive. It is noted that the trend in the industry is to narrow the frame, and the consumer will be demanding L/S Conductive Ink Market: Photovoltaic and Touch Screen Sectors

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