ScreenWeb | screenweb.com

(June 2006) posted on Tue Jun 27, 2006

Learn about the function and construction of RFID tags and how screen printing and other imaging methods are used to produce these devices.

By Wim Zoomer

• 
• 
• 
• 

 

Table 3 Comparison of Screen-Printing Methods
Characteristic	Flatbed	Rotary
Print speed	low	high
Substrate	sheet	web
Run length	prototype and very short	short to medium

Rotary screen printing, flexo, and gravure are excellent techniques to manufacture large quantities of RFID antennas reel-to-reel. The run length of UHF antennas determines the most suitable print technique. Generally, two passes are required to print HF antennas using flexo and gravure, compared to one pass using rotary screen printing. Since double-pass production introduces the possibility of registration problems, rotary screen has become a dominant method for producing HF antennas in all run sizes. It also is used for short to medium run lengths of UHF antennas.

The subtractive method

For the subtractive method of RFID antenna production (sometimes called the print-and-etch method), the substrate is a laminate consisting of a plastic base material, such as polyester, covered with a layer of copper or aluminum that is 20-25 microns thick. A mask of etch resist is screen printed on the metallic surface of the laminate. This mask is a positive copy of the shape of the antenna, and it protects the metal underneath from being attacked by the etching agent (Figure 3). When the aggressive etching agent is applied, the agent dissolves the copper or aluminum that is not covered by the mask. Next, a stripping solution is applied to remove the mask, and the finished antenna remains (Figure 4).

The additive method

The additive method (also called the print-and-plate method) is similar to the subtractive method. It involves applying a thin deposit (a few microns) of conductive catalytic ink in the positive shape of the antenna onto a plastic substrate. This special ink contains metal particles. After the ink is applied, the printed material undergoes a galvanic process in which copper is plated onto the substrate, adhering only to the pattern created by the conductive ink. The process continues until the amount of copper deposited on the substrate reaches a thickness that provides the proper level of conductivity.

The future of RFID technology

Because the price of chips used in RFID devices is still relatively high, the use of RFID in the near future will be limited to niche applications for multiple-use HF tags. Such applications will include personal identification products, as well as tags for tracking books and documents. Rather than being used for single-product identification, long-range UHF tags will find use in logistics applications such as tagging boxes, pallets, and containers of multiple products.

As the demand for RFID tags and labels increases, the price of the chips used in these devices will come down. Consequently, we can expect to see applications for RFID technology expand. RFID specialists expect a substantial increase in the use of RFID products to occur between 2010 and 2015. When that time comes, the effectiveness that screen printing already has shown in producing antennas for RFID tags guarantees the process a bright future in this market.

About the author

Wim Zoomer is owner of The Netherlands-based Technical Language, a consulting and communication business that focuses on screen printing and other printing processes. He has written numerous articles for industry journals and is frequently called on to translate technical documents, manuals, books, and marketing materials between English, French, German, Spanish, and Dutch. He recently completed a book entitled Printing Flat Glass. For more information, visit Zoomer's Website at www.technical language.eu.