AN830 Datasheet | Microchip Technology

RFID Tag and COB Development Guide with Microchip’s RFID Devices Author: Youbok Lee, Ph.D. Microchip Technology Inc. Since the direct die att achment reduces a step for making the COB package, it is widely used for low cost and high volume applications such as smart labels. The direct die att achment can be achieved with two dif ferent methods: (a) wire bonding or (b) flip-chip with bumped die. For the flip-chip, it needs a special bumping on the die’s bond pads. Typically the bump material is made of gold with approximately 25 um of height. The flip-chip assembly process att aches the bumped area to the antenna tr aces. Several bumping and flip chip assembly methods are available for RFID t ags. The wire bonding method needs a relatively simple process for the die attachment. The die is directly wirebonded to the antenna, and covers the wire bonded area with a black colored epoxy glob top. For small volume pr oduction, the wir e-bonding method is still les s expensive than using the flip-chip process. However, it is less efficient for high volume production. The flip-chip method is preferred for high volume production. The read range of an RFID a t g is greatly affected by the tag’s size, tuning, circuit Q, de vice’s power consumption and data modulation depth. The tag’s size must be chosen depending on it s application and cost constraints. Tags must be tuned precisely to the reader ’s carrier frequency for long range applications. Since the tag’s antenna circuit consists of a bination of L and C ponents, the tolerance of the ponent often causes the variation in the read range between t ags. Once the induct ance is designed, it s tolerance is typically within 1 ~ 2%. Therefore, a t ag’s tuning variation is mostly due to the capacitance tolerance. The capacitance used for the antenna circuit or COB must be chosen carefully. For example, the tolerance must be kept within ~5% and the capacitor’s Q factor should be greater than 100 at the operating...