RFID Assembly

RFID (Radio Frequency Identification) tags are used as an alternative to bar codes for inventory control and theft protection. They are typically used in mass quantities and therefore must be produced for pennies a piece. Sizes are typically a few millimeters square down to several hundred microns.

All steps of RFID assembly can be accomplished with a FINEPLACER^® in either a manual or automatic system, with several optional configurations available.

RFID chip at fingertip

What are the Challenges?

Need for a flexible and easy to use system for process development
Quick adaptation to different bonding technologies required
High variety of designs creates many variables in parameters
Demand on specialized bonding equipment with very accurate thermal management
As RFID tech matures, component viewing and handling will become more critical

The Finetech Solution

Substrate Materials and Chip Characteristics

PET substrate

The typical substrate material is Polyethylenterephthalate (PET), thin (down to 0.1 mm), soft, flexible and thermally sensitive (max. 80°C). These properties necessitate well controlled process parameters during the bonding process. Furthermore, an appropriate vacuum holder is necessary to ensure an even working area.

Because of the substrate’s “floppiness”, underfill or encapsulation is obligatory.
Components are passive RF circuits having two or three bumps. Being typical two-pole circuits, they need an additional third bump only for mechanical stability.

Process Development in Preparation of Full Scale Production

The most common use of a FINEPLACER^® in the RFID domain is as a process development tool. Due to its modular application flexibility, the tool offers several processes for evaluation prior to full scale production, such as adhesive bonding, thermo-sonic bonding, dispense and UV cure. Optimized process parameters can be readily evaluated, such as temperature, time, force and ultra-sonic energy.

R&D test assemblies can be set up quickly for rapid prototyping to find the correct material combination and to generate samples for:

Adhesive testing
Ageing tests
Electrical optimization
Fatigue tests

Bonding Method 1: Ultrasonic Bonding

Overlay image of component’s underside and structure on substrate
RFID chip after placement

During alignment and placement, the chip is held on the die collet by vacuum. During the bonding process, the die collet executes transverse oscillations, transferring energy to the die/substrate-interface by friction. Typical frequencies are ~60 kHz.

Typical bonding parameters for an RFID chip are:

Power = 1 W
T = from room temperature up to 80°C
Time (of ultrasonic vibration) = 500 ms

Bonding Method 2: Adhesive Technology – ACP

Overlay image of component’s underside and structure on substrate, including ACP dot
Process camera view of chip and antenna
RFID chip after placement and bonding with ACP

ACP is dispensed onto the antenna and a chip picked from a wafer, aligned and placed. During handling, the chip is held by vacuum. Using the process camera, placement and subsequent curing can be viewed on the monitor.

Integrated Process Management (IPM)

Integrated Process Management (IPM)
Principle of process gas integration
Operating software for bonding

The Integrated Process Management (IPM) is the center piece of a FINEPLACER^® system¹ - the place where it all comes together. IPM is more than just thermal management. It synchronizes the control of all process modules and their related parameters:

Controlled and precisely balanced interaction of top and bottom (pre-)heating and cooling
Control of temperature, time, force, power, energy, flow
Controlled process gas integration for reduced solder contamination, minimized surface tension effects and smooth spherical solder residues

IPM is very complex, yet easy to access. Via the GUI of the operating software, the user has perfect control of all required adjustments. Just drag 'n drop to define temperature ramps or activate process modules. All settings are represented in only one profile, making for a very intuitive work flow.

The operating software provides an ever-growing library of profiles for all kinds of processes. It also offers comprehensive data logging functions essential for statistical process control.

In combination with the system-to-system process transfer capability this is as easy as process development can get.

¹ _{FINEPLACER^® core offers co-ordinated top and bottom heating but does not support IPM}