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Flip Chip ASSEMBLIES

Description:

A Polymer Thick Film (PTF) or copper flexible circuit with a low I/O die (customer supplied) attached to the circuit using a conductive adhesive and an underfill material.

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Applications:

• RFID passive and active transponders integrating a PTF antenna.
• Low cost assemblies for consumer electronics.
• Integrated into a sub-assembly for OEM applications or to serve as an LCD driver.

Presentation Options:

• Singulated; Either integrated to an SMT circuit assembly or as a discrete circuit.
• Reel or fanfold; Assemblies may be supplied in continuous web with or without tractor feed for use in automated assembly line.

Design Considerations

• Poly-Flex flip chip applications will normally integrate die with .016" (0.4mm) pitch, or greater. PTF trace routing is the driver for this restriction.
• PTF ink has inherent resistance of 0.015 ohm/sq/mil.
• Multiple low cost substrate options are available, however the standard offer is on PET.

Assembly Features and Specifications

• Environmental

Storage Temperature: -40C to 85C
Environmental stability: 85C / 85% R.H., 1000 Hours (see Graph 1 below)
Humidity Range: 10% to 85%
Temperature Shock: -40C to 85C, 250 cycles (see Graph 2 below)

Graph 1	Graph 2

• Flip Chip Assembly Construction: See Figure 1 for typical cross section

IC / Die: typically specified by customer
Substrate: .004" or .005" polyester (PET)
Clear PET preferred
Alternative substrates may be considered

Conductors: PTF inks, including Ag and C loaded polymers.

Dielectrics: (if required) - Poly-Flex produces hydrophobic dielectric material for a wide variety of applications. Custom dielectric material integration is also feasible.

Joining Material: Patented Ag loaded isotropic conductive adhesive (Poly-Solder®).

Underfill: Alpha MPM underfill encapsulant. Other encapsulant materials have also been qualified.

Encapsulation: Poly-Flex encapsulant material or others per the specification.

Bumping Options: Metallized bumps include electroless Ni / Au, Sn / Pb, Au stud bumping or polymer options.

Die Presentation: Poly-Flex's leading edge process can integrate die provided in tape and reel packaging or pick directly from the wafer. Direct pick from the wafer enables placement tac rates of >10000 per hour on a single placement system for optimal applications.

Figure 1: Flip Chip assembly to PTF circuit Cross Section

 

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