Die Attach

Die Attach Techniques

Die attach or die bonding is the process of attaching a semiconductor die to a package, a substrate such as a PCB board or another die. The die attach process is fundamental to multiple types of packaging.

Examples

CMOS gold bumped — CMOS overlay with the MZM

Die stacking of batteries — Stack of solid state batteries

Die Attach Processes

The four common types of die attach processes offer differing bond properties and use either distinct workflow procedures or different materials.

Adhesive Bonding Adhesive die attach makes use of adhesives such as epoxy and polyimide to form a bond between a die and a package/substrate/another die. Read
Eutectic Bonding Eutectic bonding refers to attaching a die to a package or a substrate using a metal alloy as an intermediate layer to form a continuous bond. A eutectic bond is formed when the metal alloy in the melted state forms atomic contact with the die and the substrate. Read
Solder Attach Die is attached using a solder/solder paste.
Flip Chip Flip chip is a die attach method where the electrical connections between the chip and package/substrate are made directly by inverting the die face-down onto the substrate/package. Read

Additional Information

Die bonding processes are application specific where the operating conditions, environment and reliability requirements for the electronic device are considered. Forming a bond/joint between the die and the package, substrate or another die and its precise placement is a multifunctional process which aims to achieve the following:

Mechanically fix the die onto the package, substrate or another die.
Create a uniform contact between the die and other surfaces.
Good heat dissipation for the die and to withstand temperature extremes without degrading.
High thermal stability to reduce temperature induced mechanical stress in the bond/joint between the die and the package, substrate or another die.

General Die Attach Work Flow

Bonding Material Selection

A bonding material such as adhesive, eutectic preform or solder paste is deposited on a specific area of the substrate/package. The bonding material may be dispensed or dip coated on a substrate/package. In case of flip chip, gold balls/bumps are deposited first on the die.

Die Pick & Place

A die to be bonded is picked up from a die carrier or sawn wafer using vacuum, it is aligned and placed on a specific location on the substrate/package. The die to be bonded may arrive sorted into die carriers such as waffle tray, gel pack, tape or as a sawn wafer on backing tape.

Curing

A bonding material may need to undergo curing such as adhesives. Eutectic bonding uses scrubbing as an intermediate step whereas solder and flip chip process may require reflow.

Packaged Die Placement

As a final step, the package and attached die may be placed back in a waffle pack.

Die Attach at our Facility

At the Advanced Packaging Facility, we have used all the die attach processes. The facility contains a Tresky 3002 FC1-XP semi-automatic die bonder which has an integrated precise pick and place function. It has a heated work stage for eutectic bonding, an integrated dip coating needle and epoxy dispenser for adhesive and solder die attach options. The die bonder allows picking a die from a pre-sawn wafer using an additional die ejection vacuum tool to separates the bare die from the wafer backing tape. We also have a high precision Finetech FINEPLACER lambda flip-chip bonding machine which has a placement accuracy of up to 0.5 µm.