Thermocompression

Thermocompression bonding can be used for wire bonding or Flip Chip bonding. It needs contacts made of ductile materials, e.g. stud bumps created from Au wires. These can be located on either the substrate or component. On the opposite side, flat contacts, preferably of the same material, serve as bonding partners.

Without the necessity of liquefying the contact material, thermocompression bonding generates a joint by material engagement, providing acceptable mechanical firmness and steadiness as well as a good electrical conductance. Especially in connection with Flip Chip bonding, this process improves the RF properties of the bonding joint.

Au stud bump, magnification 300x, ø ≈ 50 µm

What are the Challenges?

Apply force and heat to the component simultaneously
Minimize substrate heater's compliance to absorb bonding force without deformation
Prevent thermal drift of heated area over a large temperature range (requires sophisticated support elements in connection with thermally compensated materials)
Provide thermally and mechanically stable component heater
Provide stable, fine resolution bonding force control to bond even the thinnest and most brittle materials as well as large components with lots of bumps
Achieve micron range coplanarity between component and substrate (requires adapted tooling or sensors and activators to detect and compensate deviations)

The Finetech Solution

Principle of Thermocompression Bonding

Principle of thermocompression bonding

To create a Thermocompression joint, component and substrate are first heated to roughly 300°C, and then pressed together for about half a second with defined bonding force. The joint builds up by diffusion welding and can be burdened immediately.

Thermocompression Parameters

Stud bumps on Au layer

Gold (Au):
T = 200 … 320ºC
F = 0.1 … 0.7 N/bump

Indium (In):
T > 60ºC
F = 0.02 N/bump

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}