Heavy Wire Bonder Set a New Standard

Posted on 01 May 2019

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Quality and machine integrated tests

The designers have implemented an abundance of measures to reach a significant improvement in bond quality for fully automatic heavy wire bonders.

By Herbert Stürmann, Hesse & Knipps

 

Quality assurance

Industry’s target is the reduction of the failure rate to “0 ppm”. Innovations are demanded to achieve this challenge in an acceptable timeframe.

Bondhead integrated quality tests

For many years now a non-destructive test for heavy wire bonders has been called for which allows 100% control and can examine a wide range of possible quality errors. Generally, the integrated pull and shear test are suitable for this. Pull tests show in particular bad or non-bondable surfaces and cratering. Shear tests show weak points in the intermetallic connection.

The newly developed Hesse & Knipps bondhead is worldwide in its uniqueness as it is the only head containing the integrated pulltest and the integrated sheartest. The sensors integrated in the bondhead enable fast and safe pull and shear tests which can be set by the user with regard to his qualitative targets.

PIQC (Process Integrated Quality Control)

Both functions are integrated in the bondhead in such a way that the freespace around the bondhead is not at all constricted and the heavy wire bonder can be used in all applications without restrictions. The newly developed technical solution is applied for worldwide patent.

Bondhead

The Hesse & Knipps PIQC – Process Integrated Quality Control (patent EP1 023 0139 B1) is being integrated in the heavy wire bonder BJ920. PIQC enables the acquisition and assessment of several feedback values which influence bond quality. This quality control method is currently being tested in the field.

E-Box: reproducible set-up system for cutter, wire guide, bond wedge

Maximum accuracy is required when exchanging the wedge, the cutter and the wire guide in order to avoid quality reduction because of incorrect tool settings. The E-box allows micron-precise settings of the tools, allows immediate visual control by the operator and prevents shift-shift and techniciantechnician set-up variations. Control procedures and re-adjustments become unnecessary while the life time of the tools is increased. The time required for tool set-up compared to the usual procedure is reduced by about 70%.

The E-box allows micron-precise settings of the tools

Vibration elimination

It is widely known that the axes movements of the bonder can bring the complete assembly to vibration. If residual vibrations have not subsided during the bond process, it can negatively influence the bond process: considerable quality problems can occur due to lack of reproducibility and measurement methods of the bond process. State of the art sensor and control technology ensure that machine vibrations have no disturbing influence on the welding process or do not even occur. Beside the optimum touchdown detection (300ms), a high precision bondforce control is integrated. The touchdown and deformation sensor has practically no signal propagation delay. Its resolution is 0.1µm, the bond force is controlled to ± 1 cN accuracy. Furthermore, no sensor calibration is necessary.

The risk of damaging components with increasingly sensitive semiconductors is considerably reduced. The control system VC920 plays an important role in reducing the risk of field failures.

"Active" cutter system

The newly developed active cutter system is decoupled from the Z-axis and requires no pusher. This increases the free space for bonding inside packages. The system enlarges the setting window for cutting and so allows a much quicker cut process. The absolute repeated accuracy of the cutting system improves the quality as the risk of cutting into the substrate is prevented. The cutter life time is increased considerably. The system produces constant cut depths even with tolerances in the product.

Further features

The heavy wire bonder BJ920 has numerous other features: large working area (380 mm x 500 mm), intelligent and complete software concept, specifically developed pattern recognition system, transducers with different frequencies, fully digital generator with a wide frequency range, and much more. The machine concept fulfils the most demanding user requirements from automotive to leadframe applications. Preparations are underway for the adaptation for ribbon applications.

 

 

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