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Method for a thermo-compression bonding process with ultrasonic feedback imaging

IP.com Disclosure Number: IPCOM000008989D
Publication Date: 2002-Jul-29
Document File: 6 page(s) / 744K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a thermo-compression bonding process with ultrasonic feedback imaging. Benefits include improved product reliability.

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Method for a thermo-compression bonding process with ultrasonic feedback imaging

Disclosed is a method for a thermo-compression bonding process with ultrasonic feedback imaging. Benefits include improved product reliability.

Background

              Ultrasonic vibrations are conventionally used for breaking down oxides on solder joints and interfaces to reduce requirements for flux to insure proper wetting of the solder.

              Improved process control may be critical to controlling solder joint shape, solder thermal interface material spreading to reduce stress concentration enabling smaller bump geometries and thinner solder thermal interface material thicknesses. Poor solder joint shape (see Figure 1) leads to solder fatigue and cracking (see Figure 2).

      The conventional thermo-compression bonding process enables control of temperature, time, pressure, and displacement. These parameters are programmed into a recipe and applied similarly to all units being processed with no real-time feedback to optimize the process.

      Optimizing the process achieves best results and increases bump geometries and thermal interface material (TIM) thickness to improve the yield and quality of outgoing material.

General description

      The disclosed method is a thermo-compression bonding process utilizing ultrasonic vibrations to generate an image from the echo pulse to determine the progression and quality of the solder joint being formed. This real-time image of the solder joint can be used to modify the thermal compression bonding process conditions, including:

·        Temperature

·        Force

·        Displacement

·        Vibration frequency

·        Dwell time

              This method reduces voids, improves solder wetting, and controls the solder join shape. In addition, the image provides feedback that can be used as for quality control to determine if the results of the bonding process are acceptable. The method can also be used with an x-ray or acoustic microscopy tool.

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