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Introduction:-
A Bond Test Process is performed to determine the strength of an adhesive to hold together two materials while being stressed. After the bond has been applied, it is tested the strength of the bond by exerting force on the adhesive in an attempt to detach it from the material.
Purpose of Bond Test Process:-
The overall bonding of a material may be thought of as its bond strength, which is determined by the sort of stress applied to the bond and the temperature at which the test is conducted. The direction of the force applied to the bond will also affect its strength.
There are various types of Bond Testing in the semiconductor industry which are following:-
1) Wire Pull Test
2) Die Share Test
3) Ball Shear Test
4) Wedge Shear Test
5) Wedge Bond Wire Pull Test
The Bond Test equipment such as Nordson Dage 4600 Bond Tester, Stellar 4000 Bond Tester, Dage PC 2400 Bond Tester, and Hook-pull Test gauge.
1) Wire Pull Test:-
Wire Pull Test is one of the most common bonding tests to check the strength of the wire after the bond has been applied. In this test, a wire is pulled upward direction from the surface of the leadframe by a Hook-Pull tool until a bond is a failure or the wire breaks. There are two following methods to check the strength of the wire with its bond.
a) Destructive Wire Bond Pull Test:-
This test determines the minimum force applied to break the bond. This test method helps to an evaluation of the quality of the wire bond system. The pull force at rupture to check the strength of the wire is most frequently presented in the units of Grams.
b) Non-Destructive Wire Bond Pull Test:-
This test ensures the bond is not broken. This is achieved by applying a certain force that is determined by the type of device, wire diameter, and other parameters specified in the product specification and pull test procedure. The below images are showing the process of the Wire Pull test with the Hook-Pull tool.
2) Die Shear Test:-
The Die Shear is the minimal force required to shear the die and test the strength of the adhesion between the die and the substrate. Die shearing is determined by the size of the die’s surface area. The main parameters for Die Shear testing are speed and tool height. These parameters are similar to those which are used for the Solder Ball Shear test.
A Wedge-shaped Shear Tool is used with specified speed and the height where a die is bonded. This Wedge-shaped tool is perpendicular to the metal’s top surface and parallel to the edge of the die. During the shearing process, the Shear Tools ensure that the die remains parallel and that the weight is evenly spread. The die is then pushed against the Wedge-shaped tool until the test object fails or reaches the pre-determined force. The below image represents the Die Shear test.
3) Ball Shear Test:-
The Ball Shear Test is the most reliable test to determine the strength of the Solder Ball on the surface of the substrate. The Shear tool is positioned at an accurate height above the substrate’s surface and the force is recorded during the test. An accurate Ball Shear Test requires multi-axis control settings, and accurate speed and tool height, soft landing force, and firm clamping of the tool.
The Shear Tool is flat in shape but as an alternate, the cavity Shear Tool can be used for this testing process. The Cavity tool spreads the stress across a larger area, reducing ball deformation. The alignment of the Shear Tool to the bond is attained by the control of the X-axis and Y-axis through Joyst.
4) Wedge Shear Test:-
The Wedge Shear Bond test process is used to check the quality and strength of Wedge bonded joints from its surface by the Shear Tool. The tool must be adjusted to the Wedge and a high force can occur to perform this test.
A Wedge-shaped Shear Tool is used with specified speed and height. This Shear Tool is positioned at an accurate height above the substrate’s surface. The force is measured during this process until the wedge is sheared. The below image is showing the Wedge Shear Bond test.
5) Wedge Bond Wire Pull Test:-
Wedge Bond Wire pull test is used to check the quality and strength of a bonded wire. This test requires a high force with an accurate height of the Shear Tool and requires an automatic touchdown of the tool. Then Z-stage moves up with precision shear height. The shear tool height and the touchdown should be very accurate to measure the result.
A C-shaped Hook-pull tool is used to do this process as given in the below images.
