scholarly journals Effect of Structural Design Parameters on Wafer Level CSP Ball Shear Strength and Their Influence on Accelerated Thermal Cycling Reliability

2009 ◽  
Author(s):  
Nikhil Lakhkar ◽  
Puligandla Viswanadham ◽  
Dereje Agonafer
Keyword(s):  
Thermal Cycling ◽  
Shear Test ◽  
Solder Ball ◽  
Wafer Level ◽  
Ball Shear ◽  
Ball Size ◽  
Ball Shear Test ◽  
Accelerated Thermal Cycling ◽  
Ball Shear Strength ◽  
Board Level

Ball shear testing is typically conducted in Wafer level chip scale package (WLCSP) fabrication to estimate the strength of the solder ball attachment. Generally, the solder ball shear strength is dependent on the solder ball size, pad size, solder/pad interface treatment, reflow temperature and time. Solder ball strength is also a function of ram speed and height at which the ball is sheared with respect to the wafer. Recent investigations suggest that ball shear test is being used as an indicator for board level reliability of assemblies. In current market lead time for launching a new product is very short. Unfortunately, it takes several weeks to qualify a new product by board level qualification process. If there is a methodology through which one can predict the board level performance by extrapolating the wafer level test, it will save great amount of resources in testing and millions of dollars worth of testing time. In the first part of this study, we conducted a wafer level ball shear test. A DOE was created for varying wafer level structural parameters like solder ball size and type. Ball shear tests and Accelerated thermal cycling have similar failure signatures of compression on inner side and tension on outer side. Thus, for specific cases there is a possibility of correlating the two failure methodologies based on their failure signatures. Strain rate for ball shear test was determined based on shear speed and solder pad diameter. Strain rate for accelerated thermal cycling was determined based on difference in CTE between board and package. In this paper, results from ball shear test and accelerated thermal cycling are compared to find correlations for specific cases. The correlations derived from this study are statistical and empirical.

A New Method for the Solder Ball Pull Test Using a Shape Memory Alloy Tube

2004 ◽  
Author(s):  
Jeffery Lo ◽  
Dennis Lau ◽  
S. W. Ricky Lee ◽  
Simon Chan ◽  
Frank Chan ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Shear Test ◽  
Solder Ball ◽  
Shear Loading ◽  
Ball Shear ◽  
Pull Test ◽  
Ball Shear Test ◽  
Attachment Strength ◽  
Inner Diameter

The solder ball shear test is a commonly used method to evaluate the attachment strength of solder balls. However, some previous studies indicated that the solder ball shear test may not be suitable for showing the effect of intermetallic compound (IMC) growth due to thermal aging. This is because the IMC layer is thin and not susceptible to the shear loading. Since the IMC layer consists of brittle materials, the ball pull test should be a better method to evaluate the solder ball attachment strength. The major challenge of conducting a solder ball pull test is how to grip the solder ball. This paper presents an innovative method for conducting the solder ball pull test. A shape memory alloy (SMA) tube is used to grip the solder ball and pull it off from the substrate. The inner diameter of the SMA tube is originally smaller than the diameter of the solder ball under testing. Once the temperature is raised to higher than the switching temperature of SMA, the SMA tube will expand radially, resulting an inner diameter larger than the solder ball. After the SMA tube cools down, the tube contracts and grips the solder ball firmly. The solder ball can then be pulled off from the attached substrate by frictional force. A prototype of the aforementioned solder ball pull test device has been developed. Some preliminary testing results are presented in this paper.

Optimum Shear Height for Evaluation of Pb-Free Solder Ball Shear Strength

2005 ◽  
Vol 486-487 ◽  
pp. 269-272 ◽  
Author(s):  
Jong Woong Kim ◽  
Sun Kyu Park ◽  
Seung Boo Jung
Keyword(s):  
Solder Ball ◽  
High Standard ◽  
Test Results ◽  
Element Analysis ◽  
Test Parameter ◽  
Ball Shear ◽  
Ball Shear Test ◽  
Ball Surface ◽  
Free Solder ◽  
Ball Shear Strength

Ball shear test was investigated in terms of the effects of important test parameter, i.e., shear height, with an experimental and non-linear finite element analysis for evaluating the solder joint integrity of area array packages. The substrate was a common SMD type with solder bond pad openings of 460 ㎛ in diameter. It was observed that increasing the shear height, at a fixed shear speed, has the effect of decreasing the shear force. The high shear height could cause some bad effects on the test results such as unexpected high standard deviation values or shear tip sliding from the solder ball surface. The low shear height conditions were favorable for screening the type of brittle interfacial fractures or the degraded layers in the interfaces.

The mechanics of the solder ball shear test and the effect of shear rate

2006 ◽  
Vol 417 (1-2) ◽  
pp. 259-274 ◽  
Author(s):  
Julian Yan Hon Chia ◽  
Brian Cotterell ◽  
Tai Chong Chai
Keyword(s):  
Shear Rate ◽  
Shear Test ◽  
Solder Ball ◽  
Ball Shear ◽  
Ball Shear Test

Accelerated Thermal Cycling Guidelines for Electronic Packages in Military Avionics Thermal Environment

2004 ◽  
Vol 126 (2) ◽  
pp. 256-264 ◽  
Author(s):  
Raghuram V. Pucha ◽  
Krishna Tunga ◽  
James Pyland ◽  
Suresh K. Sitaraman
Keyword(s):  
Thermal Cycling ◽  
Thermal Environment ◽  
Inelastic Strain ◽  
Electronic Packages ◽  
Strain Accumulation ◽  
Material Models ◽  
Process Mechanics ◽  
Accelerated Thermal Cycling ◽  
Damage Mapping ◽  
Board Level

A field-use induced damage mapping methodology is presented that can take into consideration the field-use thermal environment profile to develop accelerated thermal cycling guidelines for packages intended to be used in military avionics thermal environment. The board-level assembly process mechanics and critical geometric features with appropriate material models are taken into consideration while developing the methodology. The models developed are validated against in-house and published accelerated thermal cycling experimental data. The developed mapping methodology is employed to design alternate accelerated thermal cycles by matching the creep and plastic strain contributions to total inelastic strain accumulation in solder under military field-use and accelerated thermal cycling environments, while reducing the time for accelerated thermal cycling and qualification.

Effects of Tooling Tip Wear and Fixture Rigidity on Solder Ball Shear and Ball Pull Tests

2007 ◽  
Author(s):  
Fubin Song ◽  
S. W. Ricky Lee
Keyword(s):  
Shear Test ◽  
Failure Modes ◽  
Progressive Failure ◽  
Rigid Plate ◽  
Ball Shear ◽  
Pull Test ◽  
Pull Strength ◽  
Ball Shear Test ◽  
Significant Difference ◽  
Pull Tests

The present study is aimed at evaluating the effect of ball shear tool wear and fixture rigidity on ball shear and ball pull tests respectively. In particular, the emphasis is placed on understanding the progressive failure mechanism during the ball shear test. The location of crack initiating is investigated on two kinds of shear tool with different wear features. In this paper, the experimental investigation is presented. Specimens with PBGA solder balls are fabricated and a series of ball shear and pull tests are conducted. In the shear test, the shear tool is stopped at a certain stage during test, and then the specimens are inspected by SEM. The failure modes and location of cracks are characterized. From the ball attachment strength and crack location of the ball shear test, no significant difference is found between the shear tools with different wear features. For investigating the effect of fixture rigidity on the ball pull test, two kinds of PBGA package with different sizes was fixed on the fixtures with and without gluing on a rigid plate. The failure modes and ball pull strength with different fixture rigidity were compared. The test results indicate that more brittle failures are found on the specimens without gluing on the rigid plate during the ball pull test, both on two kinds of package with different sizes. In addition, the data scattering of ball pull strength is large on the case without gluing on rigid plate.

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