One of the key requirements for the plastic packages is to meet warpage requirements. Electronic packages experience various levels of temperature exposures during assembly processes. This is caused by the CTE mismatch of various materials involved, resulting in package deformation or deviation from the ideal state of flatness i.e. warpage. If this warpage is excessive, it can cause short or non-wet during solder ball attachment process as well as during board mounting process. Package warpage is typically temperature dependent.
Amkor measures package warpage for all type of packages at room temperature, and elevated temperature condition using Shadow moir’e tool. For warpage at high temperature condition Amkor fully comply JEDEC methodology (JESD22B112). Amkor also offer package warpage prediction using finite element tool for any package type at any temperature conditions.
The CTE mismatch and modulus of various materials within a package can result in excessives stresses during package assembly or actual use. Sometimes thermal stress at different interface or bulk material exceeds the failure strength and causes failure or delamination. Early prediction of these stresses during the design stage is necessary to avoid potential reliability concerns. Amkor has in-house capability for experimental and numerical analysis to investigate the package level stresses at die backside, UBM layer, substrate Cu traces, low K layers, and solder bumps, during assembly or test conditions. Finite element analysis is also used extensively to select proper materials during design stage.
Package level temperature cycle test are conducted to determine the ability of Flip Chip solder bumps to withstand the induced mechanical stress due to change of temperatures with time. In addition, Amkor provides bump level fatigue stress quantitative analysis for SnPb, high Pb, and Pb free solder bumps using finite element tool.
Interfacial delamination or fracture is one of the critical issues in packaging reliability. Most of the materials used for underfilling or molding are sensitive to moisture. Depending on the degree of moisture absorption, deabsorption, and intrinsic adhesion strength at the interface for various material types, delamination might occur between various interfaces. Therefore, characterizing materials for their adhesion strength with other surfaces is very important. Amkor conducts standard button shear, and four point bend test to evaluate the adhesion strength of various underfill and mold compound materials for different end conditions. In addition, moisture absorption simulations are performed at the package level to determine moisture concentration at various interfaces which can then be related to potential delamination.
Board level reliability is one of most important aspects of package selection. Electronic assemblies experience varied field use stress conditions during their useful life and package-to-board interconnects are required to survive these conditions. As part of our strategy to provide complete packaging solutions to our customers, Amkor offers solder joint reliability characterization of all package styles.
Amkor employs the following three temperature cycle test conditions for board level reliability, depending on the intended end use application of the package. All of these three conditions comply with IPC-9701 specifications. In-situ electrical testing is performed to identify failures.
|Condition (°C)||Min. Temp. (°C)||Max. Temp (Minutes)||Ramp Up Time (Minutes)||Ramp Down Time (Minutes)||High Temp. Dwell (Minutes)||Low Temp. Dwell (Minutes)||Cycle Duration (Minutes)|
|TC1||-40||125||15 (+5 / -0)||15 (+5 / -0)||15 (+0 / -5)||15 (+0 / -5)||60|
|TC2||-55||125||2 - 3||2 - 3||12 - 13||12 - 13||30|
|TC3||0||100||10(+2 / -0)||10 (+2 / -0)||10 (+0 / -2)||10 (+0 / -2)||40|
This test is implemented to provide a controlled environment to reproduce the interconnect failure mode commonly experienced during drop loading of handheld electronic systems (e.g., mobile phones, PDAs, etc.). Amkor took the lead in developing a board level drop test standard (JESD22-B111) and all tests are conducted as per this specification.
The cyclic bend test consists of bending the printed circuit board assemblies using a 4-point bend test fixture. This test may be used to reproduce solder joint failures experienced in packages mounted on key pads.
In addition to the above test capabilities, Amkor also offers solder joint life prediction capability using finite element simulation. The simulation provides a quick estimation of expected reliability and is used extensively in the pre-design stage. The life prediction approach correctly predicts the location of critical solder joint, location of failure (board or package side) with a high degree of accuracy for actual values.
Simulation capabilities also include board level bend and drop simulations, where a relative comparison is provided for package and board material and design attributes.
For more information on our Mechanical Package Characterization and Board Level Reliability services, please contact an Amkor Regional Sales Office near you or fill out the Request for Information Form.
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