Tan, Kian Heong (2016) Non-sticking on ground ring improvement for copper wire bonding with DMAIC approach. Masters thesis, Universiti Teknikal Malaysia Melaka.
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Abstract
Semiconductor industries are in the process of converting gold wire bonding to copper wire bonding because of significant cost saving from gold price.The conversion from gold to copper also gives rise to many challenges due to the copper wire properties.Copper wire bonding is very sensitive to the combination of wire type,wire bonder, capillary,bonding parameters,bond pad technology,lead frame plating,pretreatment and others materials or processes that directly or indirectly in contact with the interconnect wire.Typically in semiconductor,wire bond connect bond pad to lead finger.In some application,ground bond is needed to connect ground ring to lead finger.In the past,ground bond with gold wire did not posed much problem.With the introduction of copper wire and pre-plated frame,wire bond reject become more significant.From manufacturing data,for copper wire bonding on ground,3% of yield loss was observed because of non-sticking on ground ring (NSOG). Consequently, this will affect the margin of cost saving for the copper wire introduction.Factors affecting the high yield loss need to be studied with systematic method in order to reduce the NSOG reject to acceptable level (0.5%) for manufacturing.Fundamental knowledge of copper wire bonding and DMAIC methodology were reviewed.Two methods of optimization (DOE and DMAIC) are regularly employed by researcher to solve specific problem.There exists a gap in the understanding of copper wire bonding on pre-plated ground ring which is overhang.This gap will be covered in this project.Overall,DMAIC methodology is used in this project.The first objective of this project is to determine factor that influence NSOG defect.This is accomplished with hypothesis testing on identified factors from C&E matrix. P-value of 0.05 or less serves as guideline to determine the significance of each factor.The second objective is to develop mathematical model to describe NSOG defect.This is possible with the DOE and ANOVA analysis.Final objective is to improve NSOG defect to acceptable level (0.5%) for manufacturing purpose with DMAIC approach.At the end of Analyse phase,ground bond parameters;copper wire FAB hardness; and clamp and paddle are determined as significant factors.Mathematical model for NSOG defect was proposed which is a linear model with interaction terms of ultrasonic power,bond force and bond time.From the multi responses DOE optimization,process window was derived to minimize NSOG defect; and to maximize ball pull and ball shear value.Small scale study with different machines was carried out in the Improve phase.In Control phase,performance of NSOGwas monitored.With DMAIC approach, NSOG defect was confirmed to meet objective of 0.5% and below for manufacturing condition.Stable and sustainable performance improvement is proven with various tools in DMAIC.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | Metal bonding, Process control, Copper wire |
| Subjects: | T Technology > T Technology (General) T Technology > TS Manufactures |
| Divisions: | Library > Tesis > FKP |
| Depositing User: | Mohd. Nazir Taib |
| Date Deposited: | 03 Apr 2018 02:45 |
| Last Modified: | 29 Dec 2022 16:11 |
| URI: | http://eprints.utem.edu.my/id/eprint/20567 |
| Statistic Details: | View Download Statistic |
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