Influence Of Gold Silver Plating Thickness On Palladium Coated Copper Wire On Stitch Bonding

Tey, Sock Chien (2016) Influence Of Gold Silver Plating Thickness On Palladium Coated Copper Wire On Stitch Bonding. Masters thesis, Universiti Teknikal Malaysia Melaka.

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Low cost, high reliable and robust semiconductor packages are required in order for semiconductor manufacturer to stay competitive in the industry. This requires a stable manufacturing process that able to maintain high production yield, reduce customer reject and scrap cost. Currently, combination of Ni/Pd/AuAg preplated Cu alloy leadframe and Palladium coated copper (PCC) wire is used in the wire bonding process of semiconductor package due to its robustness package performances. Nevertheless,studies on the influence of plating layer thickness of roughened preplated leadframe to the stitch bonding strength of the PCC wire is still lacking and not well understood. The purpose of the current study is to investigate the effect of thickness of AuAg plating (i.e. the top plating layer) of the preplated leadframe on the PCC stitch wire bonding. Regression and ANOVA analysis showed AuAg plating’s thickness of preplated leadframe was the predominant factor on the stitch bonding strength of PCC wire bonding. The bonding force is the second dominant force, followed by the bonding time.However, the DoE results shows AuAg plating thickness has no significant influence (P value >0.05) on the frequency of machine stoppages (i.e. caused by ‘no tail’ and ‘nonstick on lead’ failure on PCC wire stitch bond). Stitch pull strength of PCC wire bonding on the preplated leadframe increased from 10.10 gram-force to 11.20 gram-force,when the AuAg plating’s thickness increased from 7.0 to 35.2 nm. Cross-sectional view micrographs of all the stitch bond samples showed failure mode at stitch bond heel,implied the mechanical failure caused by stitch pull test, may be initiated by crack located at the mechanical deformed wire regions (i.e. stitch bond heel). Lower deformation on bond heel observed with thicker AuAg thickness. This is verified by stitch bond thickness data that exhibited thicker stitch bond heel thicknesses when stitch bonding was performed on leadframe with larger AuAg thickness. Stitch remains’ length increases with larger AuAg thickness because the resulted thicker stitch heels able to withstand higher stitch pull strength, thus elongated further before break up. Thus, both design of experiments and microstructure analysis results supported the stitch pull strength results as function of AuAg plating thickness. Stitch bonding between PCC wire and leadframe was formed through interdiffusion involving Pd species from PCC wire and Au and Ag species from AuAg plating at the bonding interface. Bonded sample with larger AuAg plating thickness exhibited wider interdiffusion zone, thus further strengthened the stitch bond shear strength. This later prevents shear failure at stitch bond interface during stitch pull test. Higher stitch bond strength further strengthens the package reliability. Thus, it enables semiconductor package application extend into automotive industry like power, safety and engine control applications.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Metal bonding, Copper wire, Gold Silver Plating Thickness, Palladium Coated Copper Wire, Stitch Bonding
Subjects: T Technology > T Technology (General)
T Technology > TS Manufactures
Divisions: Library > Tesis > FKP
Depositing User: Muhammad Afiz Ahmad
Date Deposited: 31 Mar 2017 01:31
Last Modified: 30 Nov 2020 14:51
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