The role of friction coefficient on the stitch bondability in Pd coated Cu and bare Cu wire bonding

Rezvani, Alireza; Nan, Chunyan; Mayer, Michael; Qin, Ivy

doi:10.1109/ectc.2012.6249140

Cited by 2 publications

(1 citation statement)

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“…To include the effect of the roughness of different capillaries, the friction coefficient is measured for each case with other counterparts. To measure the friction coefficient, a custom designed test setup (discussed ear·lier in [11]) is used. The mechanical prope1ties of PCC wire is exu·acted by using a custom designed uniaxial tensile test machine.…”

Section: Finite Element Model Of Stitch Bondmentioning

confidence: 99%

Stitch Bond Process of Pd-Coated Cu Wire: Experimental and Numerical Studies of Process Parameters and Materials

Rezvani

Mayer

Qin

et al. 2013

International Symposium on Microelectronics

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Cost reduction is the main driver in the recent transition to Cu wire bonding from predominate Au wire bonding. Other cost reduction in packaging comes from new developments in substrates and lead frames, for example, Pre-Plated Frames (PPF) and uPPF for QFP and QFN reduce the plating and material cost. However, 2nd bonds (stitch bonds) can be more challenging on some of the new leadframe types due to the rough smface finish and thin plating thickness. Pd-coated Cu (PCC) wire has been recently introduced to improve the wire bonding process with bare Cu wire, mainly to improve reliability and enhance the stitch bond process. More ftmdamental studies are required to understand the influences of bonding parameters and bonding tools to improve stitch bondability. The stitch bond process of 0.7 mil diameter PCC wire on Au/Ni/Pd-plated quad flat-no lead (QFN) PPF substrate is investigated in this study. Two capillaries with the same geometiy but different smface finishes are used to investigate the effect of capillruy smface finish on the stitch bond process. The two capillruy types are a polished finish type which is cotmnonly used for Au wire bonding, and a granulru· finish capillaty that has a much rougher smface fmish. Process window between no stick on lead (NSOL) atld sh01t tail is compared. The effect of process parameters including bond force and table scmb amplitude is studied. The process window test results revealed that the granulru· capillary has larger process window and a lower chance of sh01t tail occtm·ence. It has been shown that a higher scmb amplitude increases the chance of successfill stitch bond fonnation. To ftnther compare the capillaty smface finishes, 3 sets of parameter settings with different bond force atld scmb amplitude ru·e tested. For all three pru·ameter sets tested, the granular capillruy showed better quality in bond su·ength. The grrumlru· capillruy resulted in higher stitch pull strength compared to the polished type. A finite element model (FEM) of the process was developed to better understand the experimental observations. The amount of smface expansion (plastic defonnation) of the wire at the wire and subsu·ate interface was extracted from tl1e model and attributed to the degree of adhesion (bonding). The model was used to confinn the experimental observation of adhesion (bonding) with different smface finish.

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Section: Finite Element Model Of Stitch Bondmentioning

confidence: 99%