14 - 16 June 2010

14 June 2010

I continued working on the report of determining optimum process parameter for PHICOM3 24k wire bonder using 50um gold wire. In the mean time, I gained cognizance on the input parameters considered significant in die bonding as well as wire bonding processes. First off, factors influencing die bonding are temperature, bond force and process delay. On the other hand, spark current, spark time, bond force and USG influence wire bonding process. USG stands for ultrasonic generator. At the other end of the spectrum, output responses akin to die bonding process are die shear analysis and Dvth analysis. For die shear analysis, die sheared pictures will be taken to analyze the Si/Au remains, which must be greater than 75% to be considered acceptable. As for Dvth analysis, cross sectional pictures on die bonded lead frame will be taken to be perceived for any gaps between die and lead frame as well as the presence of copper interconnect. On the other hand, for wire bonding process, ball diameter, ball height, ball shear and wire pull are the output responses.

USG plays a role in allowing the ball bond to be attached nicely to the bondpad. USG, together with bond force, are preponderant in influencing ball bond strength; while spark current and spark time are predominantly influential in ball size. I was taught that low spark current and spark time, together with high bond force and USG are not acceptable. This particular combination of input parameters will engender with ball that may not have any height at all.

I also learnt that the range of ball diameter is governed by the bondpad size. It should be within the bondpad size to avoid offbond. Besides that, the ball height lower limit should be half of the wire diameter, while its upper limit must be one and a half that of the wire diameter.

Moving on to Minitab, I had gained knowledge on generating various plots, which are momentous in analyzing sets of data. First off, normal and Pareto plots will enable us to determine the significance of input parameters. Next, optimization plot will help us in determining the optimum process parameters. Furthermore, contour plot is used when we intend to determine the range of feasible process parameters.

15 June 2010

Previously, I learnt that temperature, bond force and process delay are significant parameters influencing die-bonding process. However, die-bonding process can be categorized into eutectic bonding and epoxy bonding. Those 3 factors are only significant to eutectic bonding. As for epoxy bonding, only bond force is significant. Even so, its influence in the epoxy bonding is still small.

16 June 2010

Went to hospital for follow-up on my injured spine.