SMTA International Conference Proceedings


Author: Daniel F. Baldwin et al.
Company: Siemens Dematic EAS
Date Published: 9/22/2002   Conference: SMTA International

Abstract: The use of 0201 packages is increasing from year to year as the industry continues on its drive to smaller, lighter, faster. An array of ten 0201s takes up almost 1/3 the space of an array of 0402s. Therefore, components can be grouped tighter together to reduce board size. The main problem with the introduction of 0201 components is that the process window decreases as the size of the component decreases.

An 0201 component has been shown to have ten times the likelihood to tombstone when compared to a 1206 and almost 2 ½ times as likely to tombstone as compared to an 04021. For this reason, a lot of attention must be paid to the design and processing of 0201 components for surface mount assembly.

In general, it has been found that the static factors (i.e. board and stencil design) have a much larger effect on the number of defects than the dynamic factors of the assembly process (i.e. print parameters, placement parameters, and reflow parameters). Some dynamic factors do have a large impact upon the assembly process (i.e. air versus nitrogen environment in the reflow), but overall the static design factors have a much greater impact upon the number of defects.

Over the course of the study, the optimum assembly parameters were found and the effect of the design parameters on these assembly parameters will be shown in terms of defect per million numbers.

Presented in this paper is the data from those studies as well as the data gathered after large evaluation runs in which many components were processed. Studied process parameters were broken out by individual process steps initially, and then studied over the entire process.

Some of the process parameters that were examined were print force, print speed, and stencil wipe frequency for the printing process and reflow atmosphere, profile shape, and ramp rate for the reflow process. From these studies, a reliable process window was obtained for a high speed 0201 assembly process that was proven to provide a DPM of less than 200.

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