Prevention on tilted units for small size wafer level package in taping

Miniaturization of portable and hand-held electronic devices is driving the need for smaller foot print on PCB. Wafer Level Package, WLP is an example that facing this challenge of package miniturisation. Units placement into carrier tape pocket has become critical for such products. WLP package with bump causing uneven contact between pick up tool and the package has made it more challenging to achieve accurate unit positioning in pocket during taping process. Additional challenges faced is existing machine was designed for minimum package size of 0.5mm × 0.5mm. This paper will share systematic approach to prevent tilted units in case of WLP package size less than 0.5mm × 0.5mm. DMAIC approach with 6 sigma tools has been applied. Material selection, process parameter setting and indexing track design are the 3 main areas that have been studied in detail. As for material selection, different types of cover tape and rubber tip have been evaluated. Because of small size and light weight, units tend to tilt easily if there is excessive vibration. Thus, vacuum setting has been evaluated in order to understand the impact on tilted units which caused by excessive vibration during taping. Apart from material selection and vacuum setting, indexing track design also has been studied. With the new error proof track design and optimum selection of materials, the tilted units have been reduced towards zero ppm.