Micro bumping via Paste Dispensing Technology for Advanced Packaging

Solder paste dispensing technology has been widely used in the semiconductor industry for many years for die attach application. The industry is driving towards a complex design for advance packaging, with component design layout with smaller footprints. Traditional stencil printing cannot be applied to certain packaging designs, particularly those with irregular substrates or space limitations. Therefore, dispensing is a suitable alternative method. Ultra-fine solder paste for dispensing (≥80 µm) is only achievable with the correct combination of paste formulation and dispensing equipment. Solder pastes with consistent powder size distribution and spherical finer powder shape is needed to dispense a finer dot of ≥80 µm. Type 6 powders processed by Welco technology have a tight powder size distribution and are highly spherical. Solder paste made with this powder and a water-soluble flux platform provide consistent dispensing volume, while eliminating the needle clogging and missing dots issue. Time pressure and squeeze pump dispensing methods for solder paste application were validated. This paper will discuss the paste formulation and dispensing equipment’s contribution to enable dispensing of dot size ≥80 µm.(a)Time pressure dispensing method evaluated and dot size achieved 200-250 µm without defects.(b)Squeezing dispensing method evaluated, successfully dispensed dot size 80-100 µm without significant defects such as missing and inconsistent dots.