Wafer and/or chip bonding adhesives for 3D package

Abstract

For 3D package application the demanded feature of chip bonding adhesive was discussed and the material was developed, which was wafer level process compatible NCF (Non conductive sheet). It should be high flowability for lamination on a bumped wafer surface without void, diced with wafer without deformation or sticking dust, transparent for alignment mark detection and low coefficient of thermal expansion (CTE) for the package thermal cycle durability. The nano particle dispersed and highly loaded NCF has been developed to satisfy the demanded characteristics. The CTE was 37 o C/ppm and 1% weight loss temperature is higher than 350 o C.The photosensitive NCF has been also developed. Bump top adhesive can be removed completely by photolithography before bonding process. It can wipe off the anxiety of adhesive residue between bump and pad. This material is also good for lamination and has high heat resistance of 1% weight loss temperature higher than 300 o C.

Low temperature touch down and suppressing filler trapping bonding process with a wafer level pre-applied underfilling film adhesive

“…As a material removing and window opening technology on electrode top, using a photosensitive adhesive and photolithographic via opening process was proposed [5]. CMP (Chemical mechanical polish) is well known as clean and flat wafer surface making technology [6,7].…”

Flip chip assembly with wafer level NCF

“…TCB (thermal compression bonding) combined with pre applied encapsulation material has also been used for flip chip assembly from the advantage of finer bump pitch capability and stress relief at the bump root. There are two types of pre applied encapsulation material, one is a paste material which is called NCP (Non Conductive Paste) [1] and the other one is NCF (Non Conductive Film) which is a b-stage film [2][3][4]. NCF is a film type adhesive and the character has an advantage of wafer level process compatibility.…”