Ultra-thin, flexible electronics

Ultrathin Wafer Pre-Assembly and Assembly Process Technologies: A Review

“…5,12,[14][15][16]18,20,21,27,42,86,89,90,137,143,144 In the DBG process, die singulation occurs during grinding instead of dicing. In the DBG process flow for ultrathin dies, 14,42,84,89,143 first a wafer is partially diced from its frontside to the desired final die thickness by blade dicing, laser scribing, wet etching, plasma etching, or a combination of these ( Figure 40). Second, the wafer is transferred on to a temporary rigid carrier with its frontside attached to the carrier.…”

“…15,46,182 This has led to the higher use of flip-chip bonding to avert problems with silicon cracking. [6][7][8]42,43,60,182,183 However, the cost and process complexity of flip-chip technology have been major hindrances over wire bonding. 184 Wire bonds offer flexibility to match different dies to standard leadframe and substrate designs, and they often are more cost effective than flip-chip alternatives.…”

“…The attachment of ultrathin dies onto substrates by flip-chip bonding can result in uneven gaps between the solder bumps and pads on the substrate due to die bow, which would cause non uniform solder joint connections and open failures. 6,8,42,43 In conventional die attachment using solder or epoxy adhesive, die bow will lead to non-uniform bond-line thickness and die attach voids, which can result in die cracks due to high stress concentrations in the silicon at the edges of the voids. 44,45 In severe bow cases, this can cause an overhanging of the die edges making wire bonding at peripheral bond pads impossible owing to lack of support at the bottom of the ultrathin die.…”

Ultra-thin, flexible electronics

“…The commercial thinning process had high yield with no damage to the die edges. The thinned die were then returned in waffle packs [7]. 978-1-4244-4476-2/09/$25.00 ©2009 IEEE Final Die Thinning and Handling: Since the fabrication process utilizes silicon die thinned below 10μm, special precautions were made for handling the thinned die.…”

“…While various techniques have been developed to fabricate ultra-thin, flexible electronics [7], this paper focuses on thinned silicon die embedded in polyimide ( Figure 1). The manufacturing methods and materials, as well as some early measurements, are discussed in the following sections.…”