Reliable Peeling of Ultrathin Die With Multineedle Ejector

Abstract

Flip chip packaging as a mainstream packaging interconnect technology has proliferated rapidly within the last decade or so. With the applications of high-performance chip, its thickness and size have been much thinner and bigger, which is challenging the current assembly technique, especially for the reliable peeling of ultrathin die from the wafer due to its vulnerability and flexibility. Here, we present some significant analytical formulas to estimate die cracking stress and peeling energy in die peeling process. The effects of two factors, including peeling cracking propagation and ejecting needle configuration, are investigated using a fracture mechanics framework. Meanwhile, all analytical predictions have been verified via finite element modeling with virtual crack technique. Theoretical results have shown that die cracking stress could be effectively reduced, but it rarely works to improve peeling energy when more needles are embedded below the adhesive tape. In particular, the essence of the technique with the multineedle is discussed, compared with the normal single-needle technique, which can be used to guide the design of ultrathin die peeling process.Index Terms-Adhesive layer, chip peeling-off, die-cracking stress, energy release rate (ERR), microelectronic packaging, multineedle ejector.

Feasibility Study of an Automated Assembly Process for Ultrathin Chips

“…The needle rather punctures locally the thinned silicon material while most of the area adheres to the wafer dicing tape ( Figure 1 ). An analytical evaluation of crack formation in ultrathin silicon dies due to the usage of die-ejector tools can be found in [ 28 ].…”

Surface Adaptable and Adhesion Controllable Dry Adhesive with Shape Memory Polymer

“…As a result, a lot of transfer systems based on the micro/nano structures have been developed including not only the glass substrate but also even microparticles. [9,11,[13][14][15][16][17][18][19][20] Although the admirable adhesion of dry adhesive, a problem that has to be overcome is the easy detachment, and it might be achieved through "adhesion switching." Compared with many advancements of the artificial dry adhesive's strong adhesion, more studies for stable detachment to achieve the adhesion switching are required.…”

Thermal Controlled Tunable Adhesive for Deterministic Assembly by Transfer Printing

“…[ 15–21 ] The key in assembly process is to regulate interfacial adhesion states between strong for pick‐up and weak for printing in a robust and repeatable manner. Conventional pick‐and‐place technique, [ 22–26 ] which utilizes a small vacuum chunk to pick up and release the chip, has shown excellent performance in controlling the interfacial adhesion. [ 22 ] However, the scaling of the vacuum system down for chips with a lateral dimension smaller than 80 µm and a thickness thinner than 50 µm still remains a great challenge.…”

“…[ 22 ] However, the scaling of the vacuum system down for chips with a lateral dimension smaller than 80 µm and a thickness thinner than 50 µm still remains a great challenge. [ 23 ] Advanced transfer printing techniques based on tunable adhesives regulated by controlling viscoelasticity, [ 27–31 ] surface microstructures, [ 32–35 ] and surface topography [ 36,37 ] have been developed for deterministic assembly of ultrathin micro‐devices. These tunable adhesives are very promising despite the limited strong/weak adhesion strength ratio (i.e., adhesion switchability) or weak pick‐up adhesion, which greatly limit their broad utilities.…”