Flip Chip Assembly of Thinned Silicon Die on Flex Substrates

Banda, C. V.; Johnson, Richard W.; Zhang, Tan; Hou, Zhenwei; Charles, Harry K.

doi:10.1109/tepm.2007.914217

Cited by 55 publications

(13 citation statements)

References 9 publications

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“…This corresponds well with values reported in the literature for acceptable warpage values for thin Si dies [10,11]. This is an important conclusion as it implies that high bonding temperatures and corresponding low curing times, see Table 1, can be used for bonding on both PEN and PET foils.…”

Section: General Discussion Of the Resultssupporting

confidence: 90%

Flipchip bonding of ultrahin Si dies onto PEN/PET substrates with low cost circuitry

Brand

Kusters

Heeren

et al. 2010

3rd Electronics System Integration Technology Conference ESTC

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All-printed, cost effective, smart electronic products are expected to be used in a wide range of applications and in large quantities in our society. The substrate material for these applications will be low cost materials like PEN or PET foils. For the functionality of the printed electronics product it often will still be required to integrate a Si chip. To keep the flexibility of the package and not to add too much to the thickness, the chip needs to be integrated into the product as a bare, thinned die. Because of the low temperature stability of the PEN and PET and the use of printed conductors it is necessary to interconnect the chip using an adhesive. The current paper specifically addresses the challenges associated with this. Research efforts will be discussed on the flip chip bonding of ultrathin (i.e. thickness 20 µm) bare chips on printed circuitry on both PEN and PET foils using a typical anisotropic conductive adhesive (ACA). Based on the results it can be concluded that a reproducible, low contact resistance and a good lifetime and flexural durability can be achieved over a wide range of bonding forces and temperatures. IntroductionRecently a new class of flexible electronics is starting to emerge which is most effectively termed 'printed electronics'. This term often refers to all-printed, cost effective, smart electronic products that will find a wide range of applications in large quantities in our society. Examples include cheap sensor packages attached to food packaging to measure the ripeness of food, smart bandages that monitor the healing of wounds and smart active or passive RFID tags. These cost effective packages can include all-printed functional structures like conductive circuitry, OLED pixels, photodiodes and logics based on organic materials.The substrate material will in most cases not be polyimide as commonly used in the more traditional flexible electronics. By using polyesters like PEN (polyethylene naphtalate) or PET (polyethylene teraphtalate), the substrate costs can be reduced by a factor of 5-10 [1]. A disadvantage of polyesters is however that they are considerably less thermally stable. PEN has a glass transition temperature (T g ) of ~130o C and PET of ~85 o C while poly(imide) has a T g of ~350 o C) [1]. This limitation in thermal stability excludes many well established processes for making electronic products and/or renders the use of existing processes much more challenging.A tangible example of such a printed electronics product is the disposable smart pill blister that is under development at the Holst Centre and its industrial partners. A photograph of a first prototype of it is shown

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Section: General Discussion Of the Resultssupporting

confidence: 90%

Flipchip bonding of ultrahin Si dies onto PEN/PET substrates with low cost circuitry

Brand

Kusters

Heeren

et al. 2010

3rd Electronics System Integration Technology Conference ESTC

View full text Add to dashboard Cite

show abstract

“…Regardless of the method, it is obvious that the equipment that can handle ultrathin bare dice is unique and costly [25] and the packaging rates are low. Placement accuracy and rate for the pickand-place machines are inversely correlated.…”

Section: Contact Methods For Ultrathin Die Packagingmentioning

confidence: 99%

Laser-assisted ultrathin die packaging: Insights from a process study

Marinov

Swenson

Atanasov

et al. 2013

Microelectronic Engineering

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“…The basic inkjet-printed lines were measured and visually inspected during test breaks to Capability Assessment of Inkjet Printing for Reliable RFID Applications observe how the resistances and adhesion of silver ink on different substrates are affected by an elevated thermal/humidity environment. Figure 1a shows a sketch of RFID chip attachment (combining silicon-on-flex and print-on-slope concepts [14][15][16]) and the inkjet-printed silver lines of the presented structure. The manufactured structure whose design was adopted from an industrial partner is presented in Figure 1b, where also the bendability of the tag is demonstrated.…”

Section: Introductionmentioning

confidence: 99%

Capability Assessment of Inkjet Printing for Reliable RFID Applications

Putaala

Niittynen²,

Hannu

et al. 2017

IEEE Trans. Device Mater. Relib.

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In this paper, inkjet-printed silver traces and interconnections produced with the print-on-slope technique were used in an RFID structure operating in the UHF range. Underfill material was used to attach silicon RFID chips onto flexible, 125µm-thick polymer substrates. The cured underfill was also used as a sloped surface for printing interconnection traces from the chip to the plastic substrate's radiators. Inkjet printing was performed in one phase, producing both the interconnections to the chip and the radiators. This enables the use of a single-phase continuous roll-to-roll compatible process instead of the commonly used two-phase stop-and-go process. To further investigate the behavior of printed low-temperature nanoparticle ink and its compatibility with different substrate materials, basic conductive traces were printed onto the substrates. Thereafter, the structures were exposed to thermal/humidity tests at 85 °C temperature/85% relative humidity ("85/85") for up to a 2000-hour period. To gain an understanding of the response of the structures under stressing, the samples were intermittently characterized using a read range measurement device, followed by removal of failed samples from the test. The samples were characterized also by optical imaging and fieldemission scanning electron microscopy (FE-SEM). The bulk conductive traces were characterized electrically by measuring their resistances during test breaks. The results point out that, although some challenges are still to be overcome, inkjet printing is a feasible way of producing conductive traces for RFID structures, and that the print-on-slope technique is utilizable also in practical applications as a costeffective method with adequate reliability for producing interconnections between chip and substrate.

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Flip Chip Assembly of Thinned Silicon Die on Flex Substrates

Cited by 55 publications

References 9 publications

Flipchip bonding of ultrahin Si dies onto PEN/PET substrates with low cost circuitry

Flipchip bonding of ultrahin Si dies onto PEN/PET substrates with low cost circuitry

Laser-assisted ultrathin die packaging: Insights from a process study

Capability Assessment of Inkjet Printing for Reliable RFID Applications

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