Characterization of a no-flow underfill encapsulant during the solder reflow process

Wong, C.P.; Baldwin, D.; Vincent, Michael; Fennell, B.; Wang, L.J.; Shi, Shengjun

doi:10.1109/ectc.1998.678898

Cited by 47 publications

(11 citation statements)

References 9 publications

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“…Understanding these technical challenges, intensive development work has been carried out in many institutions and material supply companies. 6,7 Most of them use epoxy-anhydride based materials, but other chemistries have also been explored. 8 …”

Section: 6mentioning

confidence: 99%

Underfill adhesive materials for flip chip applications

Tong

2011

Advanced Adhesives in Electronics

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Section: 6mentioning

confidence: 99%

Underfill adhesive materials for flip chip applications

Tong

2011

Advanced Adhesives in Electronics

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“…The key to the success of the noflow underfill technology lies in the availability of successful no-flow underfill materials. An applicable no-flow underfill material has been developed in our lab [8], [10]. However, no-flow (compressive-flow) underfill technology still needs a separate underfill dispensing step on an individual chip.…”

Section: Introductionmentioning

confidence: 99%

Development of the wafer level compressive-flow underfill process and its involved materials

Shi

Yamashita

Wong

1999

IEEE Trans. Electron. Packag. Manufact.

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This paper describes a wafer level compressiveflow underfill process for a novel SMT transparent flip-chip technology. In this flip-chip technology, a liquid fluxable wafer level compressive-flow underfill (WLCFU) material is first coated on the active side of an entire patterned and bumped wafer. The WLCFU layer is dried at an elevated temperature to form a solid layer. The coated bumped wafer is then diced into individual chips, which are then placed on a carrier film with their active side to the tacky side of the carrier film. These diced individual chips are then picked from the tacky carrier film and placed on a substrate such as a PWB board using standard SMT equipment. At an elevated temperature (100-180 C) during solder reflow, the solid WLCFU layer can be re-melted and can easily fill in the gaps between chip and substrate. After solder reflow (190)(191)(192)(193)(194)(195)(196)(197)(198)(199)(200) C ), the WLCFU material can be fully cured. A B-stage epoxy technology is used to develop this WLCFU material and the tacky material on the carrier film. A properly selected fluxing agent is added to both the WLCFU and the tacky materials to provide sufficient fluxing capability for good solder interconnection. A thermo-gravimetrical analyzer (TGA) is used to investigate the drying kinetics and the material weight loss during the reflow process. Differential Scanning Calorimetry (DSC) is used to study the curing kinetics of the prepared formulations. A thermo-mechanical analyzer (TMA) is used to investigate the heat distortion temperature (TMA Tg) and the coefficient of thermal expansion (CTE). A dynamic-mechanical analyzer (DMA) is usedto measure the storage modulus (E 0 ) and cross-linking density () of the cured materials. A rheometer is used to investigate viscosity () change with the temperature increase during the solder reflow process. Preliminary results demonstrate the feasibility of the proposed novel flip-chip technology with the developed WLCFU and tacky materials. The basic qualifications of the WLCFU material are examined. Some technical barriers related to this technology are also discussed.Index Terms-B-stage, compressive-flow, epoxy resin, underfill encapsulant, wafer level packaging.

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“…Instead, it is limited by the consideration of the optimum integrated properties of the noflow underfill material [10]. Consequently, for the developed and some commercially available no-flow underfill materials, it was found that the fluxing capability depends on the supplier of copper pads on the substrates [11]. In order to guarantee formation of good electrical interconnects during the noflow underfilling process and provide guidance for proper transportation procedure for the copper padded substrates, it is of practical importance to investigate the relationship between the copper pad surface composition and the apparent no-flow underfill fluxing capability (measured by the wetting angle).…”

mentioning

confidence: 99%

Study on the relationship between the surface composition of copper pads and no-flow underfill fluxing capability

Shi

Wong

1999

IEEE Trans. Electron. Packag. Manufact.

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The purpose of this paper is to investigate the effect of copper pad surface composition on the wetting of solder bumps during reflow process for a certain no-flow underfill material. A purchased copper foil which is laminated on FR4 board is used as a control surface. Six different procedures are followed to prepare the surface of the copper foil with six different compositions. The XPS is then used to analyze the surface compositions of the six surfaces and the control surface. An in-house developed G25 noflow underfill encapsulant is used to examine the wetting status of eutectic solder balls on these copper surfaces. The correlation of the copper surface compositions with the solder wetting is then established. It is verified that the compositions of the copper foil surfaces strongly depend on the cleaning procedures. For G25 no-flow underfill material, copper oxide (CuO) is the main composition that prevents the solder ball from wetting the copper foils while the observed organic contamination does not have noticeable effect on the solder wetting.

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Characterization of a no-flow underfill encapsulant during the solder reflow process

Cited by 47 publications

References 9 publications

Underfill adhesive materials for flip chip applications

Underfill adhesive materials for flip chip applications

Development of the wafer level compressive-flow underfill process and its involved materials

Study on the relationship between the surface composition of copper pads and no-flow underfill fluxing capability

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