The IMAPS National meeting was recently held in Orlando FLA. Lets first take a look at some of the materials papers that were presented.
Namics presented their latest data on available underfill solutions for 2.5/3DIC. Below we see several opportunities for epoxy underfill materials.
Vacuum underfilling is replacing CUF due to decreased voiding which improves reliability. Underfill must have a high enough Tg to insure the modulus is high enough to protect bumps during thermal cycling but low enough not to crack the die.
Namics proposes that in the near future it might be possible for substrate suppliers to apply a B staged underfill prior to shipping. The customer would then perform a thermocompression bond.
Despite the obvious benefits, the drawbacks of both NCP (non conductive paste) and NCF (non conductive film) at present include required additional capital, cost more and have a longer bonding time.
Application methods for Various Underfill Solutions
Towa – Compression Molding for High End Packaging Solutions
Traditional transfer molding has been challenged to mold 2.5/3D stacked die structures since these structures have limited space for resin flow. It is also difficult to transfer mold large wafer or panel substrates.
Compression molding was developed to mold packages with minimum resin flow. The blue layer, in the figure below , is a release film which is sucked down flat to the mold. A vacuum is subsequently pulled to remove air, gas and moisture from the cavity and molding cmpd.
Dow Chemical – toughened BCB
BCB has been commercially used by the packaging community for more than 20 years. Although it has various superior properties such as low curing temp, low water absorption and low dielectric constant, being a thermoset resin, toughness and elongation are not one of them. A toughened BCB has been a “holy grail” in the BCB user community.
A new toughened BCB product has now been described by Dow. Comparative properties are shown below. As one can see most properties have been maintained while elongation has been improved 3X and shows a 2X increase in fracture toughness from 0.3 to 0.4 to 0.6 – 0.9 MPa m1/2 vs standard BCB.
A cross section of a via in this toughened BCB is shown below.
Volume 3 of 3D Integration Handbook being readied
It was 2008 when the Handbook of 3D Integration was published by Wiley VCH. Since then it has been the most referenced 3D treatis on the market. Much has happened since 2008 and we, the editors, felt that rather than update the first two volumes , we would rather issue further volumes updating some chapters and adding others as required and Wiley VCH agreed.
Volume 3, due to be published 1st quarter of 2014 will be focused on processing and will include chapters on 2.5D interposers, TSV formation, bond/debond, thin, reveal and backside processing, reliability and metrology. Authors in this volume, in addition to the editors, include Eric Beyne (IMEC), (EVG); Hiroaki Ikeda (ASET); James Lu (RPI); Thorsten Matthias (EVG); Rama Pulligadda (Brewer); Sesh Ramaswami (Applied Materials); Fred Roozeboom (TNO); Rao Tummala (GaTech); Larry Smith (Sematech); Doug Yu (TSMC) .
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