Gel encapsulation is gradually replaced by epoxy encapsulation for power modules due to the miniature of epoxy encapsulation. The epoxy and the copper substrate form a dissimilar bond. Generally, the mismatch of the coefficient of thermal expansion (CTE) is thought as the reason for the bond failure. Here, we investigated the influence of copper/epoxy interface interaction on reliability under various reliability tests. It shows that besides the mismatch of CTE, the interfacial interaction also influences greatly. Copper diffuses into epoxy. The diffused copper causes epoxy degradation under high temperatures and humidity, which fails the copper/epoxy bond.
In this paper, a two-step plasma-treated copper-copper direct bonding performed in ambient condition, followed by pressure-less annealing, is reported. A decent shear strength of ~38 MPa is achieved. The hermeticity of the bonded copper dies degrades with prolonged exposure in the ambient. No undesirable materials are observed at the copper-copper bonding interface, which suggests the formation of high-quality bonding. This bonding technology would be applicable for high-throughput 3D heterogeneous integration and advanced packaging.
Vacuum ultraviolet (VUV, λ = 172 nm) excimer radiation can be used to hydrophilize polymer surfaces and remove contaminants. This method allows for the formation of stronger interactions, which improve the adhesion between the treated surface and a coating without reliance on the conventional anchor effect. Herein, the surface modification of cyclo olefin polymer films using VUV light was explored, and the effect of this treatment on the adhesion strength was evaluated. Under suitable conditions, the adhesion strength between electroless-deposited copper and the cyclo olefin polymer substrate can be significantly improved by VUV pre-treatment. Furthermore, we investigated the adhesion mechanism of electroless plating on surface reformed resin by VUV irradiation using a scanning transmission electron microscope.
growing interconnect technology scales by variety, topology, counts, mandate improved and efficient techniques for their handling. Table based formats proved most robust for this function regardless of the exact geometrical pattern involved. The methodology outlined can support description of any desired geometrical pattern, as well as secondary properties of the interconnects. The secondary properties can be also processed for derived functionality such as interconnect mirroring or associated metal grids.
Single circle diameter bump wafer is generally used. Recently, 2 circle diameter (2CD) wafer is on the rise. 2CD wafer is a kind of wafer which has two different size vias. In the conventional 2CD wafer, solder layer such as SnAg alloy is electroplated on Cu bump. However, it has become difficult to adjust the bump height. Because the size of the via has become smaller and the density has increased. These changes result in the difference in the thickness on the small and large diameters. Thus, SnAg alloy is plated again on the small vias to adjust the bump height in the reflow process. Considering these circumstances, it is desired that the bump thickness of small vias is thicker than large vias. In order to breakthrough this problem, we made height difference by increasing Cu thickness of small vias only with one Cu electroplating step.
