Correlating Interfacial Moisture Content and Adhesive Fracture Energy of Polymer Coatings on Different Surfaces

Abstract

Sn-Ag-Cu alloy. The Sn-Ag-Cu-Ge alloy solder ball had higher ball shear strength than the Sn-Ag-Cu alloy after an aging test at 150°C. The Sn-Ag-Cu-Ge alloy solder has better characteristics for both thermal oxidation and thermal reliability test. Therefore, it can be concluded that the Sn-Ag-Cu-Ge alloy is a good candidate to solve the oxidation problem, which is the most critical problem of the Pb-free solder. ExperimentalTwo solder ball compositions (in wt%) chosen in this study were : Sn3.0Ag0.5Cu and Sn3.0Ag0.5Cu0.05Ge, and had a diameter of 0.450 mm. The substrate used was CSP with 144 pad openings and each pad was 0.38 mm in diameter. The pads had an electroplated Ni/Au surface finish over Cu trace, with about 0.5 and 5.0 lm in thickness respectively. The solder balls from each composition were bonded to the CSP substrate using a water soluble flux under a reflow oven. The reflow condition is that preheating was done for 2 min at 150°C, the peak temperature was 235°C, and the dwell time was 60 sec.The solder balls after one were then analyzed or subjected to either multiple reflow up to 5 times or aging at 150°C for a duration up to 500 hs. XPS was utilized to check the oxide layer thickness and examine the surface chemical composition. We assumed that the oxide thickness can be defined by oxygen concentration under three atomic percent. The mechanical joint strength of the bonded balls was evaluated with Dage shear tester using a shear speed of 200 lm/s at a shear height of 10 lm.It is well known that ambient moisture and other environmental influences are detrimental to the adhesion of polymeric materials to metal surfaces. The primary reason why adhesion loss occurs is believed to be due to moisture accumulation at the polymer/metal interface. This is why adhesion loss does not generally correlate with the bulk moisture content of the polymer. In this work, we present measurements of the interfacial moisture content and adhesion for a series of polymer coatings having different surface chemistries. Measurements were made after reaching an apparent equilibrium in either a dry (0 % relative humidity) or wet (100 % relative humidity) environment. The loss of adhesion is found to correlate directly with interfacial water content. Surface treatments that resulted in a more hydrophilic surface lead to an increase in the interfacial water content and a decrease in interfacial fracture energy.Ambient moisture is well known to adversely affect the durability and performance of adhesive joints and coatings. [1] The interplay between the mechanical stress and chemical changes in the adhesive joint due to moisture adsorption is generally believed to be the root cause of failure of the adhesive application. Failure typically occurs at the polymer/metal interface, indicating that the primary mechanism for failure is not degradation of the bulk polymer. Instead, the structure of the coating near the interface is the determining factor in COMMUNICATIONS 114

Atmospheric pressure plasma treatment of amorphous polyethylene terephthalate for enhanced heatsealing properties

“…The chamber used for testing contains water and the sealing surface of the tray is submerged below this level allowing the trays to be tested in an aqueous environment. This is generally observed to degrade an adhesive bond [24]. The burst test also takes into account any areas of poor sealing brought about by the heatsealing technique as the tray will fail at the weakest point along the sealing surface.…”

Revisiting the Challenges in Fabricating Uniform Coatings with Polyfunctional Molecules on High Surface Energy Materials

“…This led to the use of silanes that are capable of changing the surface affinity to water vapor [18] without affecting mechanical properties of the materials. Ever since their discovery, silanes have been widely used in the manufacture of composites, and also for various coatings applications [53,54]. Trialkoxysilanes are the most commonly used coupling agents in composite manufacturing due to favorable compatibility with many polymer resins [19].…”

“…As water comes in contact with surfaces of hydrophilic or polar materials, the structure of water at the interface differs from the bulk, and interferes with mechanical and chemical behaviors of surfaces and materials (Figure 6a). Therefore, the interfaces in exposure to water or humidity gain significant importance not only to control mechanical and chemical behavior of surface and material, but also to explore new applications [6,54,[80][81][82][83][84][85][86]. Even though understanding of this bound water layer remains incomplete, it has been shown that the changes in structure of water are dominated by hydrogen bond networks and its dynamic evolution [82,[87][88][89].…”

TRIBOLOGY OF UHMWPE THIN FILMS ON Si WITH INTERFACIAL LAYERS AND MODIFICATIONS

“…Moisture contents can change the surface energy of a substrate that strongly affects the adhesion strength of a coating. 17 Moy and Karasz, 18 Lee and Peppas 19 and Nogueira et al 20 showed that the moisture content on the substrate lowers the glass transition temperature of the coatings that deteriorates film mechanical properties. Wong and Broutman 21 and Xu and Ashbee 22 proved that the moisture contents create cracks or voids in the coatings.…”