Kinetic Study of Wet Chemical Treatments on the Surface Roughness of Epoxy Polymer Layers for Buildup Layers

Abstract

The adhesion of plated metal layers to epoxy polymer surfaces is of prime importance for the reliability of interconnections in microelectronics. An increase in the roughness of the polymer surface, caused by chemical treatment, plays an important part in the adhesion strength of plated metal layers by increasing the total area of interaction between both layers. This kinetic study of the influence of chemical treatments on the surface of the polymer consists of two parts. In Part I the kinetics of sweller treatments and of the solvent were examined in detail and a kinetic model for the influence of sweller and solvent was developed. In this second part the kinetics of the formation of roughness at the polymer surface due to oxidative liquid treatments is examined. A kinetic model is developed based on experimental studies, compromising the combined effects of sweller-oxidizer treatments and the influence of diffusion of the different components. A number of examples are given and verified by experiment. The roughness of the treated polymer samples is measured experimentally by atomic force microscopy. Time-dependant mass measurements were used to record mass changes due to diffusion and reaction.The continuing striving in microelectronics to miniaturize and/or the necessity for electronic circuits to operate in harsh environments, together with the increased signal frequencies and higher density of functions necessary, necessitates further advances in interconnection technologies. A prime requirement for these is a good adhesion between polymers and plated copper layers. It is obvious that the surface properties of the polymer have a big impact on the adhesion of the metal to the polymer. By chemical treatment of the surface the characteristics ͑physical and chemical͒ of it can be changed in order to improve adhesion. Hence there has been intense recent research into improving the adhesion of plated copper onto polymer surfaces.A number of publications 1-3 exist on surface treatments with wet chemicals to improve adhesion strength of copper on epoxy resins. These authors made a phenomenological study on copper laminated foils but not on plated copper surfaces. Li and Tummala 4 studied the effect of wet chemical pretreatments on the interfacial adhesion between plated copper layers and epoxy polymers. According to these authors adhesion between two layers depends first on the physical and mechanical adhesion, caused by the roughness between both layers, and second on the chemical adhesion which is caused by interactions between polymer molecules and the plated metal. These findings are based on earlier work described by Wake. 5 The effects of wet chemical treatments on interfacial adhesion and roughness has not been well studied and understood, 6,7 Recently Ge et al. 8 studied the influence of surface modification on epoxy/copper systems. According to these authors wet-chemical treatments produce a large number of microcavities to anchor deposited electroless copper. Mechanical interlocking was found to have a do...

A Photocurable Pd Nanoparticle/Silica Nanoparticle/Acrylic Polymer Hybrid Layer for Direct Electroless Copper Deposition on a Polymer Substrate

“…This process enables direct electroless copper deposition on a smooth polymer film and could be applicable for manufacturing printed circuits on a flexible film. In common electroless processes, metals are deposited onto a polymer surface that has a micrometer-scale roughness formed by chemical etching [10,11], which can affect the physical properties of the metal film and damage the polymer substrate.…”

“…The obtained hybrid films are expected to be metallized by means of electroless plating due to the catalytic activity of the metal nanoparticles. Common electroless processes involve three main steps: i) surface preparation, ii) surface activation or surface seeding with a catalyst, and iii) the electroless plating process itself [10,11]. While surface preparation, such as etching to increase the surface roughness, is necessary to provide good adhesion, it can affect the physical properties of the deposited metal film and damage the polymer substrate.…”

Chemical Modification of Buildup Epoxy Surfaces for Altering the Adhesion of Electrochemically Deposited Copper

“…19,20 The first reaction is the reaction with the trichlorotricyanuryl compound for 24 h; the second treatment is the reaction with the IDA solution. Table III shows that the mass changes are limited to 1.5 wt %.…”

“…According to Coppens, 16 a fractal surface also influences diffusion of components. In order to maximize adhesion, Wool and Long 15 suggested development of pretreatments that can generate fractal surfaces to which high adhesion by mechanical interlocking could be expected.The kinetics of roughness formation due to wet-chemical treatments was extensively studied in our previous publications, [17][18][19][20] in which the effects of swellers and oxidizers in the bulk of the polymer and on its surface were qualitatively and quantitatively determined. These previous studies revealed a number of synergetic effects between the sweller and oxidizer treatments.…”

“…The kinetics of roughness formation due to wet-chemical treatments was extensively studied in our previous publications, [17][18][19][20] in which the effects of swellers and oxidizers in the bulk of the polymer and on its surface were qualitatively and quantitatively determined. These previous studies revealed a number of synergetic effects between the sweller and oxidizer treatments.…”