Preparation of Highly Uniform and Monodisperse PS/Cu Composite Microspheres Using Electroless Plating

Abstract

Highly uniform and monodisperse core-shell microspheres composed of a polystyrene (PS) core and a copper shell were prepared by dispersion polymerization of styrene followed by electroless copper plating. The formation of copper shell on PS surface was confirmed by FESEM, TEM, XRD and TGA. As a result, the plating bath composition had an important influence on the morphology of PS/Cu composites. The addition of Na 2 EDTA and La 2 O 3 as a complexant and a stabilizer led to the formation of a more compact copper shell on PS surface. The formation mechanism was explored by the linear sweep voltammetry method, and the different morphology might mostly result from the various nucleation rates. Tailoring of shell thickness can be achieved through altering the loading of PS in the ECP bath. Conductivity of the PS/Cu composites with a shell thickness of 195 nm is up to 2.2×10 5 S/m. The PS/Cu composites may have great potential to be used as fillers of anisotropic conductive film for their uniform diameter, low density and good conductivity.As the requirements for interconnection and joining materials in microelectronics packaging applications have moved toward ultrafine-pitch bonding and environmental friendliness, anisotropic conductive film (ACF) has gained much attention as an alternative to tin/lead (Sn/Pb) solders. 1,2 ACF not only allow products to be thinner, smaller and lighter, but also offer good electrical performance and stability. 3 ACFs mainly consist of polymeric binder matrices and conductive fillers. 4 When heat and pressure are applied during bonding, the electric connection is established only in the Z-direction by using a relatively low weight loading of conductive fillers, typically 1-10 wt%. 5 Originally, carbon fibers were used as the conductive fillers for ACF. Then, the fillers were replaced by lead-free solder spheres and metal spheres, such as nickel, silver and gold-coated Ni spheres. 6 For instance, there has been growing interest in copper with various sizes and shapes used as filler of isotropic or anisotropic conductive adhesive owing to its high electrical, thermal conductivity, low cost and electro-migration tendency. 7-10

Highly Porous Copper with Hollow Microsphere Structure from Polystyrene Templates via Electroless Plating

“…This was consistent with the results in recent report. 28 The reason of this phenomenon was not yet to be clarified, but the most reasonable explanation appeared to be that the addition of stabilizers interrupted the growth of copper deposits.…”

Shell structure control of monodisperse polystyrene‐silver composite microspheres and synthesis of epoxy resin‐based anisotropic conductive adhesives

“…The synthesis of PS‐Ag composite microspheres was based on the already reported method 14 with minor modifications. The synthesis steps of PS‐Ag composite microspheres were summarized in the Supporting information.…”

“…However, the conductive particles in large‐scale industrial‐grade ACAs are typically compound microspheres with a desirable monodisperse size in the range of 3–10 μm 11,12 . In this context, polymer/metal composite microspheres are interesting as conductive elements due to their wide range of particle sizes, uniform diameter, low density, desirable electrical conductivity, and moderate elasticity 13‐16 . Therefore, it is essential to investigate the polymer/metal composite microspheres with excellent properties.…”

“…11,12 In this context, polymer/metal composite microspheres are interesting as conductive elements due to their wide range of particle sizes, uniform diameter, low density, desirable electrical conductivity, and moderate elasticity. [13][14][15][16] Therefore, it is essential to investigate the polymer/metal composite microspheres with excellent properties.…”

Electrical conductive Cu/glass fibre composites prepared by electroless plating

“…A number of papers and reports about the core–shell structure composites synthesised by the electroless plating method have appeared in the literature in recent years. The choice of the core materials might be the key point here; according to the existing reports, polymer materials such as polyethylene terephthalate [7, 8], poly(glycidyl methacrylate) [9] and polystyrene [10], inorganic non‐metal materials such as carbon fibre [11], graphite [12], carbon nanotubes [13, 14] and Al 2 O 3 [15] were commonly used. In addition, Su et al [16] developed a novel convenient method for electroless copper deposition on glass substrate.…”