The role of eddy currents and nanoparticle size on AC magnetic field–induced reflow in solder/magnetic nanocomposites

Abstract

Magnetic nanoparticle (MNP)-based solder composites can facilitate solder reflow in AC magnetic fields. We compare power loss in a solder composite sample with MNP loading of different particle size distribution. Scaling of solder composite samples shows that, for smaller samples, power loss is not sufficient to realize solder reflow temperature. Additional heating can be derived from eddy current losses in Cu planes in the substrate board. Eddy current heating in Cu sheets of various thickness were evaluated to quantify their effect for low-temperature electronic assembly.

Review of electromagnetic interference shielding materials fabricated by iron ingredients

“…In the superparamagnetic state, spin uctuation remains very fast due to its small size, hence relaxation occurs at higher frequencies. 7,[14][15][16][17][18] Furthermore, some complicated structures consisting of high porosity and large surface area introduced multi-interfaces that accumulate to bound charges at the interfaces, causing the Maxwell-Wagner effect. In addition, several surfaces within complicated geometries possess unsaturated bonds that are responsible for dipole polarization.…”

Modeling of localized reflow in solder/magnetic nanocomposites for area-array packaging

“…Modeling of localized reflow in solder/magnetic nanocomposites for area-array packaging Siyang Xu, 1,a) Andrea D. Pickel, 1 Anya Prasitthipayong, 1 We have modeled the reflow process of FeCo magnetic nanoparticle (MNP)-based solder composites with eddy current power loss of substrate and magnetic power losses of solder bumps. For an area array package without MNPs when subjected to 300 kHz ac magnetic field, the eddy current power loss can result in excessive temperatures that can cause substrate damage.…”

“…In board-level electronic packaging, solder paste is reflowed over a printed circuit board (PCB), which consists of several Cu planes laminated with FR4 glass epoxy. 1 Due to the environmental and health concerns of Pb toxicity, Pbfree solders have been widely adopted and Sn-Ag-Cu (SAC) alloys are regarded as the most promising candidate. 2 Compared with Pb-Sn solders, Pb-free alloys have a higher reflow temperature ($250 C) due to their higher melting point ($217 C for Sn-3.0 wt.…”

“…For solder powders with particle diameter of 50 lm or less, these losses are negligible and do not result in significant heating. 1,3 Magnetic materials can dissipate energy via hysteretic and relaxation processes in an ac magnetic field, causing significant power loss in submicron and nanosized magnetic materials. [6][7][8][9][10][11][12][13] Previous experiments have demonstrated the reflow of novel solder-MNP composite paste by localized heating in ac magnetic fields.…”

Effects of FeCo magnetic nanoparticles on microstructure of Sn-Ag-Cu alloys

“…19 The magnetic heating in MNPs help promote localized heating and alleviate high reflow temperature challenge. 20 In the present work, we prepared the SAC solder-FeCo MNP composite paste with different MNP concentration and reflowed them by localized heating in AC magnetic fields. The microstructure and thermal behavior of samples were characterized.…”