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Thermally cycling-stable and highly heat-dissipative BGA packages manufactured by fluxless laser soldering: Experimental and numerical investigations.

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Title: Thermally cycling-stable and highly heat-dissipative BGA packages manufactured by fluxless laser soldering: Experimental and numerical investigations.
Authors: Kim, Dongjin1 (AUTHOR) dongjinkim@kitech.re.kr, Han, Seonghui1 (AUTHOR), Baik, Junha1 (AUTHOR), Park, Junwoo1 (AUTHOR), Yu, Ha-Young2 (AUTHOR), Chung, Kwansik3 (AUTHOR), Kim, Eunchae3 (AUTHOR), Yoo, Sehoon1 (AUTHOR) yoos@kitech.re.kr
Source: Microelectronics Reliability. Mar2026, Vol. 178, pN.PAG-N.PAG. 1p.
Subjects: Solder & soldering, Ball grid array technology, Metal compounds, Energy dissipation, Thermocycling, Thermal shock
Abstract: This study developed the flux-less solder ball (i.e., Sn-3wt%Ag-0.5wt%Cu) attachment technology (FLAT), a novel and eco-friendly approach that eliminates flux processing during mass reflow while significantly reducing the warpages. Furthermore, the ball grid array (BGA) package applied with FLAT was directly compared with the BGA package manufactured by the conventional mass reflow manufacturing method in terms of thermal cycling reliability. As a result, FLAT made an intermetallic compound (IMC) of less than 1.6 μm at bonding interfaces by an instantaneous laser heat source, and solidified immediately after nucleation, forming a solder ball composed of uniform and fine beta-Sn. In contrast, the conventional mass reflow soldering using flux has caused the formation of massive Cu 6 Sn 5 chunks inside the BGA package, and even the thickness of the IMC at the bonding interface with the pad exceeded 4.8 μm. The interfacial IMC layer suppressed by FLAT suppressed the spalling phenomenon during the continuous thermal cycling tests. In contrast, the interfacial IMC layer formed by the conventional mass reflow process had a relatively long aspect ratio, which promoted interdiffusion with the Sn matrix during thermal cycling, allowing the spalling of a large amount of Cu 6 Sn 5 chunks into the Sn matrix. This distinguished behavior explains the distinct pros and cons of the two processes in thermal shock resistance, which determines the rigidity and heat dissipation properties within the solder. This study systematically addresses the thermal cycling behaviors of BGA packages manufactured by FLAT and MR, and heat transfer performances originated from this IMC growth behavior through numerical calculation. • Low-energy process without cleaning through fluxless laser soldering • Exceptional IMC control through low-energy process • IMC thickness control to improve micro-heat transfer performance [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:This study developed the flux-less solder ball (i.e., Sn-3wt%Ag-0.5wt%Cu) attachment technology (FLAT), a novel and eco-friendly approach that eliminates flux processing during mass reflow while significantly reducing the warpages. Furthermore, the ball grid array (BGA) package applied with FLAT was directly compared with the BGA package manufactured by the conventional mass reflow manufacturing method in terms of thermal cycling reliability. As a result, FLAT made an intermetallic compound (IMC) of less than 1.6 μm at bonding interfaces by an instantaneous laser heat source, and solidified immediately after nucleation, forming a solder ball composed of uniform and fine beta-Sn. In contrast, the conventional mass reflow soldering using flux has caused the formation of massive Cu 6 Sn 5 chunks inside the BGA package, and even the thickness of the IMC at the bonding interface with the pad exceeded 4.8 μm. The interfacial IMC layer suppressed by FLAT suppressed the spalling phenomenon during the continuous thermal cycling tests. In contrast, the interfacial IMC layer formed by the conventional mass reflow process had a relatively long aspect ratio, which promoted interdiffusion with the Sn matrix during thermal cycling, allowing the spalling of a large amount of Cu 6 Sn 5 chunks into the Sn matrix. This distinguished behavior explains the distinct pros and cons of the two processes in thermal shock resistance, which determines the rigidity and heat dissipation properties within the solder. This study systematically addresses the thermal cycling behaviors of BGA packages manufactured by FLAT and MR, and heat transfer performances originated from this IMC growth behavior through numerical calculation. • Low-energy process without cleaning through fluxless laser soldering • Exceptional IMC control through low-energy process • IMC thickness control to improve micro-heat transfer performance [ABSTRACT FROM AUTHOR]
ISSN:00262714
DOI:10.1016/j.microrel.2026.116018