Materials and Technologies in Reflow Soldering

Topic Information

Dear Colleagues,

Reflow soldering is the most widespread soldering technology used in the microelectronics industry for assembly, especially of Surface Mounted Devices. This process is applied to prepare the solder joints in mass manufacturing of Surface Mount Devices to attach them to the Printed Wiring Board (PWBs) both electrically and mechanically. The steps before the actual reflow soldering process involve printing/depositing solder paste to the contact surfaces (pads) of the PWB and placing the components into the deposited solder paste. The reflow process heats the entire assembly to a temperature beyond the melting point of the solder alloy, then cools down it to solidify the solder alloy and create the solder joints. Although this technology is widely applied by the electronics industry, it is still the subject of intense research and development. We welcome papers on the following topics:

• New soldering technologies and soldering ovens/devices, including new heat-transfer methods and thermal management of ovens;
• New application areas for reflow soldering;
• Improved process steps reached by artificial intelligence and statistical tools;
• Novel soldering materials, new alloys, application of nanoparticles in solder alloys; composite solders;
• Novel characterization and measurement methods of the reflow soldering process and solder joints;
• Reliability and quality improvement of solder joints.

Prof. Dr. Balázs Illés
Dr. Oliver Krammer
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Alloys alloys	-	-	2022	15.0 days *	CHF 1000
Catalysts catalysts	3.9	6.3	2011	14.3 Days	CHF 2700
Materials materials	3.4	5.2	2008	13.9 Days	CHF 2600
Metals metals	2.9	4.4	2011	15 Days	CHF 2600
Nanomaterials nanomaterials	5.3	7.4	2010	13.6 Days	CHF 2900

* Median value for all MDPI journals in the second half of 2023.

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Published Papers (4 papers)

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All Alloys Catalysts Materials Metals Nanomaterials

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10 pages, 1822 KiB  

Open AccessArticle

Effect of Nanosized Ni Reinforcements on the Structure of the Sn-3.0Ag-0.5Cu Alloy in Liquid and After-Reflow Solid States

by Andriy Yakymovych and Ihor Shtablavyi

Metals 2023, 13(6), 1093; https://doi.org/10.3390/met13061093 - 09 Jun 2023

Cited by 2 | Viewed by 892

Abstract

The Sn-Ag-Cu (SAC) alloy family is commonly used in lead-free solders employed in the electronics industry, for instance, SAC305, SAC387, SAC405, etc. However, the trend in manufacturing small electronic products and device miniaturization faces some disadvantages in terms of mechanical properties and their [...] Read more.

The Sn-Ag-Cu (SAC) alloy family is commonly used in lead-free solders employed in the electronics industry, for instance, SAC305, SAC387, SAC405, etc. However, the trend in manufacturing small electronic products and device miniaturization faces some disadvantages in terms of mechanical properties and their higher melting temperatures compared to Pb-Sn solders, prompting new research relating to the reinforcement of existing SAC solders. The current study presents structural features of nanocomposite (Sn-3.0Ag-0.5Cu)_100−x(nanoNi)_x solders with 0.5 wt.%, 1.0 wt.%, and 2.0 wt.% Ni. Structural analysis of the investigated samples were performed by means of X-ray diffraction in a liquid state and scanning electron microscopy (SEM). SEM showed the mutual substitution of Ni and Cu atoms in the Cu₆Sn₅ and Ni₃Sn₄ phases, respectively. The performed structural studies in liquid and solid states provided essential information concerning the structural transformations of liquid Sn-3.0Ag-0.5Cu alloys caused by minor additions of nanosized Ni powder. The melting point and degree of undercooling of the samples were investigated by DTA analysis. Full article

(This article belongs to the Topic Materials and Technologies in Reflow Soldering)

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12 pages, 3100 KiB  

Open AccessArticle

NiCrBSi Coatings Fabricated on 45 Steel Using Large Spot Laser Cladding

by Longjie Zhao, Huijun Yu, Yanxiang Wang, Zhihuan Zhao, Weihai Song and Chuanzhong Chen

Materials 2022, 15(18), 6246; https://doi.org/10.3390/ma15186246 - 08 Sep 2022

Cited by 2 | Viewed by 1141

Abstract

Ni35 coatings were fabricated on 45 steel using a CO₂ laser at various parameters. A relatively large spot (10 mm diameter) was adopted, which was beneficial to the coating quality and the cladding efficiency. The cross-sectional geometry, phase constituent, and microstructure of [...] Read more.

Ni35 coatings were fabricated on 45 steel using a CO₂ laser at various parameters. A relatively large spot (10 mm diameter) was adopted, which was beneficial to the coating quality and the cladding efficiency. The cross-sectional geometry, phase constituent, and microstructure of the coatings were investigated. With a lower specific energy, coating height increased, while coating width, melted depth, dilution rate, width to height ratio and contact angle decreased. Ni35 coating primarily consisted of γ-Ni, FeNi₃, Ni₃B, Cr₂₃C₆, and Cr₅B₃. Dendrites with flower-like, fishbone-like, pearl-like, and column-like morphologies were observed. The fraction of flower-like dendrites increased gradually with the decrease in scanning velocity due to the dendrite growth direction evolution. With the decrease in scanning velocity, the microstructure of the heat-affected zone transformed from martensite to martensite + sorbite and finally sorbite. The maximum microhardness of the Ni35 coating reached 451.8 HV_0.2, which was about double that of the substrate (220 HV_0.2). Full article

(This article belongs to the Topic Materials and Technologies in Reflow Soldering)

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14 pages, 13462 KiB  

Open AccessArticle

Influence of Scanning Speed on the Microstructure and Wear Resistance of Laser Alloying Coatings on Ti-6Al-4V Substrate

by Huijun Yu, Xiaoxi Meng, Zifan Wang and Chuanzhong Chen

Materials 2022, 15(17), 5819; https://doi.org/10.3390/ma15175819 - 24 Aug 2022

Cited by 3 | Viewed by 1025

Abstract

Laser alloying has attracted significant attentions due to the advantages of high processing precision, good controllability and low heat effects on the substrate. However, the complexity of laser alloying requires further attentions on its processing parameters. This study aims at improving the wear [...] Read more.

Laser alloying has attracted significant attentions due to the advantages of high processing precision, good controllability and low heat effects on the substrate. However, the complexity of laser alloying requires further attentions on its processing parameters. This study aims at improving the wear resistance of the Ti-6Al-4V substrate by means of laser surface alloying with Ni-coated graphite (G@Ni). The effect of laser scanning speed is explored. The result suggests that the coating has a high surface quality and excellent metallurgical bonding with the substrate. NiTi and NiTi₂ have a eutectic microstructure as well as in the TiC ceramic-reinforced phase as dendrites distribute in the γ-Ni matrix of the coatings. At higher scanning speeds, the lower energy density and shorter existence time of the molten pool refines the microstructure of the coating, improving its microhardness. At the scanning speed of 15 mm/s, the coating has the lowest wear weight loss due to its high microhardness and dense structure. This paper explores the influence of scanning speed on the microstructure and properties of the coatings, expanding the application of laser alloying on the surface modification of Ti-6Al-4V alloys. Full article

(This article belongs to the Topic Materials and Technologies in Reflow Soldering)

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11 pages, 3938 KiB  

Open AccessArticle

Microstructure and Wear Resistance of a Composite Coating Prepared by Laser Alloying with Ni-Coated Graphite on Ti-6Al-4V Alloy

by Huijun Yu, Lu Lu, Zifan Wang and Chuanzhong Chen

Materials 2022, 15(16), 5512; https://doi.org/10.3390/ma15165512 - 11 Aug 2022

Cited by 7 | Viewed by 1303

Abstract

Titanium alloys are widely used in high-tech fields, while its disadvantages such as low hardness, high coefficient of friction and poor wear resistance have restricted its applications. This study focuses on improving the friction and wear resistance of Ti-6Al-4V titanium alloys by means [...] Read more.

Titanium alloys are widely used in high-tech fields, while its disadvantages such as low hardness, high coefficient of friction and poor wear resistance have restricted its applications. This study focuses on improving the friction and wear resistance of Ti-6Al-4V titanium alloys by means of laser surface alloying with Ni-coated graphite (G@Ni). The results suggest that Ni acts as a protective layer to hinder the direct contact and reaction of C and Ti in the molten pool. A part of graphite is unmelted and finally remains to form a self-lubricating wear-resistant composite coating with a compact structure. The average hardness of the coating is approximately four times that of the substrate owing to the TiC hard phase and compact microstructures as the reinforcing phase. The residual graphite in the coating plays a friction-reduction role during the wear test. The wear resistance is increased to 8.53 times that of the substrate according to wear mass loss. This study can effectively enhance the performance and expand the application of the titanium alloys by improving the wear resistance and reducing the friction. Full article

(This article belongs to the Topic Materials and Technologies in Reflow Soldering)

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