Influence of heating direction on BGA solder balls structure

Otahal, Alexandr; Somer, Jakub; Szendiuch, Ivan

doi:10.23919/empc.2017.8346878

Cited by 4 publications

(4 citation statements)

References 12 publications

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“…In the context of our previous research published at EMPC 2017 [19] it can be hypothesized that intermetallic layers are partly influenced by movements of the melted solder due to different concentration and the temperature gradients.…”

Section: Resultsmentioning

confidence: 98%

“…In Figs. 5, 6 and 7 from [19], the intermetallic interfaces for Bottom IR, Top IR and Both IR samples are presented. In addition to the copper layer and the IMC layer, the nickel-phosphorus layer can also be observed.…”

Section: Resultsmentioning

confidence: 99%

“…contributes to a certain extent to the growth of intermetallic crystals and their spalling [16][17][18]. In [19], the influence of the direction of heat flow on the crystallographic orientation of solder balls SAC305 for soldering on the Dummy BGA case was determined, namely the creation of more nuclei with different crystallographic orientations for soldering from the top side and both sides at the same time (upper and lower heating). Research in [20] describes the phenomenon, when the application of the DC electric current to the drop of the tin solder placed on the copper surface affected the wettability and formation of the intermetallic layer.…”

Section: Discussionmentioning

confidence: 99%

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Influence of heat flow direction on solder ball interfacial layer

Otahal

Szendiuch

2018

Journal of Electrical Engineering

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This paper deals with the research of an intermetallic layer of SAC305 solder balls soldered from three directions of the heat flow in the ball-attach process for BGA package. From the point of view of the heat flow direction, the samples were soldered by infrared heating. The heat sources were placed on the top, bottom and both lateral sides of the BGA package. After the solder balls-attach process, a metallographic cross-section was performed, followed by selective etching to visualize the relief of the intermetallic layer. Images of the interfacial between the solder and solder pad were taken from the created samples, followed by measurement of the average thickness and root mean square roughness of the intermetallic layer. The results showed changes in the intermetallic layer. The largest thickness of the intermetallic layer was observed on samples soldered from the top and both sides. Soldering with the bottom infrared heater resulted to the smallest thickness of the intermetallic layer. The same trend was in the roughness of the IMC layer. The greatest roughness was found for samples soldered by the top and both side heaters. The top soldered samples exhibit the smallest roughness.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Influence of heat flow direction on solder ball interfacial layer

Otahal

Szendiuch

2018

Journal of Electrical Engineering

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“…Many studies observed and confirmed that the formation of voids strongly depends on the reflow soldering parameters, including preheating zone, peak temperature, and soaking time [7]. The direction of heat flow and cooling can also have an influence on the properties and structure of the resulting solder joints and voids' formation, which was confirmed by [8][9][10].…”

Section: Introductionmentioning

confidence: 97%

Analysis of solder mask roughness and stencil shape influence on void formation in solder joints

2023

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Voids inside solder joints are empty spaces negatively affecting the mechanical, thermal, and electrical properties of the solder joint. This article deals with this problematics using two novel approaches to reduce voids’ occurrence. The first approach is the change of the roughness of the solder mask to influence the flux spreading around the solder pad. The second approach is the deposition of the same volume of the solder paste to the solder pads using a modified, thicker stencil with smaller apertures. The experiments were performed for solder pastes containing SAC305 alloy and two types of fluxes (ROL0/ROL1). Solder joints were inspected by X-ray imaging, and the shots were subsequently processed by image analysis. For determination of the spreading area of the flux around the solder pad during the reflow process, the tested boards were scanned by a confocal digital microscope. The results showed that more aggressive flux caused less voiding in terms of the average area of voids covering the soldering pad. Analysis of samples prepared with modified stencils showed a much lower proportion of voids than with the standard stencil. Furthermore, the results revealed that the selection of the solder mask type significantly influenced the voids’ formation within solder joints in the case of the unmodified stencil for solder paste deposition. On the other hand, when the modified stencils were used for sample preparation, the solder mask had no further impact on voiding. Therefore, modifying the stencil can be pointed out as a preferable and effective way.

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