Temperature-Dependent Sheet Resistance and Surface Characterization of Thin Copper Films Bonded to FR4 Composite under Mechanical Vibrations
Electrical boards, also called printed circuit boards, constitute the basis of most electronic devices. These boards are mainly fabricated of thin copper films bonded to fiber epoxy laminates, such as FR4. Being the most important functional component of these devices, they sometimes undergo mechani...
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MDPI AG
2023-07-01
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| Series: | Applied Sciences |
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| Online Access: | https://www.mdpi.com/2076-3417/13/13/7941 |
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| author | Sufyan Azam Shadi Munshi Mohamed K. Hassan Alex Fragoso |
| author_facet | Sufyan Azam Shadi Munshi Mohamed K. Hassan Alex Fragoso |
| author_sort | Sufyan Azam |
| collection | DOAJ |
| description | Electrical boards, also called printed circuit boards, constitute the basis of most electronic devices. These boards are mainly fabricated of thin copper films bonded to fiber epoxy laminates, such as FR4. Being the most important functional component of these devices, they sometimes undergo mechanical stresses such as shock and vibration during transport and operation that can induce electrical failure and malfunction; hence, studies addressing the effects of vibrations on their electrical properties have important applications. In this paper, small cantilever samples made of bare copper bonded to FR4 with three isolated rectangular zones were studied to analyze, for the first time, variations in electrical properties such as sheet resistance and resistivity before and after 200 k, 500 k, and 800 k vibration cycles at three different temperatures (25, 35, and 45 °C). A significant rise in resistance equivalent to 1657% of the initial value was observed from 0 to 800 k vibration cycles. These changes were accompanied by a 95% decrease in conductivity, from 4.1 × 10<sup>7</sup> to 2.3 × 10<sup>6</sup> S/m, whereas very little change in the electrical properties was observed due to temperature rise. Surface analysis by ESEM showed cracks ~1 µm in width and several millimeters in length with a crack density of ~8 cracks per mm after 800 k cycles. The surface composition (100% copper) was not altered even upon a high number of vibration cycles, and static drop contact angle measurements of 117–119 degrees indicated an increase in the hydrophobicity of the surface attributed to increased surface roughness and the accumulation of very small air bubbles on the cracks. |
| first_indexed | 2024-03-11T01:46:12Z |
| format | Article |
| id | doaj.art-772e7c8f152449008940f6fd7051bcdb |
| institution | Directory Open Access Journal |
| issn | 2076-3417 |
| language | English |
| last_indexed | 2024-03-11T01:46:12Z |
| publishDate | 2023-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Applied Sciences |
| spelling | doaj.art-772e7c8f152449008940f6fd7051bcdb2023-11-18T16:13:39ZengMDPI AGApplied Sciences2076-34172023-07-011313794110.3390/app13137941Temperature-Dependent Sheet Resistance and Surface Characterization of Thin Copper Films Bonded to FR4 Composite under Mechanical VibrationsSufyan Azam0Shadi Munshi1Mohamed K. Hassan2Alex Fragoso3Mechanical Engineering Department, Umm Al-Qura University, Makkah 21955, Saudi ArabiaMechanical Engineering Department, Umm Al-Qura University, Makkah 21955, Saudi ArabiaMechanical Engineering Department, Umm Al-Qura University, Makkah 21955, Saudi ArabiaDepartament d’Enginyeria Química, Universitat Rovira i Virgili, 43007 Tarragona, SpainElectrical boards, also called printed circuit boards, constitute the basis of most electronic devices. These boards are mainly fabricated of thin copper films bonded to fiber epoxy laminates, such as FR4. Being the most important functional component of these devices, they sometimes undergo mechanical stresses such as shock and vibration during transport and operation that can induce electrical failure and malfunction; hence, studies addressing the effects of vibrations on their electrical properties have important applications. In this paper, small cantilever samples made of bare copper bonded to FR4 with three isolated rectangular zones were studied to analyze, for the first time, variations in electrical properties such as sheet resistance and resistivity before and after 200 k, 500 k, and 800 k vibration cycles at three different temperatures (25, 35, and 45 °C). A significant rise in resistance equivalent to 1657% of the initial value was observed from 0 to 800 k vibration cycles. These changes were accompanied by a 95% decrease in conductivity, from 4.1 × 10<sup>7</sup> to 2.3 × 10<sup>6</sup> S/m, whereas very little change in the electrical properties was observed due to temperature rise. Surface analysis by ESEM showed cracks ~1 µm in width and several millimeters in length with a crack density of ~8 cracks per mm after 800 k cycles. The surface composition (100% copper) was not altered even upon a high number of vibration cycles, and static drop contact angle measurements of 117–119 degrees indicated an increase in the hydrophobicity of the surface attributed to increased surface roughness and the accumulation of very small air bubbles on the cracks.https://www.mdpi.com/2076-3417/13/13/7941copper/FR4 compositeprinted circuit boardsheet resistancevibrationsconductivityresistivity |
| spellingShingle | Sufyan Azam Shadi Munshi Mohamed K. Hassan Alex Fragoso Temperature-Dependent Sheet Resistance and Surface Characterization of Thin Copper Films Bonded to FR4 Composite under Mechanical Vibrations Applied Sciences copper/FR4 composite printed circuit board sheet resistance vibrations conductivity resistivity |
| title | Temperature-Dependent Sheet Resistance and Surface Characterization of Thin Copper Films Bonded to FR4 Composite under Mechanical Vibrations |
| title_full | Temperature-Dependent Sheet Resistance and Surface Characterization of Thin Copper Films Bonded to FR4 Composite under Mechanical Vibrations |
| title_fullStr | Temperature-Dependent Sheet Resistance and Surface Characterization of Thin Copper Films Bonded to FR4 Composite under Mechanical Vibrations |
| title_full_unstemmed | Temperature-Dependent Sheet Resistance and Surface Characterization of Thin Copper Films Bonded to FR4 Composite under Mechanical Vibrations |
| title_short | Temperature-Dependent Sheet Resistance and Surface Characterization of Thin Copper Films Bonded to FR4 Composite under Mechanical Vibrations |
| title_sort | temperature dependent sheet resistance and surface characterization of thin copper films bonded to fr4 composite under mechanical vibrations |
| topic | copper/FR4 composite printed circuit board sheet resistance vibrations conductivity resistivity |
| url | https://www.mdpi.com/2076-3417/13/13/7941 |
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