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An Epoxy Bonding Apparatus for Applications under Extreme Environment

Published online by Cambridge University Press:  23 February 2016

Runkun Jiang ,
Lei Mei  and
Q. M. Zhang
Runkun Jiang*
Affiliation:
Electrical Engineering Department and Materials Research Institute, N303 Millennium Science Complex, The Pennsylvania State University, University Park, PA 16802, U.S.A.
Lei Mei
Affiliation:
Electrical Engineering Department and Materials Research Institute, N303 Millennium Science Complex, The Pennsylvania State University, University Park, PA 16802, U.S.A.
Q. M. Zhang
Affiliation:
Electrical Engineering Department and Materials Research Institute, N303 Millennium Science Complex, The Pennsylvania State University, University Park, PA 16802, U.S.A.
*
*(Email: jiangrunkun198942@gmail.com)
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Abstract

A number of electrical components and devices work in extreme environment such as high temperature, high pressure, strong vibration, corrosive chemicals, etc. A common practice to protect them is to shield them in materials that are mechanically and chemically resistant to these harsh conditions. In this scenario, epoxy bonding is preferred and it is crucial to have high bonding strength. One example is the acoustic transducers used in oil drilling. The temperature can reach 200 °C and the pressure can reach 140 MPa. The piezoelectric ceramic parts cannot withstand these conditions so different packaging materials are used such as polyether ether ketone (PEEK).

Here an epoxy bonding apparatus is presented that has demonstrated ultrahigh bonding strength. Though epoxy resin is degassed before applying, which gets rid of air bubbles generated in the mixing process, there is trapped air when two surfaces are closed together. This trapped air has minuscule effect for applications in ambient environment, but under extreme environment, it compromises the bonding strength majorly. We devised a vacuum system that contains a motorized stage with the bonding parts attached. After the epoxy is applied and the system is pumped to 1% vacuum, a computer controls the motor to move the bonding parts into contact. Since the entire operation is in vacuum, it leaves no trapped air and results in increased bonding strength. This apparatus confirmed the importance of surface preparation, including removal of air by starting the cure in vacuum (5 mm Hg) and subsequently releasing the vacuum [1].

Another technique to improve the bonding strength utilizes the finding that a uniform epoxy resin layer between 50 µm and 150 µm [2] results in the optimal bonding strength. Here we applied spacers such as optic fiber (125 µm in diameter) or glass fiber fabric (150 µm in thickness) in between the bonding surfaces. These spacers ensure that the epoxy resin layer is of uniform thickness. It also utilizes the principle of glass-epoxy compositing to increase mechanical strength by fiber reinforcement and load distribution [3, 4].

The above bonding apparatus has been proven to increase the bonding strength by experiments. Acoustic transducers bonded with this technique passed the high pressure, high temperature tests resembling the oil drilling conditions.

Keywords

acousticpiezoelectricbonding
Type
Articles
Information
MRS Advances , Volume 1 , Issue 21: Nanomaterials and Synthesis , 2016 , pp. 1525 - 1530
Copyright
Copyright © Materials Research Society 2016 

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References

REFERENCES

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Wayne Johnson, R., Extreme Environment Electronics, http://www.eng.auburn.edu/∼johnson/, Retrieved November 2015Google Scholar
Jiang, Runkun, et al. , High-Power Broadband Piezocomposite Transducers for Logging-While-Drilling Applications, International Workshop on Acoustic Transduction Materials and Devices, May 2015 Google Scholar
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