Study of the Thermomechanical Performance of FR-4 Laminates During the Reflow Process

  • Moisés HinojosaEmail author
  • Carlos A. Rodríguez
  • Jorge A. Aldaco
  • Javier Morales-Castillo
  • Armando E. Leal
  • Víctor Salinas


The behavior of FR4 laminates for printed circuit boards (PCBs) during a double reflow process and the main factors associated with warpage are discussed. The microstructure, glass transition temperature (Tg), decomposition temperature (Td), coefficient of thermal expansion (CTE), time to delamination and % water absorption were characterized, and the temperature profiles in the board during its pass through the reflow oven were recorded. Bow and twist measurements were taken on a set of 30 PCBs. Both Td and Tg were found to be below their nominal values. The CTE is highly anisotropic and vary at different locations, and it is more than three times higher in the through thickness middle section with respect to the bottom and top locations. Temporary temperature gradients of more than 50 degrees between different locations were detected at the start of the reflow step as a result, the bow values were found to be strongly anisotropic, particularly after the first reflow, in which different sides can present bow values up to more than six times higher than others, with maxima values of 0.47 mm. The anisotropy of the CTE appears to affect only slightly the twist values. Compared with the first reflow, the bow and twist values are lower, exhibit less dispersion and are more homogeneous for the second reflow. The histograms of both bow and twist do not seem to follow a normal distribution, possibly as a result of the combined effect of spatial variations and anisotropy of properties as well as the temperature gradients during reflow.


bow coefficient of thermal expansion PCBs reflow process thermomechanical performance twist warpage 



This work was supported by Yazaki Service S. de R. L. and the Mexican Council for Science and Technology (Conacyt).


  1. 1.
    C.F. Coombs, Jr., Printed Circuits Handbook, 6th ed., McGraw-Hill, New York, 2008Google Scholar
  2. 2.
    D. Adams, T. MacFadden, R. Maradiaga, R. Curry, Understanding PCB Design Variables That Contribute to Warpage During Module-Carrier Attachment, in SMTA International Conference Proceedings (2016).Google Scholar
  3. 3.
    A. Mircea, Main Aspects Concerning PCB manufacturing optimization, Circuit World, 2012, 38(2), p 75–82CrossRefGoogle Scholar
  4. 4.
    R. Polanský, P. Prosr, and M. Cermák, Determination of the Thermal Endurance of PCB FR4 Epoxy Laminates Via Thermal Analyses, Polym. Degrad. Stab., 2014, 105, p 107–115CrossRefGoogle Scholar
  5. 5.
    E. T. Haugan, P. Dalsjø, Norwegian Defence Research Establishment, Characterization of the Material Properties of Two FR4 Printed Circuit Board Laminates, ISBN 978-82-464-2322-7. (2014).Google Scholar
  6. 6.
    S. Ehrler, PCB Base Material Qualifications: Discrepancies Between Supplier Recommendations, Customer Expectations and Reality, Circuit World, 2013, 39(2), p 67–74CrossRefGoogle Scholar
  7. 7.
    The European Parliament and the Council of the European Union, 2003, Official Journal of the European Union, On the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment, pp. L. 37/19-37/23Google Scholar
  8. 8.
    J.D. Sigelko and K.N. Subramanian, Adv. Mater. Process., 2000, 157, p 47–48Google Scholar
  9. 9.
    J.L. Grenestedt and P. Hutapea, Using Waviness to Reduce Thermal Warpage in Printed Circuit Boards, Appl. Phys. Lett., 2002, 81(21), p 4079–4081CrossRefGoogle Scholar
  10. 10.
    P. S. Huang, Y. H. Lin, C. Y. Huang, M. Y. Tsai, T. C. Huang, M. C. Liao. Warpage and Curvature Determination of PCB with DIMM Socket During Reflow Process by Strain Gage Measurement, in 5th International Microsystems Packaging Assembly and Circuits Technology Conference, Taipei, pp. 1–4 (2010)Google Scholar
  11. 11.
    S. Chung and J.B. Kwak, Realistic Warpage Evaluation of Printed Board Assembly During Reflow Process, Solder. Surface Mount Technol., 2015, 27(4), p 137–145CrossRefGoogle Scholar
  12. 12.
    S.J. Joo, B. Park, D.H. Kim, D.O. Kwak, I.S. Song, J. Parkand, and H.S. Kim, Investigation of Multilayer Printed Circuit Board (PCB) Film Warpage Using Viscoelastic Properties Measured by a Vibration Test, J. Micromech. Microeng., 2015, 25(3), p 035021CrossRefGoogle Scholar
  13. 13.
    J. Al Ahmar, Fracture Mechanics Analysis of Cracks in Multilayer Ceramic Capacitors, in Electronics System-Integration Technology Conference, 2014, IEEE, pp. 1–5 (2014)Google Scholar
  14. 14.
    S. Aravamudhan, C. Combs, A. Prasad, and A. Abraham, Multiple-Faceted Approach to Minimize Printed Circuit Board Warpage in Board Assembly Process, in Proceedings of SMTA International, Sep. 25–29, Rosemont, IL, USA, pp. 168–176 (2016)Google Scholar
  15. 15.
    The Institute for Interconnecting and Packaging Electronic Circuits, 1995. IPC-TM-650 2.4.25 C Glass Transition Temperature and Cure Factor by DSC, Northbrook, IL (1995)Google Scholar
  16. 16.
    Association Connecting Electronics Industries. IPC-TM-650 Test methods manual. Decomposition Temperature (Td) of Laminate Material Using TGA, Bannockburn IL. (2006)Google Scholar
  17. 17.
    The Institute for Interconnecting and Packaging Electronic Circuits. IPC-TM-650 Test Methods Manual,, Time to Delamination (TMA Method), Northbrook, IL. 60062-6135 (1994).Google Scholar
  18. 18.
    Association Connecting Electronics Industries, IPC-TM-650 Test Methods Manual. Water Absorption, Metal Clad Plastic Laminates Water Absorption, Metal Clad Plastic Laminates. Northbrook, IL. (1985)Google Scholar
  19. 19.
    The Institute for Interconnecting and Packaging Electronic Circuits, 1994. IPC-TM-650 Test Methods Manual 2.4.24, Glass Transition Temperature and Z-Axis Thermal Expansion by TMA, Northbrook, IL (1994)Google Scholar
  20. 20.
    Association Connecting Electronics Industries, IPC-TM-650 Test Methods Manual. 2.4.22c Bow and Twist (Percentage)., Northbrook, IL. (1999)Google Scholar

Copyright information

© ASM International 2019

Authors and Affiliations

  • Moisés Hinojosa
    • 1
    Email author
  • Carlos A. Rodríguez
    • 1
  • Jorge A. Aldaco
    • 1
  • Javier Morales-Castillo
    • 1
  • Armando E. Leal
    • 1
  • Víctor Salinas
    • 2
  1. 1.Facultad de Ingeniería Mecánica y Eléctrica (FIME)Universidad Autónoma de Nuevo León (UANL)San Nicolás de los GarzaMexico
  2. 2.Yazaki (R&D) Technical CenterSan Nicolás de los GarzaMexico

Personalised recommendations