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Thermal simulation of flexible LED package enhanced with copper pillars

Yang Liu1, 2, 4, , Guoqi Zhang3, 5 and Fenglian Sun1

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 Corresponding author: Yang Liu, Email: lyang805@163.com

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Abstract: Chip on flexible substrate (COF) is a new packaging technology for light emitting diodes (LED). This paper investigated the effect of Cu-pillar in the polyimide (PI) layer on the thermal properties of COF LED packages by finite element analysis. The thermal distribution and thermal resistance were studied in both COF LED packages with and without Cu-pillar. The PI layer showed the highest thermal resistance in the typical package and led to a high chip temperature. With the addition of Cu-pillars, however, the thermal resistance of the PI layer significantly decreased due to the improvement of vertical thermal dissipation under LED chips. Based on the results of simulation and calculation, the relationship between the amount of Cu-pillar and thermal resistance of the COF package has been built. For the packages studied in this research, an 8 × 8 Cu-pillars array was adequate to improve the thermal performance of COF packages.

Key words: COFLEDCu-pillarthermal performanceFE simulation



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Fig. 1.  Schematic diagram and thermal path of COF with metal pillars introduced under the LED chip.

Fig. 2.  Thermal distribution of the packages. (a) Top surface of no Cu-pillar package. (b) Top surface of package with 8 $\times$ 8 Cu-pillars. (c) Top surface of package with 16 $\times$ 16 Cu-pillars. (d) Bottom surface of no Cu-pillar package. (e) Bottom surface of package with 8 $\times$ 8 Cu-pillars. (f) Bottom surface of package with 8 $\times$ 8 Cu-pillars.

Fig. 3.  Cross-sectional thermal distribution of the packages with (a) no Cu-pillar,(b) 8 $\times$ 8 Cu-pillars,and (c) 16 $\times$ 16 Cu-pillars.

Fig. 4.  Thermal resistance of each layer in the packages.

Fig. 5.  Relationships between heat power and chip temperature.

Fig. 6.  Relationship between $1/R_{\rm parallel}$ and area ratio of Cu-pillar.

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Table 1.   Geometric details and thermal conductivity of layers.

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Table 2.   Surface temperature and thermal resistance of the packages.

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    Received: 17 October 2014 Revised: Online: Published: 01 June 2015

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      Yang Liu, Guoqi Zhang, Fenglian Sun. Thermal simulation of flexible LED package enhanced with copper pillars[J]. Journal of Semiconductors, 2015, 36(6): 064011. doi: 10.1088/1674-4926/36/6/064011 Y Liu, G Q Zhang, F L Sun. Thermal simulation of flexible LED package enhanced with copper pillars[J]. J. Semicond., 2015, 36(6): 064011. doi: 10.1088/1674-4926/36/6/064011.Export: BibTex EndNote
      Citation:
      Yang Liu, Guoqi Zhang, Fenglian Sun. Thermal simulation of flexible LED package enhanced with copper pillars[J]. Journal of Semiconductors, 2015, 36(6): 064011. doi: 10.1088/1674-4926/36/6/064011

      Y Liu, G Q Zhang, F L Sun. Thermal simulation of flexible LED package enhanced with copper pillars[J]. J. Semicond., 2015, 36(6): 064011. doi: 10.1088/1674-4926/36/6/064011.
      Export: BibTex EndNote

      Thermal simulation of flexible LED package enhanced with copper pillars

      doi: 10.1088/1674-4926/36/6/064011
      Funds:

      Project supported by the Research and Scientific Foundation of Heilongjiang Education Department (No. 12541112).

      More Information
      • Corresponding author: Email: lyang805@163.com
      • Received Date: 2014-10-17
      • Accepted Date: 2014-11-09
      • Published Date: 2015-01-25

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