Thermal Analysis of Printed Circuit Board 2016.01

Technical Report TA No.104 Thermal Analysis and Dynamic Mechanical Analysis Product Line

Printed circuit boards (PCBs) are mounted with various electrical components and conducting layers. Depending on the operating environment, the conducting layers may be damaged by the expansion and/or softening of the PCB. Therefore, PCBs are usually reinforced by glass fiber with a low expansion coefficient and a high softening point (glass fiber-reinforced epoxy board). It is important to know the linear expansion and softening temperature of PCBs. This report introduces an example measurement of the glass transition, expansion, and softening for a glass fiber-reinforced epoxy resin. Results 50 TMA measurement We performed TMA in the X, Y, and Z directions (see figure 40 ・Load: 98 mN to the left). The Z direction undergoes the least amount of ・Heating rate: 5 ºC/min Ｚ expansion until the glass transition temperature due to its 30 ・Probe: Expansion/compression short length. However, beyond the glass transition Ｘ temperature, the coefficient of linear expansion increases. In

m 20 contrast, the coefficient of linear expansion in the X and Y  directions decreases above the glass transition temperature. 10 Ｙ To protect the conducting layers on the PCB, the layout of TMA / 122.1 ºC Ｚ epoxy resins is set such that it can restrain the thermal 0 5.77×10-5[1/ ºC] expansion even when the temperature is over the glass Ｘ transition. -10 Ｙ DMA measurement -20 ・Dimensions: 20 mm (length)×10 mm (width)×1.5 mm (thickness) 40 80 120 160 200 Temperature / ºC ・Heating rate: 2 ºC /min 0 ・Measurement mode: Dual-Cantilever Bending DSC measurement ・Frequency: 0.5, 1, 2, 5, 10 Hz ・ Sample weight: 1.5 mg 1E+11 1E+11 1E+03 ・Heating rate: 10 ºC/min 50 ºC 10 1 Hz -100 ・Sample pan: Al open 1.7×10 Pa 124.5 ºC 1E+10 1E+10 1E+02 121.3 ºC W

 132.1 ºC 1 Hz -200 129.4 ºC 1E+09 1E+09 1E+01

DSC / 142.6 ºC /Pa /Pa tanδ E’ E” -300 1E+08 1E+08 1E+00 1 Hz 136.2 ºC 1E+07 1E+07 1E-01 -400 40 80 120 160 200 Temperature /ºC 1E+06 1E+06 1E-02 40 80 120 160 200 The step in the DSC signal corresponding to the epoxy Temperature /ºC glass transition becomes smaller with increasing weight ratio of the fiberglass, and thus detection of the DMA was used to measure changes in the epoxy glass transition becomes more difficult. However, we resin hardness during heating. The elastic modulus are able to directly observe the glass transition of (E’) is constant at 1.7×1010 Pa from room epoxy resin from 120 to 150 ºC. temperature to 120 ºC. A glass transition is observed In general, glass transitions are detected as an from 120 to 170 ºC, and E’ is decreased by softening increase in the linear expansion coefficient using TMA of the epoxy resin. DMA can thus be used to assess and a change in the specific heat capacity using DSC. the strength and heat resistance of PCBs.

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