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October 2014 • The PCB Magazine 43 THIN PCBS FOR SMARTPHONES continues from the standard materials which are well in- troduced in PCB mass production. It was man- datory for all selected materials to be halogen free (HF). Relevant material and build-up properties of the applied dielectric materials are given in Table 2. For copper layers, standard 12 µm cop- per foil with single-sided, standard treatment has been applied. Experimental Procedures Board thickness measurement The thickness of the board was measured at two positions of the board as shown in Figure 4. The measurement was done manually with a digital micrometer gauge with a precision level of 0.001 mm at ambient conditions. The mea- surement was done for a random sample of 15 TVs from the production lot. While position A represents an area with lower overall copper content in the build-up, position B corresponds to an area of the built test vehicle which fea- tures a relatively high copper content in the stackup structure. Reflow performance The reflow testing was done in accordance with IPC/JEDEC J-STD-020D1T [5] . Applied mois- ture sensitivity level was level 3. The sample size was 10 test vehicles of each test vehicle type. Conditions for preconditioning are given in Table 3. Thermo cycle test The thermo cycling of the samples has been done in accordance with JEDEC JESD 22-A104D [6] , Test Condition G,2,C. Parameters are given in Table 4. Testing at the bareboard table 2: Properties of applied dielectric material. figure 4: Positions for board thickness measurements. table 3: Preconditioning for iPC/JedeC J-std- 020d1 msl3acc level reflow testing.