Qualification of the Assembly Process of Flip-Chip BGA Packages ...

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Texas Tech University, Nivetha Shivan, May 2012 In Figure 4.5, the average of the displacement from the four corners is taken and subtracted from the centre displacement which gives us 78um coplanarity. The upper spec limit for the package coplanarity for BGA is 203.2 um (8 mils) according to JEDEC standards [15]. The sample and the grating are enclosed in a thermal enclosure and the sample is heated by a heating element to various temperatures. The temperature is measured using thermocouples. Figure 4.6 shows an example of the warpage vs. temperature graph for a device which is dry and for the same device post MSL3. The x-axis in the graph originally denotes the time during which the package was exposed to a particular temperature. It is seen from the graph that the package has curved across the temperature changes post MSL3 soak. Figure 4.7 shows the temperature profile below shows the duration of exposure of the package to a particular temperature. Process 1 in the figure is the actual process which measures the displacement at the corresponding measurement points in the desired profile. Figure 4.6: Warpage vs. Temperature Graph [14] 27
Texas Tech University, Nivetha Shivan, May 2012 Figure 4.7: Package Body Temperature vs. Time [14] 4.2 Techniques used for Stress Tests (Phase I and Phase II) The devices have to undergo stress tests for qualification of the packaging materials. 4.2.1 MSL3 Pre-conditioning Technique [17, 18] The following describes the ovens, chambers and other equipments used in this technique: � Bake Oven capable of operating at 125 +5/- deg C. � Temperature Cycle Chamber capable of operating – 65 deg C to 150 deg C � Moisture chambers capable of operating at 85C/85% RH, 85C/60% RH, and 30C/60% RH (Cincinnati Subzero Z-8) � Solder reflow equipment - Vitronics Isotherm hot air convection oven or equivalent � Ultrasonic Cleaner with frequency of 20-40 KHz 28
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Page 11 and 12: 1.3 Requirements of an IC Package [
Page 13 and 14: 1.5.2 Tape Automated Bonding [4] Te
Page 15 and 16: 2.1 What is Qualification? [7] Texa
Page 23 and 24: 3.1.1.2 Underfill material [9] Texa
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Page 41 and 42: 4.2.3 Pressure Cooker Technique [20
Page 45 and 46: 4.3.1.3 Leakage Test Texas Tech Uni
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Qualification of the Assembly Process of Flip-Chip BGA Packages ...

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