evaluation of stencil foil materials, suppliers and ... - IPC Outlook
evaluation of stencil foil materials, suppliers and ... - IPC Outlook
evaluation of stencil foil materials, suppliers and ... - IPC Outlook
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As originally published in the SMTA International Conference Proceedings.Thickness MeasurementsTable 3. Foil Thickness MeasurementsMaterial No. SupplierThcknss ThcknssSpec Avg% Diff4 C 4.5 5.5 23%8 B 4.5 4.3 6%9 B 4.5 4.5 0%10 B 4.0 4.4 9%1 11 B 4.0 3.9 2%14 C 4.5 5.6 24%17 D 4.5 4.4 3%26 D 4.5 4.4 2%27 D 4.5 4.4 3%2 B 4.0 4.7 16%3 B 4.0 4.6 16%12 C 4.5 3.7 19%213 C 4.5 4.3 4%15 B 4.5 4.7 5%16 B 4.5 5.0 11%18 D 4.5 4.5 0%19 D 4.5 4.5 0%6 A 4.0 4.0 0%37 A 4.0 4.0 0%20 D 4.0 4.1 1%21 D 4.0 4.0 0%1 A 4.0 4.0 0%45 A 4.0 4.0 0%22 D 4.0 4.1 1%23 D 4.0 4.0 0%524 D 4.0 4.0 0%25 D 4.0 4.1 2%KEY: 0‐3% 4‐10% >10%To calculate actual transfer efficiencies <strong>and</strong> area ratios, the<strong>stencil</strong>s’ apertures <strong>and</strong> thicknesses were measured. Theapertures were measured on the PCB side with a Microvueautomated vision system; 20 <strong>of</strong> each aperture size weremeasured per <strong>stencil</strong> <strong>and</strong> the average is reported in table 2.The <strong>foil</strong> thicknesses were measured at all four corners <strong>of</strong> theprint area with a Mitotoyo 12” throat micrometer; theiraverages are reported in table 3. The average figuresreported in the tables are used to calculate the apertures’actual volumes <strong>and</strong> area ratios.Paste VolumesTable 4. Paste volumes in cubic milsBGA PasteMaterial No. SupplierVolume123450201 PasteVolume4 C 281 6268 B 306 6679 B 255 57110 B 241 58811 B 267 59914 C 290 61917 D 308 66526 D 312 69127 D 315 6892 B 251 5763 B 267 60812 C 200 48713 C 185 45415 B 260 66516 B 293 64218 D 296 64719 D 263 6356 A 352 7417 A 320 66520 D 347 72421 D 293 6221 A 306 6705 A 282 59822 D 339 71123 D 337 71124 D 313 75025 D 321 635The measured solder paste volumes, shown in table 4, arethe averages <strong>of</strong> the individual measurements for eachfeature. St<strong>and</strong>ard deviations <strong>and</strong> coefficients <strong>of</strong> variationwere also calculated but not shown. Most CVs for theBGAs were less than 10%; the highest CVs were 16%.