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ESD11B Fiches technique(PDF) 5 Page - ON Semiconductor |
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ESD11B Fiches technique(HTML) 5 Page - ON Semiconductor |
5 / 6 page ESD11B www.onsemi.com 5 It is imperative that the coating is conformal, uniform, and free of impurities to insure a consistent mounting process. Due to the package’s extremely small size, we only recommend the use of the electroless nickel/ immersion gold metallization over the copper pads. PCB Circuit Trace Width The width of the PCB circuit trace plays an important role in the reduction of component tilting when the solder is reflowed. A solderable circuit trace allows the solder to wick or run down the trace, reducing the overall thickness of the solder on the PCB and under the component. Due to the small nature of the solder pad and component, the solder on the PCB will tend to form a bump causing the component to slide down the side of that solder bump resulting in a tilted component on the PCB. Allowing the solder to wick or run down the PCB circuit trace, will reduce the solder thickness and in turn prevent the solder from forming a ball on the PCB pad. This was observed during ON Semiconductor board mounting evaluations. The best results to prevent tilting used a PCB circuit trace equal to the width of the mounting pad. The length of the solder wicking or run out is controlled by the solder mask opening. Solder Type Solder pastes such as Cookson Electronics’ WS3060 with a Type 4 or smaller sphere size are recommended. WS3060 has a water-soluble flux for cleaning. Cookson Electronics’ PNC0106A can be used if a no-clean flux is preferred. Solder Stencil Screening Stencil screening of the solder paste onto the PCB is commonly used in the industry. The recommended stencil thickness for this part is 0.1 mm (0.004 in). The sidewalls of the stencil openings should be tapered approximately five degrees along with an electro-polish finish to aid in the release of the paste when the stencil is removed from the PCB. See Figure 9 for the recommended stencil opening size and pitch shown on the recommended PCB mounting pads and solder mask opening from Figure 6. Figure 9. Recommended Stencil Pattern. A second stencil option is shown in Figure 10. This option increases the amount of solder paste applied to the PCB through the stencil. This second option increases the stencil opening size and pitch. The PCB mounting pads and solder mask opening on the board do not change from the recommendations in Figure 6. Figure 10. Maximum Stencil Pattern Note: If the maximum stencil opening option from Figure 10 is used, tilt may occur on some of the packages. This was evident in the board mounting study we conducted. The stencil with the largest openings may improve solder release from the stencil along with slightly increasing the package shear strength. Package Placement Due to the small package size and because the pads are on the underside of the package, an automated pick and place procedure with magnification is recommended. A dual image optical system where the underside of the package can be aligned to the PCB should be used. Pick and place equipment with a standard tolerance of +/- 0.05 mm (0.002 in) or better is recommended. The package self aligns during the reflow process due to the surface tension of the solder. |
Numéro de pièce similaire - ESD11B |
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Description similaire - ESD11B |
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