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AB190 データシート(PDF) 6 Page - Lumileds Lighting Company |
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AB190 データシート(HTML) 6 Page - Lumileds Lighting Company |
6 / 11 page AB190 LUXEON IR Compact Line Application Brief 20170725 ©2017 Lumileds Holding B.V. All rights reserved. 6 2.3 Minimum Spacing A minimum edge to edge spacing between LUXEON IR Compact of 0.2mm can generally be achieved with modern pick and place equipment. Placing multiple LUXEON emitters too close to each other may adversely impact the ability of the PCB to dissipate the heat from the emitters. Also, the light output for each LED may drop due to optical absorption by adjacent LED packages. 3. Assembly Process Guidelines 3.1 Stencil Design The appropriate stencil design for the LUXEON IR Compact emitter is included in the PCB footprint design (see Figure 6). Lumileds has successfully evaluated a stencil thickness of 4 mils (102µm). 3.2 Solder Paste Lumileds successfully tested a lead-free, no clean SAC 305 solder paste from Alpha® OM-340, type 4. However, since application environments vary widely, Lumileds recommends that customers perform their own solder paste evaluation in order to ensure it is suitable for the targeted application. 3.3 Solder Paste Screen Printing In general there are three methods to align the stencil to the PCB during solder paste screen printing: 1. The stencil is manually aligned to the PCB prior to printing. No adjustments are made during printing. 2. The stencil is manually aligned to the PCB prior to printing. During printing, the machine keeps track of the PCB fiducial mark(s) and makes any necessary adjustments to maintain proper alignment with the PCB. 3. A technician performs a crude alignment of the stencil to the PCB. During printing, the machine keeps track of the PCB fiducial mark(s) and the stencil fiducial mark(s) and maintains proper alignment between the fiducials throughout the process. Method 1 has the worst accuracy and repeatability of the three methods discussed. Method 2 offers the same accuracy as method 1 but ensures better repeatability. Method 3 has the best accuracy and best repeatability of the 3 methods discussed. Depending on what screen printing method is used, the size of the anode and cathode solder mask openings on the PCB may have to be enlarged to compensate for any misalignments between the stencil and the PCB panel. Note that any enlargement in the solder mask opening for anode and cathode pads may reduce the solder reflow placement accuracy. In order to ensure proper alignment between the stencil and the PCB as well as reliable transfer of solder paste onto the PCB, all PCB panels should be rigidly supported during solder paste printing. Instead of placing the PCB panel on multiple support pins, it is best to place the PCB panel on a single solid plate. This is particularly important for PCB panels which contain v-scores or perforated holes for de-panel purposes. Figure 7 shows the outcome of a well-controlled stencil printing process according to method 3 above. In this example, the recommended stencil pattern of Figure 5 was used in combination with a stencil thickness of 4 mils and a solder paste from Alpha® OM-340. Also the stencil aperture wall used should be smooth to aid smooth release of solder paste. |
同様の部品番号 - AB190 |
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同様の説明 - AB190 |
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