【正文】 mouse and monitor e) Boards from the screen print operation move into the Pick and Place f) A camera takes a picture of the ponent being placed, this picture is pared to the ponent description in the machine program g) The puter checks for bent leads and correct placement on the PCB h) Board exits from the machine i) Nozzles “pick up” and “place” ponents j) Component is placed on the PCB 1) ____ 2) ____ 3) ____ 4) ____ 5) _____ 6) ____ 7) ____ 8) ____ 9) ____ 10) ____ LOGO Module 4 – Unit 4 DFM – SMT Placement Process, Pick and Place basic troubleshooting, Optimization of Placement Process 43 Unit 4 ( Hours) ?Objectives ? By the end of Unit 4, you will be able to: ? Summarize the DFM considerations ? Apply basic troubleshooting techniques for mon pick and place problems ? Use the discussed concepts to optimize the placement process 44 SMT Placement Process ? Leads of U19 are extending out of the pads (toe overhang) which are violations of IPC610 all classes. Remended size of the pad “outside” from the lead is . From heel to back end of pad is mm. Between back end of pad and ponent body, a minimum of mm is required. Please refer the diagram below ? L15 pads size too big, which is causing the ponent to “float” during reflow. 50% pads width reduction is remended ? Bodies of ponents C60, C3, U12 socket, U15, C28, C30, R60, R63, are all too close to board edge (minimum = 4mm). Machine transfer conveyers will displace these Minimum Solder fillet heel foot Minimum Minimum Minimum (remended ) Solder fillet toe Minimum heel foot 45 DFM PCBA SMT Placement Process ? The leads of ponent in locations DS12 and DS13 overhang pads on PCB by on each side. ? Aspect part number: AS02720021 ? Part manufacturer: Siemens ? Manuf. Part number: LSGT770K ? The body of transformer T1 is in contact with the leads of the micro modules U12. The ponent to ponent distance between the micro module and transformer T1 need to be increased. A minimum distance of ” from the land of micro module and the land of transformer T1 is strongly remended ? T1 had to be hand soldered because of interference between the location pins and the PCB, causing lifted pins. It is strongly remended to change T1 from SMT to PTH ? It is remended to increase the pads size for U12 by in width for better mechanical strength. Bigger leads would also help 46 DFM PCBA SMT Placement Process ? Unable to place SMT connectors (P5800, 5801, 6100, 6101) by machine on 1st run, due to problems capturing the length of the part in camera. This has now been resolved ? Still unable to place connectors 407789494 (X10) due to no SMT pick place pad on top of the connector to allow for vacuum pick up (see drawings) ? Minor “pick up” error L100 L200. Error was overe by the replacement of part feeder adjusting pick up offset ? Heat pipes HS18 on bottom side were moved to end of placement program due to them moving on the board on account of their weight (placement speed reduced, moving table moves slower) Pick Place Pad Side View 47 0201 Placement Process Component Attachment Pad L S W Attachment Pad Dimension Stencil aperture position relative to attachment pad Stencil aperture Outward solder paste shift Inward solder Paste shift Centered solder paste Attachment pad 48 0201 Placement Process (cont.) Noclean air flow Watersoluble air reflow Noclean nitrogen reflow 9 12 0 40 80 120 160 200 Attachment pad spacing (mils) Number of solder joint failures Assembly defects by attachment pad spacing and assembly process type. For all process types, more solder joint defects occur at the larger pad spacing Pad length (mils) Number of solder joint defects Noclean air flow Watersoluble air reflow Noclean nitrogen reflow 8 12 16 0 100 200 300 400 500 600 Attachment defects by attachment pad length and assembly process type. Results suggest that optimal pad length at ” for all process types Assembly defects by attachment pad width and assembly process type. Generally, for the process types, yield improves as pad width increases Noclean air flow Watersoluble air reflow Noclean nitrogen reflow 0 100 200 300 400 500 600 12 15 18 Pad width (mils) Number of solder joint defects 49 0201 Placement Process (cont.) ? Flexible setting of placement parameters for reliable and robust 0201 placement under different circumstances. The placement parameters at SIPLACE can be optimized: ? Different placement profiles ? 3 different air kiss settings ? No air kiss ? Short air kiss ? Normal air kiss as used 50 Component Spacing Minimum Spacing Preferred Spacing (Unit: mils) Descrete Low Descrete Tall QFP