OVERVIEW • Component Trends • 01005 • LED • PoP • Printing • Placement • Reflow • Rework • Inspection
Component Trends -The new smallest device is an 01005 -0.010” X 0.005” -0.4mm X 0.2mm -Just 1/4 the size of an 0201!
Component Trends • LED’s • Wide range of sizes • Concave or convex lens • Solar PV can use similar package style • 2012 ?? • Applications such as: • Cell phones • Light bulb replacement • Street lights • Automotive • Everywhere!
Component Trends • PoP-Literally an IC package or packages on top of an already placed IC package • Three step process • Gel flux or “dipping” paste • Two ways to process • With standard SMT assy. • As a separate process
New Component Trends=New Assembly Challenges • Printing process • Equipment capabilities • Stencil design • Type of paste • Placement equipment • Placement accuracy • Component feeding • Nozzle design • Placement pressure • Component centering • Reflow process • Oven profile • Component self alignment
Printing Process • Equipment Capabilities • Print Accuracy • Print Repeatability • Print Quality • Stencil Design • Aperture Size • Stencil Thickness • E Form or Laser cut • Foil material • Paste Choice • Lead or No Lead • Types 3, 4, 5
Printing Process • LED’s and PoP are not significantly affected • 01005 size vs. Printer accuracy • 0.010” X 0.005” • Printer must have an accuracy of 0.008” (20 micron) + • Stencil must have same tolerance • PCB stretch?
Printing Process • 01005 Stencil design factors • Thickness typically 3 mils (2.5-3.5 per IPC 7525-A) • Effects on other parts? • Paste release • Reduction typically 10% (5% for LF) • 1 mil on this PCB (8x10 mil pad) • Electroformed technology • Aperture Area Ratio • Aperture area WXL Wall area W+LX2Xthickness
Printing Process • Type IV Solder paste mesh size is optimal for 01005 and PoP. • Effect on other parts • Solder balling • Type III is usually best for LED’s • Leaded vs No Lead
Pick Process -PoP is not a problem -LED’s must present flat -01005 Component feeding • As the component size keeps decreasing, so does the ability to reliably supply components to the machine. • Feeder advance-must be consistent • Auto correct-must assure pick is in the center of the component • Component presence-need method other than vacuum (laser) to insure the part is there
Placement Process • Placement accuracy • Most studies agree that the placement accuracy of the pick and place machine needs to be 50 micron (0.05mm or 2mils) in X and Y and 10 degrees for theta.
Typical PoP assembly process Fluxer
POP Placement Process (1) Placement on the first tier (3) Flux coating (second tier) (4) Placement on the second tier (first chip) (2) Mounted component height measurement
POP Placement Process POP Placement Example
Placement Process Component centering-Laser or Vision? -The laser typically has approximately 3 x the pixels as a CCD or Digital camera. -Laser is faster -LED and 01005 use laser -PoP use vision
Illuminates Center of Nozzle Light receiving elements Placement Process Laser Technology “String Art”-The nozzle rotates the component through the laser finding the edge of the component by creating a shadow on the Laser Receiver. Based on the outline made by the String Art, the machine recognizes the difference between the nozzle location and component center, then adjusts the placement position. String Art
Placement Process • Nozzle design • Very critical for LED and 01005 • “Blow Off”? • Local fiducials? • Placement pressure • PCB stretch-”OPASS” • Offset Placement After Solder Screening
2-1 2-3 2-1 1-1 2-3 1-2 JUKI’s Solution Self Contained in Machine How It Works 1） Correct for fiducials 2） Using the local fiducial function, the machine will check the solder paste position relative to the pad locations Corrected placement between PCB pads and print misalignment 3） Components are placed centered on the solder paste print, not the pads Placement corrected for print offset Machine self-contained Example of Component Placement Solution Placement on PCB pads Traditional 2012 lands 1608 lands Fiducial mark ☆ Placement centered on solder paste print, not pads Placement of component on misaligned stencil or stretched PCB Placement centered on paste
1） Self-alignment is improved by placing on paste → Results are good up to about 0.1mm (half size of 01005), but neighboring pads can affect larger offsets 01005 chip 0201 ＆0402 chip print 0.10 / placement 0 print 0.10 / placement 0.10 print 0.19 / placement 0.19 print 0.16 / placement 0 OK OK NG NG Comparison of Placement Offset Results good even with larger offset 6/16
Placement Process-01005’s OPASS-offset placement after solder stenciling -compensate for these problems. • Billboard • Skewed • Tombstone
Reflow Process • Oven profile • Minimal impact unless LF • Cold solder on 01005 (N2?) • Solder balls on larger parts • Component self alignment • Tombstoning
Rework • 01005-yea right • PoP-hot gas or IR station • Must remove the whole package • LED-conductive tweezers or hot air pencil • Hot gas station destroys the part
Inspection • 01005-typically need an upgraded camera on AOI systems • PoP-very difficult. Must have X Ray and 3D is preferred (at least have oblique view) • LED-no problem
Summary • All aspects of the PCB assembly process are affected • Different parts have different challenges • New components present new challenges but also new opportunities • Utilize your partners-Circuit Technology and many others can help you. WWW.circuittechnology.com • What’s next??