Advanced SMT

Design & Assembly Advanced SMT

PCB DESIGN and PCB FABRICATION

  1. PCB Design Guidelines
  2. PCB Pad surface plating finish
  3. Wire Bond: PCB, Rigid-Flex and Flex plating
  4. PCB Panel Requirements
  5. PCB global, image and local Fiducials

STENCIL DESIGN and SOLDER PASTE

  1. Stencil Design Guidelines
  2. Solder Paste

Advanced SMT ASSEMBLY and FLIP CHIP

  1. PCB Assembly Documentation
  2. High Performance Solder Paste Printing
  3. High Precision SMT Pick & Place
  4. Advanced Flip Chip Assembly
  5. Convection Solder Reflow and Thermal Profiler

High Resolution AOI, XRAY and METROLOGY

  1. 2D + 3D High Resolution AOI for Microelectronics
  2. Microfocus 160Kv XRAY Inspection (including Flip Chip)
  3. Metrology: Measurement of Substrate and Assembly

MICROELECTRONICS: clearly the SMT market is trending fast to ultra-small Semiconductor industry requirements.

“AmTECH specializes in Advanced Microelectronics with SMT, Flip-Chip, Die-Attach, Wire-Bond and Encapsulation on PCB, Rigid-Flex, Flex and Ceramic substrates”.

1. PCB DESIGN GUIDELINES

A well designed and manufactured PCB (Printed Circuit Board) is required for optimum manufacturing assembly yields and electrical performance.

  1. Solder Mask Defined (SMD) pads have solder mask opening that are smaller than metal pads. (≤0.2mm circles/ ≤0.4mm pitch)
  2. Non Solder Mask Defined (NSMD) pads have solder mask openings that are larger than metal pads. (≥0.25mm circles/ ≥0.5mm pitch)
  3. The land pattern size for SMD or NSMD metal pads must be 100% the same size for each component pad.
  4. Use IPC-7351 land pattern calculator and component Technical Data Sheet as a reference for PCB Design pad sizes.
  5. The land to land spacing for passive components ≥ 0.2mm (8 mils).
  6. The land to land spacing for SMT IC’s ≥ 0.5mm (20 mils).
  7. The distance between the bodies of two IC’s ≥ 1.0mm (40 mils).
  8. The space between SMT and PTH components ≥ 2.0mm (80 mils).
  9. All passive components and IC’s shall be parallel to each other and their solder lands perpendicular to the SMT reflow conveyor travel direction.
  10. Similar types of components should be aligned on the board in the same orientation for ease of component placement, soldering and inspection.
  11. Pin #1 on each IC, and connector to be marked on the layout.
  12. Polarity of LED, Diodes and Capacitors to be marked on the layout.
  13. Small passive components, ≤1.0mm pitch IC’s, low profile, and low weight components can be placed on the 2nd side of the PC Board.
  14. Liquid Photo Imaging (LPI) solder mask for 50um (2.0mil) pad clearance.
  15. Liquid Direct Imaging (LDI) solder mask for 25um (1.0mil) pad clearance.
  16. Filled and Flat Vias required on pads to be soldered during reflow process.
  17. Component Keep-Out: ≥3.0mm (120 mils) required in the two long edges of the finished PCB for the conveyor; unless borders on PCB panel.
  18. Minimum drill hole ≥200um (8mil) with ≥ 350um (14mil) annular ring.
  19. Minimum trace width and space: ≥ 100um (4mil). Warp and Twist ≤1%.
  20. Route and Retain for ≥1.6mm thick PCB, V-Score for ≥0.8mm to ≤1.6mm thick PCB, Laser cut for ≤0.5mm thin PCB and ≤0.2mm thin Flex.

2. PCB Pad Surface Plating Finish

Finish Name Description Comments
ENEPIG Electroless Nickel, Electroless Palladium, Immersion Gold Gold Wire Bond
Fine-Pitch SMT
ENIG Electroless Nickel,
Immersion Gold

Aluminum Wire Bond
Fine-Pitch SMT

Silver
Immersion

Electroless Nickel,
Immersion Silver
No Wire Bonding
Fine-Pitch SMT
Copper OSP Organic Solderability
Preservative (OSP)

No Wire Bonding
Fine-Pitch SMT

HASL Hot Air Solder Leveling
(inconsistent solder thickness)

No Wire Bonding
No Fine-Pitch SMT

3. WIRE BOND: PCB, Rigid-Flex and Flex gold plating

IPC-4556 ENEPIG Thickenss
3rd level Au ≥0.1 um (≥ 4 uinches) Immersion Gold
2nd level Pd 0.05 – 0.30 um (2 – 12 uinches) Electroless Palladium
1st level Ni 3-6 um (118 – 236 uinches) Electroless Nickel

 

IPC-4552 ENIG Thickenss
3rd level Au ≥0.05 um (≥ 2 uinches) Immersion Gold
1st level Ni 3-6 um (118 – 236 uinches) Electroless Nickel

4. PANEL DIMENSION, BORDERS and TOOLING HOLES

Description Standard Production
Panel Size STD ≤300x250mm Preferred, ≤500x380mm Maximum
Panel Size MICRO ≤100x100mm Preferred, ≤250x180mm Maximum
Panel Thickness STD 1.0mm to 5.0mm (40-200mil)
Panel Thickness MICRO 0.3mm to 0.8mm (Flex 0.1mm to 0.2mm)
Panel Borders 10mm width borders (Minimum 2-sides for conveyor)
Tooling Holes 5mm from X and Y Panel/ Board edge (3-holes)
Tooling Hole diameter 3mm non-plated hole (120mil)
Soldermask Opening Tooling Hole plus 0.5mm. = 3.5mm (140mil)

5. FIDUCIAL MARK

  • Fiducial marks facilitate the accurate placement of components.
Description Standard Production
Global Fiducial 1.5mm (1.0–1.5mm) solid filled circle (Qty=3)
Image Fiducial 1.0mm (0.5-1.0mm) solid filled circle (Qty=3)
Local Fiducial 0.5mm (0.25-0.5mm) solid filled circle (Qty=3)
Soldermask Clearance ≥0.25mm (10mil)
Soldermask Opening Fiducial diameter plus 0.5mm (20mil)

6. STENCIL DESIGN GUIDELINES

  • Stencil aperture openings should be 1:1 to PCB pad sizes.
  • Square Pads with 0.05mm radius corners on ≤0.3mm circles.
  • QFN ground pads: 20% volume reduction to avoid “floating”.
  • Windowpane with bracing struts of 0.5mm (20mil) on ≥50mm (200mil) apertures/ solder pads. The resulting apertures should not exceed 50mm (200mil) in any direction.
Description Standard Production
Stencil Thickness 5 mil ≥ 0.6mm pitch; 1005 (0402) Passive Components
Stencil Thickness 4 mil ≥ 0.5mm pitch; 0603 (0201) Passive Components
Stencil Thickness 3 mil ≥ 0.4mm pitch; 01005 Passive Components
Stencil Fabrication 5mil Laser Cut
Stencil Fabrication 4 mil Laser Cut with optional electro-polish
Stencil Fabrication 3 mil Laser Cut with optional gold coating
Aspect Ratio ≥1.5 W/T = ≥1.5 (Aperture Width/Stencil Thickness)
Area Ratio ≥0.66 L*W / 2*(L+W)*T = ≥0.66 (Aperture Area/ Aperture Walls Area)

7. SOLDER PASTE: RoHS, Non-RoHS (J-STD-005)

  • Solder paste Type 3: 25-45um particle ≥0.25mm circles, ≥0.5mm pitch
  • Solder paste Type 4: 20-38um particle ≥0.20mm circles, ≥0.4mm pitch
  • Solder paste Type 5: 15-25um particle ≥0.15mm circles, ≥0.3mm pitch
  • Storage @ 0-10°C. Shelf life: 6-months @ 0-10°C
  • Pot Life @ +25°C (working life): 2-weeks
  • Thaw: Warm up 3-4 hours @ 25°C prior to use.

8. PCB ASSEMBLY DOCUMENTATION

  • PCB FAB Drawing, panel drawing, dimensions and FAB notes
  • Gerber Files for PCB Fabrication
  • PCB Assembly Drawing, including Assembly notes
  • Bill of Materials including PN, Designator, Description and Manufacturer
  • Technical Data Sheet for key components including Flip-Chip and Die.
  • Pick & Place Data: XY Centroid Data, and Theta Rotation.

9. High-Performance SOLDER PASTE PRINTING

  • Stencil: Laser cut 3-5 mil thick (75-125um). Gold coated for 3 mil
  • Squeegee: 3S Metal, Programmable 45° to 65°
  • Squeegee Pressure: 1.5 to 2.0 lbs. /linear inch. (0.35 Kg/cm)
  • Print Speed: 2.0 to 4.0 in/sec (50-100 mm/sec) 4.0 in/sec optimal
  • Stencil Release Speed: 0.02 in/sec. (0.5mm/sec)
  • Under stencil wiping every 5-10 boards.
Description Standard Specification
Print accuracy +/-5um (0.2mils) @3s accuracy
Print Circle (Min.) 150um print diameter (6 mil); 300um (12 mil) pitch
PCB Size 50x50mm (2”x2”) to 500x380mm (20”x15”)
Print Inspection Automatic Print Inspection
Cleaning System Programmable  under Stencil Cleaning System
Vacuum System Vacuum Print Nest for Thin PCB and Flex (0.1-0.5mm)
Print Head 3S Programmable 45° to 65°
Tooling Quick-Tool for PCB support
Substrate PCB, Rigid-Flex, Flex or Ceramic substrate

10. High-Precision SMT PICK and PLACE

  • Placement Accuracy: +/-35um Passive, +/-25um @ 3s IC Components
  • Components: 01005 mm Passive to 45×45 mm IC, ≥0.3 mm pitch
  • Leadless Ultra Small: BTC ≥0.6×0.3×0.3mm to 1x1x0.5mm
  • HM High-speed multi-purpose Pick & Place head (10 nozzles)
  • Number of feeders: 140 Feeders, 8mm width tape reels.
Description Standard Specification
Placement accuracy +/-35um @3s Passive; +/-25um @3s IC Components
Components 01005 mm Passive to 45×45 mm IC, ≥0.3 mm pitch
Leadless Ultra Small BTC ≥0.6×0.3×0.3mm to ≤1x1x0.5mm
PCB Size 50x50mm (2”x2”) to 500x380mm (20”x15”)
Pick & Place Head HM High-speed multi-purpose head (10 Nozzles)
Number of Feeders 140 Feeders, 8mm width tape reels

11. Advanced FLIP CHIP ASSEMBLY. (Datacon EVO Plus)

Flip Chip is a method of interconnecting IC chips with solder bumps/balls that have been deposited onto the top-side IC chip pads to a substrate. The IC chip is flipped over during assembly so that its top-side faces down.
The solder bumps/balls are deposited on the top-side chip pads of the wafer during the final wafer processing steps. Solder balls are eutectic or lead-free.

  • Flip-Chip Assembly: 150um to 300um (6-12 mils) pitch.
  • Ball/Bump Size: 75um to 150um (3-6 mils).

Contact Pitch
um (mil)

Ball/ Bump Size
um
PCB Pad Size
um
PCB Pad Size
Variation
300um (12mil) 150-160um 160um 150-160um
250um (10mil) 125-135um 135um 125-135um
200um (8mil) 100-110um 110um 100-110um
150m (6mil) 75-85um 85um 75-85um

 

Description Standard Production
Flip-Chip Ball or Bump Eutectic Sn63Pb37 or Lead-free SAC305
Flip-Chip Attach Gel Flux clean or no-clean
Underfill Namics 8437-2
Die Size 20 mil²/ 500um² to 1”/ 25mm²
Die Thickness 6mils/ 0.15mm to 40mils/ 1mm
Flip-Chip to PCB Edge 20 mil/ 500um
F/C to SMT Component 20mil/ 500um
Flip-Chip Pick from: Wafer (4”-12”), Waffle-Pack, or Gel-Pak
Flip-Chip place to: PCB, Rigid-Flex, Flex or Ceramic substrate
Visual Inspection 160Kv XRAY   

12. CONVECTION Solder Reflow and MOLE Thermal Profiler

LEAD-FREE (RoHS) reflow profile process guideline:

  • Slow Ramp: 130°C to 180°C for 60-90 seconds.
  • Time Above Liquidus (TAL): 40-80 seconds
  • Peak Temperature: 230°C to 250°C.
  • Ramp down to 25°C: 1-4°C per second.
Description Standard Specification
Number of Zones (10) Zone, top and bottom heaters up to 350°C
Heated Tunnel 120” Heated Tunnel, plus (2) Cooling Zones
Air or Nitrogen Air or Nitrogen reflow with Inert Atmosphere <100 PPM
Thermal Profiler ECD super Mole Gold Thermal Profiler, RF and USB
Thermocouples 6-Channel K-Type, 1.5 Million data point memory

13. Advanced 2D + 3D High Resolution AOI for Microelectronics

Description High Resolution 3D Specification
Top-Down Camera 12 Mega Pixel
4-Side Camera 6 Mega Pixel
Field of View (FOV) 21x21mm (0.83”x0.83”)
3D Resolution 9.0um (0.35mil)
2D Resolution 7.2um (0.28mil)
Max. Componenet Height 8.0mm (315mil)
3D Acquisition Rate 140 fps (frames per second)
Projector Power 3X Standard Resolution
Projector LED Blue
  • Multi-function system with (1) top-down and (4) side cameras
  • Advanced 2D + 3D High Resolution AOI, min. component size 01005
  • Maximum Inspection Area: L480 mm x W400 mm (19”x16”)
  • Part Defects: position, missing, wrong, polarity, skew, tombstone
  • Lead Defects: bent, lifted, tilted, bridging
  • Solder Defects: open, short, insufficient, solder balls

14. Microfocus 160Kv XRAY INSPECTION (including Flip Chip)

  • Extended BGA and Flip-Chip Inspection including void analysis
  • SMT and Advancedx Microelectronics Assembly Inspection
  • Semiconductor Packaging including Wire Bonding inspection
  • Bottom Termination Components: QFN, BGA, LGA, CSP, Flip-Chip
  • 2000X geometric magnification and 17,500X image magnification
  • X-Ray tube with 25-160 kV voltage range, and <1 um detail detectability

15. METROLOGY: measurement of substrate and assembly

  • Precision X, Y, and Z Linear Ways, Programmable Zoom Lens
  • XY=2.6um+L/175, Z=3.0um+L/150 accuracy, 315x315mm work area
  • Camera and Optics: High-Res Color, Zoom Range 36:1 (15X-540X)
  • InSpec Metrology Software: point & click, proprietary edge detection
  • Advanced Illumination: Multi-Ring LED Lighting: Surface, Profile and Axial