workshop on smt · pdf filepad design for passive smd components ... foil thickness...
TRANSCRIPT
![Page 1: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/1.jpg)
Workshop on SMT Stencils
Sakthivel Padmanapan
1 SMTA Chennai 30th May 2014
![Page 2: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/2.jpg)
2
What is STENCIL?
SMTA Chennai 30th May 2014
![Page 3: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/3.jpg)
3
In general,
the stencil is a simple tool to
make repetitive impression.
Is being commonly used by
every one at least once in life
time.
SMTA Chennai 30th May 2014
![Page 4: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/4.jpg)
4
Varieties of STENCILS
SMTA Chennai 30th May 2014
![Page 5: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/5.jpg)
5
Varieties of STENCILS
SMTA Chennai 30th May 2014
![Page 6: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/6.jpg)
6
What is SMT Stencil?
The Stencil foil is tensioned and fixed to the frame by polyester
mesh. The Tension of the Stencil Foil is around 40N/cm (± 5N/cm)
Aluminium Frame
Polyester Mesh
Stencil Foil Aperture Layout
SMTA Chennai 30th May 2014
![Page 7: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/7.jpg)
7
Stencil Printing
SMTA Chennai 30th May 2014
![Page 8: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/8.jpg)
8
1. Aligning Board to Stencil
Stencil Printing Process
SMTA Chennai 30th May 2014
![Page 9: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/9.jpg)
9
2. Moving Squeegee on the Stencil Filling Apertures
Stencil Printing Process
SMTA Chennai 30th May 2014
![Page 10: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/10.jpg)
10
3. Separating Stencil from the Board
Stencil Printing Process
SMTA Chennai 30th May 2014
![Page 11: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/11.jpg)
The holes, or apertures, are formed by one of these
three methods:
These TWO processes are subtractive in that
the removal of material from the stencil foil,
either by chemical etching or laser cutting,
creates the aperture.
Chemical Etching
Laser Cutting
Electroforming Electroforming, is an additive process whereby
the stencil foil is created by electroforming
nickel.
Manufacturing Technology
11 SMTA Chennai 30th May 2014
![Page 12: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/12.jpg)
Electroformed Stencil
12
Manufacturing Process
SMTA Chennai 30th May 2014
![Page 13: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/13.jpg)
Advantages
No stress in the material
Any thickness
Cost price independent from
number of apertures
Tapered slots
High precision
Higher initial cost
Higher processing time
Film tooling required
Disadvantages
Electroformed Stencil…
13 SMTA Chennai 30th May 2014
![Page 14: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/14.jpg)
Chemical Etching Stencil
14
Manufacturing Process
SMTA Chennai 30th May 2014
![Page 15: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/15.jpg)
Advantages
Other materials possible
Low Cost
Rough aperture sidewalls
Hour Glass Shape of sidewalls
Process releases tension in stainless steel
Restricted to Minimum pitch size is 0.63mm
Disadvantages
Chemical Etching Stencil…
15 SMTA Chennai 30th May 2014
![Page 16: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/16.jpg)
Chemical Etching Stencil…
16 SMTA Chennai 30th May 2014
![Page 17: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/17.jpg)
Stencil Manufacturing by Laser Cutting
Laser Cut Stencil
17 SMTA Chennai 30th May 2014
![Page 18: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/18.jpg)
• The repeatability of dimensions in laser-cut
stencils is generally better than that of
chemical etching.
• With laser cutting, there are no photo films
requiring precise alignment or protection from
moisture
Why Laser Cut STENCILS?
18 SMTA Chennai 30th May 2014
![Page 19: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/19.jpg)
Gerber File Processing
DfM Study Check Plot
Confirmation Hole Cutting Hole Checking
Deburring &
Polish Cutting
Welding
Silkscreen Assembly
Gluing Surface
Smoothening
Meshed Frame
Framing Stencil &
Aluminium Frame
Final QC
Packing
Yes
With Frame
Sub Assembly
Main Process
Fra
mele
ss
No
Laser Cut Stencil Manufacturing
19 SMTA Chennai 30th May 2014
![Page 20: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/20.jpg)
Works Direct from
CAD/CAM Data
Preferably in
GERBER-X format
Other CAD outputs
also can be taken
a) AutoCAD DXF/DWG
b) HPGL format
c) CNC data
INPUT
20 SMTA Chennai 30th May 2014
![Page 21: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/21.jpg)
Advantages
Faster Production
Turn around.
Tapered slots
No film tooling
Rough aperture sidewalls
Additional Deburring process
to smoothen the hole wall.
Disadvantages
Laser Cut Stencil Manufacturing…
21 SMTA Chennai 30th May 2014
![Page 22: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/22.jpg)
Technology
Technology
Accurate apertures
High number of
holes
Long production
runs
Fast delivery
Paste yield
Price/ performance
Etched - +++ + ++ + +
Laser* +++ +++ +++ +++ +++ +++
Electroformed +++ +++ +++ + +++ +++
* Laser Cut Stencils with Hole Wall & Surface Polish
Comparison of Technologies
22 SMTA Chennai 30th May 2014
![Page 23: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/23.jpg)
On Design:
Aperture Design
Aperture Reduction
Component PAD Geometric
On the Stencil
De-Burring Process
Stencil Material
Laser Cutting Parameters
On the Performance of the Stencil
DfM Analysis Skill
Manufacturing Experience
Effect of Squeegee Blades
Controllable Elements
23 SMTA Chennai 30th May 2014
![Page 24: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/24.jpg)
24
Aperture Dimensional Parameters
Empirical relationships between
aperture size and thickness
Aspect Ratio (for components with L>5W)
Width / Thickness (W/T)
should be > 1.5
Area Aspect Ratio (for components with L=W)
(LW) / (2T(L+W))
should be ≥ 0.66
24
![Page 25: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/25.jpg)
Aspect ratio ensures that the aperture will allow the printed material to release
onto the substrate
Area ratio ensures that the forces pulling a material onto the pad are greater
than the forces holding it in the aperture
Aspect Ratio and Area Ratio Rules
25
≥ 0.66
Pad Pulling Tension (P) ---------------------------------- = Retaining Wall Tension (R)
Aperture (Length (L) x Width (W)) -------------------------------------------------------------------- Stencil Thickness (T) x Aperture Perimeter (2 x (L+W))
25 SMTA Chennai 30th May 2014
![Page 26: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/26.jpg)
26
Aperture openings which are 0.010 to 0.030 mm larger on the contact side
(PCB side) than on the squeegee side based on foil thickness.
Trapezoidal apertures, which enhances effective solder paste release, also
form a “brick-like” deposit that assists firm component placement
Trapezoidal Shaped Apertures
26
![Page 27: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/27.jpg)
27
DfM Analysis on Aperture Design
A : CAD PAD width
B : 1/4 Cutting work
C : Mask reinforcing band
width (1.0 ㎜) D:Outside :
0.3㎜ extension
Slitting of Heat
Sink area
--Centre PAD Cut : Hourglass
shape application
- → Inside 0.18㎜, outside
0.195㎜
-Dummy PAD : Medial 10% Cut
Hourglass shape DNA
-Reverence (the way) 5%
extension
-A Round (Oblong) outside
application
Solder Bridging
at QFN Pads
-R/C Chip
-Medial 25% Cut
-Solder Ball prevention
Mid Chip
Solder Balling
Result After DfM Design Stencil Design Photo Defect
SMTA Chennai 30th May 2014
![Page 28: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/28.jpg)
28
Stencil Design Guide
SMTA Chennai 30th May 2014
![Page 29: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/29.jpg)
29
After Print
Stencil Output
CAD Data
Rounded Inverse
Home Plate
Inverse
Home Plate Home Plate Design
PAD Design for PASSIVE SMD Components
SMTA Chennai 30th May 2014
![Page 30: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/30.jpg)
Experimental
Apertures
5 & 6 mil foils
“Best Case”
For MCSB
5 mil foil
“Worst Case”
For MCSB
6 mil foil
Not
recommended
Potential
squeegee &
stencil damage
30
PAD Design for PASSIVE SMD Components
30 SMTA Chennai 30th May 2014
![Page 31: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/31.jpg)
31
Home Plate Zipper Pads
MELF Pads Cross Pattern
Before After Before After
Before After Before After
PAD Design for SMD Components
SMTA Chennai 30th May 2014
![Page 32: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/32.jpg)
32
Deburring Process (POLISHING)
Electro Polishing
F2 Polishing
Pumice Polishing
SMTA Chennai 30th May 2014
![Page 33: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/33.jpg)
33
ELECTRO POLISHING
SMTA Chennai 30th May 2014
![Page 34: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/34.jpg)
Why is F2 Polish:
This F2 Polishing done after Laser Cutting to Deburr the Aperture.
The F2 Polishing was developed for the next generation Laser Cut Stencils. This
polishing technology is UNIQUE compared to “Chemical Polishing” and “Electro
Polishing”.
F2 Polishing (Deburring Process)
34
F2 POLISHING
SMTA Chennai 30th May 2014
![Page 35: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/35.jpg)
Before F2 processing After F2 processing
Opening diameter :
0.200mm
Stencil thickness : 0.150mm
Due to extremely smooth processing surface and high dimensional
precision, the applied solder paste volume can be uniform and stable.
F2 Polishing – Aperture Hole Wall Deburring
35 SMTA Chennai 30th May 2014
![Page 36: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/36.jpg)
Before
Polish
After
Polish
[Pitch 0.400mm, Aperture width 0.210mm on 0.150mm thickness]
Effect of F2 Polishing after QFP Printing
36 SMTA Chennai 30th May 2014
![Page 37: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/37.jpg)
SMTA Chennai 30th May 2014
Plane Eye View - No Coating Plane Eye View – After NANO Coating
NANO COATING
37
![Page 38: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/38.jpg)
SMTA Chennai 30th May 2014
Top View after NANO Coating
Top View No NANO Coating
NANO COATING
38
![Page 39: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/39.jpg)
SMTA Chennai 30th May 2014
Side View No NANO Coating
Side View - NANO Coating
NANO COATING
39
![Page 40: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/40.jpg)
SMTA Chennai 30th May 2014
Water Droplet Test
NANO COATING
Nano Coated
(L)
No NANO Coat
(R)
40
![Page 41: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/41.jpg)
Stencil surface finish Controls proper paste roll over the stencil. Paste should not slip
Stencil wall finish Controls proper paste flow & release from apertures.
Paste should slip on the wall but not stick to it
Dependent on the manufacturing method and secondary operations
Trapezoidal shape for the apertures Controls stencil release characteristics also dependent on
manufacturing method
Stencil Physical Parameters for Paste Release
41 41 SMTA Chennai 30th May 2014
![Page 42: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/42.jpg)
Stencil Material:
SUS 304
Fine Grain SUS
Nickel
Stencil Material:
SUS 304 : For normal stencil with better paste release option
Fine Grain SUS : Used for Ultra Fine Pitch component pads
Stencil Material Storage:
All Stencil materials like Stainless Steel Foils, Screen Mesh, Adhesive Glue
should be stored at controlled environment. The storage room to be maintained
the temperature below 22 deg C.
Materials
42 SMTA Chennai 30th May 2014
![Page 43: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/43.jpg)
SEM observation of etched surface
The etching Magnified View of Etched Portion
Grain Size Aperture Wall after Laser Cut
Conventional SUS-304
Fine Grain SS
Conventional SUS vs Fine Grain Material
Materials
43 SMTA Chennai 30th May 2014
![Page 44: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/44.jpg)
The operators would often run machines faster than the manufacturers recommendations, creating poor hole wall quality. Other
problems encountered included warping or oil canning of the stencil material as well as burn marks on or around the apertures.
This is what happens when the Laser Cutting parameters
are adjusted to increase the stencil quantity.
Cutting Parameters
44 SMTA Chennai 30th May 2014
![Page 45: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/45.jpg)
This is what Happens when the Laser Cutting parameters are
Controlled and adjusted to increase the stencil quality.
“A knowledgeable, fully trained staff can run a well-made laser system free of
Burr, with smooth walls and a high quality finish”.
“Stencils that have been modified for the component footprint/design and have
been properly run on a good laser system, will have maximum paste release and
barring outside influences (operator error, poor board quality, non-standard
component sizes, etc.), will run defect free.
45
Cutting Parameters
SMTA Chennai 30th May 2014
![Page 46: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/46.jpg)
Basic stencil design:
- For surface mounted passive components aperture reduction rules apply
- For SM perimeter styles components (QFPs, QFNs) aperture reduction rules
apply; foil thickness calculation is necessary
- For common plastic BGA packages (pitch>1.27 mm) round aperture is
recommended with reduction considerations
- For fine-pitch plastic BGAs (pitch<1.27) square aperture recommended, aperture
reduction rules do not apply
Step stencils for Pin-in-Paste technology:
- For squeegee side steps, technological distance to the nearest surface mounted
component is 36x step_thickness
- For contact side steps, recommended technological distance to the nearest
surface mounted component is 1.6x step_thickness·foil_thickness
SUMMARY
46 SMTA Chennai 30th May 2014
![Page 47: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/47.jpg)
The Effect Of Squeegees
47 SMTA Chennai 30th May 2014
![Page 48: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/48.jpg)
Tempered Spring Steel Alloy assures
many thousands of flexures while
maintaining original shape, unlike
softer etched blades made from
stencil material.
48
The Effect Of Squeegees
SMTA Chennai 30th May 2014
![Page 49: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/49.jpg)
Permalex Edge Metal Squeegees
eliminate pumping and
scavenging
Improving solder paste deposit
quality.
The smooth, lubricated edge
reduces stencil pulling and
stretching, improving pad
registration and stencil life.
49
The Effect Of Squeegees
SMTA Chennai 30th May 2014
![Page 50: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/50.jpg)
Check that your squeegee, stencil and
pcboard “stack” are parrallel and rigid
as possible
Set squeegee pressure for a “clean
wipe”
Start at a low squeegee pressure force
and adjust UP until a clean wipe is
achieved;
Add 10% more for variations.
50
The Effect Of Squeegees
SMTA Chennai 30th May 2014
![Page 51: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/51.jpg)
ANY
QUESTIONS ?
DISCUSSION…
51 SMTA Chennai 30th May 2014
![Page 52: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/52.jpg)
Sakthivel Padmanapan Email: [email protected]
Mobile: +91 99419 11328
ASAHITEC STENCILS PRIVATE LIMITED
Double Dragon Industrial Park
Kannur Village, Kottaiyur,
Thiruvallur Dist.
Pincode 602108
Speaker Contact
52 SMTA Chennai 30th May 2014
![Page 53: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/53.jpg)
53 SMTA Chennai 30th May 2014
![Page 54: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/54.jpg)
Cutting Overlapping Mismatch due to
increase of Cutting Speed
54 SMTA Chennai 30th May 2014
![Page 55: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/55.jpg)
Improper Overlap at Curves - @ QFP Pads due
to increase of Cutting Speed
55 SMTA Chennai 30th May 2014
![Page 56: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/56.jpg)
Oval Shaped BGA Pads
56 SMTA Chennai 30th May 2014
![Page 57: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/57.jpg)
Oval Shaped BGA Pads
57 SMTA Chennai 30th May 2014
![Page 58: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/58.jpg)
Oval Shaped BGA Pads
58 SMTA Chennai 30th May 2014
![Page 59: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/59.jpg)
Burrs @ Pad Edge... Oxidation leads to heavy burr...
Increase of Productivity….. Increase of Process Problems…! 59 SMTA Chennai 30th May 2014
![Page 60: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/60.jpg)
Good Stencil: Resistor Pad - Just Cut; No Polish.....
Process Friendly… Better Yield…. 60 SMTA Chennai 30th May 2014
![Page 61: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/61.jpg)
Smooth Curves @ QFP Pads....
Process Friendly… Better Yield…. 61 SMTA Chennai 30th May 2014
![Page 62: Workshop on SMT · PDF filePAD Design for PASSIVE SMD Components ... foil thickness calculation is necessary ... Step stencils for Pin-in-Paste technology:](https://reader031.vdocument.in/reader031/viewer/2022030510/5ab986ae7f8b9aa6018dffcc/html5/thumbnails/62.jpg)
What is SMT Stencil?
The SMT stencil is a simple tool — typically a sheet of
75–200 μm thick metal foil, on which apertures are
formed according to the solder pads on the printed
circuit board for applying either solder paste or flux or
glue on to a substrate.
Stencil printing provides a fast, mass solder paste
deposition process; relatively inexpensive, appropriate
and recommended for mass production.
62 SMTA Chennai 30th May 2014