Download - Stencil Printing Presentation
-
8/11/2019 Stencil Printing Presentation
1/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Stencil Printing Technology
Seminar
Tim LukeRegional Manager
-
8/11/2019 Stencil Printing Presentation
2/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Agenda
Solder Paste Basics
Environment
Fine Feature Printing
Stencil
Board
Paste
Printer
Process Stability
-
8/11/2019 Stencil Printing Presentation
3/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Standard Alpha Labels
Lead-Bearing
Lead-Free
Solder Paste Basics
-
8/11/2019 Stencil Printing Presentation
4/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
LOT # DECIPHERING
Alpha Metals Lot# 11130945
1 = 2011
11 = November
30 = 30th
day of November
9 = Mixer Size
45 = 45th
Sequential Production
Batch That Day
Solder Paste Basics
-
8/11/2019 Stencil Printing Presentation
5/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Product Configuration Deciphering
Product ConfigurationProduct Configuration
SAC305 OM-338 88.5-3-M13
SAC 305 = Powder Alloy
OM-338 = Flux System
88.5 = Metal Percent, by weight
(50% metal by volume) 3 = Powder Size
M13 = Viscosity Range
Solder Paste Basics
-
8/11/2019 Stencil Printing Presentation
6/45PRIVILEGED AND CONFIDENTIAL MATERIALS
STORAGE & HANDLING
Not Sure - Defer to manufactures
guidelines
Alpha Metals general guidelines
Refrigeration @ 33-45F
FIFO Inventory
Warm-up procedure
Be aware of heat and blowing air
Solder Paste Basics
-
8/11/2019 Stencil Printing Presentation
7/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Warm-up Procedure
Warm-up
Controlled Environment,
Room temp for 4hrs
Follow DocumentedProcedure
Do Not Open ColdContainer:
Warm-up paste beforeopening or dispensing toavoid moisture condensingonto paste.
Avoid HeatingJars/Cartridges to
Accelerate Warm-up
Accelerates mostreactions
Dries pasteprematurely
Reduces paste tackand stencil life
Solder Paste Basics
-
8/11/2019 Stencil Printing Presentation
8/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Operating Environment
Adequate environmental conditions are a
necessity for robust printing process
Solder paste condition is a function of its
environment, which includes;
Temperature
Humidity
Air Flow
Cleanliness
Solder Paste Basics
-
8/11/2019 Stencil Printing Presentation
9/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Environmental InfluencesTemperature: Minimizing process temperature window
will result in a more stable process.
Operating outside of the desired range can cause slumping or
excessive drying out of the paste.
Monitor Performance Outside of Window
Humidity: Minimizing process humidity window will resultin a more stable process
Less than 30% can result in the paste drying out, volatiles will
evaporate. Results in aperture clogging and skips orinconsistent deposit volumes.
Greater than 60% can cause the paste to absorb moisture from
the air causing out gassing during reflow, resulting in slump and
solder balls.
Solder Paste Basics
-
8/11/2019 Stencil Printing Presentation
10/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Environmental InfluencesAir Flow: Keep air flow in the print area to a minimum.
Increased air flow will drive off the volatiles in the paste resulting
in diminished print and reflow performance.
Keep doors and hoods closed.
Do not direct environmental controls at printer or printed boards.
Cleanliness: Keep the printer clean.
Solder paste buildup in the work nest or other moving areas will
decrease the effectiveness of the board support and the
repeatability of the machine.
Solder on board supports can contaminate future boards,possibly causing solder balls.
Dried solder mixed into the paste can cause aperture clogging
Cross contamination of cleaning solvents will effect solder paste
performance.
Solder Paste Basics
-
8/11/2019 Stencil Printing Presentation
11/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Objective
Consistently Deposit a Specific Mass of
Solder in a Specific Location
-
8/11/2019 Stencil Printing Presentation
12/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Fine Feature Printing
Key Inputs
-
8/11/2019 Stencil Printing Presentation
13/45
-
8/11/2019 Stencil Printing Presentation
14/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Stencils
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
15/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
16/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Area Ratio Calculation
Force Balance
Area of aperture walls
Area of circuit side opening
=AR
For circular apertures,
D T
(D/2)2=AR
Where D = diameter
T = foil thickness
For square apertures,
4 D T
D2=AR
Where D = side of square
T = foil thickness
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
17/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Area Ratio CalculationBoth formulae reduce algebraically to:
4 T
D=AR
Where D = Diameter of circle or
Side of square
T = foil thickness
Squares and circles of the same dimension
have the same area ratio
Squares have 4/ (27%)
more volume for the
same AR
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
18/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
19/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Stencil Design
Fine Feature Printing
Reconcile Paste Requirements
Most Difficult to Print
Minimize Post Reflow Requirements
Maximize Area Ratio
Know Error Sources
Powder Type -
Packs
Flux Chemistry
Releases
Decrease Foil Thickness
Step and Stepless
Step Stencils
Keep Outs
Reverse Taper
Preforms
Tape and Reel
Stencil Scaling
-
8/11/2019 Stencil Printing Presentation
20/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
21/45PRIVILEGED AND CONFIDENTIAL MATERIALS
10 mil circle in 4 mil foi l
AR = 0.63
TE = 49.4%Aperture Volume = 314 mil3
Deposit Volume = 155 mil3
10 mil circle in 5 mil foil
AR = 0.5
TE = 22.3%Aperture Volume = 393 mil3
Deposit Volume = 88 mil3
Reducing the stencil thickness by 20%
increases the deposit volume by 76%!
Fine Feature Printing
Stencil Design
-
8/11/2019 Stencil Printing Presentation
22/45
-
8/11/2019 Stencil Printing Presentation
23/45PRIVILEGED AND CONFIDENTIAL MATERIALS
Boards
Mask Registration and Design
Minimize MCSB
Prevent Shorts
Registration Tell Tale
Over Etching
Increased Skips
Alignment
Bridges/Shorts
Ledged Ink -
Gasket
Mask Cure
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
24/45
Fi F P i i
-
8/11/2019 Stencil Printing Presentation
25/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Fine Feature Printing
Mask Location
Keep Out
Not Fully Cured Mask or Legend Inkcan Contribute
Rough Surface Better
Alignment and Placement Pressure
Reduce Foil Thickness
MCSB
Too Much
Solder Paste and/or in
the wrong location
Fi F t P i ti
-
8/11/2019 Stencil Printing Presentation
26/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
MCSB Mask Design
Fine Feature Printing
Fi F t P i ti
-
8/11/2019 Stencil Printing Presentation
27/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
FUNCTION OF PASTE INGREDIENTS
METAL
Melts & bonds to formconnection
FLUX SYSTEM
Wets surfaces
Cleans metal surface
Conducts heat
ACTIVATOR
Oxide reduction
ROSIN
Tack -
HT, Rheology
Activator
ADDITIVES
Tack -
LT, Release,Suspension, Smell,Detergent, Rheology
SOLVENT
Dissolve chemistry,Maintain Suspension
Fine Feature Printing
Fi F t P i ti
-
8/11/2019 Stencil Printing Presentation
28/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
PASTE Roll diameter = 1-2 cm (Refer to Manufacture guidelines)Keep paste off squeegee holders
Steady State
Small More Frequent Additions
Dime
1.8 cm
Penny
1.9 cm
Nickel
2.1 cm Quarter
2.4 cm
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
29/45
Fi F t P i ti
-
8/11/2019 Stencil Printing Presentation
30/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Printer
Blades
Attack Angle
Print Speed -
f(paste
and thru put)
Blade Pressure
f(print
speed and attack angle)
Stencil Release Rate
f(paste
and aperture)
Board Support
Dedicated vs. Pins
Board Clamping
Edge vs. Top
Fine Feature Printing
Fi F t P i ti
-
8/11/2019 Stencil Printing Presentation
31/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Attach Angle
Combination of Static and Dynamic Angles
Low Angle May Improve Paste Packing
Most Important with Low Area Ratio
f(Blade
Compliancy, Blade Holder, PrintSpeed and Print Pressure)
Fine Feature Printing
Fi F t P i ti
-
8/11/2019 Stencil Printing Presentation
32/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
ThinStandard
64
62
60
58
7.255.44
82
64
62
60
58
Blade
Mean
Pressure (Kg)
Release (mm/sec)
Main Effects Plot for Volume TE of CVP-370 PasteData Means
0.15mm Apertures and 0.15mm Gap
Main Effects for 0.3mm Pitch/01005
Fine Feature Printing
Fi F t P i ti
-
8/11/2019 Stencil Printing Presentation
33/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Blade
Pressure (Kg)
Release (mm/sec)
ThinStandard
7.255.447.255.44
82828282
120
100
80
60
40
20
0
Volume
60
100
Boxplot of Volume TE for 0.15mm Apertures with 0.15mm Gap
Fewer Outliers with Thinner Blade
More Volume TE with Thinner Blade
0.3mm Pitch, AR = 0.47
Fine Feature Printing
Fine Feat re Printing
-
8/11/2019 Stencil Printing Presentation
34/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Distribution for 0.3mm Pitch, AR = 0.47
87.575.062.550.037.525.012.5
Median
Mean
65.5065.2565.0064.7564.5064.2564.00
1st Q uartile 59.231
Median 64.870
3rd Q uartile 70.452Maximum 90.834
64.091 65.068
64.337 65.334
8.294 8.986
A -Squared 1.22
P-V alue < 0.005
Mean 64.580
StDev 8.626
V ariance 74.412
Skewness -0.221408
Kurtosis 0.226652
N 1200
Minimum 32.214
A nderson-Darling Normality Test
95% C onfidence Interval for Mean
95% C onfidence Interval for Median
95% C onfidence Interval for StDev95 % C onfidence Intervals
Summary for Volume TE (%)Blade = Thin, Paste = CV_370, AR = 0.49342
87.575.062.550.037.525.012.5
Median
Mean
59.058.558.057.5
1st Q uartile 51.703
Median 58.348
3rd Q ua rtile 65.462Maximum 92.089
57.343 58.554
57.638 58.992
10.281 11.138
A -Squared 1.63
P-V alue < 0.005
Mean 57.949
StDev 10.693
V ariance 114.330
S kew ness -0.49932
Kurtosis 1.47222
N 1200
Minimum 2.872
A nderson-Darling Normality Test
95% C onfidence Interval for Mean
95% C onfidence Interval for Median
95% C onfidence Interval for StDev95% Confidence Intervals
Summary for Volume TE (%)Blade = Standard, Paste = CV_370, AR = 0.49342
Fine Feature Printing
Thinner Blade
Tighter Distribution Greater average Transfer Efficiency
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
35/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Board Support
Dedicated vs. Pins
Lowest Cost of Ownership
Component Density
Turn Around Time
Both Prone to Cleanliness Issues
Fine Feature Printing
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
36/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Board Clamping
Fine Feature Printing
Top Clamping
Secure, but loss of gasket at edge of board Edge Clamping
Good gasket, but issue with thin boards bowing
Calibration/Maintenance
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
37/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Printer
Automated Stencil Cleaning
Paste Rheology
Temp and Humidity
Print Speed and Pressure
Gasket
Board Design and Support
Stencil Aperture Design and Tension
Finest Pitch
Solvent
Steady State
Fine Feature Printing
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
38/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Determining Wipe Frequency
Wipe the Stencil
Print 2-3 boards
Jog vision system out to inspect
stencil apertures.
Repeat this until you see
squeeze out.
Subtract 1 -
2 prints from thenumber of prints to arrive at
your wipe frequency.
Fine Feature Printing
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
39/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Print to Fail Wipe Frequency
Fine Feature Printing
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
40/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Printer
Stencil Release Rate
Function of Solder Paste
Controlled separation of the board from thestencil after the print (slow snap-off)
Minimum of 2X Foil Thickness, More if
High Density
The board is pulled
from Stencil slowly untilthe paste deposit clears
the apertures Faster Separation Speed
2x stencil
Thickness
Board
Fine Feature Printing
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
41/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Real Time Release Videos
Fast (1 in/sec) vs.
Slow (0.1 in/sec)Separation
3.9 in/sec
8.5 mil Circle
0.53 AR
4 mil thick LC
OM338
Type 3 Powder
Slow: 2005_03_03_009
Fast: 2005_03_07_009
Fine Feature Printing
-
8/11/2019 Stencil Printing Presentation
42/45
-
8/11/2019 Stencil Printing Presentation
43/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
Process Stability
Minimize Variation
Steady State
Dummy Boards
Auto Stencil Wipe
Inventory Control
MSL
FIFO
Lot Tractability
-
8/11/2019 Stencil Printing Presentation
44/45
PRIVILEGED AND CONFIDENTIAL MATERIALS
QFNs
Pad Design
Aperture Design
Defects
Floating
Wetting
Voiding
-
8/11/2019 Stencil Printing Presentation
45/45
Questions?