1 PRIVILEGED AND CONFIDENTIAL MATERIALS 1991 – 2014 TechLead Corporation “Stencil Design, Materials & Processes for Today’s Miniaturized Electronics Assembly” Bruce Barton, Alent Jim Price, ASM/DEK Ben Scott, Datum Alloys Sue Holmes, Photo Stencil Tony Lentz, FCT Assembly Ahne Oosterhof, Eastwood Consulting 1991 – 2014 TechLead Corporation “Stencil Design, Materials & Processes for Today’s Miniaturized Electronics Assembly” Miniaturization of all electronics from tablets & smart phones to implantable medical devices continues to drive assembly complexity & creates major challenges in yield & reliability. Stencils play a key role in these assemblies as we approach several physical limitations in the printing processes, particularly those for applying solder paste. This panel explores the options currently in use as well as future directions for ensuring high yield, high quality & reliable electronics assemblies of all types. Topics of discussion include stencil materials, processes, coatings & design; solder & flux formulations; as well as interactions between components, boards & reflow processes.
18
Embed
“Stencil Design, Materials & Processes for Today’s ... · Today’s Miniaturized Electronics Assembly ... balance of adhesive forces between stencil aperture side ... 3- Area
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1 PRIVILEGED AND CONFIDENTIAL MATERIALS
1991 – 2014 TechLead Corporation
“Stencil Design, Materials & Processes for
Today’s Miniaturized Electronics Assembly”
Bruce Barton, Alent
Jim Price, ASM/DEK
Ben Scott, Datum Alloys
Sue Holmes, Photo Stencil
Tony Lentz, FCT Assembly
Ahne Oosterhof, Eastwood Consulting
1991 – 2014 TechLead Corporation
“Stencil Design, Materials & Processes for
Today’s Miniaturized Electronics Assembly”
Miniaturization of all electronics from tablets & smart phones to implantable medical devices continues to drive assembly complexity & creates major challenges in yield & reliability. Stencils play a key role in these assemblies as we approach several physical limitations in the printing processes, particularly those for applying solder paste. This panel explores the options currently in use as well as future directions for ensuring high yield, high quality & reliable electronics assemblies of all types. Topics of discussion include stencil materials, processes, coatings & design; solder & flux formulations; as well as interactions between components, boards & reflow processes.
2 PRIVILEGED AND CONFIDENTIAL MATERIALS
1991 – 2014 TechLead Corporation
Stencil Design, Materials & Processes for
Today’s Miniaturized Electronics Assembly
Rheology & Thixotropy – Bruce Barton, Alent
Specialized Printing Tools – Jim Price, ASM DEK
Stencil Metallurgy – Ben Scott, Datum Alloys
Specialty Stencils (3D) – Sue Holmes, Photo Stencil
Stencil Coatings – Tony Lentz, FCT Assembly
User Perspective – Ahne Oosterhof, Eastwood
Consulting
an Alent plc Company
ALPHA
Technical Services
Group
Bruce Barton
3 PRIVILEGED AND CONFIDENTIAL MATERIALS
Highly Confidential and Privileged Information of Alpha an Alent plc Company
Detailed Cause and Effect
Machine
Process Parameters
Stroke
Length
Print Speed
Print
Pressure
Print Gap
Aperture
Size
Aperture
Geometry Aperture
Layout Material
Method of
Fabrication
Stencil
Area Ratio Thickness
OPERATION & METRICS EQUIPMENT &
TOOLING
Particle Size /
Distribution
Metallurgy Slump Environment
Viscosity
Paste
Residue
Rheology Solid
Content
Flux
Warpage
Pad Geometry
Cleanliness
Pad Metallurgy
Thickness Mask Issues Component
Mix
MATERIALS PERSONNEL &
ENVIRONMENT
Handling
Setup Board
Chemistry Activity Level
Residue
Aspect
Ratio
Squeegee
Material
Angle of Blade
Separation Speed
Frequency of
Cleaning
Auto./
Semi Auto.
Alignment
Accuracy
Repeatability Maintenance
Procedures Ease of
Operation
Serviceability
Cleaning
Hardness
Set-up Time
Stencil Cleaning Frequency
Procedures
Rate of Wear
GOOD
PRINT
Standard
Procedures
Paste Storage Stencil Storage Handling
Metrology
Repeatability Reproducibility
Procedures Training
Viscosity
Environment
Temperature Humidity
Support
Discipline
Chemistry
Process
Control
Defect Data
Collection
SPC Program Continuous
Improvement
Size & Shape of Edge
Length
Planarity
Pad Finish
Taper
Polish
Knead Parameters
Paste Bead
Diameter
Fine Feature Printing
Highly Confidential and Privileged Information of Alpha an Alent plc Company
Measuring Rheology
Because solder paste is subjected to a range of shear
forces, and the viscosity is different at each force,
rheology of solder paste is key. There are three
very common ways to measure solder paste
viscosity. Brookfield viscometry, Malcolm
Viscometry and Bohlin Rheology. Brookfield
viscometry is not commonly used because it is not
easy to vary the shear rate applied to the paste and
make multiple measurements. The viscosity shear
curve is very steep at low viscosity. Very small
changes in shear have very large changes in
viscosity.
4 PRIVILEGED AND CONFIDENTIAL MATERIALS
Highly Confidential and Privileged Information of Alpha an Alent plc Company
Thixotropic nature of solder paste Viscosity vs. Malcolm RPM
3 topics 1- Broadband printing (printing solder paste when both small pitch and normal pitch components are on the same substrate . 2- 3D Electroform Stencils for printing paste or flux when components are already attached to the substrate. 3- Area Ratio Calculator for determining proper aperture size, stencil thickness and stencil type for acceptable paste transfer