5th Micro TCA-Workshop
Failure Prevention for µ-Components
Rainer Taube
Why are we a good choice for our customers
Portfolio
Circuit Board Design
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Complex Impedance Controlled Multilayer
HDI & Rigid Flex Technology
Modern Software for Layer Stack and
Impedance Calculation
Manufacturing of Assemblies and Devices
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Base IPC-A-610 Class 2 & 3
(> 40% Class 3 Products)
Worldwide Purchasing
AOI, X-Ray, XRF, F-Test, Boundary Scan
BurnIn, Cleaning & Coating
Challenging Rework of Assemblies
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Balling, Reballing and Exchange
of Complex BGAs/µBGAs
Interposer Solutions
Customer Industries
Energy Conversion
Oil Exploration
Medical Equipment
Image/Data Processing
Space Applications
Research & Development
Latest Achievements
Processing of 300µ pitch wafer level CSP on very small and thin
circuit boards
 Comprehensive risk analysis
required
 Extremely demanding
solder paste printing
X-Ray of 300µm
pitch component
 Special fixture for processing
of very thin board panels
 Complete X-Ray inspection
Customer comment:
„… we tried several EMS companies before to find a reliable partner but never
got a yield like yours and no other one could meet the deadline.“
Component Packages - State of the Art
2-pin/Chip
 2012 Rohm M03015 = I012006 = 0.3 x 0.15
dimensional accuracy of ±5 microns
 2013 Murata M0201 = I008004 = 0.25 x 0.125
 2014 Murata Start of mass production
Most Advanced Package – 250µm Class
Package 470 x 470 µm
Pitch 250µm
Terminal size 115 x 65 µm
Size Comparison THT - SMT
0207
Wave soldering
10mm
I-01005
Reflow soldering
M-0201
Wave soldering
I- 1206
M- 3.2
0805
2.0
0603
1.6
0402
1.0
0201 01005 008004 inch
0.6 0.4
0.25
mm
Wave versus Reflow Soldering
No movement during soldering
Max. land dimensions uncritical
Min. land dimensions critical
Unlimited solder volume
Movement during soldering possible
Max and min land dimensions critical
Limited solder volume
Remember!
Pitch defines soldering technology
Pitch >= 1.27mm/50mil wave and reflow soldering possible
Pitch < 1.27mm/50mil only reflow soldering possible
Results of Wrong Land Dimensioning
Twisting
Shifting
Tombstoning
Open Solder Joints
Trailers
From Gullwing to Flat Bottom Terminals
SOT-323
SOT-323F
SOT-523
Strong relation between terminal type
– solder joint – land pattern –
manufacturability
& reliability
Examples for solder joint requirements
according to IPC-A-610F
TSSP-2-3
BTC Variations
BTC with non wettable flanks
Most common
Copper leadframe
Separated by sawing or punching
No solderable surface on flanks after
sawing or punching
B(S)TC with wettable flanks
Less common
Expensive
Additional metallisation process after
separation may be neccessary
BTC (QFN)-packages show much
variations, high risk to use
standard landpattern from design
system libraries
Inhomogeneous Termination Configurations
The Proportional Land Dimensioning Concept
Land dimensions are directly related to
Terminal Type
Terminal Size
Terminal Height
Two Classes of Component Terminals
Facing wettable areas
Facing & vertical wettable
areas
Terminal Class I
Facing flat wettable areas
1:1 optimized stress distribution in solder joint – higher reliability
J-STD-001
Type
Land Size
7.5.3
Bottom Only Chip
1:1
7.5.12
Tall Profile Bottom Only
1:1
7.5.14
BGA
1:1
7.5.15
BTC
1:1
No protrusion required
Terminal Class II
Flat facing and vertical wettable areas
Protrusion required
J-STD-001
Typ
Protrusion
7.5.4
Rectangular or Square End Chip
% Terminal Height
7.5.5
Cylindrical End Cap
% Terminal Diameter
7.5.6
Castellated
% Terminal Height
7.5.7
Gull Wing
% Leadframe Thickness
7.5.9
J-Leads
% Leadframe Thickness
7.5.11
Flat Lug Leads
% Leadframe Thickness
7.5.13
L-Inward
% Terminal Height
Paste Printing for I-01005 Resistors
Resistorsiderständen
Pad 150x225µm
Stencil 75µm
Paste Typ 4
Pad 150x225µm
Stencil 100µm
Paste Typ 4
Paste Printing and Solder Joints I-01005
Pad 150x225µm Pitch 350µm 50µm Protrusion
Stencil 75µm
Paste Typ 5
Proportions on Circuit Boards
Component I-0201
600x300x300µm
Pad: 200x300µm
Stencil Thickness 75µm
Copper thickness up to 50µm
Solder mask thickness 20-30µm
Right termination embedded in copper plane
generates soldermask defined pad with
soldermask on copper
Risks: Different height of paste deposit
Different volume of paste
Risk of tilting of component during placement
Increased risk of tombstoning
Risk Factor: Height of Solder Mask
Example
Unreliable solder joints through
elevated BTC
Mix of soldermask and metal
defined pads
Pad 2
Component is lying on top of
solder mask plus legend print.
Solder volume is not sufficient to
bridge the gap between land
surface and component bottom
terminal
Pad 1
Erratic created solder mask defined pads can
cause risks due to different needs of solder paste
Risk Factor: Height of Legend Printing
Example
Increased tombstoning caused by
artefacts of legend printing under
the body of 0201 capacitors.
Mix of soldermask and metal
defined pads
Component center elevated by
soldermask and legend print.
Pad 1
Effect of seesawing increases risk of
tombstoning
Avoid legend printing (silkscreen)
wherever possible!
Voiding Testboard
Soldermask Defined
Non Soldermask Defined
imm. Sn
New Concept
imm. NiAu
Usual Configuration
Surface-Volume Ratio
The ratio of degassing surface to solder volume is increased by soldermask
defined thermal pads!
1mm
1mm
4,6mm - 5mm
4,6mm - 5mm
Soldermask defined
Degassing surface:
1,00mm x 0,05mm x 4 x 16 = 3,20mm²
Metal defined
Degassing surface :
5,00mm x 0,05mm x 4 = 1,00mm²
Testboard Soldered
Soldermask Defined
Non Soldermask Defined
imm. Sn
imm. NiAu
Reduced voiding
Better void distribution
Some Guidance for Failure Prevention
Circuit board design is in a transition from 2 dimensional layer oriented
construction model to a true 3 dimensional volume- and material oriented concept
1. Precise land pattern dimensioning required – preferred according to Proportional Concept
Land = Component termination + 25µm (5%P*)
circumferential
2. Precise dimensioning of solder mask
Solder mask clearance = Land + 50µm (10%P)
circumferential
3. Precise dimensioning of paste depots
Paste depot = Land - 12,5-25µm (2.5-5%P)
circumferential
Simultaneously obey 3 rules for stencil determination:
Paste type, aspekt ratio and area ratio
4. To avoid drain of solder, connected traces < than land width (max. 50%W)
5. All connected copper features have to be covered with solder mask in a distance of 50µm (or
10%P).
6. No open vias in peripheral lands or thermal pads
7. Specification of max. solder mask height
8. No silkscreen, at minimum avoidance in areas of µ-Components
9. Specification of copper thickness
* W = Land width
* P = Pitch
A wish at the end
µ-Components cannot be handled by tweezers anymore
0603
Smallest tweezer
0402
0201
EMS companies need handling tools for circuit boards with µComponents
 Breakaway tabs
 Fiducials (placed as components)
Looking forward
for Your!
Demands and Challenges
© Copyright 2016 Rainer Taube - TAUBE ELECTRONIC GmbH
Reprint or reproduction, even partially or in modified form only allowed with
written permission of the Author.
Contact
TAUBE ELECTRONIC GmbH
Nostitzstraße 30
D-10965 Berlin
Telefon 030 69 59 25 0
e-mail: r.taube@taube-electronic.de