omikron - Westak

TM
OMIKRON
IMMERSION WHITE TIN
Revised 2/19/98
Florida CirTech, Inc.
Greeley, Colorado USA
CT
Florida CirTech, Inc.
1309 North 17th Avenue
Greeley, CO 80631
Telephone: 1-800-686-6504 Fax: (970) 346-8331
Table of Contents
Pages
I.
Introduction
1-2
II.
Comparison of OMIKRONTM to other alternative coatings
3-4
III.
Comparison of OMIKRONTM to conventional immersion tin
5-8
IV.
OMIKRONTM process
A.
Vertical mode
B.
Horizontal mode
9
10
Characterizing the OMIKRON surface-SERA
A.
The SERA unit
B.
Typical SERA scan
C.
OMIKRONTM thickness as a function of time and temp.
11
12
13
VI.
Summary of test results
14
VII.
Conclusions
15
V.
Introduction
Solder Mask Over Bare Copper (SMOBC) has become the preferred
manufacturing method for producing printed circuit boards today. The solder coating of
the finished boards using Hot Air Leveling (HAL) has led some manufacturing designs to
be pushed to the limit. Today’s finer pitch and demand for flatter pads have pushed the
industry to search for HAL alternatives.
As a leading manufacturer of chemicals and materials for the printed circuit board
and electronic assembly industry, Florida CirTech has devoted a large amount of time and
energy in developing an alternative to HAL that satisfies both industries it serves. The
result of this is OMIKRONTM, a novel immersion tin coating that satisfies and in many
cases exceeds the requirements expected of a SMOBC coating. OMIKRONTM is used in
either a vertical or horizontal mode. It has been used extensively in Europe for over two
years, and is now being well received by board manufacturers, assemblers and OEMs in
the United States. To summarize, OMIKRONTM has the following characteristics:
Property
Result
1.
Superior solderability at final assembly
No clean fluxes and solder
pastes work and wet well
2.
Flat and uniform surface
Less bridging on fine pitch
3.
Very long shelf life
Wide operating window
4.
Withstands multiple heat cycles
Wide operating window
5.
Can test quality and thickness of coating
Feedback on deposit quality
Process control
6.
Capable of being electrically tested
Boards tested after FAB prior
to assembly
7.
Optically apparent
Immediately diagnose any
copper surface problems prior
to coating
8.
One metal system
No introduction of metals that
can poison wave solder pot
9.
Wide plating window
User friendly for PCFAB shops
10.
Cost effective
Economically acceptable as a
viable HAL replacement by OEMs
Florida CirTech Inc.
Greeley, Colorado USA
-1-
OMIKRON
TM
IMPROVED IMMERSION WHITE* TIN PROCESS
DESIGNED AS A REPLACEMENT COATING
FOR HOT AIR LEVELING
BENEFITS :
*
COMPATIBLE WITH ALL ASSEMBLY FLUXES AND SOLDER PASTES
*
EASE OF OPERATION
*
CAPABLE OF PASSING MULTIPLE ASSEMBLY CYCLES
*
UNIFORM FLAT AND DENSE SOLDERABLE SURFACE
*
MEETS AND EXCEEDS SIEMENS SHELF- LIFE TEST ( 4 HOURS AT 155 C )
*
NO POISONING OF ASSEMBLER’S SOLDER POT
*
PERFECT FOR FINE PITCH APPLICATION
*
COST EFFECTIVE COATING
*
IBM TECHNICAL REPORT
Florida CirTech Inc.
Greeley, Colorado USA
-2-
COMPARISON OF COATINGS
PROPERTIES
OMIKRON
TM
HAL
Ni/Au
ORGANIC
SILVER
PROBLEM
YES
YES
YES
FINE PITCH APPLICATIONS
YES
FLATNESS OF PAD
YES
NO
YES
YES
YES
MULTIPLE SOLDERABILITY
YES
YES
YES
PROBLEM
YES
ELECTRICAL TESTING
YES
YES
YES
PROBLEM
?
HIGH
MEDIUM
LOW
HIGH
NONE
HIGH
NONE
NONE
NONE
CONTROLLABILITY
HIGH
LOW
MEDIUM
HIGH
MEDIUM
VERTICAL AND
HORIZONTAL PROCESSING
YES
YES
NO
YES
NO
MEDIUM
MEDIUM
HIGH
MEDIUM
HIGH
COMPATIBLE WITH
ALL FLUX
YES
YES
NO
NO
YES
SOLDER POT
CONTAMINATION
NO
NO
YES
NO
NO
SOLDER MASK
COMPATIBILITY
YES
YES
PROBLEM
YES
YES
REWORKABILITY
YES
YES
PROBLEM
PROBLEM
PROBLEM
LONG
LONG
MEDIUM
MEDIUM
WASTE TREATMENT
DIMENSIONAL STRESS
COST FACTOR
SHELF LIFE
MEDIUM
LONG
Florida CirTech Inc.
Greeley, Colorado USA
-3-
Thickness Of Finishes in
Micro Inches
H Hot Air
Leveling:
O OMIKRON
White Tin
G Electroless
Gold
P Electroless
Palladium
S Electroless
Silver
T Thick OSP
t thin OSP
300
250
200
150
100
50
0
H
O
G
S
T
t
P
Florida CirTech Inc.
Greeley, Colorado USA
-4-
TM
OMIKRON
TO IMPROVE LONG TERM
SOLDERABILITY
ENHANCED DISPLACEMENT REACTION MECHANISM
Cu 6Sn5
Sn (WHITE TIN)
OMIKRON REACTION
O
+2
Cu + Sn
Cu 3Sn
Sn (GRAY TIN)
Florida CirTech Inc.
Greeley, Colorado USA
-5-
COMPARISON OF IMMERSION TINS
SEM PHOTOS OF DEPOSITS
TM
OMIKRON
WHITE TIN
COMMERCIAL
GRAY TIN
FINE GRAIN
HEXAGONAL
CRYSTAL
LARGE GRAIN
ORTHORHOMBIC
CRYSTAL
Florida CirTech Inc.
Greeley, Colorado USA
-6-
COMPARISON OF IMMERSION TINS
TM
OMIKRON
WHITE TIN
COMMERCIAL
GRAY TIN
LONG TERM
SOLDERABILITY
SHORT TERM
SOLDERABILITY
STABLE
UNSTABLE
DENSE
POROUS
FINE GRAIN
HEXAGANOL CRYSTAL
STRUCTURE
LARGE GRAIN
ORTHORHOMBIC
CRYSTAL STRUCTURE
Florida CirTech Inc.
Greeley, Colorado USA
-7-
Comparison Of Immersion Tins
White Tin, OMIKRON
TM
Commerical Gray Tin
Sn O
Tin
Cu6Sn5
Copper
Sn O2
Tin
Cu3Sn
Copper
NOT DRAWN TO SCALE
Florida CirTech Inc.
Greeley, Colorado USA
-8-
OMIKRON Immersion Tin Process Flow
TM
Water Rinse CirEtch 100 Water Rinse
10%
Micro-Etch
2-4 min.
1-2 min.
1-2 min.
85-110F
1Lb./gal.
30-60 sec.
75-85F
OV-4
Pre-Dip
25%
1-2 min.
60-90F
OA-8
Immersion
Tin
100%
30 seconds
room temp
55-80F
OA-8 Water Rinse Water Rinse
Immersion (warm)
Tin
2-4 min.
1-2 min.
100%
8-9 min.
140-160F
Florida CirTech Inc.
Greeley, Colorado USA
-9-
Florida CirTech, ECI and PILL.
A winning team to support your
conveyorized OMIKRON process.
-10-
The ECI Model QC-100 Surface-Scan
Analysis of OMIKRONTM Immersion Tin Coating
The ECI Model QC-100 Surface-Scan incorporates two applications used for the
evaluation of the protective effectiveness and conditions of OmikronTM immersion tin
coating. These tests are performed on the SMT pads or inside of the through holes.
1.
Quick Check (Non - destructive analysis of tin coating surface conditions)
This application is used for non-destructive determination of the surface conditions of the
immersion tin coating using Sequential Electrochemical Reduction Analysis (SERA). Surface
oxides such as SnO, SnO2 and oxidized Cu-Sn intermetallics (if any) will be accurately detected
and quantified. Other compounds or contaminants will be also detected. During this quick test
(2 - 3 minutes), all reducible species (oxides etc.) are removed from the tin surface.
2.
Detailed Analysis (Electrochemical oxidation of tin coating)
This analysis provides the information about the thickness of tin coating and the amount of
underlying copper-tin intermetallic compounds. During this test, the layers of coating are slowly
dissolved into the test electrolyte from the small area on the surface tin deposit (1.6 mm
diameter). A typical scan is shown for an OMIKRON sample on the next page.
Additional QC-100 Applications:
*Surface analysis of a copper substrate prior to the placement of the final finish (HASL, etc.)
*Detection of oxides, sulfides and other contaminants
*Surface analysis of tin/lead coatings
*Evaluation of gold deposit cleanliness
Hardware and Software Specifications
The analytical system consists of the following:
*IBM PC compatible QC-100 Analyzer
*Measuring Stand for analysis of boards up to 15" x
24" (larger sizes optional) with single test head
used for analysis of PTHs or SMT pads
*HP color printer
*Pressure regulator with flow meter for
monitoring inert gas consumption
*User-friendly software running in MS-Windows 3.X
or Windows 95
*Data storage in MS Access format (MS Access
Included)
-11-
Immersion Tin
Electrochemical Oxidation Test
0.6
0.4
0.2
Oxidation of e-phase
Oxidation of n-phase
0
-0.2
Oxidation of tin coating
-0.4
-0.6
0
100
200
300
Time (sec)
-12-
400
500
Thickness(Microns)
OMIKRON thickness as a function of
time and temperature
1.2
1
0.8
0.6
0.4
0.2
0
3 Min
6 Min
9 Min
1
2
3
4
5
6
7
8
9
Run number
OMIKRON (Virgin)
Tin Thickness(Microns)
Temp(F) 3 Min
6 Min
9 Min
Run #
1
120
0.25
0.44
0.552
2
125
0.338
0.501
0.538
3
130
0.338
0.514
0.621
4
135
0.348
0.575
0.718
5
140
0.375
0.552
0.598
6
145
0.426
0.547
0.691
7
150
0.389
0.663
0.7
8
155
0.565
0.7888
0.9
9
160
0.616
0.876
1.108
-13-
Summary of OMIKRONTM testing
Test
Purpose
Result
1.
2.
SIR testing
Electromigration
Pass SIR?
Dendritic and Tin Whiskers?
Pass
Pass
3.
Solder Wettability tests
Determine solderability of
OMIKRON versus HAL and
Silver coating.
OMIKRON is #1
4.
Heat Cycling tests
Pass. Multiple reflow cycles?
Pass(3or more)heat cycles.
5.
Microetch dependence
Surface preparation dependence
Wide window
6.
Tin conc. , specific
gravity , pH and copper.
conc. test
Determine solution operating
Window
Wide window
7.
Immersion time and
temperature test
Determine immersion time
dependence
Characterization
8.
Aging test
Determine degradation of
OMIKRON as aged at 107C up
to 24 hours.
9.
Coplanarity and
for OMIKRON
Reproducibility study
Thirty six samples run.
Excellent results
10.
Rework Simulation
and aged samples.
Thirty two samples run.
Pass for non-aged
11.
Ionic contamination
OMIKRON versus HAL
Pass
12.
Microsection analysis
Solderability aged and nonaged.
Pass
Note: SERA: Selective Electrochemical Reduction Analysis
Tests 1-3 performed by Trace Laboratories.
Tests 4-7 performed by Florida CirTech.
Tests 8-12 performed by Parlex and Florida CirTech.
-14-
Acceptable up to 24 hours.
Conclusion
OMIKRONTM is the clear choice as the superior alternative to hot air leveling. It
provides excellent solderability, a flat and uniform surface, a shelf life of over one year and
is easy to test. OMIKRONTM avoids all the problems associated with other alternative
coatings with a cost that is competitive with or lower than the rest. OMIKRONTM is a
“white tin” rather than the traditional “gray tin” and thereby provides a more dense, fine
grain crystal structure.
OMIKRONTM has excelled both in laboratory tests and in actual use in PCFAB and
assembly shops throughout the United States and Europe. Facilities using OMIKRONTM
will have a competitive advantage over those using other coatings. For more information,
please contact your local Florida CirTech sales representative or our main office at
1-800-686-6504.
-15-
Florida CirTech Inc.
Greeley, Colorado USA