Hot-dip tinned copper
and copper alloy strip
Hot-dip tinned strip
Hot-dip tinning
Production
Hot-dip tinned copper alloy strip has been
an important Wieland product for over
thirty years.
The cleaned and activated strip is passed
through a molten tin bath. When the strip
exits the bath, the surplus molten metal
is removed by means of an “air-knife” in
order to achieve the required coating
thickness.
This high performance Wieland strip is
being constantly improved based on the
feedback received from our customers.
As a result, Wieland can offer a variety of
different hot-dip tinning finishes meeting
a wide range of requirements.
During recent years many companies
worldwide have followed our example
and created production facilities for this
product. Despite this, in the eyes of
many customers Wieland has been able
to maintain its position as market leader
for this product worldwide.
Hot-dip tinned Wieland strip is coated
with pure tin – SnPUR®, or a low SnAg
alloy – SnTOP®. Special tinning finishes
such as SnTEM® can be produced by
further treatment of pure hot-dip tin
plating.
The coating thickness is measured and
controlled by means of fluorescent X-ray
analysis of both strip sides. This process
is monitored with the aid of statistical
process control (SPC). The strip is
subsequently cooled.
A stationary fluorescent X-ray machine
as well as a unit operating according
to the coulometric method are used
for quality control and calibration. By
the coulometric measurement only the
thickness of tin on top of the intermetallic
layer is recorded.
The coated wide strip is then slit and
coiled / traverse wound according to the
customers‘ specification.
cooling
hot air
levelling
degreasing
drying
flux
2
liquid tin
or solder
Applications
Hot-dip tinned strip is used for a great
variety of products, such as connectors,
cable shoes, contacts, ground contacts,
soldering lugs, electromagnetic wave
shields, bus bars for alternators, battery
clamps, etc.
SnPUR®
SnTEM®
Hot-dip tinned surfaces with pure tin
plating possess low hardness and
therefore excellent ductility. Due to the
fact that the coatings are in an as-solidified
condition, they have very low stresses.
If whiskers are induced by external
stresses, they only grow to a minimal
length, which is two to three times the
grain diameter.
For SnTEM the tin coating is being
transformed by an annealing process into
a very hard but at the same time brittle
intermetallic compound. Compared to
tin itself, this CuSn surface exhibits a
reduced friction coefficient. This may
prove advantageous in the production of
multiway connectors as it reduces mating
and unmating forces and improves wear
resistance. The coating thicknesses are
0.7 µm – 2 µm.
With the exception of SnTEM, the
various plating types can be soldered
with all lead-containing and lead-free soft
solders.
coating thickness
inspection
The intermetallic phase formed by
the tinning process acts as a natural
diffusion barrier up to 80 °C ensuring
good solderability even after prolonged
storage below this temperature.
adjusting
Hot-dip tinning process
with automatic
coating thickness control
SnTOP®
For SnTOP the profile of properties is
determined, apart from the coating
thickness, by alloying tin with silver and
copper. The overeutectic composition
with 4 % silver leads to both solid
solution and precipitation hardening
of the coating. As a consequence, the
friction coefficient is reduced, resistance
to both wear and fretting corrosion is
improved, and voltage drop at the contact
points is reduced. The microstructure
allows temperatures of up to 170 °C
and guarantees good formability. For
applications in the temperature range of
- 40 °C to + 170 °C, SnTOP represents
a low-priced alternative to silver-plated
surfaces. Furthermore it ensures good
solderability and is a perfect substitute
for SnPb in view of the ban on lead
since 2006.
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Comparison of coatings
Properties
Types of coating
The coating properties result from
the plating structure and the type of
tinning. Tinned strip which has been
manufactured using the latest technology has a homogeneous plating structure
with tight thickness tolerances. Porefree coatings protect the base metal
against oxidation and corrosion. Hot-dip
tinning results in a compact intermetallic
compound between base metal and free
tin, prime requisite for excellent coating
adherence.
Pure tin Thermic tin 100 % IMP SnAgCuX The high hardness of the intermetallic
layer results in a harder coating compared
to electro-plated tin. This leads to a better
wear resistance.
Depending on the type of tinning the
surface is of a shiny light grey colour.
SnPUR®
SnTEM®
SnTOP®
SnPUR®
SnTOP®
SnTEM®
Cu6Sn5-IMP
Cu3Sn-IMP
pure tin
SnTOP®
electroplated with
Sn + reflow
electroplated with
Sn
base metal
Figure 1
Plating structure of hot-dip tinned surfaces on copper alloys compared to electroplating.
Wear resistance
2,5
Friction force (N)
2
Ag
1,5
SnPUR ®
1
SnTEM ®
SnTOP ®
0,5
0
0
5
10
15
20
25
Cycles
Figure 2
Macrowear test, friction force as a function of the number of cycles determined in laboratory
tests with identical surface combination; test layout: rider on flat, amplitude 3 mm, without
lubrication.
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Special ­coatings
Differential tinning
Coating thickness and properties
Coating
thickness
Application
0.7–2 µm
1–2 µm
1–3 µm
2–4 µm
2–5 µm
3–7 µm
5–10 µm
Tinning types
SnPUR®
SnTOP®
SnTEM®
reduced insertion and withdrawal forces
+
++
+++
good corrosion resistance
+
++
-
good solderability
+
++
-
Table 1
Preferred coating thickness ranges and tinning types for different applications. Alternative
thickness ranges on request. (Rating: +++ excellent, ++ good, + suitable, - not available)
SnTEM®
SnTOP®
Partially de-tinned strip
Wear resistance
Surface hardness (N/mm2)
1000
Tinned, contour-milled strip
Tinned, contour-milled strip allows
adaption of different functional zones
in a spring component to their specific
functional requirements. The milled areas
are bare. Tinned, contour-milled strip is
available in coils or traverse wound on
drums.
Solderability
4000
2000
This type of strip has different tin
thicknesses on either side, so two
different tinning properties can be
combined in one strip. The side with a
thinner tin coating shows good sliding
properties whereas the side with the
thicker coating offers advantages for
soldering. This surface finish is available
in the SnPUR and SnTOP qualities as well
as in the combination SnPUR/SnTEM.
500
SnPUR®
0
2
4
6
Coating thickness (μm)
8
10
Partially de-tinned strip is a special type
of contour-milled strip. The tin layer is
completely removed in the milled areas.
Thickness reduction of the base metal is
max. 0.03 mm. The partially de-tinned
strip is an economic version of the socalled partially tinned strip. De-tinned
strip is supplied in coils or traverse wound
on drums.
Available sizes for contour-milled strip and
de-tinned strip:
Strip width:
2.0–140.0 mm
Milled width:
0.5–100.0 mm
Strip thickness: 0.2–1.6 mm
Min. residual
thickness:
approx. 0.08 mm
Figure 3
Universal hardness HU depending on the coating thickness of the different tinning types.
5
Delivery programme/formats available
Dimensions and
­tolerances
300
280
Sizes
Thickness 0.1 up to and incl. 1.6 mm.
Width 6 up to and incl. 300 mm.
See also figure 4.
Edges
Standard:Slit and bare
Special: Tinned, available sizes on
request
Coating thickness
There are different ranges suitable for most
commercial applications (see table 1).
240
220
200
Strip width (mm)
Dimensional tolerances
The substrate is produced according to
the applicable EN standards. Smaller
tolerances on request.
260
180
160
140
120
Strip in coil
100
80
60
40
Multicoil®
Traverse
wound coils
20
0
0 0,20,40,60,81,01,21,41,61,8
Strip thickness (mm)
Figure 4
Available size range for hot-dip tinned strip.
There may be limitations as a function of alloy and temper.
Delivery formats
Strip in coil
The maximum single coil weight is
10 kg/mm strip width. Exact coil
weights depending on base material,
strip thickness, width and coating
thickness can be supplied on request.
The recommended nominal inner coil
diameter is 300 – 400 mm.
Traverse wound coils
The strip is traverse wound onto
cardboard cores (no flanges) or on steel,
wooden or plastic drums (with flanges).
Upon request, the cores may also be
made of the same materials as the strip, i.
e. brass strip onto brass core and bronze
strip onto bronze cores.
6
Various types of drums with different
sizes are available. The max. net weight
of traverse wound coils is 1,500 kg.
Please refer to figure 4 for available
sizes.
Wieland-MULTICOIL®
The Wieland-MULTICOIL consists of
a stack of coils welded together to
produce a single long strip. This allows
the operator to process the entire stack
without interruption.
The maximum pallet weight for multicoils
is 5 tons. Please refer to figure 4 for
available sizes.
Quality assurance
Terms of delivery
Quality assurance
Orders are executed according to
Wieland’s General Conditions of Sale
listed on the reverse side of every order
confirmation, or available separately. The
strip is produced in compliance with the
applicable standards, unless otherwise
agreed between the parties. Delivery
according to customers’ specifications
can be agreed upon.
For many years, customers all over the
world have been relying on Wieland for
consistent high-level quality. Wieland
products are subject to stringent control
throughout the production process,
beginning with incoming of raw materials
and ending with shipment of the finished
product.
Technical service
Wieland supplies quality products and,
what is more, tries to be a reliable partner
to its customers.
The experts of Wieland’s Technical
Marketing shall be pleased to discuss
with you at an early stage of engineering
any question you may have with regard to
alloy, temper, sizes, tolerances, material
qualities, packing, etc.
Within the system of operator inspection,
responsible members of the staff are in
charge of checking the product very
carefully at every stage of its manufacture
according to well-established procedures
and schedules to ensure that the
specified quality requirements are met.
The finished product is not released for
shipment unless it complies with the
order confirmation in every respect.
The quality management of WielandWerke AG is based on DIN EN ISO 9001. In
addition, the quality system of the Rolled
Products Division, including the plants
at Vöhringen, Villingen and Langenberg,
complies with the requirements of the
valid version of TS 16949.
B U R E A U V E R I TA S Q U A L I T Y
INTERNATIONAL (BVQI), an independent
certification body operating worldwide,
has thoroughly analysed Wieland’s Quality
System and certified that it complies with
the above mentioned standards.
The certificate is subject to revision audits
through BVQI’s own auditors once a
year. The approval of Wieland’s Quality
System by BVQI means reliability for our
customers, since we are able to always
supply material which corresponds with
their order.
Work schedules and test results are
stored and available when needed, a
prerequisite for consistent high-level
quality.
They have the knowledge and the
experience to supply useful information
and help you achieve optimal production
results. For the development of new alloys
and new or improved Wieland products,
as well as specific metallurgical problems,
we can draw on the experience of the
scientists and technicians in the Research
and Development Department.
The test laboratories in the R&D
department are accredited to DIN EN
45001 and DIN EN ISO 9001.
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www.wieland.com
Graf-Arco-Str. 36, 89079 Ulm, Germany, Phone +49 731 944 0, Fax +49 731 944 2820, info@wieland.com
This brochure is for your general information only and is not subject to revision. No claims can be derived from it unless there is evidence of intent or gross negligence.
The data presented is not guaranteed and does not replace expert advice.
0541-02 012/09.12 Sz 0,5 ODH (R+G)
Wieland-Werke AG