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1. In the 1990's, a problem was revealed that lead (Pb) contained in
soldering materials of waste electronic components was melted away by
acid rain and contaminated groundwater.
2. In the 2000,major electrical machinery manufacturers, has begun to use
lead-free solder into practical use.
3. The use of lead-free solder has become mainstream due to the
increasing global trend in environmental issues such as the RoHS
directive (the restriction on the use of hazardous substances which will be
enforced by the European Union starting July 1, 2006).
WHY HAS LEAD-FREE SOLDER BECOME
MAINSTREAM?
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Symbol
• During electrical repair, it is critical
to make sure that no Lead is introduced.
This symbol indicates that the product is
lead- free.
• All lead-free PBAs will be marked
with this symbol.
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Work Station
• A lead-free work area must
be set up completely separated
from work areas that are used to
make lead repairs. The lead-free
work area must also be clearly labeled
with the lead free symbol as shown
in the adjacent picture. The items on this
desk must remain lead-free.
They must be adequately labeled to
make their lead-free Status clearly
and easily recognized.
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Solder Joints:
When servicing PBAS that have
been manufactured with LFS
(lead-free solder paste), LFS
must be used!
if not, there is a high risk of
unreliable soldering
joints!
Lead-free solder joints are more difficult
to inspect because they do not have shiny
surfaces like leaded solder joints.
Also, lead-free solder does not flow as well as
leaded solder, so some of the solder pad
areas may remain exposed.
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1. Poor solderability
Lack of lead (Pb) decreases the flowability of solder, resulting in poor
solderability
This is problematic not only for targeting P.W.B. or components, but also for
the tips of soldering irons.
It is known that poor solderability cannot be improved significantly by raising
the soldering temperature.
Good Solderability Poor solderability
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2. Higher melting point
In general, the melting point of lead-free solder is 20°C to 45°C higher than
conventional eutectic solder many recently-developed devices are heat-
sensitive.
There are cases in which the high melting point affects not only the iron
tips(It is said that using lead-free solder decreases the tip life by 4 to 5 times
compared with eutectic solder.)but also devices and P.W.B.
Eroded iron tip Flux and Solder Spatter
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Soldering problems reported after the change to
lead-free solder are:
• Feeding of improper amount of solder
• Overheating and cracking
• Solder coming off
• Resin joint or protrusion icicle
• Bridging
Moreover, additional cost is required because iron tips must be replaced
more frequently.
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Examples of common soldering failures
RESIN JOINT
Because a flux film is present between the metals to be joined ,the metals
are not electrically connected with each other. Even if they are temporarily
connected, they will come off when they are used.
This failure frequently occurs in the case of uneven heat conduction. To
prevent this, adjust the position of the soldering iron placement.
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COLD JOINT
• This is the most common failure. In general, soldering conditions with a
rough surface and no brightness on the soldering part are called "Cold-
Joint". This failure weakens the joint strength, causing the jointed parts to
come off when they are exposed to impact or vibration.
This failure frequently occurs :
• when the heating temperature is low and the soldering tip is removed before
the solder completely melts.
• when the joint part is moved before the solder hardens (cold joint)
• When too much heat is applied to the joint part (overheating).
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INSUFFICIENT SOLDER
• This failure indicates the condition that solder does not thoroughly spread
over the wire and the wire is partially exposed. This failure frequently occurs
in the case where the wire or terminal surface is dirty or oxidized, or
exposed to uneven heat application, or where the amount of heat is not
enough to solder.
To prevent this, clean the wire or terminal surface and adjust the iron
position so that the soldering tip is placed on an appropriate part.
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OVERHEATING
This failure indicates the condition that solder spreads over the terminal
excessively. This failure frequently occurs in the case where the heating
time is too long or too much or when applying solder too much.
Solder drop will not cause serious problem. However, if it causes a
short-circuit between terminals, it will result in a critical failure.
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For soldering, we must
• clean the parts to be jointed.
• put the soldering iron at an appropriate position.
• apply heat for an appropriate time.
• feed solder in an appropriate quantity.
• When large and small metal pieces are compared, it is natural that the small
metal piece is heated earlier than the large one. Furthermore, solder will flow to
a part at a higher temperature because of its characteristic. To do soldering
well, we must make use of this characteristic.
• Thermal conductivity is considerably improved by feeding a small amount of
solder to the soldering tip.
• Soldering usually cannot be done well the first time. Try to solder many times
and you can improve your skill by trial and error.
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What is the solution for successful soldering using
lead-free solder?
Simply raising the temperature of a soldering iron because of the high
melting point may result in faster oxidation and erosion. The problems with
lead-free solder can be solved by using products which offer special
characteristics described below.
It is these characteristics that are most important when using lead-free
solder.
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1. Soldering iron
Accurate temperature control and excellent thermal recovery rate enable the
use of lead-free solder without the need for setting a higher temperature.
HAKKO FX-951 HAKKO FM-203 HAKKO FM-2026 HAKKO 938
These tools iron tips compatible with lead-free solder by changing solder
plating to tin plating.
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2. Solder feeding
Splashes of solder and flux can be reduced by making a groove in solder.
HAKKO 374 HAKKO 375
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3. SOLDER BATH
For a flow solder bath, the special treatments given to the areas susceptible
to erosion by solder can reduce the frequency of replacement of
deteriorated parts.
For a static solder pot, there is a pot, which deteriorates faster when using
lead-free solder, so that it can be replaced more easily.
This reduces the need for repair compared with conventional solder pot.
The waiting time before operation can also be reduced by setting
parameters according to solder types to make solder melting time shorter.
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4. Thermometer
Conventional thermometers use a sensor which plates eutectic solder in a
measuring point to allow thermal conductivity.
Changing the solder on the measuring point into tin plating can prevent
unnecessary soldering ingredients from adhering to the iron tip.
HAKKO FG-100 HAKKO FG-101
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5. Cleaner
Wire type cleaners help less oxidation which is a common problem during
cleaning.
Wire type cleaners help less oxidation
after cleaning because they remove oxides
and excessive solder while leaving some
solder on the iron tip.
Sponge type cleaners completely remove
solder from the iron tip, which is one of
the causes of enhanced oxidation of a
tip in lead-free soldering.
Another disadvantage is that the temperature of the tip greatly decreases
due to a sponge absorbing water.
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6. Maintenance
The wettability of an iron tip can be recovered by removing oxides adhered
to the tip with a rotating brush. This allows the tip to be used again.
HAKKO FS-100
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1.Desoldering tool
New heater structure improves thermal recovery rate, reduces
temperature drop during work, and improves workability of lead-free
solder.
Moreover, the shorter distance between the nozzle and filter pipe
reduces the chance of clogging with solder.
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2.Hot air
Applying hot air uniformly to a target eliminates temperature variation
in the target, enabling efficient rework.
HAKKO FR-801 HAKKO FR-802
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CHEMICAL PASTE
Fine, pure Sn particle with high activation ability removes oxides
adhering to an iron tip. The tip can recover its wettability and can be
used again.
HAKKO FS-100
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WETTABILITY
"Wetness" is the phenomenon that a liquid which makes contact with a solid
flows and spreads out.
"Wettability" is the property of a metal surface which expresses the
spreadability.
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N2 System (Nitrogen gas)
N2 gas and preheating effect improves the solderbility greatly!
If in trouble because of the poor solderbility of lead-free solder, HAKKO N2
System can be brought to the settlement.
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1.Preheating effect
The preheating effect is achieved by passing Nitrogen gas along the heating
element in the hand piece.
Soldering can be done on multilayer PWB and high density PWB sensitive to
heat without raising the temperature of the tip excessively, even when the
melting point of lead-free solder is high.
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2. Improvement of wettability and spreadability
By using the HAKKO N2 System, the wetting and spreading are excellent
for eutectic solder, lead-free solder and high-temperature solder, comparing
with our conventional soldering iron.
This feature prevents failed soldering due to bridges while producing great
effect on repair works.
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3.Preventing oxidation
Oxidization of solder and soldering tip can be prevented by using Nitrogen
gas, which passes along the nozzle ass'y uniformly.
Example1
• HAKKO FX-951
• HAKKO FM-2026
N2 Gas Generator:
HAKKO FX-780 Connectable with
all models of N2 soldering irons
Flowmeter:
HAKKO FX-791Connectable with all models of N2 soldering irons.
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Example 2
• HAKKO FM-203
• HAKKO FM-2026
N2 Gas Generator:
HAKKO FX-780 Connectable with all
models of N2 soldering irons
Flowmeter:
HAKKO FX-791 Connectable with all models of N2
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Example 3
• HAKKO 938
• HAKKO 957
N2 Gas Generator:
HAKKO FX780 Connectable with
all models of N soldering irons
Flowmeter:
HAKKO FX-791Connectable with all models of N2 soldering irons
