Assembly LED

Assembly Instructions
Vishay Semiconductors
Assembly Instructions
SOLDERING INSTRUCTIONS
Protection against overheating is essential when a
device is being soldered. It is recommended,
therefore, that the connection wires are left as long as
possible. The time during which the specified
maximum permissible device junction temperature is
exceeded at the soldering process should be as short
as possible (one minute maximum). In the case of
plastic encapsulated devices, the maximum
permissible soldering temperature is governed by the
maximum permissible heat that may be applied to the
encapsulant rather than by the maximum permissible
junction temperature.
The maximum soldering iron (or solder bath)
temperatures are given in Tab. 1. At temperatures far
above the glass transition point, the epoxy softens
plastically. During soldering, no forces must be
transmitted from the pins to the case (e.g., by
spreading the pins or by creation of mechanical
tension during devices insertion, clinching or crimping
processes).
GENERAL
Optoelectronic semiconductor devices can be
mounted in any position. Connection wires may be
bent provided the bend is not less than 1.5 mm from
the bottom of the case. During bending, no forces must
be transmitted from the pins to the case (e.g., by
spreading the pins).
If the device is to be mounted near heat generating
components, the resultant increase in ambient
temperature must be taken into account.
IRON SOLDERING
WAVE SOLDERING
IRON
TEMPERATURE
DISTANCE OF
THE SOLDERING
POSITION FROM
THE LOWER
EDGE OF THE
CASE
MAXIMUM
ALLOWABLE
SEE
TEMPERATURESOLDERING
TIME
SOLDERING
TEMPERATURE
FROM THE
LOWER TIME
PROFILES
DISTANCE OF
THE SOLDERING
POSITION EDGE
OF THE CASE
MAXIMUM
ALLOWABLE
SOLDERING
TIME
Devices in plastic
case ≥ 3 mm
≤ 260 °C
≤ 300 °C
≥ 2.0 mm
≥ 5.0 mm
5s
3s
235 °C
260 °C
≥ 2.0 mm
≥ 2.0 mm
8s
5s
Devices in plastic
case < 3 mm
≤ 300 °C
≥ 5.0 mm
3s
260 °C
≥ 2.0 mm
3s
TELUX
≤ 260 °C
≥ 2.0 mm
5s
260 °C
≥ 1.5 mm
5s
SMD
n.A
n.A
n.A
260 °C
n.A
5s
Mini
n.A
n.A
n.A
n.A
n.A
n.A
0603 LED
n.A
n.A
n.A
n.A
n.A
n.A
Table 1. Maximum Soldering Temperatures
MOISTURE SENSITIVITY LEVELS (JEDEC LEVEL)
SOAK REQUIREMENTS
FLOOR LIFE
STANDARD
LEVEL
TIME
CONDITIONS
TIME (HOURS)
CONDITIONS
1
Unlimited
≤ 30 °C/85 % RH
168 + 5 /- 0
85 °C/85 % RH
85 °C 60 % RH
ACCELERATED EQUIVALENT
TIME (HOURS)
CONDITIONS
60 °C/60 % RH
2
1 year
≤ 30 °C/85 % RH
168 + 5 /- 0
2a
4 weeks
≤ 30 °C/85 % RH
696 + 5 /- 0
30 °C/60 % RH
120 + 1 /- 0
3
168 hours
≤ 30 °C/85 % RH
192 + 5 /- 0
30 °C/60 % RH
40 + 1 /- 0
60 °C/60 % RH
4
72 hours
≤ 30 °C/85 % RH
96 + 2 /- 0
30 °C/60 % RH
20 + 0.5 /- 0
60 °C/60 % RH
5
48 hours
≤ 30 °C/85 % RH
72 + 2 /- 0
30 °C/60 % RH
20 + 0.5 /- 0
60 °C/60 % RH
5a
24 hours
≤ 30 °C/85 % RH
72 + 2 /- 0
30 °C/60 % RH
20 + 0.5 /- 0
60 °C/60 % RH
6
Time on Label (TOL)
≤ 30 °C/85 % RH
TOL
30 °C/60 % RH
Tabel 2. JEDEC Level
Document Number: 80092
Rev. 1.3, 08-May-07
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Assembly Instructions
Vishay Semiconductors
SOLDERING METHODS
There are several methods in use to solder devices on
to the substrate. Some of them are listed in the
following:
(a) Soldering in the vapor phase
Soldering in saturated vapor is also known as
condensation soldering. This soldering process is
used as a batch system (dual vapor system) or as a
continuous single vapor system. Both systems may
also include preheating of the assemblies to prevent
high temperature shock and other undesired effects.
(b) Reflow soldering
The heating rate in an IR furnace depends on the
absorption coefficients of the material surfaces and on
the ratio of the component’s mass to its irradiated
surface.
The temperature of parts in an IR furnace, with a
mixture of radiation and convection, cannot be
determined in advance. Temperature measurement
may be performed by measuring the temperature of a
certain component while it is beeing transported
through the furnace.
The temperatures of small components, soldered
together with larger ones, may rise up to 280 °C.
Influencing parameters on the internal temperature of
the component are as follows:
• Time and power
• Mass of the component
• Size of the component
• Size of the printed circuit board
• Absorption coefficient of the surfaces
• Packing density
• Wavelength spectrum of the radiation source
• Ratio of radiated and convected energy
Temperature-time profiles of the entire process and
the influencing parameters are given in figure 1.
(c) Wave soldering
In wave soldering, one or more continuously
replenished waves of molten solder are generated,
while the substrates to be soldered are moved in one
direction across the wave’s crest.
Temperature-time profiles of the entire process are
given in figure 2.
(d) Iron soldering
This process cannot be carried out in a controlled way.
It should not be considered for use in applications
where reliability is important. There is no SMD
classification for this process.
(e) Laser soldering
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This is an excess heating soldering method. The
energy absorbed may heat the device to a much
higher temperature than desired. There is no SMD
classification for this process at the moment.
(f) Resistance soldering
This is a soldering method which uses temperature
controlled tools (thermodes) for making solder joints.
There is no SMD classification for this process at the
moment.
(g) Solderability of parts with pure tin plating and SnPb
solder at lower temperature.
Soldering of parts can also be processed below
215 °C. In a test the solderability of SMD LEDs in
PLCC2 package was tested with:
• Plating Sn 10 - 18 µm on CuFe lead frame
• Pre aging 155 °C, 4 h
• Bath temperature 205 °C
• Dipping time 2 s
All the samples showed 100 % wetting after this test
and the diffusion of the SnPb in the Sn surface was
completed. To check the solderability of individual
parts on lower soldering temperatures we recommend
to do an suitable test like the above one.
Warning
Devices in PLCC-packages are sensitive to moisture
release if they are subjected to infrared reflow or a
similar solder process (e.g. wave soldering). After
opening the bag, they must be:
1. stored at ambient of < 20 % relative humidity (RH)
2. mounted within required time acc. Jedec Level
printed on label. (< 30 °C/60 % RH)
Devices require baking before mounting if 1. or 2. is not
met and humidity indicator card is > 20 % at 23 ± 5 °C.
If baking is required, devices may be baked for
192 hours at 40 °C + 5 °C - 0 °C and < 5 % RH.
For any devices avoid any mechanical stress on the
package via the leads.
Document Number: 80092
Rev. 1.3, 08-May-07
Assembly Instructions
Vishay Semiconductors
TEMPERATURE-TIME PROFILES
IR Reflow Soldering Profile for Lead (Pb)-free Soldering
Preconditioning acc. to JEDEC Level 2a
300
Temperature (°C)
max. 260 °C
245 °C
255 °C
240 °C
217 °C
250
200
max. 30 s
150
max. 100 s
max. 120 s
100
max. ramp down 6 °C/s
max. ramp up 3 °C/s
50
0
0
50
100
150
Time (s)
200
250
300
max. 2 cycles allowed
19885
Figure 1. Vishay Lead (Pb)-free Reflow Soldering Profile
(acc. to J-STD-020C)
948625
300
max. 240 °C
10 s
ca. 230 °C
Temperature (°C)
250
200
215 °C
150
max 40 s
max. 160 °C
100
90 s to 120 s
Lead Temperature
50
Full Line: Typical
Dotted: Process Limits
2 K/s to 4 K/s
0
0
50
100
150
200
250
Time (s)
Figure 2. Vishay Lead (Pb)-free Reflow Soldering Profile
300
5s
Temperature (°C)
250
Lead Temperature
235 °C to 260 °C
fullline: typical
dotted line: process limits
second
wave
first wave
200
ca. 2 K/s
ca. 200 K/s
150
forced
100 100 °C to 130 °C cooling
ca. 5 K/s
2 K/s
50
0
0
0
5
100
150
200
HEAT REMOVAL
To keep the thermal equilibrium, the heat generated in
the semiconductor junction(s) during operation will
always move to outside the device.
In the case of low power devices, the natural heat
conductive path between the case and surrounding air
is usually adequate for this purpose. The heat
generated in the junction is conveyed to the case or
header by conduction rather than convection. A
measure of the effectiveness of heat conduction is the
inner thermal resistance or thermal resistance junction
case, RthJC, the value of which is governed by the
construction of the device.
Any heat transfer from the case to the surrounding air
involves radiation convection and conduction, the
effectiveness of transfer being expressed in terms of
an RthCA value, i.e., the external or case ambient
thermal resistance. The total thermal resistance,
junction ambient is consequently:
RthJA = RthJC + RthCA
The total maximum power dissipation, Ptotmax of a
semiconductor device can be expressed as follows:
T jmax – T amb
T jmax – T amb
P totmax = ----------------------------------- = ------------------------------------R thJA
R thJC + R thCA
where:
Tjmax the maximum allowable junction temperature
Tamb the highest ambient temperature likely to be
reached under the most unfavorable conditions
RthJC the thermal resistance, junction case
RthJA the thermal resistance, junction ambient, is
specified for the components. The following
diagram shows how the different installation
conditions effect the thermal resistance
RthCA the thermal resistance, case ambient,
depends on cooling conditions. If a heat
dissipator or sink is used, RthCA depends on the
thermal contact between case and heat sink,
heat propagation conditions in the sink and the
rate at which heat is transferred to the
surrounding air.
For further details about thermal management see
„TELUX Application Note“.
250
Time (s)
18188
Figure 3. Double wave soldering of opto devices
(all packages)
Document Number: 80092
Rev. 1.3, 08-May-07
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Assembly Instructions
Vishay Semiconductors
94 8162
100
b
RthJA (%)
l
3
90
c
≥ 100
a
80
51
0.14 mm 2 Cu isolated
25
5
Length l (mm)
94 8161
Figure 4. Thermal resistance junction / ambient vs. lead length
Figure 6. In the case of wire contacts (curve b, figure 3)
Cu
2.5
From
underneath
2.5
From
underneath
2.54
2.54
100 mm2
Side view
Cathode
l
Side view
94 8164
Figure 5. In the case of assembly on PC board with heatsink
(curve a, figure 3)
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l
94 8163
Figure 7. In the case of assembly on PC board, no heatsink
(curve c, figure 3)
Document Number: 80092
Rev. 1.3, 08-May-07
Assembly Instructions
Vishay Semiconductors
CLEANING
Soldered assemblies are washable with the following
solvents:
1.
A mixture of 1, 1.2-trichlorotrifluoroethane,
70 ± 5 % by weight and 2-propanol (isopropyl
alcohol), 30 ± 5 % by weight.
Commercially available grades (industrial use)
should be used.Warning: The component 1,
1.2-trichlorofluoroethane is hazardous to the
environment. Therefore this solvent must not be
used where the solvent specified in 2 or 3 is
adquate.
2. 2-propanol (isopropyl alcohol).
Commercially available grades (industrial use)
should be used.
3. Demineralized or distilled water having a resistivity
of not less than 500 mΩ corresponding to a
conductivity of 2 mS/m
Caution: The
use
of
tetrachlor,
acetone,
trichloroetylene or similar is NOT ALLOWED!
Document Number: 80092
Rev. 1.3, 08-May-07
WARNING
Exceeding any one of the ratings (soldering, cleaning
or short time exceeding the railings) could result in
irreversible changes in the ratings.
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