Power MOS FET
Attention of Handling Semiconductor Devices
1.
R07ZZ0004EJ0200
(Previous: RJJ27G0013-0100Z)
Rev.2.00
Aug 18, 2014
Selection of Semiconductor Devices
Semiconductor reliability is remarkably affected by using conditions such as electronic circuits, mounting,
environments, etc. In order to keep high reliability of our semiconductor devices for customer’s use important hints on
selecting the maximum rating, derating, and device package are explained in this chapter.
1.1
Maximum Ratings
The maximum ratings of a semiconductor device are usually defined by the “absolute maximum ratings” and can not be
exceeded in any circumstances, even momentarily. For example, it is defined by the JIS C 7030 as follows:
Note: “Absolute Maximum Ratings”: Absolute maximum ratings are limiting values of operating and environmental
conditions being applied to any transistor, and are officially specified for each type of transistor. These limiting
values have not to be exceeded under any worst conditions. These values are determined by transistor
manufactures and assure enough ability of transistors as far as their absolute maximum ratings are not exceeded
(Reference: JIS C 7030).
If a device operates in excess of the absolute maximum ratings, even momentarily, the device may immediately be
degraded or broken. Even if it goes on operating, its lifetime should be considerably reduced. Therefore, in designing
an electronic circuit using semiconductor devices, it is necessary to consider that the maximum ratings of devices
shouldn’t be exceeded under any changes of external conditions. Furthermore, it should be noted that most of ratings
are closely related to each other and ratings are not always allowed at the same time. For example, even if a current and
a voltage applied to a transistor are individually within their maximum ratings, the collector dissipation should also be
kept within the maximum rating at the same time, because power consumption is the product of current and voltage. In
addition to maximum D.C. ratings, it is necessary to consider ratings of ASO, loading locus, peak voltage, and peak
current when devices are used in pulse condition.
1.2
Consideration about Derating
It is a very important matter for high reliable design to decide the degree of derating from the maximum ratings.
Derating of RENESAS semiconductor devices are already mentioned. Here it is noted that the derating items during
system design, depending on the semiconductor device are electrical stress (voltage, current, power, load)
environmental stress (temperature, humidity) and mechanical stress (vibration, shock).
Table 1 shows some examples of derating standards to be used for reliability designs.
Items for junction temperature are forecast to allow usage over ten years in intermittent operation for about three hours
a day. Furthermore, the values in parentheses (“()”) are forecast to be conditions for high-reliability, allowing all-night
around-the-clock operation over ten years.
It is desirable to consider the derating standards during system designing for its reliability. Examples of improper
deratings are shown in tables 2 and 3.
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Attention of Handling Semiconductor Devices
Table 1 An example of a derating standard*1
Derating factors*2
Temperature Junction
temperature
Device ambient
temperature
Others
Humidity
Voltage
Current
Power
Pulse*3
Notes: 1.
2.
3.
Transistor
Remarks
110°C or less
(especially for high
(Tj = 60°C or less)
reliability application)
—
(especially for high
(Ta = 0 to 45°C)
reliability application)
Consumption power, ambient temperature, heat
radiation conditions
Tj = PD × θja + Ta
Relative humidity RH = 45 to 75%
Others
Printed circuit boards are coated in case of
condensation by rapid change of temperature
Tolerance voltage Max rating × 0.8 or less
Overload voltage
Make the proper preventive way for overvoltage,
including breakdowns by static electricity
Mean current
IC × 0.5 or less
Peak current
iC (peak) × 0.8 or less
Mean power
Max rating × 0.5 or less
ASO
Not to exceed the maximum ratings specified in
each catalog
Surge
iC (peak) or less
Exclude special applications.
Fill the requirements as many of these derating items as possible at the same time.
For the transient state peak voltage, current, power and junction temperature including surges are
normally limited by the maximum ratings and the averages of the above values are used for
reliability derating. Since the ASO varies with the operating circuit, contact our engineering
division when designing.
Table 2 The hFE Down when Maximum Rating is Exceeded (Example 1)
Description
Transistor
A high reverse voltage was applied between emitter and base of a transistor in the
monostable multi-vibrator circuit while it is switching.
Since the applied voltage exceeded the maximum rating, the low current hFE was down
as shown in the graph. Degradation of hFE is shown by using VCC parameter in the
circuit diagram.
36k
1k
0.05μ
VCC
36k
0.05μ
1k
hFE Drop rate (%)
Item
Device
Details
VCC = 6V
0
–40
12V
–80
18V
500
1,000(hr)
Countermeasures (1) Inhibition of break-down (Reduce VCC voltage).
(2) Use another transistor with a higher emitter to base voltage tolerance.
(3) Take a circuit margin for hFE.
Classification
Maximum rating
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Attention of Handling Semiconductor Devices
Table 3 Short Circuit by ON/OFF Cycles (Example 2)
Item
Device
Details
Description
Silicon power transistor (TO-3P)
The silicon power transistor used in a power supply unit was operated for approximately
20 hours and 150 ON/OFF cycles per day. After one to two years’ operation, short
circuit occurred between the collector and emitter. The ON/OFF cycles (PC) were too
frequent, and accordingly, the junction temperature difference (Tj) rose 90°C and the
number of ON/OFF cycles was 50,000 per year. The trouble cause was determined as
ASO destruction due to the soldering fatigue between the chip and the heat sink.
Countermeasures To derate ON/OFF cycles, lower the junction temperature difference to 50°C or less and
improve radiation fins. If possible, design a system to reduce the number of ON/OFF
cycles.
Classification
Derating
1.3
Selection of Package Type
Package types are generally classified to two, one is the hermetic sealed type using metal or glass and the other is the
plastic molded type.
Selection of package types should be done with considering the purpose of system, environment, reliability, cost etc.
The reliability of plastic molded-type semiconductor devices has been greatly improved.
Recently, their applications have also been expanded to automobiles, measuring and control systems, and computer
terminal equipment operated under relatively severe conditions.
Actually, field application data has revealed that their trouble factors under favorable indoor environmental conditions
are equivalent to those of the hermetically sealed type.
2.
Precautions for Physical Handling
There are considerable precautions when semiconductor devices are attached to circuits. In order not to impair the
reliability of the semiconductor devices during installation, care should be taken in forming and cutting leads, mounting
on to circuit boards, soldering, surplus flux removal, attaching to the heat sink, arrangement of component parts, circuit
board coating, etc.
2.1
Forming and Cutting Leads
When forming and cutting the lead wires of semiconductor devices, be careful of the following points:
(1) When bending the lead wires, hold the lead wires securely between the package and the point to be bent with a pair
of pliers. Then, bend them, holding the open end of the leads with your fingers, so that no bending stress is applied
to the package, as illustrated in figure 1. Do not bend the leads by holding the package. The same consideration
should be paid when many devices are simultaneously bent using lead forming machines (See figure 2).
× Wrong
Right
Figure 1 Bending the Lead Wires
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W1
W2
W3
Lead forming mechanism
t
W1
Clamp mechanism
Spaced
(t) must be the necessary distance between the package and the clamp (W1) even if the leads are pulled
toward W3.
Figure 2 Bending the Lead Wires Using a Mould
(2) When bending the lead wires at right angles, make the bend at least 3 mm away from the package end as illustrated
in figure 3 (A). Do not bend them more than 90°. When they must be bent less than 90°, allow a space of more
than 1.5 mm (See figure 3 (B)).
(3) Do not repeatedly bend the leads.
(4) Do not bend them sideways as shown in figure 3 (C).
(5) Do not pull the leads with excessive force, to prevent the device from being broken. The prescribed tensile strength
depends on their cross-sectional areas as already mentioned in RENESAS Reliability Hand book.
(6) Take care not to use any improper jig or pliers for bending, since the surfaces in contact with the plated surfaces of
the lead wires may be damaged. It is advisable to use a tool with a contact area of 0.5 mm radius. Table 4 shows an
example of a lead forming failure.
A
B
3.0min
1.5min
Right
Right
C
D
×
Wrong
×
Wrong
Figure 3 Places and Angles for Lead Wire Bending
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Attention of Handling Semiconductor Devices
Table 4 An Example of Lead Forming Failure
Item
Device
Details
Description
Power transistor (TO-220AB)
Since the lead wires of the transistor were not
securely held by the clamping tool, while the lead
X Lead wire
was being bent wires were loosened resulting in
open circuit. Excessive stress was applied in the
Transistor
Clamping tool
“X” direction and the internal bonding wire was
Bent
broken.
Countermeasures Hold the lead wire firmly at a point between the place to be bent and the end of the
transistor while being bent as illustrated. Also refer to paragraph 2.1.
Classification
Physical handling (lead forming and cutting)
2.2
Mounting on the Circuit Board
Do not apply excessive stress to the lead wires of semiconductor devices when attaching them to the circuit board.
Refer to figure 4.
(1) Make installation holes on the circuit board at intervals corresponding to the distance between lead wires, so that no
excessive stress is produced when mounting.
(2) Do not force the lead wires through the holes during insertion. This will create excessive stress on the device.
(3) Leave proper space between the device and the circuit board surface. Insertion of a spacer between them is
recommended.
(4) Do not apply any additional stress to the device already attached to the board. For example, if a device is connected
to a heat sink after the leads of the device have been soldered to the board, stresses produced by small differences in
lead wire length and component distance will be concentrated on the leads. As the result, problems like detached
leads, broken packages, or broken bonding wires may occur. In order to prevent these accurately position the device
first and solder the leads later.
(5) Refer to paragraph 2.1 when automatic forming and soldering machines are used.
× Wrong
Right
Semiconductor device
Printed circuit board
Same installation hole and lead spacing
Right
Semiconductor device
Same installation hole and lead spacing
Installation holes are positioned improperly
× Wrong
Printed circuit board
Device is smoothly inserted into the
board by a gentle push.
A lead wire is pulled from the bottom with pliers
Figure 4 Mounting Method to Printed Circuit Boards
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Power MOS FET
2.3
Attention of Handling Semiconductor Devices
Soldering
It is not good in general to leave semiconductor devices at high temperatures for a long term. Regardless of the
soldering method, whether it may be a soldering iron or the flowing solder method, soldering must be done in the
shorter time and at the lowest temperature possible. Your soldering work must meet test conditions of soldering heat,
tolerability, namely, 260°C for 10 seconds and 350°C for 3 seconds at a point 1 to 1.5 mm away from the end of the
device. An example of junction temperature increasing curves during soldering obtained from a plastic package small
power transistor is shown in figure 5. These data were measured after dipping the transistors into the soldering baths at
260°C and 350°C, respectively, for the prescribed periods. If transistors are soldered at temperatures or periods of time
exceeding the ratings, their temperature rises and may be degraded or in the worst case broken.
Use of a strong alkali or acid flux may corrode the lead wires, deteriorating device characteristics. The recommended
soldering iron is the type that is operated with a secondary voltage supplied by a transformer and grounded to prevent
current leads. (See figure 6). Try to solder the lead wires at the farthest point from the device surface.
260°C soldering bath
Pick up
200
Exposed to air
Junction temperature (°C)
Junction temperature (°C)
200
Transistor
100
1.5mm
Solder
0
260°C
20 40 60 80 100
140 180
Time (sec.)
240
Exposed to air
100
Transistor
1.5mm
Solder
0
300
350°C soldering bath Pick up
10
20
30
350°C
10
20
40
50
30
60
Time (sec.)
Figure 5 Junction Temperature Curves During Soldering
AC
100 V
C
24 V
Soldering tip
1 MΩ
A soldering iron which has no leak current at tip, and does not induce electric potentials and grounded is
recommended.
Figure 6 Recommended Soldering Iron
2.4
Removing Residual Flux
To ensure the reliability and lifetime of electronic systems, residual flux must be removed from circuit boards.
Detergent or ultrasonic cleaning is usually applied. If cholorous detergent is used for the plastic molded devices,
package corrosion may occur. Since cleaning over extended periods or at high temperatures will cause swollen chip
coating due to solvent permeation, pay special attention to these precautions prior to determining the type of detergent
and cleaning condition. (Isopropylalkohol is recommended as a detergent with respect to dissolution and toxicity.) Do
not use any trichloroethylene solvent. For ultrasonic washing, the following conditions are advisable:
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Power MOS FET
•
•
•
•
Attention of Handling Semiconductor Devices
Frequency: 28 to 29 kHz (to avoid device resonation)
Ultrasonic output: 15W/l (once)
Do not allow the devices to contact the generator source directly.
Washing time: Less than 30 seconds
Table 5 shows an example of a detergent problem.
Table 5 Example of Detergent Problem (Example 4)
Item
Device
Details
Description
Power transistor (TO-220AB)
Plastic molded power transistors were rinsed in an organic solvent for extended periods.
The solvent entered through a gap in the header and the plastic reacted with the internal
chip coat, and the swollen chip coat resulted in wire breakage.
Countermeasures Modification of cleaning method (Cleaning period was reduced to not more than 30 sec.)
Classification
Handling (rinsing)
2.5
Mounting to the Heat Sink
The heat sink is normally used to radiate heat from the power device preventing a rise of the junction temperature.
Semiconductor devices must be mounted carefully to the heat sink so that heat is efficiently radiated and the
semiconductor reliability is not impaired.
(1) Use a suitable silicon grease
In order to improve heat radiation efficiency by increasing the heat conductivity from the transistor to the heat sink,
a thin layer of silicon grease is evenly applied to the contact surfaces before they are coupled together. There are
some types of silicon grease which penetrate the transistor and swell internal chip coat. To prevent chip coat
swelling, a special oil featuring outstanding oil separation and excellent permeation to the mold resin is employed.
Use G746 (Shinetsu Chemical Industry Co., Ltd.) or its equivalent. Use of other grease may not be guaranteed.
Note that the resin will crack during screw tightening when employing a high-viscosity silicone grease. An
excessive amount of grease may cause excessive stress, except for metal-enclosed semiconductor devices.
Table 6 shows trouble which occurred due to improper silicone grease.
(2) Tighten the package with the proper torque
If the tightening torque is too loose, thermal resistance will be increased. On the contrary, if it is too tight, the
device will be distorted and its pellet and lead wires may be broken.
To avoid such troubles, apply proper torque to tighten the package according to the torque range listed in table 7.
For your reference, figure 7 and figure 8 show the relation between thermal resistance and insulator thickness, or
tightening torque, respectively.
Table 6 Chip Coating Resin Swollen by Silicone Grease (Example 5)
Item
Device
Details
Description
Power transistor (TO-220AB)
To obtain better heat radiation through reduction of thermal resistance between the
device and the heat sink, silicone grease is applied to their mating surfaces. The oil
contained in the silicone grease was aborded in the chip coat resin, thus swolling and
breaking the package. This type of trouble occurs with dimethyl system silicone oil.
Shinetsu G 746 silicone grease is recommendable to prevent swelling. Swelling is
promoted by power applied to the device during operation.
Countermeasures When silicone grease is used for devices whose chips are coated with resin, the
undermentioned silicone grease is recommended to prevent swelling:
G 746 manufactured by Shinetsu Chemical Ind. Co., Ltd..
Classification
Handling (improper grease)
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Attention of Handling Semiconductor Devices
Table 7 Optimum Tightening Torque for Typical Packages
External forms
TO-220
TO-220FM, TO-220CFM
TO-3P, TO-3PL
TO-3PFM
TO-3PL
Thermal resistance of insulator
(including contact thermal resistance) θc+θj (°C/W)
Optimum torque (N•m)
0.4 to 0.6
0.4 to 0.6
0.6 to 0.8
0.4 to 0.6
0.6 to 0.8
4.0
(0.6N•m)
lar
My
3.0
Without silicone grease
2.0
r
Myla
Mica
1.0
0
a
Mic
0.05
Silicone grease applied
0.10
0.15
0.20
Thickness of insulator d (mm)
Figure 7 Relation between Thermal Resistance and Insulator Thickness
Contact thermal resistance θc (°C/W)
1.0
0.8
Without silicone grease
0.6
0.4
Silicone grease applied
0.2
0
0.2
0.4
0.6
0.8
Tightening torque (N•m)
1.0
Figure 8 Relation between Contact Thermal Resistance and Tightening Torque
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An example of a package broken during installation is shown in table 8.
(3) Heat sink flatness
If heat sinks don’t properly match with the semi-conductor device, they may fail to radiate heat, or deterioration of
characteristics and the crack of regin results in abnormal stress. When mounting the device on a heat sink, observe
the following precautions:
(i) Do not allow the heat sink to bend upwards, downwards, or twist to such an extent leaving more than 0.05 mm
from the screw holes of the header.
(ii) Check to ensure that aluminum, copper, or iron plate edges are smooth without burrs and that all screw holes
have been chamfered.
(iii) The surface of the heat sink in contact with devices must be polished flat.
(iv) Make sure that metallic chips or foreign matter is not left between the heat sink and the header.
(4) Inhibition of direct soldering to the radiation fin of the device.
If the radiation fin of the transistor is directly soldered, junction temperature will rise far above the rating and the
device may be broken or its lifetime is remarkably reduced.
Table 8 Package Broken by Installation (Example 6)
Item
Device
Details
Description
Power transistor (TO-220AB)
When the transistors were mounted, a torque larger than 10 kg.cm was accidentally
applied by a pneumatic screwdriver. Also, since excessively large installation holes
were provided on the heat sink, the mating surfaces of the header and plastic were
separated. Some pneumatic screwdrivers increase their torques. Should a torque
exceed 8 kg.cm, should the mounting holes on the heat sink be larger than the screw
head, or should the surface around the mounting holes be uneven, the header may be
distorted and the header become separated from the plastic.
Countermeasures Do not apply excessive torque. Recommended torque for the TO-220 type is between 4
and 6 kg.cm. Flatness of the heat sink surface shall not exceed 50 µm. Never drill
mounting holes larger than the screw head. Also, be sure to use the provided washers
(YZ033S)
Classification
Handling (Mounting)
(5) Don’t stress the package mechanically
If a screw driver or fastening jig hits the plastic package while tightening the heat sink, not only the package may be
cracked but the mechanical stress may be transmitted to the inside of the device and wire fatigue may result in
breakage or disconnection.
(6) Don’t mount devices to a heat sink after soldering them
If a device is mounted on a heat sink whose lead wires have already been soldered to the circuit board, excessive
stress will be concentrated on the lead wires due differences in lead wire length and distance between the heat sink
and the device on the board. This may cause the loosened lead wires, package damage, or disconnection of a
bonding wire. Therefore, solder the lead wires of the device after mounting it on a heat sink.
(7) Do not cut or change the shape of the radiation fin and package of the device.
Do not cut or modify the radiation fin and package of the device under any circumstances, in order to prevent any
increase in thermal resistance or abnormal stress.
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(8) Use the recommended parts (spacer, washer, lug terminal, screw, nut, etc.) for the power device installation (see
figure 9).
TO-220AB type
TO-3P type
Screw (3φ)
Screw (3φ)
Metal washer
Metal washer
Metal spacer (YZ033 S)
Insulator (SK16B)
Insulator (SK022A)
Heat sink
Heat sink
Insulation washer
Metal washer
Metal washer
Spring washer
Nut (3φ)
Spring washer
Nut (3φ)
Figure 9 Examples of Power Transistor Installations
(9) Use only suitable screws
Machine screws and tapping screws are used to mount the heat sink on the transistor. Observe the following
precautions:
(i) Use binding-head screws, truss-head screws (JIS-*B1101, Slotted-head Machine Screws), or their equivalent.
* Japanese Industrial Standards
(ii) Do not use flat head screws which cause abnormal stress in the device (see figure 10).
(iii) Apply the proper torque to tighten the tapping screws listed in table 8.
(iv) When a tapping screw is used, use only a screw with a diameter small than the installation hole of the device,
so that the device is not tapped while tapping the heat sink.
(10) Diameters of heat sink screw holes
(i) If diameter is too large: Do not make or chamfer a diameter of screw hole on the heat sink larger than that of the
head of the screw to be passed. Especially, take care when mounting a device using a copper flange (TO-220AB,
TO-3P etc.) on a heat sink, because the copper flange and plastic package are easily deformed by the tightening
torque.
(ii) If diameter is too small: When a tapping screw is inserted, excessive torque may be applied to heat sinks or a
desired contact thermal resistance may not be obtained.
(11) Other precautions and recommendations for heat sink installation
(i) When two or more devices are attached to same heat sink, the thermal resistance of each device is increased (see
figure 11).
(ii) Heat sink must have a suitable shape and dimensions for efficient radiation. Use a forced air-colling device etc.,
if necessary (figure 12 and figure 13).
Binding-head Screw
Truss-head Screw
(Use round-head screws, panhead screws, truss-head screws, binding-head screws, or flat fillister-head
screws.)
Figure 10 Types of Recommended Screws
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Junction temperature ΔTj (°C)
120
100
es
80
vic
2
de
60
e
vic
1
de
40
20
0
5
10
15
20
25
30
Collector dissipation (W)
Notes:
(1) Heat sink, aluminium plate (mm) 300 × 200 × 1.5
(2) Method of installation:
(a) Position: As illustrated (unit: mm)
200
300
70min
(b) Tightening torque: 9 kg•cm.
(c) Silicone oil was applied to the contact surface and mylar was not used.
(d) Natural ventilation, horizontal position
Heat sink thermal resistance (°C/W)
Figure 11 Thermal Resistance with 2 Devices on a Heat Sink
20
Natural ventilation, Horizontal position
10
Aluminium plate
(1.5mm thick)
5
Copper plate (3mm thick)
2
1
20
50
100
200
500
1,000
Heat sink area S (cm2)
Figure 12 Relation between the Heat Sink are and Thermal Resistance
Table 9 Characteristic Failure Caused by Temperature Increase (Example 7)
Item
Device
Details
Description
Transistor
A transistor mounted just above a heat generating component changed its biased point
caused by the temperature increase. The instrument resulted in a failure.
Countermeasures Relocate the transistor to a well ventilated position.
Classification
Handling (component parts positioning)
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Table 10 Noise Failure in Poor Environments (Example 8)
Description
Small signal transistor
Dust on the external surface of a transistor mounted in the differential pre-amplifier unit
of an audio frequency amplifier caused deterioration of the insulation between the
terminals. As the result of this, the transistor generated noise. It was positioned in the
dusty place of system.
Countermeasures (1) Relocate the transistor to a cleaner place.
(2) Coat the printed circuit board with resin.
Classification
Handling (Component parts positioning)
Thermal resistance θj-a(°C/W)
per device between junction and air
Item
Device
Details
8
6
4
2 Transistors
2
0
1 Transistor
2
4
6
8
10
Air velocity (m/s)
Notes: 1. Insulator was not used and silicone oil was applied to the contact surface.
2. Ventilation: As illustrated
Air current direction
Figure 13 Thermal Resistance with Forced Air-cooling
2.6
Positioning of Component Parts
Reliability and characteristics of semiconductor devices are remarkably affected by operating environments. Therefore,
it is not only important to exam operating temperatures and the heat radiation methods, but also the positioning of each
semiconductor devices in the system, to obtain high reliability.
Improper positioning of a semiconductors are as follows:
(1) By heat generators such as large resistors, the heat sink or semiconductor device itself may be heated. A device in
such a location may have its reliability reduced because of abnormal heat (see table 9).
(2) High voltage circuit and corners on the bottom of instrument may sometime be dusty. Insulation of devices will be
deteriorated by dust. This can be prevented by coating the semiconductor device and printed circuit board with
water-proof resin (see table 10).
Coating applied to the printed circuit board is an extremely effective means of improving system reliability. For
example, such coating prevents misoperation caused by short circuit between the printed circuit board wiring and
the semiconductor terminals due to deposited conductive materials, noise caused by deposited dirt and moisture
absorption, trouble caused by overcurrent, and metallic migration (Ag migration) due to condensed moisture or
other adverse environmental conditions.
For systems operated under adverse environmental conditions such as high humidity, condensed moisture, and a
dusty atmosphere, the printed circuit boards shall be coated to ensure long-term, trouble-free service.
(3) In high voltage or high frequency equipment, surge voltage may be induced to semiconductors depending on the
method of wires bundling and path of connecting wires.
Take care not to expose the semiconductors to such conditions. Refer to paragraph 3.2.
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(4) When installing the test terminals in the printed circuit board, carefully select its position in order to be free from
any abnormal voltage source, during maintenance and service.
3.
Mounting Precautions
To make reliable circuits, it is necessary to consider the applications of derating and safety allowances for possible
fluctuations of characteristics during operation, in addition to the satisfaction of initial device ratings incorporated. The
problems to be taken up, for making reliable circuits, are methods of wiring, external surge, reactive load, noise margin,
area of safety operation (ASO), reverse bias, fly-back pulse, static charge, pulse stress, and others.
3.1
General Precautions
The important things to assure the reliability of system are: Use them within the maximum ratings specified in the
brochure, and pay special attention to the operating environments detailed below.
(1) Try to lower ambient temperatures in semiconductors.
(2) Operate the semiconductors within the prescribed ratings for power voltage, input voltage, and power consumption.
Also, apply deratings.
(3) Take care not to allow any induction voltage or overvoltage, accompanied by noise, to the input, output, or power
source terminals. Also, care must be used not to let strong electromagnetic waves affect semiconductors.
(4) Try to prevent electrostatic charges.
(5) Since high-speed devices are made using fine patterns add a protective circuit on the input, or modify the circuit so
that it is not impressed by static-electrical pulses.
(6) Take care not to impress unbalanced voltage of ON/OFF power.
If a power voltage is applied to the input or power terminals whose grounding terminal is floating, excessive stress
will be put on the device.
3.2
Noise and Surge Countermeasures
The problems of surge voltage, static charge, and noise are common to all semiconductor devices and the necessary
countermeasures should be taken to eliminate the causes of these problems.
In general, electronic equipment is designed considering about a 10% voltage fluctuation from commercial electric
power-sources. However, if any equipment which produces surge voltage is operated in the near area, it may cause
failures and malfunctions in other electronic equipment through line voltage. The similar type of noise in the form of
pulse is also produced in the power supply lines by thunderbolt. To reduce the influence of line surges, it is useful to
connect a filter to the A.C. input line as shown in figure 14. If there is a possibility that the component parts or
semiconductors in the circuit will directly be exposed to a surge or static charge, a shielding system must be provided.
When installing a shielding circuit, make sure that the ground impedance is low enough.
If there is a possibility that a static charge or surge pulse will be applied to the devices in the form of noise, a protective
circuit shown in figure 15 may be connected, in special cases. In this circuit, a suitable value of Ri × Ci Time Constant
must be determined to absorb surge noise without affecting circuit operation.
L1
C
AC100V
L2
Primary (P)
Secondary (S)
Figure 14 An Example of a Surge Absorption Circuit
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Power MOS FET
Attention of Handling Semiconductor Devices
Object circuit
(Semiconductor device)
External surge
External noise
R1
Separate
circuit
R2
R3
C1
External surge
External noise
C3
C2
Ri Ci is determined depending
an operating conditions.
Figure 15 An Example of a Protection Circuit for Surge
Table 11 Breakdown Caused by Surge Voltage (Example 9)
Item
Device
Details
Description
Transistor
During electronic equipment assembly, a transistor emitter was shorted to its base.
It was found that a discharge in the high-voltage circuit induced a surge voltage,
breaking the transistor.
Countermeasures (1) To absorb the surge voltage, install a resistor in series or a C.R.
(2) Insulate the high-voltage circuit.
(3) Add a bypass circuit for high-voltage.
Classification
Mounting (Protection from surge)
Table 12 Transistor Breakdown in a Strong Magnetic Field (Example 10)
Item
Device
Details
Description
Transistor
The transistor emitter in the control circuit was shorted to the collector due to noise
induced in the signal line. Due to the fact that the equipment was operated in a strong
magnetic field and the signal line was extended too far, noise was induced. In addition,
the noise protection system was not sufficient.
Countermeasures (1) Connect a capacitor between base and emitter.
(2) Shield the signal line which passes through the strong magnetic field.
Classification
Mounting (noise)
3.3
Relation between Characteristic Parameters and Reliability
Characteristic parameters and their required ranges for each semiconductor device are fixed according to function and
application.
The importances of these parameters are sometimes different in designing systems.
Cares must be needed for important parameters, for instance taking a margin of initial characteristic or considering a
derating.
With regard to take a margin, it is important to choose a device with considering the operating limit of system or to
apply the statistical designing
method, or to design with considering the value of failure judgement already mentioned in chapter 2.
Parameter changing is little in use. Therefore in general it is allowable to design using initial characteristic values.
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Attention of Handling Semiconductor Devices
Cares mentioned above should be taken when parameters are very important for system margin.
The following points are essential for parameter assessment:
(1) Is the parameter important? Does it cause the system failure?
(2) Consider the initial value margin of the parameter.
(3) Does it vary with time or not? If yes, does it fluctuate in an allowable direction?
(4) Is the fluctuation allowable or not in relation to other devices being used?
(5) Is their redundancy in the design?
(6) Is it possible to employ a statistical designing method for the parameters?
4.
Reliability test methods and failure determination criteria for semiconductor
devices
The reliability test methods currently employed in the industry to check the reliability of semiconductor devices vary
depending on the purposes of the tests. Moreover, when performing a reliability test, what need to be determined first
should be the definitions of defects and failures (failure determination criteria).
Outlined below are the reliability test methods and the failure determination criteria for discrete components.
4.1
Reliability test methods
(1) When performing a reliability test, an appropriate test method should be chosen, proper test conditions should be
selected and reliable determination criteria should be set out fitting to applications of the product or to the purposes
of the test.
For example, if a test is meant to find out the limits or if a test is meant to determine if a product conforms to the
specifications would require different test plans, respectively. What to use as the failure detection mode should also
be important and the environmental factors relevant to the structures, production processes and using conditions of
respective devices, means "stress", should normally be used as the failure detection mode. Meanwhile, such stress
can be singular or multiplex depending on the circumstances.
When applying multiplex stress, it is necessary to consider the actual using environments.
Upon the above prerequisites, objectives of implementing the reliability tests should be to make accurate
presuppositions and to contribute to enhancement of the reliabilities of the object devices. For this purpose, it
becomes necessary to accumulate the accomplishments of various reliability tests and to feed back the failure
analysis results.
(2) While, as the reliability tests, tests under the actual using conditions should be ideal but, in majority of the cases, it
becomes extremely difficult to acquire accurate and sufficient data within the limited time and costs. Consequently,
it is necessary to simulate them as far as feasible.
In such cases, although stress conditions not as far as causing breakage will usually be selected as the stress strength,
depending on the circumstances, stress conditions causing breakage may sometimes be applied intentionally to
cause failures in an earlier stage for the failure analysis purposes.
Meanwhile, from the viewpoint of reproducibility of the reliability tests, standardized test methods should also
become necessary. The EIAJ Standard, JIS Standard, IEC Standard, MIL Standard, etc. prescribe these test methods.
They are exemplified in
Table 13 below, listing their typical reliability test standards. Table 14 exemplifies the results of reliability tests
conducted for a discrete component and Table 15 exemplifies the failure determination criteria for reliability tests
for discrete components for your reference, respectively.
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Power MOS FET
Attention of Handling Semiconductor Devices
Table 13 Typical reliability test standards
JEITA (Japan Electronics and Information Technology industries Association) Standards
JEITA ED-4701: Environmental and durability test methods for semiconductor devices
JIS (Japan Industrial Standard) Standards
JIS C7021:Environmental test methods and durability test methods for individual semiconductor
devices
JIS C7022:Environmental test methods and durability test methods for integrated circuits of
semiconductors
IEC (International Electrotechnical Commission) Standards
Publication 68: Environmental test methods
Publication 749: Mechanical test methods and environmental test methods for semiconductor
devices
MIL (U.S. Military Standard) Standards
MIL-STD-202F: Test methods for electronic parts and electric parts
MIL-STD-750C: Test methods for individual semiconductor devices
MIL-STD-883D: Micro-Electronics test methods
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Attention of Handling Semiconductor Devices
Table 14 Exemplified test results of 2SK1170
Categorization
Mechanical tests
Test items
Natural drop test
Vibration fatigue test
Constant acceleration
test
Impact drop test
Terminal pulling test
Terminal bending test
Environmental
tests
Life tests
Temperature cycling
test
Withstand soldering
heat test
Solderability test
Temperature cycling
life test
Pressure Cooker Test
Continuous high
temperature test
Continuous low
temperature test
High temperature
reverse bias test
Operating life test
High-temperature,
high-humidity test
High-temperature,
high-humidity reverse
bias test
Intermittent operation
test
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Test conditions
h = 75cm Onto a maple board. For 3
times.
f = 60Hz, 196m/S2, for 32h in the X, Y
and Z-directions.
196000m/S2,1 min / in the X, Y and
Z-directions.
14700m/S2, 0.5ms. For 3 times / in the
X, Y and Z-directions
Load: 25N, Tensile stress for 30 sec.
Load: 10N, Bending by 90° to a single
direction for 2 times.
Ta = –55°C to +150°C, for 10 cycles.
Numbers of
defectives/Numbers
of samples
0 / 1152
0 / 22
0 / 22
0 / 22
0 / 22
0 / 22
0 / 1152
T = 260°C, dipping the lead for 10 sec.
0 / 22
T = 230° ± 5°C, for 5 sec. to see if solder
covers 95% or more of the surfaces.
Ta = –55°C to +150°C,
for 200 cycles.
Ta = 121°C, for 96h.
Ta = 150°C, for 1,000h.
0 / 22
0 / 22
0 / 22
Ta = –55°C, for 1,000h.
0 / 22
Ta = 150°C, VDSS = 500 V, for 1,000h.
0 / 22
Ta = 25°C, Tch = 150°C, for 1,000h.
Ta = 85°C, RH = 85%, for 1,000h.
0 / 22
0 / 22
Ta = 85°C, RH = 85%, VDSS = 500 V,
for 1,000h.
0 / 22
ΔTc = 90°C, for 10,000 cycles.
0 / 22
0 / 22
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Power MOS FET
Attention of Handling Semiconductor Devices
Table 15 Exemplary failure determination criteria for reliability tests for a discrete component
Test items
Electrical
Breakdown voltage
characteristics Leak current
| yts |, hFE
rate of change
VDS(on)
VCE(sat), VBE(sat)
Vth
Open circuit and
shorting
Appearance
and others
Failure determination criteria (Note)
Lower limit
Upper limit
L ×0.8
—
—
U×2
–30
+30
—
U × 1.2
Units
V
μA
%
V
L × 0.8
U × 1.2
V
—
The open circuit, semi-open-circuit,
shorting and semi-shorting include
high-temperature and low-temperature
failures.
Airtightness leak test Major leakage / Minor leakage
—
Appearance
According to the limit samples
According to the limit samples
Rusting and
discoloration
Solderability
According to the limit samples
Marking
According to the limit samples
Notes: U: Upper limit of the initial specification
L: Lower limit of the initial specification
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Remarks
Applicable to airtightsealed devices
—
—
—
—
Page 18 of 19
Power MOS FET
Attention of Handling Semiconductor Devices
Website and Support
Renesas Electronics Website
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Inquiries
http://www.renesas.com/contact/
All trademarks and registered trademarks are the property of their respective owners.
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Revision History
Rev.
1.00
2.00
Date
Aug. 18, 2004
Aug. 18, 2014
Description
Page
Summary
̵
First edition issued
P.1
1.2: Text addition
P.2
Table 1: Amended of Relative humidity
A-1
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