Philips Semiconductors
Thyristors and Triacs Introduction
NEW PRODUCTS
Philips Semiconductors are working intensively on
bringing new products to the market to meet the
requirementsofexistingandnewdevelopingapplications
areas. These arethe new products and technologies that
appear for the first time in this data handbook.
HIGH COMMUTATION TRIACS
Philips range of high commutation triacs now include two
new devices rated at 8 A and 25 A. These devices have
high off-state dV/dt and commutation capability, and are
ideal for use in motor control circuits and other inductive
switching applications. (Types: BTA208, BTA225).
ISOLATED THYRISTORS AND TRIACS
TheIndustryStandard-BT151thyristorplusawiderange
of standard and high-commutation triacs are now
available in the SOT186A isolated package, featuring
isolation voltage up to 2500 Vrms. The SOT186A
package allows two or more power devices to share a
common heatsink, without the need for insulating bushes
and spacers, or alternatively allows the heatsink to be
grounded. (Types: BT151X, BT136X, BT137X, BT138X,
BT139X, BTA208X, BTA212X, BTA216X).
SURFACE MOUNTING BT169
The popular BT169D, sensitive gate thyristor, used in a
wide variety of consumer applications is now available in
aSOT223envelope, suitableforsurfacemounting(Type:
BT169DW).
NEW 5 A RATED THYRISTOR
The BT300 series is a range of 5 A rated thyristors with
similar characteristics to the BT151, available in 500 V,
600 V and 800 V grades. It is intended for lower power
applications where the 7.5 A rating of the BT151 is not
required (Types: BT300-500R, BT300-600R,
BT300-800R).
NEW 5 A RATED, LOGIC LEVEL THYRISTOR
The BT258 series is a range of 5 A rated, sensitive gate
thyristors available in 500 V, 600 V and 800 V grades.
TheBT258maybeinterfaceddirectlytomicrocontrollers,
logic integrated circuits and other low power gate trigger
circuits. This device is particularly suitable for
microprocessor controlled domestic appliances and low
power consumer products. (Types: BT258-500R,
BT258-600R, BT258-800R)
ADDITIONAL VOLTAGE GRADES FOR BT150
Uptonow,theBT150hasonlybeenavailableinthe500 V
grade. Additional voltage grades of 600 V and 800 V are
now available. (Types: BT150-600R, BT150-800R)
UNENCAPSULATED, PASSIVATED, SILICON POWER CHIPS
All the devices in this data handbook are available as
unencapsulated dice complete with passivation and
metallised contact pads, but without bond wires or any
other connections or encapsulation. Contact your
Regional or National Sales Office for details.
APPLICATIONS
For further information on applications which use
thyristors and triacs, refer to the new handbook "Triacs
and thyristors - an application guide" (Order
code: 9397-750-00372).
For further information on other power semiconductor
applications, refer to the "Power Semiconductor
Applications Handbook" (Order code:9398-652-85011).
February 1996
Philips Semiconductors
Thyristors and Triacs Introduction
PHILIPS THYRISTORS AND TRIACS
The Phase 2 Process
The basic principle of using a PNPN structure to produce
a thyristor, and a NPNPN structure (with two PNPN’s in
antiparallel) to produce a triac has been known for
decades. The factors controlling various important
parameters, such as blocking voltages, on-state voltage
drop, trigger current, latching and holding current,
off-statedV/dt,triaccommutationandsurgecapabilityare
also well known.
The modern challenge of making good thyristors and
triacs lies not so much in innovative design concepts as
in perfection of manufacturing technology.
Philips products are characterised by the use of well
established, stable processes in both diffusion and
assembly, giving devices of high quality and reliability.
The strengths and special features of these products are
outlined below.
Exceptfor thosedesigned forspecialist applicationssuch
asGTO’sandASCR’s,mostcommonthyristorsandtriacs
are specified to have voltage blocking capability in both
directions. This means that in the PNPN or NPNPN
structures, two opposing PN junctions need to be
designed to withstand the rated voltage.
This is normally achieved by starting with a suitably low
doped N type silicon wafer into which two P regions are
diffused simultaneously from opposite sides, resulting in
asymmetricPNPstructurewherebothPNjunctionshave
highvoltageblockingcapability.FurtherN-typediffusions
are then put into both sides of the structure, (for a triac).
The result is a NPNPN structure with a symmetrical
blockingvoltage.BothoftheseblockingPNjunctionsnow
need to be passivated at the point where they intersect
the silicon surface, and there are two common methods
for doing this, shown in the diagrams below.
Fig.1. Phase 1 structure and Passivation.
Fig.2. Phase 2 structure and Passivation.
In Philips terminology we call these "Phase 1" and
"Phase 2" technologies respectively.
As can be seen, Phase 1 passivation requires a
simultaneous etching of mesa troughs from both sides
followed by the deposition of passivants such as
negatively charged glass. The advantages of this
technique are small chip size and fewer processing
stages. No aluminium isolation diffusion or photolith are
required, hence the overall chip cost is lower.
By contrast, the Phase 2 technology requires an
aluminiumisolation diffusion prior to the fabrication of the
PNPN or NPNPN structure, which has the effect of
bringing both blocking PN junctions to the top surface.
These can then be passivated with trough etching and
glass deposition on the top side only.
Themain advantageofthePhase 2technologyis a much
more mechanically robust structure, due to the fact that
the edge of the chip is not reduced in thickness. Minor
damage to the edges does not intrude into the active
region. A further advantage isthat the flat bottom surface
is compatible with automatic die bonding in assembly.
The main disadvantage is increased cost in comparison
with the Phase 1 process.
Philips has progressed from Phase 1 to Phase 2
passivation technology, despite its higher cost, because
of the advantages of mechanical ruggedness and lower
vulnerability to handling damage.
It is our belief that Philips thyristors and triacs produced
using Phase 2 technology have fewer manufacturing
defects, and are more reliable than devices produced by
competitors who are still using the Phase 1 structure.
Passivation
TheuseofthePhase 2passivationstructurecoupledwith
the well developed glass mesa passivation technology at
Philips results in devices with high voltage blocking
capability and extremely stable characteristics. The
structure is also less vulnerable to edge damage
compared to the alternative Phase 1 passivation.
N
P
P
MT1 G
MT2
glass
N
N
P
P
N
P
P
MT1 G
MT2
glass
N
N
February 1996
Philips Semiconductors
Thyristors and Triacs Introduction
The typical off-state breakdown voltage of our thyristors
and triacs is in excess of 1000V, with a very tight
distribution, so much so that we normally consider any
devices with blocking voltages less than 500V to be
defective.Forexample,our200Vand400Vgradedevices
are tested to withstand 500V.
In contrast, competitors using Phase 1 passivation who
deliver true 200V and 400V devices, i.e. devices whose
breakdown voltages are just above 200V or 400V, are
likelytosufferfrom glasscracksorchippedcornerswhich
can progress to the extent that they cause quality and
reliability problems.
Assembly
The absence of troughs and glass on the bottom surface
of our chips allows us to use automated assembly. We
use diebonding technology which involves scrubbing the
chips onto heated leadframes that are precoated with
solder. This technique gives an excellent, void free
contact with low thermal resistance and avoids having to
subject the chips to long duration, high temperature
furnacing. Compared to our main competitors, our
devices have superior die bonds and lower thermal
resistance, which means that they operate at a lower
junction temperature for the same dissipation, and thus
have higher reliability.
Another feature of this assembly method is that, along
with the ultrasonic wire bonding used to connect to the
top of the chip, it gives our devices a high thermal fatigue
capability. Thus they have excellent on-state reliability as
well as extremely stable off-state characteristics.
Fig.3. Die bonding onto leadframes, wire bonding.
Unencapsulated Dice
Because of the advantages of the Philips process and
assembly techniques outlined above, our family of triacs
and thyristors are ideal for use in unencapsulated form,
in applications where space and height areat a premium.
The glass passivation protects the, otherwise exposed
surface regions giving highly stable device
characteristics. The silicon wafers are 100% electrically
testedandarenormallysuppliedsawn,onbluefilmframe
carriers. Unsawn wafers can be supplied where
necessary.
Philips Semiconductors have a wealth of experience of
supplying devices in this form and are able to provide
expert advice on the subject of mounting, soldering and
attaching bond wires to unpackaged dice.
Thyristor and Triac Ratings
A rating is a value that establishes either a limiting
capability or a limiting condition for an electronic device.
It is determined for specified values of environment and
operation, and may be stated in any suitable terms.
Limiting conditions may be either maxima or minima.
All limiting values quoted in this data handbook are
Absolute Maximum Ratings - limiting values of operating
and environmental conditions applicable to any device of
a specified type, as defined by its published data.
The equipment manufacturer should design so that,
initially and throughout the life of the device, no absolute
maximum value is exceeded with any device, under the
worst probable operating conditions.
VOLTAGE RATINGS
VDRM, Repetitivepeakoff-statevoltage.Themaximum
VRRM allowable instantaneous forward or reverse
voltageincluding transients. The rated valuesof
VDRM(max) and VRRM(max) may be applied
continuously over the entire operating junction
temperature range, provided that the thermal
resistancebetweenjunction andambientiskept
low enough to avoid the possibility of thermal
runaway.
CURRENT RATINGS
IT(AV) Average on-state current. The average rated
current is that value which under steady state
conditions will result in the rated temperature
Tjmax being reached when the mounting base or
heatsink is at a given temperature. Graphs of
on-state dissipation versus IT(AV) or IT(RMS) are
providedinthedatasheets.Therighthandscale
of each graph shows the maximum allowable
mounting base or heatsink temperature for a
given dissipation.
IT(RMS) RMS on-state current. For a given average
current, the power dissipated at small
conduction angles is much higher than at large
conduction angles. This is a result of the higher
rms currents at small conduction angles.
Operating the device at rms currents above the
rated value is likely to result in rapid thermal
cyclingof the chipand thebond wires whichcan
lead to reliability problems.
ITSM Non-repetitive peak on-state current. The
maximum allowable peak, on-state surge
current which may be applied no morethan 100
times in the life of the device. The data sheet
condition assumes a starting junction
temperature equal to Tjmax, and a sinusoidal
surgecurrentatamainsfrequencyof50/ 60 Hz.
For a triac, a full sine wave of current is applied.
MT1
MT2
G
solder
lead frame
gate wire
MT1 wire
MT2 connection
chip
back metallisation
February 1996
Philips Semiconductors
Thyristors and Triacs Introduction
Immediately after the surge, the mains voltage
is reapplied with a peak value equal to the full
rated off-state voltage, VDRM. Graphs in the data
sheet show the variation of ITSM with surge
duration.
I2t Devicefuserating.Forcorrect circuitprotection,
the I2t of a protective fuse must be less than the
I2t of the device. In the data sheets, the device
rating is numerically equal to ITSM2/200 and
assumes a 10ms fusing time.
dIT/dt The maximum allowable rate of rise of on-state
current after gate triggering. The theory
underlying this rating is that, where the rate of
rise of main current is very rapid immediately
aftertriggering, local ’hotspot’ heatingwill occur
in a small part of the device active area close to
the gate, leading to device degradation or
complete failure. In practise, true dIT/dt failures
of this kind are very rare. The only conditions
wheredIT/dthasbeenobservedtocausefailures
is in triacs operated in the T2-, G+ quadrant
whereacombinationofhighdIT/dtandhighpeak
current(in excess ofthe data sheetratings), can
cause damage to the gate structure. For this
reason, operation of our triacs in the T2-, G+
quadrant should be avoided wherever possible.
dIT/dt VBO or dVD/dt triggered. Where a device is
triggered by exceeding the breakdown voltage,
or by a high rate of rise of off-state voltage, as
opposed to injecting current into the gate, it is
necessary to limit the dIT/dt. A note in the data
sheetspecifiesthemaximumallowabledIT/dtfor
this mode of triggering.
THERMAL RATINGS
Rth j-mb Steady state thermal resistances. Junction to
Rth j-hs mounting base is used for TO220AB envelope.
Rth j-sp Junction to heatsink for devices in full pack,
Rth j-lead isolated envelopes, SOT186 and SOT186A.
Junction to solder point is used for devices in
SOT223 surface mounting envelope. Junction
to lead is used for devices in SOT54 (TO92)
small signal outline. The maximum value of the
thermalresistanceisgiveninthedatasheet,and
isusedtospecify thedevice rating.The average
junction temperature rise for a given dissipation
is given by multiplying the average dissipation
by the thermal resistance.
Note that for triacs, two values of thermal
resistance are quoted; one for half cycle
operation and one for full cycle operation. This
is because only half of the chip carries current
in each half cycle allowing the non-conducting
half to cool down between conduction periods.
The net effect is to reduce the average thermal
resistance for full cycle conduction.
Rth j-a Typical values of junction to ambient thermal
resistance aregiven in the data sheet assuming
thatthedevice is mountedverticallyon aprinted
circuit board, in free air.
Zth j-mb, Whilst the average junction temperature rise
Zth j-hs maybefoundfromthethermalresistancefigure,
the peak junction temperature requires
knowledge of the current waveform and the
transient thermal impedance. The thermal
impedance curves in the data sheets are based
on rectangular power pulses. The junction
temperature rise due to a rectangular power
pulse, is given by multiplying the peak
dissipation during the pulse by the thermal
impedance Zth j-mb for the given pulse width.
Analysis methods for non-rectangular pulses
are covered in the Power Semiconductor
Applications handbook.
Tjmax The maximum operating junction temperature
range for all our thyristors and triacs is 125˚C.
This applies in either the on-state or off-state,
and for either half cycle or full cycle conduction.
It is permissible for the junction temperature to
exceed Tj max for short periods during
non-repetitive surges, but for repetitive
operation the peak junction temperature must
remain below Tj max.
Tstg The limiting storage temperature range for all
our thyristors and triacs is -40˚C to 150˚C.
PG(AV), The average and peak gate power dissipation,
PGM,I
GM, andthemaximumgatevoltageandgatecurrent.
VGM Exceedingthegateratingscancausethedevice
to degrade gradually, or fail completely.
Thyristor and Triac Characteristics
A characteristic is an inherent and measurable property
ofadevice.Suchapropertymaybeexpressedasavalue
for stated or recognized conditions. A characteristic may
alsobe a set of relatedvalues, usually shown ingraphical
form.
STATIC CHARACTERISTICS
VTOn-statevoltage.Thetabulatedvalueinthedata
sheet is the maximum, instantaneous on-state
voltage measured under pulse conditions to
avoid excessive dissipation, at a junction
temperature of 25˚C. The data sheet also
contains a graph showing the maximum and
typical characteristics at 125˚C and the
maximum characteristic at 25˚C. The maximum
characteristic at 125˚C is used to calculate the
dissipation for a given average or rms current,
and hence the graph of on-state dissipation
versus averageor rms current in the data sheet.
February 1996
Philips Semiconductors
Thyristors and Triacs Introduction
The on-state voltage/ current characteristic of a
diode, thyristor or triac may be approximated by
a piecewise linear model as shown in the figure
below; where RSis the slope of the tangent to
the curve at the rated current, and VOis the
voltage axis intercept. The on-state voltage is
then VT = VO + IT.RS, and the instantaneous
dissipation is PT = VO.IT + IT2.RS. where ITis the
instantaneous on-state current.
It can be shown that the average on-state
dissipation for any current waveform is:
PT(AV) = VO.IT(AV) + IT(RMS)2.RS, where IT(AV) is the
average on-state current and IT(RMS) is the rms
value of the on-state current. Graphs in the
published data show on-state dissipation as a
function of average current for thyristors and
versus rms current for triacs. Sinusoidal current
waveforms are assumed and the graphs show
dissipation over a range of conduction angles
Fig.4. Piecewise linear approximation to thyristor and
triac on-state characteristic.
IGT Gate trigger current. The data sheet shows the
typical and maximum gate trigger current at a
junctiontemperatureof25˚C.Agraphinthedata
sheet shows the variation of normalised IGT with
temperature.
When designing a triac gate trigger circuit,
triggering in the T2-, G+ quadrant should be
avoided if possible. The gate trigger current in
this quadrant is much higher than in the other
three quadrants and the device is more
susceptible to turn-on dIT/dt failure.
VGT Gate trigger voltage. The data sheet shows the
typical and maximum gate trigger voltage at a
gate current equal to IGT, at a junction
temperature of 25˚C. A graph in the data sheet
shows the variation of normalised VGT with
temperature.
To ensure that a device will not trigger, the gate
voltage must be held below the minimum gate
trigger voltage. The data sheet quotes VGT(min) at
themaximumjunctiontemperature(125˚C),and
the maximum off-state voltage (VDRM(max)).
ILLatching current. The latching current is the
value of on-state current required to maintain
conduction at the instant when the gate current
is removed. A graph in the data sheets shows
the variation of normalised ILwith temperature.
To trigger a thyristor or triac, a gate current
greater than the maximum device gate trigger
current IGT must be applied until the on-state
current ITrises above the maximum latching
current IL. This condition must be met at the
lowest junction temperature.
IHHoldingcurrent. The holdingcurrent is thevalue
of on-state current required to maintain
conduction once the device has fully turned on
and the gate current has been removed. The
on-statecurrentmusthavepreviouslyexceeded
the latching current IL. A graph in the data sheet
shows the variation of normalised IHwith
temperature.
To turn off (commutate) a thyristor or triac, the
load current must remain below IHfor sufficient
time to allow a return to the off-state. This
condition must be met at the highest operating
junction temperature (125˚C).
ID,I
RThe maximum off-state leakage current,
specified at rated VDRM(max),V
RRM(max) at 125˚C.
DYNAMIC CHARACTERISTICS
dVD/dt Critical rate of rise of off-state voltage.
Displacement current caused by a high rate of
riseofoff-statevoltagecaninduceagatecurrent
sufficient to trigger the device. Devices with
sensitive gates are particularly susceptible to
dVD/dt triggering, and since gate trigger current
decreases as junction temperature increases,
the condition is worse when the device is hot.
Thedatasheetfigureis specifiedat125˚Cusing
an exponential waveform and a maximum
applied voltage of 67% VDRM(max). The dVD/dt is
measured to 63% of the maximum voltage.
To prevent sensitive gate devices from false
triggering due to high rates of rise of off state
voltage, 1 kΩresistor in parallel with a 10nF
capacitor may be fitted between gate and
cathode (gate and terminal 1 for a triac). This
approach is less effective for standard gate
devices. In this case, the preferred option is to
fit an RC snubber between anode and cathode
(T2andT1foratriac)toreducethedVD/dtbelow
the critical value.
0VT / V
50
40
30
20
10
0 0.5 1.51.0
IT / A
slope Rs
Vo
February 1996
Philips Semiconductors
Thyristors and Triacs Introduction
Fig.5. Exponential waveform used for measurement
of critical off-state dV
D
/dt. The dV
D
/dt is the average
slope between 10% and 63% of the maximum applied
voltage V
DM
.
tgt Gate controlled turn-on time. A typical turn on
time of 2 µs is specified for all our thyristors and
triacs.
tqCircuit commutated turn-off time. A typical turn
off time of 70 µs is specified for standard gate
thyristorsand100µsforsensitivegatethyristors.
TRIAC COMMUTATION
A triac is an AC conduction device and may be thought
of as two thyristors in antiparallel, monolithically
integrated onto the same silicon chip. In phase control
circuits, the triac often has to be triggered into conduction
part way into each half cycle. This means that at the end
of each half cycle the on-state current in one direction
must drop to zero and not resume in the other direction
until the device is triggered again. This commutation
turn-off capability is at the heart of triac power control
applications. If the triac were truly two separate thyristors
in antiparallel, this requirement would not present any
problems. However, as the two are on the same piece of
silicon there is the possibility that the unrecombined
charge of one thyristor as it turns off may act as gate
current to trigger the other thyristor as the voltage rises
in the opposite direction. This phenomenon is called
commutation failure.
There are two components of current which can act as
gate current to cause commutation failure. One of these
is the displacement current generated by the reapplied
dVcom/dt. The other is the recombination current, which is
mainly determined by the rate of fall of commutating
current, dIcom/dt. Both tend to create a lateral volt drop in
the emitter of the opposing thyristor which triggers the
deviceintheoppositedirectiontotheoriginalcurrentflow.
At low rates of fall of current, dIcom/dt, the ammount of
unrecombined charge is small and commutation failure
occurs mainly because of the rate of rise of off-state
voltage,dVcom/dt.Thissituationisworstforinductiveloads
where the rate of rise of voltage can be very high when
commutation occurs. The conventional remedy for this
type of commutation failure is to fit a snubber across the
deviceto limit therate of riseof off-state voltagedVcom/dt.
At high values of dIcom/dt, the recombination current
dominates and, above a critical value of dIcom/dt, the
device will not commutate even at fairly low values of
dVcom/dt. Under these conditions, a snubber will not
prevent commutationfailure, and the bestoption is to use
a High Commutation Triac.
HIGH COMMUTATION TRIACS
Philips HighCommutation Triacs attemptto separate the
two antiparallel thyristor structures to prevent the
unrecombinedchargefrom theconductinghalfbecoming
gate current in the other half. This is accomplished by
lateral separation of the top and bottom emitters, more
extensive emitter and peripheral shorting, and by a
modifiedgatedesignwhich prevents triggering inthe T2-,
G+ quadrant.
The device design, in addition to giving high immunity to
commutation failure, also improves the off-state dVD/dt
capability. They will commutate the full rated current up
to 125˚C without the aid of a snubber and will also
withstand extremely high ratesof rise of off-state voltage,
in excess of 1000 V/µs. High commutation triacs can
simplify circuit design by eliminating the need for RC
snubbers. Typical applications include; motor starting,
wherethetriacmayberequiredtocommutatethestarting
current; the switching of d.c. operated relay coils where
thetimeconstantofthecoilismuchgreaterthanthemains
period and static switching where it is required to turn the
triac off whilst it is carrying an overload current.
dVcom/dt Critical rate of rise of commutating voltage. For
conventional, as opposed to high commutation
triacs, the data sheet conditions specify a
junctiontemperatureof95˚CandadIcom/dtgiven
by2.√2.π.f.IT(RMS),wherefisthemainsfrequency
(assumed to be 50Hz). This value is the
maximumrateofchangeofcurrentwhichoccurs
atthezerocrossingforasinewavecurrentequal
to therated rms value, IT(RMS). Graphs inthedata
sheet show the variation of dVcom/dt and with
junction temperature with dIcom/dt as a
parameter.
dIcom/dt Critical rate of change of commutating current.
High Commutation Triacs are intended for use
incircuits where high values of bothdIcom/dt and
dVcom/dt can occur. Commutation capability is
specified in terms of dIcom/dt, without a snubber
and at the highest junction temperature,
Tjmax = 125˚C. A graph in the data sheet shows
the variation of dIcom/dt with junction
temperature.
012345
0%
20%
40%
60%
80%
100%
No of time constants
Percentage of maximum applied voltage VDM
dVD/dt = average slope between 10% and 63% of VDM
February 1996
Philips Semiconductors
Thyristors and Triacs Introduction
Operation up to 150˚C
The maximum operating junction temperature, Tjmax of
Philips thyristors and triacs is 125˚C. Operation above
Tjmax for long periods, particularly in the off-state, can give
rise to reliability problems due to changes in
characteristics which occur as a result of mobile charge
in the glass passivation.
Furthermore, as a thyristor or triac gets hot, it becomes
more susceptible to false gate triggering, off-state dVD/dt
triggering, thermal runaway and commutation failure.
However, it has become apparent that some customers
have applications which require operation of thyristors
and triacs at higher junction temperatures.
Recent improvements in Philips glass mesa technology
backedup by extensive reliability testing hasshown that,
for certain applications, our thyristors and triacs can be
operated reliably at junction temperatures up to 150˚C.
Typical applications where 150˚C operation may be
allowedinclude:-staticswitchingofresistiveloads,power
switches for domestic appliances and electric heating
applications where the device is mounted on a high
temperature substrate.
Extending the upper operating junction temperature to
150˚C depends very much on the application. For this
reasonwe recommend that customers wishingto use our
thyristors and triacs at 150˚C contact the Field
Applications Engineer at their Regional or National sales
office.
February 1996
Philips Semiconductors
Thyristors and Triacs Introduction
QUALITY
Total Quality Management
Philips Semiconductors is
committed to be a world class,
customer driven, volume supplier
of semiconductors.
To achieve this, we operate a Total
Quality Management (TQM)
system, based on Continuous
Improvement and Quality
Assurance in all our business
activities, and Partnerships with
our customers and suppliers.
The top priority throughout the company is Continuous
Improvement.
To focus on this we will:
- Work closely with key customers, as our partners.
- Monitor progress, using customer-driven data, of
our product and services.
- Benchmark against the best.
Furthermore, all parts of the organisation must always
demonstrate:
- The presence of a strong, management-led
improvement structure.
- Commitment and participation in all areas.
- Measurable progress towards our Quality
Improvement goals.
Organisation
An organisation is in place which ensures that personnel
with the necessary organisational freedom and authority
can identify and solve quality problems, prevent
occurrence of product non-conformity and protect the
customer from non-conforming product.
Design control
A comprehensive design and development procedure is
in place which ensures that the requirements of good
design practice are met.
Particular emphasis is placed on ensuring that the initial
specification is agreed by the Customer and the
Marketing and Development functions.
There are regular formal reviews of design progress to
ensure that the initial specification will be met by the
design.
Detailed measurements are made on initial samples to
ensure that the initial specification has been met.
Process control
All processes which directly affect quality are carried out
under controlled conditions. Documented work
instructionsareavailableforallproductionprocessesand
the appropriate environmental controls are in place to
ensure consistent processing. Monitoring of the product,
processes and the environment takes place during
production.
Approval exercises are run to ensure that new processes
and new equipment perform at an acceptable level.
Written, photographicor visual standards are available at
the appropriate points in the production processes.
Corrective action
Non-conforming product found in process is investigated
and the root causes identified. Changes to product or
process are then introduced to prevent recurrence of the
problem.
Quality assurance
Based on ISO 9000 standards, customer standardssuch
as Ford TQE. Our factories are certified to ISO 9000.
Partnerships with customers
These include: PPM co-operations, design-in
agreements, ship-to-stock, just-in-time, self-qualification
programmes and application support.
Partnerships with suppliers
In addition to ISO9000 audits and close monitoring of
supplier delivery performance, we operate a Supplier
Excellence Award scheme which requires suppliers and
their sub-suppliers to use statistical process control,
perform gauge studies and use failure mode and effect
analysis (FMEA) techniques to identify and correct the
root causes of quality and delivery problems.
Product reliability
With the increasing complexity of Original Equipment
Manufacturer (OEM) equipment, component reliability
must be extremely high. Our research laboratories and
development departments study the failure mechanisms
of semiconductors. Their studies result in design rules
and process optimizations for the highest built-in product
reliability. Highly accelerated tests are applied in order to
evaluate the product reliability. Rejects from reliability
tests and from customer complaints are submitted to
failure analysis and the results applied to improve the
product or process.
Customer responses
Our quality improvement depends on joint action with our
customer. We need our customers inputs and we invite
constructive comment on all aspects of our performance.
Please contact your local sales representative.
Recognition
The high quality of our products and services is
demonstrated by many Quality Awards granted by major
customers and international organisations.
QUALITY IMPROVEMENT
PARTNERSHIPS
QUALITY ASSURANCE SYSTEM
TQM
February 1996
