LED-App-Note.pdf
If heat is not remo ved efficiently from the die there will be degradation of both performance and quality of light produced. ermal and mechanical stress weakens the wire bond, eventually leading to failur e. Wire bonds w…
If heat is not removed efficiently from the die there
will be degradation of both performance and quality
of light produced. ermal and mechanical stress
weakens the wire bond, eventually leading to failure.
Wire bonds within LEDs need to perform in all
possible environments the LED will be exposed to
in its lifespan, with this in mind the manufacturing
process needs to be carefully monitored and optimized
to guarantee a long operating life of the product.
LEDs typically fall within two major categories; high
performance LEDs and general high volume LEDs.
e testing requirements differ but both are met by
the Nordson DAGE bondtester.
Bond Testing of LEDs
Application Note
LEDs offer an energy efficient, low maintenance form
of indication and illumination. LEDs are rapidly
becoming the option for lighting design from
architectural lighting systems to medical equipment,
display systems, street lighting to automotive lighting.
Most LEDs have a natural lifespan - while degradation
failures are unavoidable, correct LED manufacturing
processes ensure that they do not fail within the planned
life of the product.
Heat generated by the LED is a key issue. Heat stresses
the die attach as well as the wire bond which causes
displacement in the bulk of moulding compound.
Typical LED device
Bond Testing of LEDs Application Note
Wire Pull Test
Wire Pull Test
e wire pull test evaluates the wire bond
quality and integrity and is also used for
wire bonding process control and process
optimisation during assembly manufacturing.
As LED wire loops can be very short and
low, the Nordson DAGE wire pull cartridge
offers 360 degree rotation of the test hook
and a wide range of tools to cater for all
geometries. e loop height measurement
feature automatically detects the height of the
loop and monitors its consistency. e wire
breaking force and loop height are saved in
the database to enable future analysis.
Test Methods
e Nordson DAGE bondtester caters for the full range of test methods including:
Wire pull Ball shear
Die shear Low profile die shear
Tweezer pull Wafer level LED
Ball Shear Test
Where the wire pull test provides one aspect of bond integrity
measurement, in order to achieve a complete test of the bond,
the Nordson DAGE ball shear cartridge provides ball shear test
capabilities that can be performed with chisel or cavity tools.
With an additional feature of tool rotation up to 180 degrees for
accurate alignment and operator convenience. e Nordson DAGE
ball shear cartridge features a touchdown sensor to allow smooth
and accurate landings on the brittle LED die. e touchdown force
is highly sensitive and accurate step back repeatability typically
better than +/-1.0µm.
Ball Shear Test
Application Note Bond Testing of LEDs
Wedge Bond Shear Test
Tweezer Pull Test
In order to achieve a complete test on an LED
wire bond, after the ball bond has been sheared,
the wire on the wedge side can be tested using
tweezers. e Nordson DAGE tweezer pull cartridge
parallel closing tweezers can be controlled to apply
the closing force very accurately to the interface;
providing consistent and accurate testing in all LED
die bond applications.
LED Die Shear Test
Die Shear Test
GaAs and other LED die materials are
very brittle, therefore an absolute parallel
alignment of the shear tool to the edges of the
die is required otherwise the die will break
before the necessary load can be applied to
test the interface. e Nordson DAGE self
aligning shear tool ensures absolute parallel
alignment. e operator simply positions the
tool to one edge and then the self aligning
adapter applies the load uniform to the whole
width of the die.
Low Profile Die Shear Test
Constant innovation means that dies are getting thinner in order to better transfer the heat to the package however the areas are
also becoming larger due to the higher light output required. In order to meet these new testing demands, the Nordson
DAGE die shear cartridge provides excellent step-back repeatability and a work holder which allows co-planarity
levelling which together ensure the high repeatability of shearing low profile dies is guaranteed.
Wafer Level Ball Shear Test
Tests can be performed on LED wafers. e high step back accuracy of the Nordson Dage bondtester allows accurate shear
tests to be performed at wafer level.
e Nordson Dage bondtester has a versatile range of standard and application specific wafer chucks.
e chucks will accommodate single or multiple wafers dependant on their diameter.
is combined with semi automatic test routines allows efficient, repeatable
and consistent bond testing for improved throughput.