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2. Full-color LED display
research based on
chip on board(COB) package
Presented By:- KESHAV KUMAR
S7, ECE
Roll No.- 53
Guided By:- Mr. Nishanth Sir

3. CONTENTS
 KEYWORDS
 INTRODUCTION
I. SCREEN
II. RGB
 RESEARCHING PROCESS
I. PACKAGING
II. PLASTIC PACKAGE METHOD
III. EXISTING SMD
IV. COB PACKAGE
V. LED CHIPS
VI. BONDING
VII. MICROGRAPH
VIII. VISUAL EFFECT
 ADVANTAGE
 CONCLUSION
 REFERENCES

4. Keywords
 Chip on board(COB)- an integrated package method
which encapsulate LED chip onto the substrate directly.
 LED display- An LED display is a flat panel display, which
uses an array of light-emitting diodes as pixels for a video
display.
 SMD(surface mounted device)- a method for producing
electronic circuits in which the components are mounted or
placed directly onto the surface of printed circuit boards
called a surface-mount device (SMD)
 Die bond- Place enlarge crystal ring with silver glue in
crystal picking frame, then pick the LED chip onto the
printed circuit board.
 Wire bond- Solder LED chip onto homologous pad of printed
circuit board with wire bonder.

5. INTRODUCTION
 LED display was sorted by color-
1. Monochrome screen
2. Double color screen
3. Full color screen
 Sorted by application place-
1. Outdoor screen
2. Indoor screen
 Sorted by control mode-
1. Synchronous control panel
2. Asynchronous control panel

6. SCREEN
Outdoor Screen Indoor Screen

8.  Sensitivity of human eyes, ability to distinguish
different colors from three different types of retinal
cones.
 One of three kinds of cones is sensitive to red(R),
green(G) or blue(B).
 When the light source disappeared, there is a delay
time called human visual inertia, it formed driving
method called dynamic scanning driving.
RGB

9. RESEARCHING PROCESS
 COB package process of LED display modules
include following steps:-
1. Die spreading
2. Fluid dispensing
3. Die bonding
4. Constant temperature backing
5. Wire bonding
6. Former test
7. Whole board molding
8. Solidification
9. Back test

10.  The most crucial steps of COB package
process are die bonding, wire bonding and
molding.
 If die bonding is bad, it will affect subsequent
wire bonding process.
PACKAGING

11.  After die bonding, wire bonding and electronic
tested to be correct, plastic package should
be done.
 Due to this consistency is better and it has a
better effect of display and high reliability.
PLASTIC PACKAGE METHOD

12.  Existing P2.0 LED display mainly uses surface mount
SMD packages lamp to assemble onto the
substrate of the LED display module by reflow
soldering.
 In which SMD, a red, a green and a blue chip is
packaged, the anode of the tri-color chips are
connected to adapt the dynamic scanning driving
of existing LED display.
EXISTING SMD

13.  COB package of the P2.0 LED display module,
which uses the 1/32 dynamic scanning driving
method.
 The module has a resolution of 32 * 32 and
contains a total of 32 * 32 * 3 LED chips used to
display.
 The entire scanning driver circuit can be
divided into four modules:-
1. External IO module
2. the row scanning module
3. the column driving module
4. LED array module.
COB PACKAGE

15.  The red, green and blue LED chips was chosen to
package the COB display module with the pixel pitch of
2.0mm.
 Among them, the red LED chip has counter electrode
vertical structure, that is to say the bottom surface of the
chip is its anode and its cathode is on the top surface;
the blue and green chip has a horizontal structure which
has a sapphire substrate and on the top surface of
which are its anode and cathode.
LED CHIPS

16.  The bonding diagram of COB LED display
module was design three R, G, B LED
chips consisting of a display pixel were
bonded on a large pad, ensuring
sufficient space for die bonding.
BONDING

17.  The module after the entire board molding
is shown that the LED display module after
the entire board molding has very good
consistency.
MICROGRAPH

18.  The three color visual effect of the sample P2.0
COB package LED display module can be
seen that the COB package has excellent
color consistency and proper luminance for
display requirement.
VISUAL EFFECT

19. ADVANTAGE
 COB package has the features as simple
processes
 Low cost
 Good visual effect
 High reliability
 Long life-span, etc.
 While SMD 3 in 1 package has many defects, for
instance, high cost, complicated processes,
lamps can easily go dead and be knocked off,
etc.
 COB can be a very good solution for package of
high definition LED display.

20. CONCLUSION
 The sort of the LED dies, controlling in the yield of die bonding and
wire bonding and precision in molding packaging.
 Before COB package, LED chip has to be carefully tested and
sorted to guarantee the brightness and chrominance.
 When designing the module substrate, enough space should be
offered for die bond and soldering plate of the wire, to ensure the
glue cover on four sides and form strong connection.
 Wire bonding direction and distance should be designed as
almost the same, this is to decrease the difficulty of soldering
operation.
 For molding packaging on the whole board, every module
should under protection with plastic packaging and also need
same packaging thickness.

21. REFERENCES
 Shih-Mim Liu, Ching-Feng Chen and Kuang-Chung Chou.” The
design and implementation of a low-cost 360-degree color LED
display system”[C].0098 3063/11/2011 IEEE:289-295.
 K.Takahashi , S.Nakajima and S.Takeuchi. “Full .color LED display
panel fabricated on a silicon microreflector “[C]. 0-7803-3744-
1/97/ IEEE 356-359.
 Joon Ho Hyun, Myung Jin Park, and Young Hwan Kim. “POSCO
LED and the IT Consilience Creative Program of MKE and
NIPA,2012”[C]978-1-4673-0219-7/122012 IEEE
 https://en.wikipedia.org/wiki/Color