This article presents the results of studies of the effect ultrasonic bonding on the current-voltage characteristic
nitrides chips with using methods of planning the experiment

Afonin, K.N.

Ryapolova, Y.V.

Soldatkin, V.S.

Tuev, V.I.

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 7 No 4, 04029(2pp) (2015) Том 7 № 4, 04029(2cc) (2015) 
 
 
2077-6772/2015/7(4)04029(2) 04029-1  2015 Sumy State University 
Short Communication 
 
Application of Ultrasonic Bonding in Leds and Led Lamps Production 
 
K.N. Afonin, Y.V. Ryapolova, V.S. Soldatkin, V.I. Tuev 
 
Tomsk State University of Control Systems and Radio Electronics, 40, Lenin Ave., Tomsk, Russia 
 
(Received 28 September; published online 10 December 2015) 
 
This article presents the results of studies of the effect ultrasonic bonding on the current-voltage char-
acteristic nitrides chips with using methods of planning the experiment. 
 
Keywords: Nitride chip, Current-voltage characteristic of the LED, Ultrasonic microwelding, Planning 
eksperiment. 
 
 PACS number: 85.30.De 
 
 
1. INTRODUCTION 
 
As the LED energy efficiency is increasing, the 
number of their possible applications is growing. The 
promising field of great economic importance is the 
development of filamentary LED emitters that are the 
base for led lamps for home and industrial application 
[1]. Compared with filament and luminescent lamps 
they have such advantages as higher light efficiency 
and longer service life [2]. The service life of modern 
LEDs based on blue nitride crystals with luminophor 
can reach up to 60 thousand hours [3]. The technology 
to produce electrical bonding of crystal chip pins with 
the body elements during LED production is well-
developed [4]. The problem of adjacent crystal chip pins 
of filamentary LED emitters bonding has not yet been 
completely solved. 
The study aim is to determine the filamentary LED 
emitter nitride crystal bonding modes that have the 
minimal impact on crystal degradation during their 
further service. The work aim provides the following 
objectives:  
а) to research the microbonding method; 
b) to bond nitride crystal electrical contacts with the 
base contacts by different bonding modes; 
c) to estimate how the selected bonding modes in-
fluence on the nitride crystal current-voltage character-
istics (CVC). 
The bonding mode influence on the crystal degrada-
tion during their further service is estimated by the 
CVC slope change. The article [4] shows that the poor 
quality bonding causes the CVC slope increase. The 
authors conclude that such a CVC change takes place 
because the impurities with breakdown paths occur in 
the semiconductor. Such localized areas have signifi-
cantly higher conductivity than the areas with the bar-
rier structure. 
 
2. MICROWELDING METHOD REVIEW 
 
Three main microbonding methods: thermal com-
pression bonding (TCB), thermosonic bonding (TSB) 
and ultrasonic bonding (USB) as well as two types of 
bonded seal: "ball-wedge" and "wedge-wedge" are exam-
ined in the study.  
The simultaneous impact of temperature and pres-
sure occurs when TCB is used. The bonding pad heats 
up to about 300 °C and consequently the metal ductility 
increases when the electrode contacts with the pad. 
USB occurs without additional heating. Ultrasonic en-
ergy disrupts the crystal structure of metal and as a 
result it becomes deformed under low clamping force 
and temporarily becoming soft and ductile provides the 
bonding. TSB occurs under the simultaneous impact of 
temperature, pressure and ultrasonic oscillations. The 
operation area heats on average from 100 to 150 °C and 
bonded seal formation time lies within 20-200 ms. TSB 
is especially effective for wire bonding to the pads from 
different metals [5]. 
TSB and USB with the wire 20-75 microns in diame-
ter are the most widely used methods to bond microcon-
ductors. This is due to better capacity of these methods 
and operation area lower temperature in comparison 
with the TCB. We decided to use TSB with a ball for-
mation at this stage. The obtained contacts are flexible 
and have high thermal and electrical conductivity and 
low direct-current resistance in contact with metal 
films. Wire diameter is 30 microns. We selected this size 
assuming that the bonded seal size should not exceed ¾ 
of the crystal bonding pad square (100 microns). The 
obtained ball size is approximately 2-3 wire diameters. 
 
3. THE RESEARCH 
 
The research has been carried out with the help of 
device iBond5000 Dual produced by Kulicke&Soffa. This 
device allows lead wire bonding both of "ball-wedge" and 
"wedge-wedge" types. We have performed the "ball-
wedge" bonding for blue nitride crystals. The quality 
control of bonded seals has been carried out visually. The 
seals have been checked for cracks and delaminations.  
It is important to select the optimum bonding mode 
for nitride crystals because ultrasound accelerates the 
nonradiative recombination appearance that results in a 
loss of up to 50 % of light flux after 10,000-15,000 service 
hours [5]. Therefore, the adequate mode shifts the re-
combination processes to 25-30 thousand service hours 
and the crystal characteristics will suit the stated ones. 
The experiment has been carried out according to the 
orthogonal central composite design. The planning ma-
trix comprising twenty-five experiments has been com-
posed in compliance with the selected method of experi-
 K.N. AFONIN, Y.V. RYAPOLOVA, ET AL. J. NANO- ELECTRON. PHYS. 7, 04029 (2015) 
 
 
04029-2 
ment. Every matrix row represents a combination of 
variable factor values: ultrasonic oscillation power Pus, 
tool (capillary) pressure F, bonding time t and tempera-
ture T. We have defined the variability intervals and cal-
culated the basic, upper and lower levels taking into ac-
count the recommendations given in the instruction man-
ual for device iBond5000, the known data on microbond-
ing and the results of preliminary experiments (Table 1). 
Three bonded seals have been performed for all bonding 
modes and thus three response functions have been taken. 
The electric power generated in the LED has been taken 
for the response function Y because one can estimate the 
CVC slope by its average value within the required range 
of direct current change. We have carried out the data 
statistical processing after their obtainment. We received 
a mathematical model of the examined process as a result 
of the data processing. The final model is presented in the 
form of the following formula: 
 
139.7657 18.9143 0.0155 0.0499Y P t P t          
 
This equation shows that the ultrasonic oscillation 
power has major impact on the response function. The 
voltage applied to the crystal and consequently the elec-
tric power increases as the ultrasonic oscillation power 
increases under the same current for different bonding 
modes.  
Our experiment confirmed the results given in the 
article [6]. Fig. 1 shows the experimentally measured 
crystal CVC before and after bonding under three groups 
of modes. The modes changing the CVC minimally but 
sufficient for the bonded seal formation have been de-
fined after estimating the ultrasound impact on CVC. 
 
 
 
Fig. 1 – Nitride crystal CVC in different bonding modes: 
mode 1 – ultrasound power 0,156 W, time 400 ms, clamping 
force 32 g; 
mode 2 – ultrasound power 0,455 W, time 400 ms, clamping 
force 32 g; 
mode 3 – ultrasound power 0,455 W, time 400 ms, clamping 
force 60 g. 
 
Table 1 – Variability intervals and levels 
 
Factor notation Рus(Х1), W F(Х2), g t(Х3), ms T(Х4), C 
Basic variability level 0,31 46 300 100 
Variability interval 0,15 14 100 15 
Upper level (+1) 0,46 60 400 115 
Lower level (-1) 0,16 32 200 85 
 
4. CONCLUSION 
 
The previously set objectives have been completely 
achieved as a result of the work done. The bonding mode 
impact on electric power generated in the LED has been 
researched with the help of orthogonal design. The ex-
periment result proves that the selected modes really 
influence on electric power. The electric power change 
results in LED CVC slope change. 
 
ACKNOWLEDGEMENTS 
 
This work has been supported financially by the 
Ministry of Education and Science of the Russian Fed-
eration in the framework of the project 
RFMEF157714X0061. 
 
 
 
 
REFERENCES 
 
1. E.F. Shubert, Light emitting diodes. Second edition (Cam-
bridge University Press: 2006). 
2. Julio Chaves, Fernando Munoz, Juan Carlos Minano, 
Pablo Benitez, Bill Parkyn, Waqidi Falicoff, Yupin Sun, 
Proc. SPIE 5529, 120 (2004). 
3. Y.S. Goncharova, I.F. Garipov, V.S. Soldatkin, Reports 
TUSUR No 2(28), 51 (2013). 
4. Y. Narukawa, M. Ichikawa, D. Sanga, M. Sano, T Mukai, 
J. Phys. D: Appl. Phys. 43, 354002 (2010). 
5. N.N. Bakin, E.F. Yauk, V.I. Tuev, 12th Int. Conf. Seminar 
on Micro/Nanotechnol. Electron Dev. (EDM’2011). 
6. R.H. Haitz, M.G. Craford, R.H. Wissman, Light-emitting 
diodes, www.accessengineeringlibrary.com. 
 
 


English

Application of Ultrasonic Bonding in Leds and Led Lamps Production

Electronic Sumy State University Institutional Repository

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ Vol. 7 No 4, 04029(2pp) (2015) Том 7 № 4, 04029(2cc) (2015)   2077-6772/2015/7(4)04029(2) 04029-1  2015 Sumy State University Short Communication  Application of Ultrasonic Bonding in Leds and Led Lamps Production  K.N. Afonin, Y.V. Ryapolova, V.S. Soldatkin, V.I. Tuev  Tomsk State University of Control Systems and Radio Electronics, 40, Lenin Ave., Tomsk, Russia  (Received 28 September; published online 10 December 2015)  This article presents the results of studies of the effect ultrasonic bonding on the current-voltage char-acteristic nitrides chips with using methods of planning the experiment.  Keywords: Nitride chip, Current-voltage characteristic of the LED, Ultrasonic microwelding, Planning eksperiment.   PACS number: 85.30.De   1. INTRODUCTION  As the LED energy efficiency is increasing, the number of their possible applications is growing. The promising field of great economic importance is the development of filamentary LED emitters that are the base for led lamps for home and industrial application [1]. Compared with filament and luminescent lamps they have such advantages as higher light efficiency and longer service life [2]. The service life of modern LEDs based on blue nitride crystals with luminophor can reach up to 60 thousand hours [3]. The technology to produce electrical bonding of crystal chip pins with the body elements during LED production is well-developed [4]. The problem of adjacent crystal chip pins of filamentary LED emitters bonding has not yet been completely solved. The study aim is to determine the filamentary LED emitter nitride crystal bonding modes that have the minimal impact on crystal degradation during their further service. The work aim provides the following objectives:  а) to research the microbonding method; b) to bond nitride crystal electrical contacts with the base contacts by different bonding modes; c) to estimate how the selected bonding modes in-fluence on the nitride crystal current-voltage character-istics (CVC). The bonding mode influence on the crystal degrada-tion during their further service is estimated by the CVC slope change. The article [4] shows that the poor quality bonding causes the CVC slope increase. The authors conclude that such a CVC change takes place because the impurities with breakdown paths occur in the semiconductor. Such localized areas have signifi-cantly higher conductivity than the areas with the bar-rier structure.  2. MICROWELDING METHOD REVIEW  Three main microbonding methods: thermal com-pression bonding (TCB), thermosonic bonding (TSB) and ultrasonic bonding (USB) as well as two types of bonded seal: "ball-wedge" and "wedge-wedge" are exam-ined in the study.  The simultaneous impact of temperature and pres-sure occurs when TCB is used. The bonding pad heats up to about 300 °C and consequently the metal ductility increases when the electrode contacts with the pad. USB occurs without additional heating. Ultrasonic en-ergy disrupts the crystal structure of metal and as a result it becomes deformed under low clamping force and temporarily becoming soft and ductile provides the bonding. TSB occurs under the simultaneous impact of temperature, pressure and ultrasonic oscillations. The operation area heats on average from 100 to 150 °C and bonded seal formation time lies within 20-200 ms. TSB is especially effective for wire bonding to the pads from different metals [5]. TSB and USB with the wire 20-75 microns in diame-ter are the most widely used methods to bond microcon-ductors. This is due to better capacity of these methods and operation area lower temperature in comparison with the TCB. We decided to use TSB with a ball for-mation at this stage. The obtained contacts are flexible and have high thermal and electrical conductivity and low direct-current resistance in contact with metal films. Wire diameter is 30 microns. We selected this size assuming that the bonded seal size should not exceed ¾ of the crystal bonding pad square (100 microns). The obtained ball size is approximately 2-3 wire diameters.  3. THE RESEARCH  The research has been carried out with the help of device iBond5000 Dual produced by Kulicke&Soffa. This device allows lead wire bonding both of "ball-wedge" and "wedge-wedge" types. We have performed the "ball-wedge" bonding for blue nitride crystals. The quality control of bonded seals has been carried out visually. The seals have been checked for cracks and delaminations.  It is important to select the optimum bonding mode for nitride crystals because ultrasound accelerates the nonradiative recombination appearance that results in a loss of up to 50 % of light flux after 10,000-15,000 service hours [5]. Therefore, the adequate mode shifts the re-combination processes to 25-30 thousand service hours and the crystal characteristics will suit the stated ones. The experiment has been carried out according to the orthogonal central composite design. The planning ma-trix comprising twenty-five experiments has been com-posed in compliance with the selected method of experi- K.N. AFONIN, Y.V. RYAPOLOVA, ET AL. J. NANO- ELECTRON. PHYS. 7, 04029 (2015)   04029-2 ment. Every matrix row represents a combination of variable factor values: ultrasonic oscillation power Pus, tool (capillary) pressure F, bonding time t and tempera-ture T. We have defined the variability intervals and cal-culated the basic, upper and lower levels taking into ac-count the recommendations given in the instruction man-ual for device iBond5000, the known data on microbond-ing and the results of preliminary experiments (Table 1). Three bonded seals have been performed for all bonding modes and thus three response functions have been taken. The electric power generated in the LED has been taken for the response function Y because one can estimate the CVC slope by its average value within the required range of direct current change. We have carried out the data statistical processing after their obtainment. We received a mathematical model of the examined process as a result of the data processing. The final model is presented in the form of the following formula:  139.7657 18.9143 0.0155 0.0499Y P t P t           This equation shows that the ultrasonic oscillation power has major impact on the response function. The voltage applied to the crystal and consequently the elec-tric power increases as the ultrasonic oscillation power increases under the same current for different bonding modes.  Our experiment confirmed the results given in the article [6]. Fig. 1 shows the experimentally measured crystal CVC before and after bonding under three groups of modes. The modes changing the CVC minimally but sufficient for the bonded seal formation have been de-fined after estimating the ultrasound impact on CVC.    Fig. 1 – Nitride crystal CVC in different bonding modes: mode 1 – ultrasound power 0,156 W, time 400 ms, clamping force 32 g; mode 2 – ultrasound power 0,455 W, time 400 ms, clamping force 32 g; mode 3 – ultrasound power 0,455 W, time 400 ms, clamping force 60 g.  Table 1 – Variability intervals and levels  Factor notation Рus(Х1), W F(Х2), g t(Х3), ms T(Х4), C Basic variability level 0,31 46 300 100 Variability interval 0,15 14 100 15 Upper level (+1) 0,46 60 400 115 Lower level (-1) 0,16 32 200 85  4. CONCLUSION  The previously set objectives have been completely achieved as a result of the work done. The bonding mode impact on electric power generated in the LED has been researched with the help of orthogonal design. The ex-periment result proves that the selected modes really influence on electric power. The electric power change results in LED CVC slope change.  ACKNOWLEDGEMENTS  This work has been supported financially by the Ministry of Education and Science of the Russian Fed-eration in the framework of the project RFMEF157714X0061.     REFERENCES  1. E.F. Shubert, Light emitting diodes. Second edition (Cam-bridge University Press: 2006). 2. Julio Chaves, Fernando Munoz, Juan Carlos Minano, Pablo Benitez, Bill Parkyn, Waqidi Falicoff, Yupin Sun, Proc. SPIE 5529, 120 (2004). 3. Y.S. Goncharova, I.F. Garipov, V.S. Soldatkin, Reports TUSUR No 2(28), 51 (2013). 4. Y. Narukawa, M. Ichikawa, D. Sanga, M. Sano, T Mukai, J. Phys. D: Appl. Phys. 43, 354002 (2010). 5. N.N. Bakin, E.F. Yauk, V.I. Tuev, 12th Int. Conf. Seminar on Micro/Nanotechnol. Electron Dev. (EDM’2011). 6. R.H. Haitz, M.G. Craford, R.H. Wissman, Light-emitting diodes, www.accessengineeringlibrary.com.   

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Application of Ultrasonic Bonding in Leds and Led Lamps Production

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