3. Waste electronic appliances
A large amount of waste electronic devices is disposed as life cycle of the
products is growing shorter.
Printed circuit boards assembly(PCBA) has various valuable metals so they are
becoming driving force as key resources of recycling industry.
Necessity of PCBAs recycling
Economic reason: ECs consist of novel metals such as Au and Ag, rare metals
such as Se, Ge and Te,
Environmental reason: they contain toxic metals like Pb and As
For both economic and environmental reasons, ECs disassembly should be
followed prior to printed circuit board recycling
Background
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4. Concept of PCBA disassembly
Background
PCBA
Refining
Metal
PCBs ECs
SeparationGrinding/separation
Metal Metal
Disassembly
Non-metal
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5. “Look and picks” Principle
The components on the boards are
identified by powerful real-time
recognition system, and disassembled
step by step according to their
connection or components types.
The components can be recovered
without damage on them enough to be
reused, the principle itself needs very
high technology system that inevitably
leads to high cost, as well as the
processing speed is too slow to applied
for mass production
Previous studies
PCBA
PCB
“Look and picks”
IC Chip
Capacitors
MLCC
CPU
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6. Previous studies
PCB ECs
“Evacuate and sort”
MLCCCapacitorCPUIC chip
“Evacuate and sort” Principle
regardless of the components type, the
components are simultaneously wiped off,
and subsequent separations, such as
magnetic separation, electrostatic
separation are followed for sorting the
components
possibly can harm the components.
the facility is simpler and more applicable
to large scale.
PCBA
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7. Disassembly apparatus
Previous studies
Fig. 1. Various types of disassembly apparatus in previous studies
(a) S. Yokoyama et al., 『Recycling of Printed Wiring Boards Mounted Electronic Components』, 1997
(b) Huang Haihong et al., 『Study on Disassembling Approaches of Electronic Components Mounted on PCBs』, 2007
(c) Lee et al., 『Disassembly and physical separation of electric electronic components layered in printed circuit boards (PCB)』, 2012
PCBs type Principal points
Detach ECs
on both sides
Regardless of
connection
type
Less powder
and loss
Continuous
process
PCBs from personal computers IR heater, impact/shearing propeller O X O X
- Liquid heating and ultrasonic O O O X
PCBs from VCR To grind solder and displace ECs X O X X
Table 1. Comparison of previous studies about PCBA disassembly
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(a) (b) (c)
8. Four main objectives
to detach the components on both sides of PCB
to detach ECs regardless of their connection types
to minimize generation of powder and loss
to be applied for continuous process
Principal mechanism
‘Evacuate and sort’ type apparatus
chose infrared heater to melt solder to disassemble ECs from boards
the apparatus is designed to employ the horizontal impact force mainly.
Objectives
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9. Experiment
Fig. 2. Printed Circuit Board Assembly used in this study
Waste printed circuit board assembly
Laptop printed circuit board assemblies made by various manufacturers
manually separated from the laptop
populated with many different electronic components
72 pieces of those board assemblies were used.
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10. M M
2
1
4
3
57
8
10 11
12
9
PCBA in
6
13
15
16
17
18
14
PCBA in
(a) (b)
Fig. 3. Electronic components disassembly apparatus used in this study (patent pending, the application number : KR10-2012-0065933): (a)
Structure of disassembly apparatus, 1. Control Panel (controllable factors: rotating speed of feeding rod, rotating speed of steel brush,
heating temperature), 2. PCBA, 3. Feed hopper, 4. Feeding rod, 5. Steel brush, 6. IR heater, 7, 8. Trapezoidal change gear, 9. Product
hopper, 10. Basket, 11, 12. Motors. (b) detailed diagram of disassembly module. 13. PCBA, 14. Feed hopper, 15. Feeding rod, 16. Steel
brush, 17. IR heater, 18. Product hopper.
Experiment
Disassembly apparatus
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11. Experiment
Disassembly evaluation
the heating temperature of IR heater was varied from 200°C to 275°C
rotating speed of feeding rod was varied from 1RPM to 9RPM
6 PCBs were tested at each condition and arithmetic mean of disassembly
efficiency was calculated
ECs removal efficiency (%) =
𝑊1−𝑊2
𝑊1−𝑊3
× 100
Where, W1: weight of PCB with ECs populated
W2: weight of PCB after the processed by the apparatus
W3: weight of PCB without any ECs
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12. Disassembly time
The disassembly time is defined as followed:
𝑡0: the time when a PCBA is fed into the module
𝑡𝑓: the time when a PCBA is removed from the
module
Disassembly time ∆𝑡 = 𝑡𝑓 − 𝑡0
Disassembly time was measured varying the
number of processed PCBAs
The regression equation of disassembly time under
the optimum condition was calculated
Experiment
𝑡 = 𝑡0
𝑡 = 𝑡𝑓
∆𝑡=𝑡𝑓−𝑡0
Disassembly
Module
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13. Connection Electronic components and their frequencies1
Type Figure CPU/GPU IC chip Oscillator
Copper
coil
Capacitor Card slot Ports
Cooling
Fan
Sub
PCB
SMT ++ +++ ++ ++ +++ ++ - - -
TMT - - - - + - ++ - -
Screw
joint
- - - - - + - + -
Rivet - - - - - - + - -
Socket
pedestal
- - - - - + - - +
1+++: Very frequently appeared, more than several tens per board and/or always expected to be appeared
++: Usually appeared, more or less than ten per board and/or always expected to be appeared
+: Rarely appeared, less than five per board and/or usually not appeared
-: Seldom appeared
Table 2. Various types of ECs on laptop PCBA and their frequencies based on connection types
Results and discussion
Laptop PCBA and their ECs
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14. Results and discussion
Laptop PCBA and their ECs
As the electronic devices need higher packaging density, the ECs are getting
smaller and SMT (surface mounting technology) is replacing THT (through-hole
technology)
The SMT makes it possible to mount ECs on both sides of PCB
It is important to scrape both sides of PCBs spontaneously for time efficiency.
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15. Results and discussion
Fig. 4. Electronic component removal efficiency under different
feeder rotating speeds and heating temperatures: (a)
1RPM, (b) 3RPM, (c) 6RPM and (d) 9RPM. Error bars at
each bar indicate standard deviations of measured
removal efficiency (unit: %). At feeder rotating speed of
1RPM, the highest ECs removal efficiency was
accomplished due to sufficient time to melt the solder.
The temperature of 250℃ was high enough to achieve
removal efficiency of 90%
Electronic component removal efficiency under different
conditions
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16. Results and discussion
Electronic component removal efficiency under different
conditions
At the rotating speed faster than 6RPM, the removal efficiency was less than
20 %, As the rotating speed slower than 3RPM, the efficiency becomes
significantly higher.
At the rotating speed of 1RPM and temperature of 250°C, the efficiency is
maximized at 93.92%.
The most common kinds of solder used in electronic appliances are Sn-Pb solder
and Sn-Ag-Cu solder (lead free).
Their melting points rage are around 180-190°C and 170-180°C, respectively,
though they vary with chemical proportion of solder
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17. Results and discussion
PCBAs before and after the process
Fig. 5. Printed circuit board before and after the process (front side)
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18. Results and discussion
PCBAs before and after the process
Fig. 6. Printed circuit board before and after the process (back side)
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19. Results and discussion
PCBAs before and after the process
Fig. 7. A sample of laptop printed circuit boards and electronic components before and after the disassembly process(feeder rotating speed:
1RPM, temperature: 250 oC). (a) slot (SMT), (b) IC chips and condensers (SMT), (c) copper coil and condensers (SMT), (d) ports (THT)
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20. Results and discussion
PCBAs before and after the process
When the temperature rises above the melting point of solder, the components are
easy to be detached from boards
All SMT components are completely removed from the board.
most of the connection between boards and components(CPU/GPU, IC chip,
oscillator, etc.) are SMT
These components have vast majority of valuable metals, so it is necessary to
disassemble these kinds of components effectively
Components connected with other types are also removed well
The crushing (and also feeding) rods do such function that they loosen the
connection between board and the component attached by rivet or screw joint
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21. Weight and weight percentage of disassembly process
products
weight and weight fraction of PCBA and disassembled PCBA parts under the
optimum condition
sample number was 12 EA
generation of loss and abrasion powder is less than 5% which is three times lower
than precedent research of 15%
Results and discussion
PCBA PCB ECs Powder loss
Weight (g) 193.65 87.73 99.5 4.29 2.13
wt.% 100 45.30 51.38 2.22 1.10
Table 3. Weight and weight fraction of disassembly process products
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22. Results and discussion
Fig. 8. Electronic components disassembly time (feeding road
rotating speed: 1RPM). Red line indicates the total removal
time and blue line indicates the average removal time to
process number of boards.
Electronic component dissembly time
𝑡 = 57.75 +
76.38
𝑛
where,
t: average removal time(sec)
n: number of boards
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23. Results and discussion
Electronic component dissembly time
The time was measured in seconds by measuring PCB passing time in the
apparatus and calculating the arithmetic mean of 3 results.
Because it is designed to be continuous process, the next PCB can be put into the
apparatus before the first PCB comes out
the more PCBs are put in, the shorter is the average removal time
This significantly shortens the processing time and is a great advantage to be
applied to massive scale
In about 130 seconds, 1 PCB completely passed the apparatus. For 5 PCBs, the
average removal time was about 70 seconds
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24. Conclusion
The PCB disassembly apparatus was developed and its
performance test was carried out.
The ECs on both sides of Notebook PCBs were scraped regardless their
connection type
The disassembly efficiency of higher than 93% was achieved.
(feeder speed: 1RPM, temperature: 250°C)
The average disassembly time was up to 70 seconds at the feeder’s rotating speed
of 1RPM.
The following further studies are needed:
1) Application on other types of PCBAs (mobile phone, PC, etc.)
2) Application on larger scale capacity
3) Economic analysis of PCB disassembly
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27. Previous studies
K. Feldmann, et al., 『Disassembly of electronic products』, 1994
Presented a significant overview of disassembly technology of printed circuit
board assemblies in waste electronic product.
provided the clear types of connections on boards such as SMT, TMT, screw joint,
etc. as well as comparison of transmission methods for desoldering.
classified the disassembly principles into “Look and picks” and “Evacuate and
sort”
Jianzhi, Li, et al., 『Printed Circuit Board Recycling: A State-of-the-Art
Survey』, 2004
gave an excellent overview of principles and case studies of disassembly
processes
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