2013년도 춘계 한국자원리싸이클링학회 학술발표 (비금속 분야)

전자부품이 실장된 폐소형가전

인쇄회로기판의 부품분리 특성

한양대학교 자원환경처리연구실

박승수, 김성민, 문 향, 한성수, 한요셉, 박재구

Contents

Background

Previous studies

Objectives

Experiment

Results and discussion

Conclusion

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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Concept of PCBA disassembly

Background

PCBA

Refining

Metal

PCBs ECs

SeparationGrinding/separation

Metal Metal

Disassembly

Non-metal4/25

“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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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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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 pointsDetach 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)

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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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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M M

21

4

3

578

10 11

12

9

PCBA in

6

13

15

1617

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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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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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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Connection Electronic components and their frequencies1

Type Figure CPU/GPU IC chip OscillatorCopper

coilCapacitor 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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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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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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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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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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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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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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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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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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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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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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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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Thank you!

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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