Vacuum-assisted Sintering in Mass Production: Challenges ... · • New application and training...

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1 19.10.2017 PINK GmbH Thermosysteme Vacuum-assisted Sintering in Mass Production: Challenges and Solutions

Transcript of Vacuum-assisted Sintering in Mass Production: Challenges ... · • New application and training...

Page 1: Vacuum-assisted Sintering in Mass Production: Challenges ... · • New application and training center: Opening 2018 General information New Building. Aaron Hutzler 19.10.2017 3

119.10.2017

PINK GmbH Thermosysteme

Vacuum-assisted Sintering in Mass Production: Challenges and Solutions

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219.10.2017Aaron Hutzler

PINK GmbH Thermosysteme

• Founded by Friedrich Pink in 1979

• Managed by his daughter Andrea Althaus

• Located in Wertheim am Main (near Frankfurt)

• Currently 130 employees

• Four fields of competence:

– Soldering Technology

– Sintering Technology

– Drying Technology

– Plasma Technology

• All product ranges depend on vacuum technology

• Affiliated company: PINK GmbH Vakuumtechnik (since 1986)

• International subsidiary: PINK Japan K.K. (since 2015)

• New application and training center: Opening 2018

General information

New Building

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Vacuum-assisted Sintering

1. Motivation for vacuum-assisted sintering

2. Case study: vacuum-assisted sintering vs. sintering on air

3. Challenges of vacuum-assisted sintering in mass production

4. Solutions for series production

5. Conclusion

Content

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Vacuum-assisted Sintering

• Sintering causes higher costs compared to soft soldering

– Sinter pastes are more expensive then soldering pastes

– New equipment is necessary: drying, pick&place, sintering press, quality inspection

– New power module design + qualification

• Cost reduction is only possible for the complete power electronic system

– Reduction of semiconductor area at same power (amps per Euro)

– Increase of maximum junction-temperature

– Reduction of cooling effort, design space and weight

– Increase of lifetime and reliability

• It is only worthwhile to invest in sintering, if the complete system is considered!

1. Motivation for sintering

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Vacuum-assisted Sintering

• Vacuum technology / controlled atmospheres ensure a high process stability and yield

– Controlled removal of paste residues

– No oxidation of surfaces

– No contamination with sulfur

– Controlled moisture within the chamber

• Cost reduction is only possible for the complete assembly line

– Higher yield at the sintering process compared to standard processes on air

– Lower deviation of reliability properties (e.g. shear force, porosity)

– Higher yield at following processes (e.g. wire bonding or molding)

• It is only worthwhile to invest in the vacuum technology, if the complete line, process

stability and yield is considered!

1. Motivation for vacuum-assisted sintering

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Vacuum-assisted Sintering

• Material used

– Silver sinter paste for direct contact to copper

– 4 mm x 4 mm chips

– DBC Al2O3 ceramic

• Sintering parameters

– Atmospheres: air, N2 and vacuum

– 12 samples per atmosphere

– 10 MPa pressure

– 2 min and 250 °C

• Shear tests for every group

2. Case study: die shear strength after sintering with different atmospheres

Figure 1: Sample DBC used for

sintering

Figure 2: Shear testing machine with sample DBC

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Vacuum-assisted Sintering

2. Case study: die shear strength after sintering with different atmospheres

Shear values of sintered dies at 10 MPa

• Under air showed a high standard deviation and a low a

mean

• Under vacuum showed a low standard deviation and a

significantly higher mean

• Under N2 showed la low standard deviation and the

highest mean

N2VacuumAir

60

50

40

30

20

10

Sh

ear

valu

es

in M

Pa

MPa

27

MPa

45 MPa

48

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Sintering on bare copper under air

• Oxygen penetrates through the sinter layer

• Oxidization of Cu surfaces

Explanation for high deviation for shear values under air

• Depending on the oxidation penetration

• Deviation of printing and pick&place processes

Explanation for the lower shear values

• Oxygen penetrates through the paste to DBC surface

• Less bonding strength due to Cu oxides

2. Case study: root-cause of lower die shear values on air

Figure 2: DBC Cu surface after die

shear - sintering under N2

Figure 1: DBC Cu surface after die

shear – sintering under air

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• Variation of sintering parameters

– Temperature: 230 °C, 250 °C, 270 °C

– Pressure: 10 MPa, 20 MPa, 30 MPa

– Time: 60s, 120s, 180s

– Atmosphere: N2, vacuum

• For N2 sintering

– Flooding with N2 to 950 mbar again

– Oxygen content: 50-100 ppm

• For vacuum sintering

– Chamber pressure at 5 mbar

2. Case study: Influence of sintering parameters under different atmospheres

Sintering Pressure

Chamber Pressure

0

200

400

600

800

1000

0

5

10

15

20

25

30

0 60 120 180 240 300 360

Ch

am

be

r P

ressu

re in

mb

ar

Sin

tering P

ress

ur

in M

Pa

Time in s

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• Results of shear values under

N2 sintering

– Temperature and time

have a huge impact

– Pressure has a low impact

2. Case study: Influence of sintering parameters under different atmospheres

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• Results of shear values under

vacuum sintering

– Temperature still has a

huge impact

– Pressure has a higher

impact

– Time has no impact

2. Case study: Influence of sintering parameters under different atmospheres

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Root-cause for sintering results under vacuum

• For this study a atmospheric pressure of 5 mbar was used

• Vacuum affects two kinds of mechanisms, that either improve or impede the sintering reaction

2. Case study: Influence of sintering parameters under different atmospheres

• Impeding the sintering reaction:

– Vapor-condensation

• Improving the sintering reaction:

– Grain boundary diffusion

– Volume diffusion

– Plastic deformation

– Creep deformation

Sintering reaction

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• Sintering under controlled atmospheres

– Can significantly increase shear values

– Can significantly lower standard deviation with the production

– Can improve the stability of the following production processes

• Vacuum has to be used at the right pressure and time to achieve good results

• Vacuum technology achieves highest occupational health and safety conditions

2. Conclusion of case study

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To get economically solutions with vacuum-assisted soldering the production must fulfil many requirement:

• Many devices per sintering run

• Short cycle time

• Stable and safe process

• Highest yield

• Low maintenance downtime

3. Challenges of vacuum-assisted sintering in mass production

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PINK solutions for vacuum-assisted sintering:

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4. Sintering system SIN200: All key facts for a successful mass production

To achieve a high throughput:

• Pressing force: up to 2.000 kN (200 tons)

• Top and bottom side stamp can be pre-heated up to 350 °C

To ensure highest yield and a reliable process:

• Exact control of inherent gas atmosphere (N2, N2/H2, HCOOH)

• Continuous high resolution force- and distance measurements enable closed-loop control

To be flexible for different products and layouts

• Press tools are exchangeable and can be customized in all needs

• Standard sintering tool available with process area: ≤280 mm diameter (61575 mm2)

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4. Sintering system SIN200: Modular design with flexible expandability

SIN200

stand-alone

SIN200+

Cooling module

SIN200+

Preheating module

Cooling module

SIN200+

Reduction module

Cooling module

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4. Foil handling concepts: Pick&place

Before entering the machine:

Foil will be placed

After the sintering process:

Foil will be removed

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4. Sintering system SIN200: Foil handling by pick&place

To ensure a stable process:

• Foil handling out of „hot zone“

• Constant foil temperature

• Separated foil handling and sintering process

• High occupational safety

To ensure highest throughput at lowest costs:

• Mounting/re-filling without downtime

• Efficiency: no waste of foil

• Foil can be re-used

• 100% traceability

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• Fully automated handling

• Robot station incl. lift station +

underfloor return

• Reloading from/to magazine by

robot is possible

Vacuum-assisted Sintering

4. Sintering system SIN200: Automation concepts for series production

Loading station with

robot handling and

integrated lift station

Underfloor return Unloading station with

robot handling and

integrated lift station

Direction of

carrier movement

Sintering Cooling

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4. Sintering system SIN200: Software and visualization by PINK

• Fully developed and maintained In-house

• Customer specific functions and layout are possible

• Real-time indication of process parameters

• Create, adapt, save and organize recipes

• View live and trend data of all sensors

• Export diagrams to Excel

• Manual control of the whole machine

• Adapt machine parameters and settings

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4. Example of silver sintering in series production: PINK and Infotech

Reload-station: Magazine into

carrier

Pick&place with temperature and pressureIGBT + Diode

Reload into PINK carrier

Foil handling Foil handling

Reload into magazine

Pre-heating Sintering Cooling

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• Services

– Customer demonstrations

– Feasibility studies

– Machine capability studies

– Prototype assembly

– Process development

– Process training

– Research- and development work

• Opening of the new application- and training center in a

few weeks

5. Application by PINK

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• Before purchase order

– Consulting during the design phase

– Development of a concept for series production

– Design of experiments, assembly of samples and evaluation of throughput and quality

– Analyzation and preparation of necessary machine modifications together with the

customer

• After purchase order

– Assembly of further samples for the next qualification phase

– Characterization and reliability testing of sintering tools

– Continuous improvement of soldering parameters and soldering jigs / fixtures

• After delivery of customized soldering machine

– Fine tuning of the soldering process

– Training of customers’ engineers and technicians

– Continuous support by PINK application and service team

5. PINK – your partner for continuous support for soldering applications

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Vacuum Soldering TechnologyPINK GmbH Thermosysteme

Contact

PINK GmbH Thermosysteme

Aaron Hutzler

Head of Application

Am Kessler 6

97877 Wertheim

Germany

Tel.: +49 (0)9342 / 919 - 0

eMail: [email protected]

www.pink.de