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Heller Industries Void Reduction

Technology Update

Presenter: Mr Joe Balackyi B.Eng Sales Manager

27th September 2017

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Heller Industries-Global Market Leader Solder Reflow & Epoxy Cure Systems

Electronic Assembly and Semiconductor Packaging

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Heller Industries Overview Company Founded: 1960

Employees: >325

Corporate Headquarters: Florham Park, NJ. USA

Manufacturing Operations ¬ Suwon Korea ¬ Shanghai China

Global Engineering ¬ 41 Engineers ¬ 4 Ph.D.’s ¬ 5 Masters Degrees

GLOCAL (Global/Local) Strategy & Support

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Heller Industries, Shanghai Heller USA (HQ)

Heller Industries, Korea

Our factories are located to best serve our customers

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New Factory in Suwon, Korea

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New Factory in Suwon, Korea

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REFLOW TECHNIQUES FOR VOID REDUCTION

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Why Reduce Voids?

Improve heat dissipation of components/solder joint to improve component life ¬ QFN Can tolerate high void % when subjected to simple temperature cycling

without live circuit Void reduction improves component longevity in case of thermal cycling plus

live circuit operation ¬ BGA BGA reliability generally not dependent on internal void % BGA reliability impacted by voids only when large voids located in path of

crack propagation ¬ Power Die/IGBT, LED Strong correlation between void %, component life, performance

¬ Conventional SMT components-Little compelling data

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Void Minimization with Conventional SMT Process

Alloy selection can be very significant

Flux formulations that evaporate earlier

Lower peak profile temperatures

Reduced solder paste deposition

Nitrogen modest impact

Stencil design pattern little impact

Pad metalization little impact

Previti, Creek, Holtzer, Hunsinger paper

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Ongoing Challenge

Voids can be reduced using conventional process levers, but….

Void % can vary outside of specs without obvious changes in process variables.

Customer fear of the unknown, lack of failure data

Vacuum reflow can greatly reduce voids and create a robust process with results well below void specs

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Vacuum Assisted Reflow

Vacuum-assisted reflow has been shown to reduce the voids in a solder joint by 99%

Pressure is dropped to 5-50 Torr (6.65 to 66.5mbar) during liquidus of the soldering process

Existing voids escape externally through the solder when vacuum is applied. ¬ Trapped gas bubbles increase in size as pressure is reduced ¬ Larger bubbles are more likely to collide with other bubbles and

ultimately collide with the edge of liquid solder to escape ¬ Larger bubbles are accelerated by stronger buoyancy forces

making them more likely to escape

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Vacuum Assisted Reflow

Pressure inside trapped gas bubble changes according to Young-Laplace Equation

Pbubble = Pambient + 2γ / r (where γ is surface tension and r is the radius of the bubble)

Bubble size is then determined by ideal gas law using Pbubble

Standard Reflow

Vacuum Assisted Reflow

Printed Solder Paste

Reflow Liquid Solder

Reflow Vacuum

Cooling Solid Solder

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Convection Reflow with Vacuum Module

Vacuum chamber is located between convection heating and cooling zones

Profile can peak before vacuum chamber or inside vacuum chamber (using IR heating)

Capable of extended or shortened liquidus timing

Capable of < 60 second cycle time

Dual lane available for faster cycle times

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Inline Vacuum Reflow System - Layout

Heat Zones Vacuum Chamber

Cooling Zones Op. Staging

Conveyor

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2156MK5 Vacuum 500mm Max Board Width

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Heller 2156 MK5-V

15 Heating Zones 4955mm Heating Length

4 Cooling Zones 1263mm Cooling

Length

Vacuum chamber for 500mm L X 450mm W board 8700 mm Total Length

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Vacuum Chamber Entrance

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Vacuum Chamber Exit

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Chamber Size

Width(mm)

0 100 200 300 400 600 700 Length (mm)350

350

500

500

P,Demo330X250

LED#1 320X450

300X300

100

200

300

400

300X250

300X100

LED#2 750X450

300X250

450X350

320X200

500X450 508X450300X100X4LANE

Eco Line 350X350

STD Line 500X450

Standard Line

Max Board Size 500L X 450W (750x450)

Min Board Size 150L X 100W

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EHC Assembly Inside Vacuum Chamber

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EHC and CBS Assembly Inside Vacuum Chamber

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Vacuum Chamber Details

Width ¬ Chamber Internal: 63 cm ¬ Max. EHC: 45 cm ¬ Min. EHC: 5 cm ¬ Max. Effective: 35 cm

Length: ¬ Chamber Internal: 59 cm ¬ Max. Effective: 35 cm

Notes: ¬ Effective dimensions are based on effective area

of IR panel inside chamber. ¬ Images show model with side-chain mesh belt

conveyor. Final product will be with EHC.

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In-Chamber IR Panel Details

5-zone IR panel

Balance temperature across products of all sizes

Direct control over zone setpoints on main control screen

PLC controlled to precisely center all products under panel

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Profile settings

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Heller Advanced Vacuum Pump Clean oil-free design

Compact footprint

Internally heated to avoid flux condensation

High capacity: 650m3/hr

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Pump Profile Controls

Heller Vacuum Ovens

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Pump Control Systems All pump-down control is handled by in-line high-speed

butterfly valve with built-in control algorithms ¬ Slow Pump Algorithm Direct control of pump-down rate in Torr / Second Set by user

¬ Slow Start Algorithm Allows reduction of valve speed during initial opening Set by user

Multi-Settings ¬ Both slow pump and slow start features can be set to multiple

values throughout pumping curve ¬ Allows for fully customizable pumping curve

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Slow Pump – Single Setting Example

0

100

200

300

400

500

600

700

800

0 1 2 3 4 5 6 7 8

Pres

sure

(Tor

r)

Time (sec)

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Slow Pump – Multi-settings Example

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12

Pres

sure

(Tor

r)

Time (sec)

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Slow Start Example

0

100

200

300

400

500

600

700

800

0 1 2 3 4 5 6 7 8

Pres

sure

(Tor

r)

Time (sec)

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Return to Atmosphere Return to Atmosphere control is performed by a Nitrogen

gas supply return to the vacuum chamber ¬ Optional control is available via with the high-speed butterfly valve

to the pump. N2 Gas supply along with the butterfly valve allows for controlled return to atmosphere pressure

Nitrogen Gas Supplied to the Vacuum Chamber ¬ Nitrogen gas supplied to the Vacuum Chamber to initiate product

cooling ¬ Optional, Nitrogen gas supply can be heated prior to the vacuum

chamber.

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Dual Lane EHC and EHC with CBS

175mm Max 175mm Max 450mm Max

Dual Lane EHC EHC with CBS

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Vacuum Cycle Chart – Optimized Cycle

0 10 20 30 40

Full Vacuum System Cycle Timing (in Seconds)

Transport into Vacuum Chamber Doors Close Pump Down Dwell @ Vacuum Repressurize Doors Open

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Vacuum Cycle – Set Values & Variables

Variables Transport Time

¬ Depends on product & final system dimensions

¬ Variable speed conveyor

Pump-down Time ¬ Slowed to reduce solder

splatter ¬ Computer Controlled 5 steps ramp and dwell Torr / second value,

Set Values Doors Opening & Closing

¬ ~ 2 Seconds ¬ Slow speed to reduce

vibration

Re-pressurize ¬ ~ 5 Seconds ¬ 2 flow rates to reduce

chance of disturbing components. Initial flow rate is slow, second flow rate higher

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Reflow Profile with Vacuum

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Vacuum Reflow Process Issues

Machine length greater with vacuum ¬ Board spacing must be > cycle time, typically < 50% oven utilization ¬ Machine length must be long for High belt speed 3 minutes to peak Short transport/cycle time.

Liquidus time flexibility ¬ Longer liquidus required for power die bonding, peak before vacuum ¬ Shorter liquidus for SMT with profile peak in vacuum using multi zone

IR panel

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Vacuum Reflow Process Issues

Solder splatter ¬ Controlled pressure drop, chamber re-fill minimizes solder splatter

when void escapes solder joint ¬ Profile peak in vacuum chamber reduces flux explosion

Flux splatter ¬ Controlled pressure drop minimizes flux splatter

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Vacuum Features/Benefits

High Capacity Vacuum Pump for short cycle times, large chambers

Vacuum control valve for slow pump-down, refill

Flux trap to minimize vacuum pump maintenance

Features vs. Cost tradeoff

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Vacuum Control and Refill

Flux Trap

Dual stage vacuum refill

Intelligent Vacuum Control Valve

Vacuum Pressure Sensor

Integrated refill diffuser

Intelligent vacuum control valve and sensor for precise vacuum process control

Integrated refill diffuser and dual stage refill for rapid and smooth chamber refill

Flux trap for flux filtration and pump protection

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Oerlikon Solvent Flush Kit

Solvent Flush Kit is recommended by Oerlikon US.

Two methods are proposed ¬ Manual ¬ Automatic

Flux Cleaner will be used.

Manual Flush Kit

Automatic Flush Kit

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Vacuum Assisted Reflow Customer Test

March 2013

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Test Conditions

Sample # Vacuum Level [torr]

Dwell Time [sec] Oxygen [PPM] Remark

1 5 30 400 2 5 120 400 3 10 30 400 4 10 60 400 5 20 30 400 6 20 60 400 7 Atmospheric - 400 8 5 15 400

Die size = 7, 10mm square

Liquidus peak = 250oC

Alloy type SAC 305 (217oC Melt Point)

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Test Results

Void Ratio(Worst Case), [%]

Sample Vacuum Level

[torr] Dwell Time

[sec] Worst Case

[%]

1 5 30 0.21

2 5 120 0.39

3 10 30 0.36

4 10 60 0.26

5 20 30 0.20

6 20 60 0.47

7 Atmospheric - 7.64

8 5 15 0.48

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Test #7 Details-No Vacuum

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Test #1 w/ 5 Torr for 30 seconds 0.21% worst case voids

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Thank You