Semiconductor Packaging for High Power Diode Lasers

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Requirements

ƒ ƒ ƒ ƒ

High volume Cost efficient Reliable Innovative

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Considerations

ƒ Mechanical different materials with distinct properties at different conditions (-40°C…+125°C)

ƒ Electrical high current at low voltage or internal conversion

ƒ Optical high intensity light source needs low/zero absorption materials

ƒ Economical the concept must work and must be affordable

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Examples

ƒ Smart laser. pulse laser for peak pulses up to P=100W with internal driver circuit

ƒ ACC - pulse laser module pulse laser-bar with 12 channels on PCB for SMT packaging

ƒ Sirilas® cw-laser module on TO263 lead-frame technology

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Smart laser package: ƒ ƒ ƒ ƒ

High current High peak optical load Current / voltage conversion Mass production

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Smart laser – general performance

Pw = 50 ns 100

ν = 1 kHz

P [W]

50A

50 -25

25

75

125

T [°C]

h 80 W @ 100° C ambient temp. h hardly any degradation at high power level and high temperature

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Popt_det [%] .

75

110 100 90 80 70 0

250

500 time [h]

750 1000

Smart laser - components

ƒ Lead frame

ƒ Laser chip ƒ Capacitors ƒ FET

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Smart laser - die bonding

Laser die Capacitor for charge acc FET Capacitor for charge acc

Die bonding: - standard process, - uses often conductive glue - high throughput and highly automized 04.07.2006 Seite: 8

Smart laser - wire bonding

Laser die Capacitor for charge acc FET Capacitor for charge acc

Wire bonding: - standard process, - using Alu or Au wire - high throughput 04.07.2006 Seite: 9

Smart laser - casting

Lead frame after die and wire bonding Casting form filled with resin

Casting: Resin needs to grant: protection against mechanical forces against humidity against solvents while offering good light output and good stability at all temperatures without damaging device and package 04.07.2006 Seite: 10

Smart laser - singulation and testing LL90_3 3 samples, Lot 01-17-01, 30ns, 1kHz, 25°C

Finished package after casting

80 70 1

Optical Power, W

60 50

2

40 3

30 20 10 0 0

5

10

15

20

ChargeVoltage, V 04.07.2006 Seite: 11

25

Singulation (after casting) and testing. Depicted is a measurement that shows that is operated at high voltage 30 the laser 35

Package for pulse laser array: ƒ ƒ ƒ ƒ

High current High optical load Multiple channel Automotive qualification

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Application: Laser range finder Peak-Power [W ]

120

3

80 2

40

1 0 0

Detects distance and velocity relative to the car driving ahead ⇒ Enables automatic Save Distance control ⇒ Range 100 - 200 m

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10

20 30 current [A]

40

50

ACC Pulse Laser Arrays: die bonding

PCB panel for easy handling and parallel processing. Offers platform during assembly and operation.

NTC for temperature control. Assembly using conductive glue. Wide position tolerances. Simple process.

Submount assembly using conductive glue. Very large die (1mm x 5mm) and therefore difficult handling. Medium requirements for placement accuracy.

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ACC Pulse Laser Arrays: wire bonding Die bonding laser bars difficult since sensitive, large chip has to be placed with excellent accuracy for proper fit to external optics.

Wire bonding: Standard process in BE production BUT: - bonding on emitter – risk of damage of die (cratering) - many channels – need to avoid cross talk and s.c. - only one wire / emitter – high current (50A / 50µmØ) 04.07.2006 Seite: 15

ACC Pulse Laser Arrays: housing and separation Housing assembly: Gluing PCB to housing. Risc of damaging die or wire bonds. Punching of PCB for separation of individual units out of frame. Risc of bending PCB and loosing glue interface

Tracing: For later reference, all samples must be traceable. Therefore logistic drops in at this working step.

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Fit housing – PCB: Tight fit requires tight specifications and tight manufacturing specs for housing and PCB mechanical interfaces: Holes in PCB and posts in housing

Package for CW Laser: ƒ High heat load ƒ High current ƒ High optical load

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Application: Hardening 2 x 1.5 kW 99% availability

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Package Concepts MCC individual pieces Laser bar

Sirilas ® volume concept

water in/out lets

Laser bar – 16 emitter Gold Wires

α matched Heatsink

Mechanical fixture

FAC lens 04.07.2006 Seite: 19

Interfaces : Current, heat, light Optical output power: up to 30W cw NA < 0.1

Thermal load: 40 to 50 W Rth ≈ 0,6 K/W

Drive current: 35 .. 40 A @ 2 V

Water cooling

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Package Technology

Laserbar Heatsink

High temperature premold TO263 type leadframe

Cylindrical lens

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Optical properties: collimated beam Raytrace simulation

Laser source

Cylindrical Lens

Window

Need to offer good beam quality and to avoid waste heating of package. 04.07.2006 Seite: 22

Assembly: die and wire bonding Die bonding: After wire bonding and lens assembly

Laser bar

Wire bonding:

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lens

• ITH = 8.4 A

2,4

60

2

50

1,6

40

1,2

30

0,8

20

0,4

10

• η = 1.28 W/A Voltage / V

• RS = 4,4 mΩ

6.4mm Laser bar @ 50 W opt power: • IOP = 48,5 A

0

• UOP = 1.81 V

0 0

• WPE = 58.6 %

10

20

30

Current, A

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40

50

Power / W; WPE / %

L-I-V characteristics

Reliability: Intermittent CW Wear out failures ( Degradation ) Random failures with. open contact

t50% = 62 MShot not seen yet

1,2

Popt [norm.]

1,0 0,8 0,6 0,4 0,2 0,0 0,0

4,0

8,0

12,0

16,0

20,0

24,0

28,0

32,0

MShot

Using hard solder and CTE matched submount reduces stress and allows for excellent reliability. Up to now, no spontaneous failure. 04.07.2006 Seite: 25

40,0 I36,0 =0A..36A op

Summary

ƒ Diode lasers are used for many distinct applications (sensing, illumination, direct application…) ƒ They operate in a very wide range of environmental conditions (-40°C….+125°C, humidity, …) ƒ Different kind of packages have been developed (high volume, highly specialized, optics, SMT….) for optimal use of die capabilties.

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