1. ASSCON Vapor Phase Soldering Physical principle Vacuum soldering
ASSCON Systemtechnik GmbH Messerschmittring Königsbrunn –

2. Benefits of ASSCON Vapour Phase Soldering
Final temperature of all components exactly defined by temperature of the vapour, lowest possible delta T (app. 1°C)
Overheating of components, delamination etc. is impossible
Heating of components is independent of shape, colour, mass and mass arrangement
100% oxidation free solder process without using inert gas
Infinitely variable programming of all kind of profiles (linear/step profile)
Profile control via TC sensor. Automatic profile adjustment. Alarm if process runs out of acceptable limits. Limits are freely programmable
Lowest possible peak temperatures. Lead free final temperature only 230°C
Void free soldering due to multivacuum technique
Lowest risk of damage compared to all other soldering technologies
Green technology due to the high efficency and low power consumption

3. Heat transfer media (GALDEN)
PERFLOUROPOLYETHER
consist of carbon, fluorine and oxygen
are liquid polymeres
most stable linkages regarding the carbon chemistry
Fluorine atoms protect the carbon structure from chemical and thermal attacks
ASSCON exclusively uses high boiling Perflouropolyether by SOLVAY with the trademark „GALDEN“
Other GALDEN applications:
Lubricants for vacuum and high temperature applications
Building protection agent
Seperation agent
Test liquid for Burn-in-Test and other Semicon applications
Basic substance for ointment and cosmetics
Coolant for high speed computer
Blood replacement substance
Oxygen transfer medium for deep sea divers

4. Properties of GALDEN High resistance to temperature
Best material compatibility
High resistance to reactive chemicals
Good dielectric properties
Low vapour pressure
No flash point
High vapour density
Excellent heat transfer coefficient
Low surface tension
No health & safety problems or special protection of operators and other staff required
No chemical activity
No potential for ozone damage
-> The use of GALDEN is absolutely safe

5. Steps of a Vapour Phase Soldering Process
Galden
heater
cooling
230°C
Galden
heater
cooling
Vapour
230°C
Starting the vapour generator (heaters)
Galden is warming up
Maximum liquid temperature is limited by the boiling point (physical law)
Further energy transfer is causing vapour production
A vapour zone is generated over the liquid layer
Vapour temperature is equal to the boiling temperature of liquid
Machine is ready to operate

6. Steps of a Vapour Phase Soldering Process
Thermocouple for auto profiling and profile control
Galden
heater
cooling
Vapour
Galden
heater
cooling
Thermocouple for auto profiling and profile control
Cold assembly is slowly entering the vapour zone down to soldering position
Vapour is condensing, vapour level stabilises near to the product soldering level
Condensed vapour forms a layer of liquid
Liquid covers PCB hermetically - zero oxidation
Energy is transfered via the liquid layer to the PCB surface. Assembly is warming up
PCB assembly temperature is ambient room temperature
Assembly is placed over the vapour zone

7. Steps of a Vapour Phase Soldering Process
Galden
heater
cooling
Galden
heater
cooling
Vapour
Thermocouple for auto profiling and profile control
Finally assembly´s temperature reaches vapour temperature
Condensation rate is going down
Vapour level is rising up again
End of condensation is monitored via Thermocouple (ASB)
PCB stays in vapour until time for parameter DTH (delay time heating) is up. DTH secures the correcttime over liquidus.
Time over liquidus is expired, assembly is transported out of vapour zone
Liquid evapourates immediately from the hot surface of the assembly
Assembly is transfered into the cooling zone
Effective cooling of the assembly with forced convection

8. Profiling (TGC Temperature gradient controlling)
Temperature gradient defines how much vapour is condensing in a certain period of time. The volume of condensing vapour is freely programmable (ETR - energy transfer rate)
The requested temperature gradient is infinitely adjustable by condensing more or less vapour molecules onto the board surface (comparable to an acceleration or deceleration with the throttle pedal in a car)
Linear or ramp profiles are very easy to program
Repeteability of profile is very good
No movment of the product in the vapour zone (stepless soldering)
Low vapour condensation rate
=> Low gradient (low ETR/low throttle)
High vapour condensation rate
=> High gradient (high ETR/full throttle)

9. Program parameters linear profile1 2 3
Test board:
Double sided FR4, 48 layers. Dimension 465 x 507 mm Metal shielded BGA´s
Linear profiling parameters:
1. Adjustment of temperature gradient: Power setting (ETR from 50 to 100%)
2. Time over liquidus: Time (sec) 3.Cooling time Time (sec)
For a linear profile only 3 parameters are required. All other internal machine parameters are activated automatically from the controller. Accuracy of the profile is controlled via an internal thermocouple. If profile runs out of limits an operator alarm is generated.

10. Program parameters step profile1 2 3 4 5
Test board:
Double sided FR4, 48 layers. Dimension 465 x 507 mm Metal shielded BGA´s
Step profiling parameters:
Preheat gradient adjustment: Time in seconds. -power setting (ETR from 50 to 100%)
2. Soak zone: Duration time in seconds.
3. Peak zone gradient adjustment: Power setting (ETR from 50 to 100%)
4.Time over liquidus:
-Time in seconds.
5.Cooling time -Time (seconds)
For a step profile we only need 6 parameters. All other internal machine parameters are activated automatically from the controller. Accuracy of profile is controlled via an internal thermocouple. If profile runs out of limits an operator alarm is generated.

11. Heating paramters for profiling
BENEFITS:
Process is controlled and automatically optimised with installed thermocouples
Temperature profile of the thermocouple´s is monitored permanently on a touch screen monitor
Temperature profile for any product can be adjusted infinitely variable by programming only a few parameters
No difficult programming of „soldering steps“ and no product movement in the vapour zone during soldering
Maximum 6 program parameters are required to generate a step profile
Experts have the possibility, to optimise and fine tune the machine in a special „advanced programming mode“

12. Automatic Recognition of the Soldering Temperature (ASB Automatic solder break)
Profile during soldering and the end of condensation is monitored automatically via thermocouple sensors (ASB). At that point PCB has physically reached nearly vapour temperature
Time over liquidus is freely adjustable and activated from the PLC controller
A valid process window and all process parameters are monitored continously. If process parameters are out of acceptable values an operator message is created with an alarm
Vapour temp. 230 °C
Liquidus temp. 217°C
ASB monitored. Melting point is reached
Time (t)
Start temp. 20°C
Time above liquidus

19. The vacuum Process in the Machine
Vacuum hood, vacuum heating device
Vacuum sealing device
Vacuum heating device activated
PCB is moving out of vapour into vacuum chamber
During transport PCB is drying
Dried PCB is placed in the vacuum hood
Vacuum chamber is hermetically sealed
Vacuum heating device on
Vacuum pump on
Voids escape out of molten solder joint
Vacuum pump, heating device off
Ventilation of vacuum chamber

20. The vacuum Process in the Machine
Immediate cooling with air or N2
Vacuum hood open,
vacuum heating device off
Vacuum sealing device open
PCB Transport into cooling zone
PCB cooling with forced air (optional with nitrogen)

22. The vacuum Process in the Solder Joint
Initial condition:
solder joint with encapsulated void
normal ambient air pressure
gas pressure inside void is equal to the outside ambient air pressure
Step 1:
Start vacuum. 50 % vacuum (approx mbar partial vacuum) acheived.
Due to the surrounding lower partial pressure the size of the void is growing until internal void pressure is equal to the surrounding pressure
Molten solder-
paste
Void
1 bar
Molten solder-
paste
Void
0,5 bar

23. The vacuum Process in the Solder Joint
Step 2:
Partial pressure is going down. Void is growing parallel. Now size of the void is big enough to form a vent duct. The over pressure in the void escapes out of the solder joint.
Step 3:
The surrounding pressure is near to the final vacuum. The over pressure of the void is compensated. The wetting force is filling up the previous void with solder
0,3 bar
0,1 bar

24. The vacuum Process in the Solder Joint
Step 4:
Final vacuum. No overpressure in the void. Venting channel is closed by wetting force of the solder. A small void with a core pressure equal to the external vacuum still remains.
Step 5:
Vacuum step is finished. Venting valves are activated. Surrounding air pressure is going back to normal ambient pressure. The „overpressure“ of the athmosphere compared to the previos inner void pressure is compressing the void. The size of the void is shrinking, until the void pressure is equal to the surrounding ambient pressure.
0,05 bar
1 bar

25. The vacuum Process in the Solder Joint
Step 6:
Vacuum process including venting is finished.
Solder paste is cooling down and solidifies.
The big void which was present at the beginning of the process is now minimised.
Solid solder paste
Miniaturised void
1 bar

26. Asscon Vapour Phase Vacuum Benefits
Most effective vacuum process
Product is totally dry when vacuum step is starting
Vacuum step is fully programmable and very flexible to meet all product requirements
Vacuum technology is installed outside the hot vapour zone. This secures long lifetime of all mechanical components, seals, bearings, valves etc. due to the low temperature exposure.
Advanced aerosol filter technology secures a minimum GALDEN consumption 24/7 capability
Easy to maintain
ASSCON is worldwide market leader in Vapour Phase vacuum technology
Largest installed customer base of vacuum systems
For the new ESA “SENTINEL” satellite project ASSCON developed the worlds biggest vapour phase vacuum soldering machine.
The heart of the satellite, the X-ray antenna is soldered with ASSCON vapour phase vacuum technology. This was the only available possibility to meet the quality requirements.
ESA “SENTINEL” x-ray satellite
Start 2012/2013
Part of the antenna during production

27. Vapour Phase under vacuum vs. normal reflow system
Normal Soldering without vacuum
ASSCON Vapour Phase Soldering with vacuum
Component soldering
BGA soldering

28. VP under vacuum vs. normal reflow system
Normal Soldering without vacuum
ASSCON Vapour Phase Soldering with vacuum
Die soldering
BGA soldering

47. Asscon Vapour Phase Vacuum soldering
FACTS:
ASSCON invented and patented vapour phase-vacuum soldering worldwide first in 1998
ASSCON introduced the new technology into the worldwide EMS market in 1999
ASSCON is the pioneer in vapour phase vacuum soldering with hundreds of vapour phase vacuum systems worldwide in operation
Vacuum systems are available for laboratory use, batch production and inline production 47

48. Warpage
The reasons of warpage is due to the different heat expansion and contraction coefficients of the materials used in components and PCB´s. This effect will be drastically seen by to the current trends towards even complex products. Warpage occurs during heating as well as cooling down.
Reparable as well as irreparable defects may occur.
Reparable:
Open soldering joints
Bridges
Irreparable:
Cracks in various sections.
Cracks in internal bonding wires of components, etc.
Source: AMKOR

49. Warpage issue due to thermal stress
Open soldering joints in the corners of a BGA
„Extreme“ WARPAGE
Head and pillow effect

50. Reducing the risk of component warpage
By taking the following steps WARPAGE effects can be minimised:
Avoid steps in the reflow profiles. Each gradient change is negative. Linear profiles or intensely smoothened soak profiles are optimum.
Avoid high heating gradients even if this will reduce the throughput.
Ensure a Delta T which is as low as possible.
Ensure a uniform energy transfer. VP equipment is optimally suitable for this purpose.
The cooling gradients need to be significantly lower than users think. The solder joints must already be under liquidus. Otherwise enormous mechanical stress will be generated.
Ensure a uniform mass distribution in the design stage of the PCB.

51. The Tombstone Effect The causes for tombstones are to be found in:
inaccurate layout
a faulty stencil geometry
bad placement
bad surface quality
In general the following will apply:
The better (the more oxygen-depleted) the soldering method, the more frequently tombstones will occur in the presence of the above circumstances.
The high surface tensions in the soldering meniscus may now cause the component to rotate upwards about one side of the component (rotational centre M) in case of a poor soldering joint geometry.

52. Tombstoning If DM3 > (DM1+DM2) then TombstoneZ Fn
D: pivot (DM = torque around pivot)
F: force surface tension
Y: small solder fillet
X: large solder fillet
DM1 = G* Y
DM2 = Fn * Z
DM3 = Fm * X
If DM3 > (DM1+DM2) then Tombstone

53. Tombstoning X F1 F2 D
Meniscus with less solder paste
Meniscus with much solder paste
Under the same soldering conditions twice the torque will develop at the component due to the large amount of soldering paste. This effect leads to an increased tombstone formation.
Torques acting on
the component:
Dm1=F1 x X
Dm2=F2 x 2X:
Legend:
F1 = F2 Force, surface tension of the meniscus
D = Pivotal point
DM1 ; DM2 => Torque about the pivotal point D
X= Lever arm on which the force F acts
In case of a small paste volume x is included in the calculation of the torques singly, and in case of a high paste volume doubly.

54. Tombstoning
Large pad with too much soldering paste for low-oxidation reflow processes.

55. Reduction of Tombstoning
Pads cannot always be easily modified. What other measures are
there to overcome Tombstoning?
A reduction of the amount of paste is imperative. Stencil thickness: from 100 up to 150 µm. A general reduction of 10 % in the stencil to compensate the printing offset (reduction of bridges and solder beads). Further reduction of the stencil aperture of 20 % up to 45 % in case of smaller components (< 08/05) or old pad design. Utilisation of a triangle or preferably stripe print. The stripe print offers a reduced initial wetting capacity since initially not the entire width of the component is wetted by tin.
Verify accurate placement, even small offset in x can cause tombstoning.
Profile optimisation to achieve a uniform heat distribution.
Use of non eutectic (“N2”) solder paste like 62.5Sn/36.5Pb/1.0Ag. Decelerated melting is reducing forces and reducing tombstoning.
Triangle print
Comp.
Stripe print
Comp.

56. Incorrect Pad and Stencil Design
Board with much too large pads and an unadjusted stencil geometry. Tombstoning is a permanent problem.

57. Stencil Design Improvement (Part 1)
Starting point was an old pad design with to big pads compared to the component metallisation. The effect was a to high solder paste volume.
-> On every board a huge number of tombstones was produced.

58. Stencil Design Improvement (Part 2)
Step 1: Stencil aperture reduction minus 40%. -> Tombstoning rate immediately was going down minus 95%.

59. Stencil Design Improvement (Part 3)
Step 2:
Stencil 10% more reduced. Now only 50% of the pad is printed with paste.
-> It is now impossible to create tombstones, even if the temperature profile is increased over the limits.
-> The wetting is still going up more then 75% of the vertical metallisation. The minimum recommended vertical wetting according to the IPC is 30%.
Source: Fa. Hekatron, Mr. Reinhold Stark, VP 2000 Dual lane.

60. Influence of the Paste Alloy on Tombstoning
To examine the influence of the alloy on the tombstoning rate respectively 10 test boards respectively comprising 100 components were tested with different alloys.
The reference is the tin lead alloy which has been known for years.
A significant difference in the defect rates can be observed.
A high SN content combined with a high AG content will result in drastically increased defect rates.
Tombstoning rate in dependant on the alloys used. SnAgCu and SnPb pastes were tested at 240°C and 210°C in vapour phase soldering systems.

61. ASSCON facts ASSCON was founded in 1995 by Claus Zabel and Heinz Seitz
Up to now more than 1200 systems are in operation
ASSCON is the biggest supplier of Vapour Phase systems worldwide
Largest customer base for vapour phase soldering systems in the world

62. Lab / proto-typing / small production volume
Low to mid volume batch production
Process development
Product size 450 x 450
One shift operation
Low operating costs
Lab and prototyping
Product size 300 x 300
Entry level for VP soldering
Lab and prototyping
Low volume batch production
Product size 450 x 450
Integrated water cooling system

63. Mid to high volume production
VP1000-mid to high volume batch production
Designed for 24/7 operation
Carrier transport
VP2000-high volume inline production
Designed for 24/7 operation
Pin and chain transport

64. PCB inline automation units
The pcb automation unit is available for: VP
VP 6000
Automated loading and unloading of pcb boards onto carrier

65. Vacuum-Systems for void free soldering
VP 800 VAC
carrier transport system
low volume batch production
laboratory use
process development
VP 6000
Batch production system
carrier transport system
mid volume batch production
24/7 capability
VP 7000
Inline production system
Carrier or pin and chain transport system
mid to high volume, high mix
24/7 capability

66. Professional Automated Soldering, PCB/Stencil Cleaning and Routing Solutions

67. Thank you very much for your attention