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Moisture Sensitive Devices A Real Production Problem.

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Presentation on theme: "Moisture Sensitive Devices A Real Production Problem."— Presentation transcript:

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2 Moisture Sensitive Devices A Real Production Problem

3 Background Moisture and Surface Mount Components do not mix Plastic packaging material very often is permeable to moisture If moisture permeable plastic packaging material levels become critical, component damage may occur when subject to reflux temperature (popcorning) Moisture induced failures are often undetectable, causing malfunction within 2 and 6 months Higher processing temperatures of unleaded solder will exacerbate the problem

4 Lead Free and Popcorning Quelle: Intel

5 Popcorning The epoxy moulding compound used in most plastic encapsulated devices is hygroscopic While processing, temperatures up to 260º C are applied Fast ramps and high temperatures prevent moisture from escaping

6 Popcorning This leads to delaminating the encapsulated interface of the die, resulting in a gas bubble This is not always visually apparent

7 Popcorning Exceeding the technical elastic limit results in cracking of the plastic packaging, water vapour escapes with a sudden burst The plastic packaging has a leak permeating oxygen slowly destroys the components

8 Popcorning

9 Popcorning Example 1 BGA device, showing crack between fibreglass substrate and plastic body moulding

10 Popcorning Example 2 QFP device, showing crack on top of plastic body moulding

11 Popcorning Example 3 Micro section through BGA device, showing delaminating and crack through conductive adhesive and fibreglass substrate

12 Popcorning Example 4 BGA device, showing crack between fibreglass substrate and plastic body moulding

13 Popcorning Example 5 QFP device, showing crack on the underside of the plastic body moulding

14 IPC-Levels for IC`s Quelle: IPC

15 IPC-Levels for IC`s Quelle: Intel

16 Component Humidity Quelle: Intel

17 Absorption Quelle: Intel

18 Absorption Quelle: Intel

19 Traditional Prevention Historically components and printed control boards have been backed to remove moisture Typically temperatures from 40 to 125 C and times of between 1 hour and 1 week have been used This adds time and a monetary cost to production Backing is still possible, only according to IPC spec

20 Problems with Baking Surface solder ability is degraded Growth of inter metallic layers is promoted, also with low temperature (40 degree C Baking is only possible one time (IPC) Ovens can be expensive to run They take up valuable space on the production floor

21 Solder Ability SOIC 14 Chip, 60/40 Sn/Pb alloy, type R flux, as received

22 SOIC 14 Chip, 60/40 Sn/Pb alloy, type R flux, C Solder Ability

23 SOIC 14 Chip, 60/40 Sn/Pb alloy, type R flux, C SOIC 14 Chip, 60/40 Sn/Pb alloy, type R flux, as received Solder Ability

24 Inter Metallic Growth Total inter metallic thickness has shown to increase by approximately 50% when baking at 125 C is used for 4 days In the case of a copper metallisation, this is mainly the Cu6 Sn5 layer but all layers are effected Inter metallic growth is a function of time and temperature The thicker inter metallic layers can lead to a reduction in solder joint integrity and in extreme cases reduce solder ability

25 Alternative Prevention Use a Drying Cabinet No reduction of solder ability as no heat is involved Oxidisation is prevented by diminishing humidity All moisture is removed by a recycling desiccant drying system Lower operating cost (compared to baking) Efficient use of factory floor space

26 Moisture Barrier Bags Moisture Barrier Bags Nitrogen Cabinets Nitrogen Cabinets Dry Air Boxes Dry Air Boxes Desiccant Dry Cabinets Desiccant Dry Cabinets Variety of Dry Storage Variety of Dry Storage

27 Pros Inexpensive start up, little investment required Cons Bags can/do remain unsealed for extended periods Silica Gel packets used past their prime Silica Gel packets improperly stored Labor intensive Pros / Cons of MBB Storage

28 Pros N2 often available N2 cabinets familiar Cons Often poorly maintained Rarely monitored for effectiveness Costly to operate Installing is necessary Not available everywhere Very pure N2 is needed to dry components, expensive!! Can hardly dry components Pros / Cons of Nitrogen Cabinets

29 Comparison of Costs using N² · Assumptions Costs of N² ~ 0.19 / m³ Power costs ~ 0.06 / KWh average N² consumption ~ 25 L / min Purchase costs of Totech Dry Cabinet ~ · Arising expenses from a N² cabinet Consumption : 25 l / min, i.e l / month, i.e m³ / month Costs: 205,20 / month, i.e / year · Arising expenses from a Totech Drying Cabinet Consumption : kW / h, i.e kW / month Costs : 2.42 / month, i.e / year Saving of costs within one year: This is equivalent to 37.5 months refinancing (Purchase costs: ) only by the N² consumption of a nitrogen cabinet (~ 3 years) (The calculation excludes installing the nitrogen cabinet and leasing costs for N² bottles.)

30 Drying Cabinets

31 History of Drying Cabinets First auto-recycling dry cabinet developed for commercial use utilizing Silica Gel, regularly being dried by a heating system 1976 First use of synthetic zeolites (as molecular sifter ) in dry cabinet designs, replacing Silica Gel 1982 New dryer design capable of managing ultra-low humidity levels, patented (Totech, Japan) 1987 Texas Instruments, with primary applying of ultra- low humidity dry cabinets for MSD storage. Before that, dry cabinets were only used for the optics industry and consumer goods

32 Cons Higher initial investment required Pros Dries without use of heat Fast de-humidification Zero maintenance Constantly monitored for effectiveness Low cost operation Air tight Mobile Pros / Cons of Desiccant Dry Cabinets

33 Recommendation for Time of Drying At the same temperature, the drying time is equal to backing time according to IPC reference. SDE-Series HSD-Series

34 Dry Cabinet Acceptance Dry Cabinet Acceptance App Dry Cabinets sold every year extensive residential use in Asia App less than 5% RH cabinets sold every year worldwide A total of 8-10 desiccant dry cabinet manufacturers worldwide Increasing demand in Europe (lead-free)

35 8-10 large suppliers worldwide Cabinet should at least go to 5% RH Great majority of cabinets built for the residential market (i.e % RH) The demand for ultra-low humidity is growing Dry Cabinet Suppliers Dry Cabinet Suppliers

36 Crystal Resonator Optical Fiber, CCD etc (LCG) Liquid Crystal Glass CSP, BGA, QFP etc Printed Circuit Boards Wafers Ceramics Various Dry Cabinet Applications

37 IPC/JEDEC 033a Application IPC/JEDEC 033a Application Dry Cabinet at 10% RH MSD packages not sealed in a MBB may be placed in a dry atmosphere cabinet, maintained at not greater than 10% RH. These dry cabinets should not be considered a MBB Storage of MSD packages in these dry cabinets should be limited to a maximum time per Table 7-1. If the time limit is exceeded they should be baked according to Table 4-2 to restore the floor life

38 Dry Cabinet at 5% RH MSD packages not sealed in a MBB may be placed in a dry atmosphere cabinet, maintained at not greater than 5% RH Storage in these dry cabinets may be considered equivalent to storage in a MBB with unlimited shelf life IPC/JEDEC 033 Application IPC/JEDEC 033 Application

39 How do they work? How do they work?

40 Functional Principles An interlocked fan causes the air to circulate through the dry unit While passing through the dry unit moisture in the air is absorbed by the zeolite desiccant During periodic rejuvenating of the zeolite desiccant by heating, the absorbed humidity is evaporated and exhausted through the external shutters of the dry unit

41 Function of Dry Unit (Moisture being exhausted during recycling period)

42 Zeolite Zeolite Synthetically produced zeolite A 47% open space High rate of absorption at low RH levels Excellent ability to regenerate

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44 To ensure a minimal inflow of outside ambient air the interlocked fan is stopped automatically when a door is opened (Extra Feature on Super-Dry) Functional Principle

45 After the doors are closed, the fan begins operating again to accelerate the moisture absorption inside the air tight Drying Cabinet Functional Principle

46 Calibrating Calibrating is possible by exchanging the complete Humidity Sensor

47 Maintenance Recommendation Running time of the interlocked fan is interrupted (30% on). Still the fan is subject to abrasion, esspecially concerning the bearings To garantee good functioning the fan must be changed after the indicated time of operational performance ( Triple operational performance by interruption enables about 10 years of functioning )

48 Basic Requirements Basic Requirements Must recover within an acceptable period of time after being accessed Must maintain a constant RH level once recovery is complete

49 Intermittent Control after Door Opening

50 Control Accuracy

51 Increase of Humidity during Blackout

52 Features of SD und HSD Convenient Digital Control Panel ON/OFF calliper on frontside Infinitaly variable humidity setting Automatic resetting temperature display Alarm function when doors are left open Delayed humidity alarm with LED Key Lock Function for the Digital Control Panel to prevent unintended changes of setting

53 SD-Series

54 Humidity Appearance

55 HSD-Series Equipped with two Dry Units

56 Humidity Appearance

57 Drying efficiency of different Cabinets

58 Improving MSD administration / control Additional drying units (2 or 3) Forced air circulation (fan interlocked with doors) Heated air Nitrogen Purge Short door opening times Minimize Recovery Time by: Minimize Recovery Time by:

59 Number of doors does not relate to number of separate environments Smaller doors bring about shorter recovery times Typically same desiccant dry units in all models Cabinets should be only as large as required Cabinet Size and Configuration

60 Option: Data Logging Function Measuring of humidity and temperature with internal storage up to measured values (8.000 recordings including date, time, humidity and temperature) Limit value monitoring for both measurement categories Inputs internal sensor for humidity and temperature Humidity measuring range: % humidity (resolution 0.5%; accuracy +/- 3%) Temperature measuring range: °C (resolution 0.5 °C; accuracy ± 1 K) Configuration By Micro Lab Plus Software Selectable looping time for reading storage: between 10 sec and 2 hours Adjustable limit values for both measurement categories Display and appliance LC - Display 2 digit for instantaneous values or MIN/MAX values Double calliper operation for all adjustments Communication RS232 standard interface Infrared interface Supply Internal lithium battery 3.6 V TL5101, exchangeable Battery durability approximately 2 years Housing Plastic, degree of protection according to IP65 Dimensions 72 mm x 23 mm; weight 55 g

61 Option: Datenlogger

62 Option: Alarm Alarm Buzzer /Light if door is open longer than 90 sec Alarm Buzzer /Light or SMS-Alarm when humidity exceeds the RH level set value longer than a specified time

63 Option: Reel Rack

64 Dubble- Reel-Rack on ball bearing move out

65 Option: Shelf Dividers

66 Option: Nitrogen Purge Continuous stand-by for amounts from l/min Automatic initiation to purge the cabinet ( max 100 l/min) after closing the doors Timer to reduce the nitrogene consumption

67 Special Purpose Solutions

68 It is important to provide Comprehensive ESD protection A closed loop feedback from sensors Forced air circulation Use of a good dessicant (zeolites with open surface structure) Summary Summary

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