MEMS Packaging & Damping Mechanisms ד " ר דן סתר תכן וייצור התקנים מיקרומכניים

 Wafer -> Chip  First Level Package : Chip- Scale-Packaging (Single or Multi-chip Module).  Second Level Package : PCB or Card.  Third Level Package : Mother Board Electronic Packaging Hierarchy

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים Step 1: Wafer Dicing Step 2: Die Placement Step 3: Die Attach Step 4: Wire Bonding Step 5: Encapsulation/Molding Step 6: Lead Forming Step 7: Solder Bumping Step 8: Package Inspection Step 9: Package Test Step 10: Laser Marking Step 11: Singulation Step 12: Packing and Shipping Typical Packaging Flow - Electronics

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים

 Applications : air bag and rollover detection sensors for automotive applications.  Hermetically Sealing and Protection from : corrosion, moisture, and debris, contamination.  “Stress Free” Package  Wafer level packaging protection involves an extra fabrication process where the micro- machine wafer is bonded to a second wafer which has appropriate cavities etched into it. MEMS Packaging

MEMS - Packaging ד " ר דן סתר תכן וייצור התקנים מיקרומכניים Functions of MEMS Packages: * Mechanical Support * Protection From Environment * Electrical Connection to Other System Components * Thermal Considerations

MEMS – Packaging (cont.) ד " ר דן סתר תכן וייצור התקנים מיקרומכניים Types of MEMS Packages * Metal Packages * Ceramic Packages * Thin-Film Multilayer Packages * Plastic Packages

MEMS – Packaging (cont.) ד " ר דן סתר תכן וייצור התקנים מיקרומכניים Package-to-MEMS Attachment: Die Attachment

MEMS – Packaging (cont.) ד " ר דן סתר תכן וייצור התקנים מיקרומכניים Chip Scale Packaging * Flip Chip Controlled Collapse Chip Connection (C4) is an interconnect technology developed by IBM during the 1960s as an alternative to manual wire bonding. Often called "flip-chip," C4 attaches a chip with the circuitry facing the substrate. C4 uses solder bumps (C4 Bumps) deposited through a Bump Mask onto wettable chip pads that connect to matching wettable substrate pads (Figure 8- 4). MEMS technology initially may not use flip chip packaging but the drive toward miniaturization may necessitate its incorporation into future designs.

MEMS – Packaging (cont.) ד " ר דן סתר תכן וייצור התקנים מיקרומכניים * Flip Chip (cont.)

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים The primary advantage of C4 is its enabling characteristics. Specific advantages include:  Size and weight reduction  Applicability for existing chip designs  Increased I/0 capability  Performance enhancement  Increased production capability  Rework/chip replacement Key considerations include:  Additional wafer processing vs. wire bond  Supplemental design groundrules  Wafer probe complexity for array bump patterns  Unique thermal considerations

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים

Wire Bonding

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים Tape Automated Bonding

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים BGA Package Ball Grid Array is a surface mount chip package that uses a grid of solder balls as its connectors. It is noted for its compact size, high lead count and low inductance, which allows lower voltages to be used. BGAs come in plastic and ceramic varieties. It essentially has evolved from the C4 technology whereas more I/Os can be utilized in the same area as in a peripherally leaded package (or chip). The CBGA and PBGA are not truly Chip Scale Packaging but the evolution to the  BGA has come out of the experience the industry has gained from the CBGA and PBGA packages.

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים BGA Package

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים  BGA Package The uBGA package is constructed utilizing a thin, flexible circuit tape for its substrate and low stress elastomer for die attachment. The die is mounted face down and its electrical pads are connected to the substrate in a method similar to TAB bonding. After bonding these leads to the die, the leads are encapsulated with an epoxy material for protection. Solder balls are attached to pads on the bottom of the substrate, in a rectangular matrix similar to other BGA packages. The backside of the die is exposed allowing heat sinking if required for thermal applications. Ball pitches available today are 0.50, 0.75, 0.80, and 1.0 mm. Other features and benefits include: 0.9 mm mounted height, excellent electrical and moisture performance, 63/37 Sn/Pb solder balls, and full in-house design services.

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים Solder Bumps

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים MCM (Multi-Chip-Modules)

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים

Chip-on-Flex (COF)

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים 3D - MCM

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים  Failure by Stiction and Wear.  Delamination.  Environmentally induce failures  Cyclic mechanical fatigue  Dampening Effect.  Packaging and development of testing methodologies. Typical MEMS Packaging Failure Modes

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים MEMS Packaging

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים WLP for MEMS Packaging

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים WLP for MEMS Packaging “Recent Development in WLP” - AMKOR “Wafer level “Hermetic” packaging for sensors / MEMS” - MOTOROLA

ד " ר דן סתר תכן וייצור התקנים מיקרומכניים MEMS – Some State of the Art Packaging Examples Solder Self Assembly Flip Chip Assembly MEMS Packaging Concepts Using Printing Techniques

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות Damping in Microsystmes There are two main damping mechanisms in Mycrosystems: The motion of a free standing plane A cantilever or a membrane, moving in a fluid without any interaction with another solid body. The damping is mainly due to the fluid properties such as: viscosity, density, pressure and temperature. The relative motion of planes in the fluid Planes (micorostructures) that are moving one raltive to the other in the fluid: Perpendicular motion: Electrostatic motion perpendicular to the substrate, Tuning fork beams. Parallel motion: Comb Drive. The damping is influenced mainly by the gap size between the solid surfaces, the fluid properties, the pressure and the motion amplitude.

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות The 1 DOF System Q: The quality factor: Equation of motion: SolutionThe natural frequency: m F C K The damping ratio: Non dimensional definition of the state solution: R d is the dimensionless response factor Non velocity solution:

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות Lower damping Q increasing. The “quality” of the system is higher R V, R d (R V ) max ; (R d ) max   nn In microsystems high Q values are needed: 10 3 < Q < 10 5

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות Damping of the motion of a free standing plane The low pressure region: The surrounding damping is negligible relative to the inner damping in the material. Empirical Q  f(P) The molecular region: The damping mechanism is due to momentum transfer between single molecules of the surrounding and the solid. The high pressure region: Continuity region. The damping is due to pressure, viscosity – drag.

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות Example: The equation of motion of a free cantilever: W L E – Young’s modulus I – Cross section moment of inertia Y – Deflection of the beam (a function of the coordinate X and the time t) N – Axial load  - Density W – Width ; L-Length ; h-thickness C – Damping coefficient h

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות Example:The equation of motion of a free cantilever: (Newell – 1988) Intrinsic Damping: Q Empiric *Molecular Region: P – ambient pressure ; l – beam’s length ; R – The univesal ideal gas constant [ J/deg K] ; M – fluid molecular mass (29g for air) T – ambient temperature [deg K] **Viscous region (continuity): Stokes Flow  f – fluid viscosity Air - 1.8x10 -5 [Ns/m 2 ] * + **

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות More effects: Acoustic Loss: Q p - Damping due to vibration energy dissipation at a given pressure: Q a – Acoustic loss: creating pressure waves. Q 0 – Internal damping. Exist even in ambient vacuum. Jeyopalan R.K. and Richards E.J., “Radiation Efficiencies of beams in Flexural Vibration:, Journal of Sound and Vibration, Vol. 67, No.1, 1979, pp The influence of Viscosity:  - Shear stress on the surface U – The velocity perpendicular components Y – The perpendicular coordinate  - Boundary layer thickness - kinematical viscosity

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות The flow equations: For a viscous non-compressible flow, the equations are evaluated in a right Cartesian coordinates systems. The vector velocity field: fulfills the Navier Stokes and the continuity equations: A shorter notation may be used: And thus while neglecting gravity - These are 2nd order elliptical equations.

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות The “Bid String” Approach: t w R The addition of mass (per unit length) for a strip of thickness t resonating in a fluid having density  f: : m f =   f t 2 /4 The ratio between the damped natural frequency and the un-damped one: Defining  m = 2m f : Blom et al (1991): Where C is the appropriate constant and K n is a constant of the n th mode

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות The “Bid String” Approach Cont.: By separating variables: The quality factor Q can be evaluated as: For F(t)=F 0 sin(  t) the time integration yields  /  and thus:

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות The “Bid String” Approach Cont.: The damping force F D can be written as: Where: f 0 – The intrinsic damping mechanism f 1 – Viscous damping: f 2 – Addition mass The equation of motion for a single bid:

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות The “Bid String” Approach Cont.: Thus: For m >> f 2 Kokubun 1987 – A model for the molecular region Hosaka et al 1994 – Free cantilever under arbitrary load.

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות Brownian Noise: A rectangular membrane: For a rectangular membrane clamped on all sides and under uniform and constant load P, the deflection is given by: T – Membrane thickness W c – Deflection at the center of the membrane 2a – Length of the membrane side K – Boltsman coefficient T – Absolute remperature m 1, m 2, P 1, P 2 – The molecular mass and average pressure of the gasses on both sides of the membrane 1.2 <  < 1.7

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות Damping of the relative motion of surfaces in a fluid * The pressure regions, the properties of flow and the damping mechanism is determined by the “Knudsen no”: – The mean free path between the moledules h m – Mean thickness of the fluid layer or the nominal gap between the surfaces. 2a – Length of the membrane side hmhm The index 0 indicates the value for 1 atm: 0 (1 atm) = 9.35  [cm] for air h m 1 The molecular region <h m < < K n < 1 Knudsen flow h m > 100 Kn < Continuity

ד " ר דן סתר ריסון במיקרומערכות הנדסת מיקרומערכות