CN109558671A - A kind of method of edge effect during simulation Flip Chip Underfill Technology - Google Patents
A kind of method of edge effect during simulation Flip Chip Underfill Technology Download PDFInfo
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- CN109558671A CN109558671A CN201811429397.0A CN201811429397A CN109558671A CN 109558671 A CN109558671 A CN 109558671A CN 201811429397 A CN201811429397 A CN 201811429397A CN 109558671 A CN109558671 A CN 109558671A
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- 238000000034 method Methods 0.000 title claims abstract description 29
- 230000000694 effects Effects 0.000 title claims abstract description 27
- 238000004088 simulation Methods 0.000 title claims abstract description 18
- 238000005516 engineering process Methods 0.000 title claims abstract description 9
- 239000012530 fluid Substances 0.000 claims abstract description 26
- 239000000463 material Substances 0.000 claims abstract description 5
- 239000003292 glue Substances 0.000 claims description 21
- 239000000758 substrate Substances 0.000 claims description 7
- 239000007787 solid Substances 0.000 claims description 6
- 230000008676 import Effects 0.000 claims description 5
- 238000004364 calculation method Methods 0.000 claims description 3
- 230000004069 differentiation Effects 0.000 abstract description 6
- 230000002093 peripheral effect Effects 0.000 abstract description 2
- 229910000679 solder Inorganic materials 0.000 description 6
- 230000005514 two-phase flow Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 3
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- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
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- 235000009165 saligot Nutrition 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
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- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/30—Circuit design
- G06F30/36—Circuit design at the analogue level
- G06F30/367—Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods
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Abstract
The invention discloses a kind of methods of edge effect during simulation Flip Chip Underfill Technology, it is characterized in that, the method includes material properties are arranged, the selection area of flip-chip is modeled, the geometrical model and boundary condition for establishing numerical simulation, using boundary condition imitation edge effect.The differentiation of fluid fronts shape at any time can be accurately predicted through the invention, especially can accurately simulate edge effect.And when simulating edge effect, the length for extending flip-chip side edge no-welding-spot region is not needed, does not need flip-chip peripheral region being included in modeling yet, can effectively mitigate computation burden.
Description
Technical field
The present invention relates to a kind of technical field of semiconductors, and in particular to a kind of simulation Flip Chip Underfill Technology process
The method of middle edge effect.
Background technique
Flip chip technology (fct) is that one kind is widely used in multi-chip module (MCM), high-frequency communication, high-performance calculation, calculating
The chip package technique in the fields such as machine, portable electronic device.In flip-chip, what bare die had an integrated circuit passes through weldering on one side
Point is directly connect with substrate.This technology has high I/O density, shorter signal path, high power consumption and high efficiency etc.
Advantage.
However, due to the coefficient of thermal expansion mismatch between bare die (2.5ppm/ DEG C) and substrate (18-24ppm/ DEG C).It is passing through
When by temperature cycles, fatigue fracture and electricity failure may occur for the higher solder joint of thermal stress in flip-chip.In order to solve this
Underfill glue is usually filled into the gap of chip and substrate by problem, to mitigate thermal stress and protect solder joint.Capillary
Pipe power drive underfill process are as follows: underfill glue is arranged in certain side of bare die.Thereafter, drive of the glue in capillary force
The gap of full chip is gradually filled under dynamic.Finally, filling glue is cured in insulating box.
In underfill process it is possible that edge effect.Edge effect refers to underfill flowing at two of bare die
The phenomenon that side edge flows faster than middle section.Edge effect may result in empty formation, to influence flip-chip
Reliability.There are mainly two types of the methods of simulation edge effect at present: the first be in lengthening model side to outermost row solder joint
Distance, the boundary condition of side edge is without sliding wall boundary condition.Second is that model is included in the region for surrounding chip
In.In first method, either extension side to outermost row solder joint distance or application without slip boundary condition,
It has any different with actual physics condition, the effect of this method simulation is also undesirable.Second method not only results in additional calculating
Burden, can also cause model convergence difficulties.
Summary of the invention
It is an object of the invention to overcome defect existing in the prior art, a kind of dynamic pressure boundary condition imitation is provided
Edge effect can accurately predict the differentiation of fluid fronts shape at any time by this method, especially can accurately simulate side
Edge effect.
The invention adopts the following technical scheme:
A kind of method of edge effect during simulation Flip Chip Underfill Technology, which is characterized in that the method
Including material properties are arranged, the selection area of flip-chip is modeled, geometrical model and the boundary of numerical simulation are established
Condition, using boundary condition imitation edge effect, boundary condition setting are as follows: if y is greater than L, export Patm- △ p, if y is small
In being equal to L, then P is exportedatm, wherein PatmFor standard atmospheric pressure, L is the fluid fronts position on side border, and △ p is fluid
Flow the pressure difference by import and fluid boundary.
Preferably, PatmValue be (10000~11000) Pa, △ p value be (800~900) Pa.
Preferably, the boundary condition calculation formula are as follows:
Wherein, p is dynamic pressure, and L is the fluid fronts position on side border, and l is a constant, and △ p is the stream of fluid
The dynamic pressure difference by import and fluid boundary, Ω is lateral boundaries, and the height in the gap between chip and substrate h, φ is level set
Function.
Preferably, the △ p is
Wherein, σ be fill glue and air surface tension coefficient, θ be fill glue the surface of solids contact angle, h be chip with
The height in gap between substrate.
Preferably, the density that the filling glue attribute specifically includes filling glue is set as (1500~2000) kg/m3, surface
Tension is (0.02~0.03) N/m, and filling contact angle of the glue on solid wall surface is (20~30) °.
The advantages and beneficial effects of the present invention are: the differentiation of fluid fronts shape at any time can accurately be predicted, especially
Edge effect can accurately be simulated.And when simulating edge effect, do not need to extend flip-chip side edge no-welding-spot region
Length does not need flip-chip peripheral region being included in modeling yet, can effectively mitigate computation burden.
Detailed description of the invention
Fig. 1 is dynamic pressure boundary condition schematic diagram of the invention；
Fig. 2 is the geometrical model and boundary condition of numerical simulation；
The grid dividing of Fig. 3 geometrical model；
The differentiation of the fluid fronts shape of Fig. 4 simulation at any time.
Specific embodiment
With reference to the accompanying drawings and examples, further description of the specific embodiments of the present invention.Following embodiment is only
For clearly illustrating technical solution of the present invention, and not intended to limit the protection scope of the present invention.
The method of edge effect, is based on COMSOL during the simulation Flip Chip Underfill Technology proposed in the present invention
Multiphysics software.Simulation edge effect is substantially simulation transient state gas liquid two-phase flow.Governing equation is continuity side
Journey, the equation of momentum and energy equation.The capture of gas-liquid interface uses level set method.Capillary drive acts through face power model
To describe.Edge effect is simulated by the dynamic pressure boundary condition of two side edges.
Continuity equation are as follows:
Wherein ρ is density, and u is velocity vector.
The equation of momentum are as follows:
Wherein p is pressure, and μ is viscosity, and I is unit matrix, and Fst is surface tension vector.Fst is counted by formula (3) and (4)
It calculates:
T=σ (I- (nnT))δ (4)
Wherein σ is surface tension coefficient, and n is the normal vector at interface, and δ is Dirac function, only the non-zero at fluid boundary.
The interface of two phase flow is captured in the present invention using level set method.This method is suitable for fixed mesh, and can capture
The change in topology at interface.In level set method, the interface of two phase flow passes through 5 implied expression of formula:
Wherein,For level set function.Therefore the interface of two phase flow is 0.5 contour surface of level set function.Other than interface
Computational domain in, level set function is initialized by formula 6:
In the computational domain within interface, initialized by formula 7:
In both the above formula, DwiFor to the distance at interface, ε is the thickness at interface.Level set function is with velocity field
EVOLUTION EQUATION are as follows:
Wherein, λ determines the degree reinitialized.
Based on level set method, viscosity and density are calculated by formula 9:
ρ=ρair+(ρwater-ρair)φ (9)
μ=μair+(μwater-μair)φ (10)
Dirac function is approximately:
The normal vector at interface is calculated by formula 12:
The model boundary condition for simulating underfill flowing is as shown in Figure 1.Capillary drive is described using face power model
Effect, i.e., the flowing of fluid by import and fluid boundary pressure differential.The pressure difference is calculated by Laplace formula:
In order to simulate edge effect, side edge uses dynamic pressure boundary condition:
L is the fluid fronts position of side edge, and l is a constant.Fig. 1 intuitively describes the boundary condition.
Embodiment 1:
Edge effect is simulated.Include the following steps: be arranged material properties, to flip-chip carry out Geometric Modeling,
Pressure boundary condition and grid dividing etc. are set.
Material properties are arranged: the density for filling glue is set as (1500~2000) kg/m3, surface tension be (0.02~
0.03) N/m, filling contact angle of the glue on solid wall surface is (20~30) °.The density for preferably filling glue is set as
1800kg/m3, surface tension 0.027N/m, filling contact angle of the glue on solid wall surface is 25.5 °.It is retouched by power rate model
State the non-newtonian feature of filling glue:
Carry out Geometric Modeling to flip-chip: the geometrical model and boundary condition of numerical simulation are as shown in Figure 2.Due to using
Symmetrical boundary condition, it is only necessary to which 1/4 region of flip-chip modeled.The size of flip chip be 6.7mm ×
6.7mm, wherein solder joint number is 25 × 25.The diameter of solder joint is 168 μm, and pitch is 262 μm.
Boundary condition: in actual calculating, boundary condition is as shown in Figure 2.Before the computation, need to be arranged filling glue and
The prime area of air occupied.The region that filling glue occupies is the red area in Fig. 2, and length is other regions full of sky
Gas.The wherein pressure boundary condition of side edge are as follows:
Wherein, p is the pressure at lateral boundaries, and Ω is side border, and l is equal to 103 μm.The boundary condition is in COMSOL software
In specific implementation are as follows:
Step 1: an integral (Intergration) is defined in component coupling (Component Couplings), by
Then double integral selectes boundary (Boundary) in geometry entity level (Geometry entity level).Integrated area
Choose the side border in figure geometrical model in domain.
Step 2: defining the fluid fronts position L on side border.A variable is defined in COMSOL, is named as L.It should
The expression formula of variable is (intop1 (phils > 0.5))/(28e-6 [m]).Wherein, intop1 (f) is indicated to being defined on integrated area
The function f in domain is integrated.This integral is defined in step 1, and as double integral, integral domain are side border.
Phils represents level set function28e-6 [m] is the width of side border in geometrical model.
Step 3: the dynamic pressure boundary condition of side border is set.Pressure boundary condition is arranged are as follows: if (y > L,
Patm- △ p, patm), by being calculated as if (y > L, 100454.65,101325).
Wherein, PatmValue be (10000~11000) Pa, △ p value be (800~900) Pa, preferably PatmValue be
The value of 101325Pa, △ p are 870.35Pa.
Grid dividing: when carrying out numerical value calculating, since each physical quantity cannot be obtained in flow field in all spatial points
Value, therefore grid dividing must be carried out.After grid dividing, each physical quantity is calculated on grid node by numerical value
It is worth, the value of physical quantity is acquired by interpolation in other spatial points.Grid dividing as shown in figure 3, grid mainly by water chestnut pole unit group
At.Grid is divided on X/Y plane by triangular element, is along the z-axis direction structured grid.Grid cell sum is
17846.The unit size parameter that grid divides on X/Y plane is as follows:
Largest unit size: 65.5 μm, minimum cell size: 19.8 μm, largest unit growth rate: 1.2, Curvature factor:
0.75, narrow zone resolution: 0.55.
Numerical value calculating parameter:
Parameter γ is set as 0.01m/s, and interfacial thickness ε is set as tpf.hmax/2, and tpf.hmax is maximum mesh unit
Size.The time step that numerical value calculates is set as 0.1s.
Fig. 4 illustrates the differentiation of the fluid fronts shape of simulation at any time, fluid fronts shape, figure when Fig. 4 (a) is 5.3s
Fluid fronts shape when 4 (b) shapes of fluid fronts when being 19.6s, Fig. 4 (c) are 23.9s.
The present invention can accurately predict the differentiation of fluid fronts shape at any time, especially can accurately simulate edge effect.
The foregoing is merely presently preferred embodiments of the present invention, is not intended to limit the invention, it is all in spirit of the invention and
Within principle, any modification, equivalent replacement, improvement and so on be should all be included in the protection scope of the present invention.
Claims (5)
1. a kind of method of edge effect during simulation Flip Chip Underfill Technology, which is characterized in that the method packet
Setting material properties are included, the selection area of flip-chip is modeled, establish the geometrical model and perimeter strip of numerical simulation
Part, using boundary condition imitation edge effect, boundary condition setting are as follows: if y is greater than L, export Patm- △ p, if y is less than
Equal to L, then P is exportedatm, wherein PatmFor standard atmospheric pressure, L is the fluid fronts position on side border, and △ p is the stream of fluid
The dynamic pressure difference by import and fluid boundary.
2. the method as described in claim 1, which is characterized in that PatmValue be (10000~11000) Pa, △ p value be
(800~900) Pa.
3. the method as described in claim 1, which is characterized in that the boundary condition calculation formula are as follows:
Wherein, p is dynamic pressure, and L is the fluid fronts position on side border, and l is a constant, △ p be fluid flowing by
Pressure difference at import and fluid boundary, Ω are lateral boundaries, and the height in the gap between chip and substrate h, φ is level set function.
4. such as the described in any item methods of claim 1 or 3, which is characterized in that the △ p is
Wherein, σ be fill glue and air surface tension coefficient, θ be fill glue the surface of solids contact angle, h be chip with
The height in gap between substrate.
5. the method as described in claim 1, which is characterized in that the filling glue attribute specifically includes the density setting of filling glue
For (1500~2000) kg/m3, surface tension is (0.02~0.03) N/m, and filling contact angle of the glue on solid wall surface is (20
~30) °.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116884883A (en) * | 2023-09-01 | 2023-10-13 | 山西创芯光电科技有限公司 | Method for reducing bubbles in infrared detector bottom filling |
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| CN101777504A (en) * | 2010-01-27 | 2010-07-14 | 江苏长电科技股份有限公司 | System level packaging method of flip chip and attached passive element on support plate chip |
| CN105069184A (en) * | 2015-07-13 | 2015-11-18 | 中国科学院过程工程研究所 | Stirred tank reactor simulation method based on immersed boundary method |
| CN106570211A (en) * | 2016-10-11 | 2017-04-19 | 中南大学 | Method and system for predicting equivalent thermal conductivity of TSV adapter plate |
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2018
- 2018-11-27 CN CN201811429397.0A patent/CN109558671A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101114622A (en) * | 2006-07-27 | 2008-01-30 | 矽品精密工业股份有限公司 | Flip-chip type semiconductor packaging structure and chip bearing member |
| CN101777504A (en) * | 2010-01-27 | 2010-07-14 | 江苏长电科技股份有限公司 | System level packaging method of flip chip and attached passive element on support plate chip |
| CN105069184A (en) * | 2015-07-13 | 2015-11-18 | 中国科学院过程工程研究所 | Stirred tank reactor simulation method based on immersed boundary method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116884883A (en) * | 2023-09-01 | 2023-10-13 | 山西创芯光电科技有限公司 | Method for reducing bubbles in infrared detector bottom filling |
| CN116884883B (en) * | 2023-09-01 | 2023-11-14 | 山西创芯光电科技有限公司 | Method for reducing bubbles in infrared detector bottom filling |
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