Abstract
With new advances in the semiconductor technology, current carrying requirements for electronic packages and interconnects (sockets) are on the rise. Although there are a lot of documented methods for determining current carrying capacity (CCC) of electrical wires, there is no specific industry standard for determining current carrying capacity of socket pins and their contact interface with package balls and pads. This paper presents a new current carrying capacity measurement method, developed specifically to address the challenges of test socket pins and their contact interface with solder balls and pads. In addition, a method for predicting CCC in future test socket pins is presented and correlated to measured data.
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Notes
Measuring both, the ambient air temperature and air velocity inside the pin block is optional as described later in Section 5.3.
Mikić’s [34] original definition of hardness specifies mean pressure based hardness value (Meyers hardness) and not Vickers hardness. Dieter [14] has pointed out that Vickers hardness can be used as substitutes for Meyer hardness due to small enough difference. Vickers hardness has been used in all calculations in this paper where hardness is called for.
The equation for thermal contact conductance between two surfaces in plastic deformation has been published twice, the first time by Cooper et al. [12] in 1969, and then revised by Mikić in 1974 [34]. Cooper’s original 1969 equation was defined as follows:
$$ {h}_s=1.45\ \frac{k_m\cdot {m}_e}{\sigma_e}{\left(\frac{P}{H_v}\right)}^{0.985} $$(18)Both equations have been tested in simulations and it was found that although their results vary by about 20%, their final impact on CCC is negligible. In the end, Mikić’s 1974 equation was used in this paper, because it was an improved revision of the earlier 1969 equation which Mikić himself coauthored and was aware of.
Contius did not specify the force-area equation for line to line contact and did not provide the details of the geometry of the cylinders he used in his measurements. Using some details that Contius provided and additional theory that was developed in subsequent years, it was possible to derive this equation. Equation 26 is a rearranged and simplified form of the line to line contact area published by Barquins [4] and Chaudhury et al. [9], with the adhesive force term removed. A detailed derivation of this equation will be published in a future publication.
Abbreviations
- a, b, c :
-
Quadratic polynomial coefficients
- I pin _ measured :
-
Measured current flowing through the pin, A.
- I pin _ derated :
-
Measured current flowing through the pin derated for tool test temperature and factor of safety, A
- T pin _ at _ room :
-
Measured pin temperature at room temperature, °C
- T pin _ at _ test :
-
Measured pin temperature at test tool temperature, °C
- T test :
-
Tester ambient temperature during test, °C
- T room :
-
Room ambient temperature, °C
- F 20 % _ drop :
-
Pin force at 20% drop from the nominal pin force, kg
- σ :
-
Equivalent Von Misses flow stress, Pa
- ε p :
-
Equivalent plastic strain
- \( {\varepsilon}_p^{\ast } \) :
-
Strain rate, \( {\varepsilon}_p^{\ast }=\dot{\varepsilon}/{\dot{\varepsilon}}_0 \)
- \( \dot{\varepsilon} \) :
-
Equivalent plastic strain rate, sec−1
- \( \dot{\varepsilon_0} \) :
-
Constant reference strain rate, sec−1. \( \dot{\varepsilon_0}=0.001\ {\sec}^{-1} \)
- A JC :
-
Johnson-Cook (J-C) constant representing quasi-static yield stress, MPa
- B JC :
-
J-C constant representing strain hardening effect, MPa
- C JC :
-
Johnson-Cook constant representing strain rate effect
- n JC :
-
Johnson-Cook constant representing strain hardening effect
- m JC :
-
Johnson-Cook constant representing thermal softening effect
- T H :
-
Homologous temperature ratio defined as \( {T}_H=\frac{\left(T-{T}_r\right)}{\left({T}_m-{T}_r\right)} \)
- T m :
-
Melting temperature of the material, K
- Tr :
-
Reference temperature (room temperature), K. Tr = 293 K
- E1, E2 :
-
Young’s modulus of each of the materials in contact, Pa
- ν1, ν2 :
-
Poisson’s ratio of each of the materials in contact
- σ1, σ2 :
-
Surface roughness of materials in contact, m
- h s :
-
Thermal contact conductance of materials in contact, \( \frac{W}{m^2\cdot K} \)
- k m :
-
Mean harmonic thermal conductivity of materials in contact, \( \frac{W}{m\cdot K} \)
- k1, k2 :
-
Thermal conductivity of each of the materials in contact, \( \frac{W}{m\cdot K} \)
- m1, m2 :
-
Slope of asperities of each of the materials in contact
- m e :
-
Effective slope of asperities
- σ e :
-
Effective surface roughness, m
- P :
-
Pressure squeezing the two materials in contact together, Pa
- H v :
-
Vickers hardness of the softer material, Pa
- k1, k2 :
-
Thermal conductivity of each of the materials in contact, \( \frac{W}{m\cdot K} \)
- g :
-
Temperature jump distance, m
- α :
-
Thermal accommodation coefficient
- γ :
-
Ratio of specific heats for the gas,\( \frac{C_p}{C_v} \)
- k g :
-
Thermal conductivity of gas,\( \frac{W}{m\cdot K} \)
- μ :
-
Dynamic Viscosity, \( \frac{kg}{m\cdot \mathit{\sec}} \)
- C v :
-
Specific heat at constant volume,\( \frac{J}{kg\cdot K} \)
- λ :
-
Mean free path, m
- δ :
-
Mean physical gas gap between materials in contact, m
- P :
-
Pressure squeezing the two materials in contact together, Pa
- H v :
-
Vickers hardness of the softer material, Pa
- h g :
-
Thermal contact conductance of the air gap, \( \frac{W}{m^2\cdot K} \)
- δ :
-
Mean physical gas gap, m
- g :
-
Temperature jump distance, m
- h s :
-
Thermal contact conductance of the two materials in contact, \( \frac{W}{m^2\cdot K} \)
- h g :
-
Thermal contact conductance of the air gap, \( \frac{W}{m^2\cdot K} \)
- A p2p :
-
Contact area for point to point contact, mm2
- A l2l :
-
Contact area for line to line contact, mm2
- k :
-
Constant relating contact area to force,\( \frac{mm^2}{kgf} \)
- F :
-
Force pushing the two materials together, kgf
- w :
-
Half width \( \left(\frac{width}{2}\right) \) of the contact line, mm
- l :
-
Length of the contact line, mm2
- F length :
-
Force applied between the two bodies in contact per unit length, \( \frac{kgf}{mm} \)
- R :
-
Contact resistance between the two bodies, Ω
- E c :
-
Composite Young’s modulus of the two materials in contact, Pa
- ν :
-
Composite Poisson’s ratio of the two materials in contact
- G :
-
Composite shear modulus of the two materials in contact, Pa
- G1, G2 :
-
Shear modulus of materials in contact, Pa
- ρ1, ρ2 :
-
Resistivity of materials in contact, Ω ⋅ m
- Pf1, Pf2 :
-
Plating factor of the material in contact, used to account for the plating on the base metal. For non-plated metal Pf1 = Pf2 = 1.
- η :
-
Empirical coefficient of order unity for clean interfaces
- H :
-
Hardness of the softer material, Pa
- ρ cont :
-
Resistivity of the contaminant film between the two surfaces in contact, Ω ⋅ m
- d cont :
-
Thickness of the contaminant film between the two surfaces in contact, m
- Ψ :
-
Plasticity index. If Ψ < 1, then the deformation is predominantly elastic. If Ψ ≥ 1, then the deformation is predominantly plastic.
- C :
-
Constant that relates contact resistance to force with units as a function of n, Ω ⋅ kgn
- n :
-
Constant that relates contact resistance to force. Unitless.
- C a :
-
Electrical contact conductance per unit area between two bodies in contact,\( \frac{S}{m^2} \)
- A :
-
Contact area between two bodies in contact, m2
- g 1 :
-
Force of gravity,\( {g}_1=9.80665\ \frac{m}{{\mathit{\sec}}^2} \)
- β :
-
Coefficient of thermal expansion (CTE),\( \frac{1}{K} \)
- ν g :
-
Kinematic Viscosity,\( \frac{m^2}{\mathit{\sec}} \)
- l pin :
-
Compressed pin length, m
- d pin :
-
Pin barrel diameter, m
- u g :
-
Velocity of fluid,\( \frac{m}{\mathit{\sec}} \)
- h natural :
-
Natural convection coefficient, \( \frac{W}{m^2\cdot K} \)
- h forced :
-
Forced convection coefficient, \( \frac{W}{m^2\cdot K} \)
- Nu :
-
Nusselt Number
- Pr :
-
Prandtl Number, \( \mathit{\Pr}=\frac{C_v\cdot \mu }{k_g} \)
- Ra :
-
Rayleigh Number, Ra = Gr ⋅ Pr
- Gr :
-
Grashof Number, \( Gr=\frac{g_1\cdot \beta \cdot \left({T}_{pin\_ at\_ room}-{T}_{room}\right)\cdot {l_{pin}}^3}{\nu_g} \)
- Re :
-
Reynolds Number, \( \mathit{\operatorname{Re}}=\frac{\rho \cdot {u}_g\cdot {d}_{pin}}{\mu } \)
- R Baycura :
-
Contact resistance between the two bodies, μΩ
- F Baycura :
-
Force pushing the two materials together, N
- C Baycura :
-
Constant that relates contact resistance to force with units as a function of nshe, \( \mu \varOmega \cdot {N}^{\frac{1}{2+{n}_{she}}} \)
- n she :
-
Strength hardening exponent of the material in contact. Unitless.
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Acknowledgments
The authors would like to thank Todd Coons, Georgios Dogiamis, and Tannaz Harirchian for their contributions to this project.
Funding
This research was funded by Intel Corporation. No funding was received from external sources
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Gurevich, E., Deshmukh, P. New Method for Determining and Predicting Test Interconnect Pin Current Carrying Capacity. J Electron Test 36, 445–460 (2020). https://doi.org/10.1007/s10836-020-05896-z
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DOI: https://doi.org/10.1007/s10836-020-05896-z