A method for predicting the influence of wire bonding failure on electromagnetic radiation performance in high-speed differential circuits

Abstract

The application discloses a kind of prediction methods of the influence of wire bonding failure on electromagnetic radiation performance in high-speed differential circuit.The application includes: first, design high-speed differential circuit with wire bonding interconnection, and carry out failure treatment to wire bonding;After that, the three-dimensional electromagnetic field numerical calculation model of high-speed differential circuit with different degradation degrees is established respectively, and the electromagnetic radiation intensity of high-speed differential circuit with different degradation degrees at probe is simulated and analyzed;After that, extract parasitic parameters, and build equivalent circuit model;After that, the total radiation field of high-speed differential circuit with different degradation degrees at probe is deduced;Finally, compare simulation analysis result and theoretical calculation result, and evaluate error.The application adopts the way of simulation analysis and theoretical derivation, and proposes the electromagnetic radiation intensity evaluation scheme of wire bonding with different failure numbers, and the method can accurately and conveniently predict the influence of wire bonding failure on electromagnetic radiation performance in the service process of chip.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic compatibility, and in particular to a method for predicting the impact of bond wire failure on electromagnetic radiation performance in high-speed differential circuits. Background Technology

[0002] As electronic devices increasingly move towards higher frequencies, higher speeds, higher integration, and miniaturization, wire bonding is widely used in integrated circuit chip packaging due to its mature manufacturing process, high packaging flexibility, and relatively low cost. Wire bonding utilizes metal wires to achieve electrical connections between chip pins and the package substrate. Simultaneously, wire bonding can disperse and withstand external stress, reducing damage to the chip. However, during chip operation, the wires carry the internal current. If the current or power is too high, the wires may overheat, leading to breakage or melting, resulting in electrical connection failure. The external environment also affects the reliability of the wires; vibration and impact can cause mechanical stress and breakage; temperature changes cause thermal expansion and contraction, leading to fatigue failure; and moisture, chemicals, or oxidants in the air can cause corrosion and oxidation, degrading electrical performance.

[0003] Differential signaling is widely used in chip design due to its advantages such as better anti-interference performance, longer transmission distance, and lower power consumption. Digital and analog interface standards, internal chip data transmission, and communication interfaces all use differential signal transmission to provide high-speed, reliable data transmission. However, during differential signal transmission, bonding wires can fail due to environmental stress. Bonding wire failure leads to asymmetry in the differential circuit, affecting not only signal transmission quality but also causing some differential signals to be converted into common-mode signals. Compared to differential signals, common-mode signals, due to their identical amplitude and phase, result in increased radiation leakage at the detection point due to superposition of radiation fields, leading to electromagnetic compatibility (EMC) issues.

[0004] Current research on wire bonding packages largely focuses on the failure modes and mechanisms of wire bonding, the manufacturing process of wire bonding, and the signal integrity of wire bonding, while research on the impact of wire bonding failure on electromagnetic radiation is relatively limited. To address this, this invention proposes a method for predicting the impact of wire bonding failure on electromagnetic radiation performance in high-speed differential circuits. This method can accurately and conveniently analyze the impact of wire bonding failure on electromagnetic radiation emissions during chip service. Summary of the Invention

[0005] Based on the above analysis, this invention proposes a method for predicting the impact of bond wire failure on electromagnetic radiation performance in high-speed differential circuits, characterized in that:

[0006] Design a high-speed differential circuit with bonded wire interconnects. The circuit consists of three parts: the first part is a transition structure composed of coaxial connectors and microstrip lines; the second part is a differential circuit composed of differential lines and bonded wires; and the third part is a circuit composed of microstrip lines and coaxial connectors. Failure handling is performed on the bonded wire portion of the circuit to accelerate the acquisition of differential circuits with different degrees of degradation.

[0007] Three-dimensional electromagnetic field numerical models of high-speed differential circuits with different degradation levels were established. A discrete voltage source port was set on one side of the differential line, and a matched load was set on the other side. The excitation signal of the model was set to a square wave signal, and the probe was set above the ground plane, 3 m away from the center of the circuit. Field-circuit co-simulation analysis was conducted to determine the electromagnetic radiation intensity E at each probe when the high-speed differential circuit transmitted differential signals with different rise times, representing the electromagnetic field intensity E at different degradation levels. sim ;

[0008] Parasitic parameters were extracted, and an equivalent circuit model was constructed. The specific steps were as follows: the bond wire model was equivalent to a π-type network composed of resistors, inductors, and capacitors. When the circuit transmits differential signals, the higher harmonic components are very small compared to the fundamental frequency signal component. Therefore, the resistance of the bond wire was simplified to the AC resistance of the bond wire when the signal frequency was the fundamental frequency. Compared to the parasitic resistance and inductance of the bond wire, the resistance and inductance of the two pads are negligible. However, the pad capacitance cannot be ignored. The first and third parts of the circuit are simplified and represented using SNP files obtained from the simulation of the three-dimensional electromagnetic field numerical calculation model.

[0009] When n bond lines with equal spacing are connected in parallel, the formula for calculating the equivalent capacitance of a π-type network can be approximated as:

[0010]

[0011] Where C wire For mutual capacitance between two bond lines with a spacing of d, C g For the capacitance to ground of a single bond wire, C pad This refers to the parasitic capacitance of the pad. C wire and C g The calculation formulas are as follows:

[0012]

[0013] Where h wire r is the average ground height of the bond line. wire Let d be the radius of the bond line. wire This refers to the spacing between the two bond lines.

[0014] This paper derives the total radiation field at the probe of a high-speed differential circuit with different degradation levels. The specific steps are as follows: First, determine the directions of the three current components, the current itself, and the position of the probe. Then, calculate the sinθ corresponding to the current in that direction. x / y / z sinφ x / y / z cosθ x / y / z cosφ x / y / z Then, the differential-mode current and common-mode current at the source and load terminals of high-speed differential circuits with different degradation levels are calculated respectively; then, the effective relative permittivity of each part of the high-speed differential circuit is calculated, and the current distribution equation is derived; finally, the differential-mode current and common-mode current in this direction are derived at their corresponding θ values. x / y / z Radiation field in the direction; and consider the radiation field θ generated by the ground plane. x / y / z The radiation field in the direction and the source and load currents at their corresponding θ x / y / z The radiation field in the direction is calculated; then the total radiation field at the probe is calculated.

[0015] Calculate the differential-mode current and common-mode current at the source and load terminals of a high-speed differential circuit with different degradation levels. The specific steps are as follows: Connect two signal sources to the two input terminals of the constructed equivalent circuit model. Set the rise time of the two signal sources to RT, the period to T, and the amplitudes to +A and -A square wave signals respectively. Ground the negative terminals of the signal sources. Connect a 50-ohm resistor to the output terminal of the equivalent circuit model, with the other end of the resistor grounded.

[0016] Calculate the effective relative permittivity of each part of the high-speed differential circuit. The effective relative permittivity of the microstrip line portion in the first and third parts of the model is calculated based on the microstrip line width and the dielectric layer height. For the second part of the model, the odd-mode and even-mode relative permittivity need to be calculated separately. The specific steps are as follows: First, calculate the parasitic inductance and capacitance of a single line, as well as its characteristic impedance; then solve the equations to calculate the inter-line coupling inductance and coupling capacitance; finally, calculate the odd-mode and even-mode effective relative permittivity separately.

[0017] The formula for calculating the effective relative permittivity of a microstrip line is:

[0018]

[0019] Where ε r h is the relative permittivity of the dielectric layer. sub ω is the height of the dielectric layer. wire This refers to the trace width.

[0020] The formula for calculating the effective relative permittivity of the odd and even modes in the differential line is:

[0021]

[0022] Where Lm and C m Let L and C represent the line coupling inductance and coupling capacitance, respectively, and L and C represent the total inductance and total capacitance of a single line, respectively. The formulas for calculating the line coupling inductance and coupling capacitance are:

[0023]

[0024] in

[0025]

[0026] Where s is the spacing between the difference lines.

[0027] The ground plane can be considered as an infinitely large metal plane, and the radiation field at the probe above the metal can be solved using the principle of mirrors. The currents at the source and load ends are very short, much smaller than 1 / 10λ, so the radiation field at the probe can be directly solved based on the current waveforms at the source and load ends.

[0028] To calculate the total radiation intensity, the specific steps are as follows: First, calculate θ corresponding to the current in each part. x / y / z The radiation field in the x, y, and z directions is calculated; then the superposition of the radiation fields generated by each part of the current in the x, y, and z directions is calculated; finally, the vector sum of the radiation fields in the three directions is calculated.

[0029] The formulas for calculating the total radiation field of the probe in the x, y, and z directions are as follows:

[0030]

[0031] Where E_part1 θ E_part2 represents the radiation field of the first part of the model. θ E_part3 represents the radiation field of the second part of the model. θ E_source represents the radiation field of the third part of the model. θ E_load represents the radiation field of the source current. θ This represents the radiated field of the load terminal current.

[0032] The formula for calculating the total radiation field is:

[0033]

[0034] Compare the simulation analysis results with the theoretical calculation results to assess the error. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the overall processing of the present invention.

[0036] Figure 2This is the equivalent circuit model of the present invention. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings.

[0038] Figure 1 The overall processing flowchart of this invention is shown in the figure.

[0039] In step 101, a high-speed differential circuit with bonded wire interconnects is designed, and the circuit is subjected to failure handling.

[0040] In step 102, a three-dimensional electromagnetic field numerical calculation model of a high-speed differential circuit with different degradation levels is established based on the structure, material, and size parameters of the high-speed differential circuit.

[0041] In step 103, the S-parameters of high-speed differential circuits with different degradation levels are simulated, the S-parameters of the first and third parts of the simulation model are simulated, and an SNP file is generated.

[0042] In step 104, a differential excitation port is set, and the excitation signal is set to a periodic square wave signal with amplitude A, period T, and rise time RT. A broadband matched load with an impedance of 50 ohms is set at the load end. A ring of probes is set around the circuit, with the probes 3 m away from the center of the circuit.

[0043] In step 105, the simulation analysis is performed on the radiation field at each detection point location around the high-speed differential circuit with different degradation levels, under the condition that the differential signal with different rise time and period is used as the excitation signal.

[0044] In step 106, based on the diameter, material, spacing, and distance to ground parameters of the bonding wires, the parasitic parameters such as DC and AC resistance, inductance, capacitance to ground, mutual capacitance, and mutual inductance of the bonding wires are calculated.

[0045] In step 107, based on the parasitic parameters of the bonding wire portion in circuits with different degradation levels, as well as parameters such as the width, spacing, and dielectric layer of the differential lines, equivalent circuit models of high-speed differential circuits with different degradation levels are constructed.

[0046] In step 108, the S-parameters of high-speed differential circuits with different degradation levels are simulated in circuit simulation software.

[0047] In step 109, the S-parameters obtained from the three-dimensional electromagnetic field numerical calculation model and the S-parameters obtained from the equivalent circuit model are compared to verify the accuracy of the equivalent circuit model.

[0048] In step 110, periodic square wave signals with the same amplitude but opposite polarity are connected to the source terminal of the equivalent circuit model, and a 50-ohm matched load is connected to the load terminal. The differential-mode and common-mode currents at the source and load terminals are calculated in high-speed differential circuits with different degradation levels.

[0049] In step 111, based on the differential-mode current and common-mode current at the source and load ends, the distribution equations of the differential-mode current and common-mode current in each part of the model structure are derived.

[0050] In step 112, the effective relative permittivity of each part of the designed circuit structure is calculated based on the trace width, dielectric layer height, and trace spacing parameters. The second part of the model requires calculating the effective relative permittivity for both odd and even modes.

[0051] In step 113, the radiation fields of each part of the current in the model in each direction at the probe are derived. At the same time, the radiation fields of the source and load currents in each direction at the probe also need to be calculated.

[0052] In step 114, the total radiation field generated at the probe by the high-speed differential circuit with different degradation levels is calculated.

[0053] In step 115, the radiation field obtained by theoretical derivation and the radiation field obtained by the three-dimensional electromagnetic field numerical calculation model are compared, and the error between the two results is calculated.

Claims

1. A method for predicting the impact of bond wire failure on electromagnetic radiation performance in high-speed differential circuits, characterized in that: Design a high-speed differential circuit with bonding wires and handle bonding wire failures. Specifically, the high-speed differential circuit consists of three parts: the first part consists of two coaxial connectors and microstrip lines; the second part is a differential circuit composed of differential lines, bonding lines, differential lines, bonding lines, differential lines, bonding lines, and differential lines; and the third part consists of two microstrip lines and coaxial connectors. Three-dimensional electromagnetic field numerical calculation models of high-speed differential circuits with different degradation levels were established to simulate and analyze the electromagnetic radiation intensity at the probe of the high-speed differential circuits with different degradation levels. Specifically, the three-dimensional electromagnetic field numerical calculation models were established based on the designed circuit structure, material and size parameters, and the dimensions, material and bond wire failure count parameters of the bonding wires. The degradation level was measured by the differential circuit asymmetry caused by the number of bond wire failures. The excitation signal of the model was a differential signal. The probe was placed above the ground plane, 3 m away from the center of the circuit. The simulation analysis method was field-circuit co-simulation. Parasitic parameters are extracted, and an equivalent circuit model is constructed. Specifically, the equivalent circuit model includes an equivalent circuit model of a differential circuit composed of bond lines with different failure numbers and an equivalent circuit model of the remaining part of the designed circuit. The electrical parameters in the equivalent circuit model of the bond line part are calculated by formula. The equivalent circuit models of the first and third parts of the model are represented by SNP files obtained by electromagnetic simulation software. The total radiation field at the probe of a high-speed differential circuit with different degradation levels is derived. Specifically, the current direction, current, and probe position of the three circuit parts are first determined, and the sinθ corresponding to the current in each direction is calculated. x / y / z sinφ x / y / z cosθ x / y / z cosφ x / y / z Then, the differential-mode current and common-mode current at the source and load terminals of high-speed differential circuits with different degradation levels are calculated respectively; then, the effective relative permittivity of the three parts of the high-speed differential circuit is calculated respectively, and the current distribution equation is derived; then, the currents of the three parts at their corresponding θ values ​​are derived respectively. x / y / z The radiation field in the direction is calculated; then the total radiation field at the probe is calculated. By comparing the simulation analysis results with the theoretical calculation results, the error of the theoretical prediction model is evaluated.

2. The method for predicting the impact of bond wire failure on electromagnetic radiation performance in a high-speed differential circuit according to claim 1, characterized in that, The first and third parts are connected by two right-angle bends; the three bonding wire sections in the differential circuit are all transmitted by multiple bonding wires connected in parallel.

3. The method for predicting the impact of bond wire failure on electromagnetic radiation performance in a high-speed differential circuit according to claim 1, characterized in that, The accuracy of the equivalent circuit model is determined by comparing and optimizing the S-parameters obtained from the simulation of the three-dimensional electromagnetic field numerical calculation model and the S-parameters obtained from the simulation of the circuit model.

4. The method for predicting the impact of bond wire failure on electromagnetic radiation performance in a high-speed differential circuit according to claim 1, characterized in that, In the high-speed differential circuit, the current direction of the first and third parts is the x-direction, the current direction of the second part is the z-direction, and the current direction of the source and load terminals is the y-direction; the directions at the probe are the x, y, and z directions at the probe.

5. The method for predicting the impact of bond wire failure on electromagnetic radiation performance in a high-speed differential circuit according to claim 1, characterized in that, The effective relative permittivity of the first and third parts of the model is the effective relative permittivity of the microstrip line; the calculation of the effective relative permittivity of the second part of the model is as follows: First, the parasitic inductance and parasitic capacitance of a single line are calculated, and then the characteristic impedance of the single line is calculated. The line coupling inductance and coupling capacitance are then calculated by solving the equations. The effective relative permittivity of the odd and even modes was then calculated.

6. The method for predicting the impact of bond wire failure on electromagnetic radiation performance in a high-speed differential circuit according to claim 1, characterized in that, The total radiation field of the calculated probe is specifically as follows: First, calculate θ corresponding to the current of each part. x / y / z The radiation field in the x, y, and z directions has radiation field components. Then, the superposition of the radiation fields generated by each part of the current in the x, y, and z directions is calculated separately; Then calculate the vector sum of the radiation fields in the three directions.

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