An accelerated test method for intermetallic compound reliability in wire bonding

Abstract

The present application relates to chip packaging technical field, specifically, it is a kind of intermetallic compound reliability in wire bonding accelerated test method. Including the following steps: S1, carry out high temperature test;S2, measure the resistance value of each sample pin;S3, set failure condition;S4, calculate the cumulative failure rate of each sample failure;S5, test data is arranged into table;S6, draw in lognormal distribution coordinate system and obtain the fitting linear equation of each accelerated temperature;S7, linear fitting;S8, the time when the cumulative failure rate under each accelerated temperature is 50%;S9, draw the interrelationship between them;S10, linear fitting is carried out again to each data point to obtain the slope of straight line;S11, the acceleration factor under accelerated test temperature is obtained by substituting Arrhenius equation, so as to obtain the test time under accelerated test temperature. Compared with prior art, the test time of intermetallic compound reliability in accelerated wire bonding is saved, and time and cost are saved.

Description

Technical Field

[0001] This invention relates to the field of chip packaging technology, and more specifically to an accelerated testing method for the reliability of intermetallic compounds in wire bonding. Background Technology

[0002] Wire bonding is a crucial step in semiconductor packaging. It typically involves bonding a chip within the package to a lead frame or substrate using metal wires under pressure from a bonding tool and ultrasonic vibration, using a specific temperature. This achieves electrical interconnection between the chip's internal and external circuitry. Commonly used metal wires include gold, silver, and copper, as well as various bonding wire materials formed through doping, alloying, composite processes, or surface treatments. Initially, a small amount of intermetallic compounds (IMCs) forms after solder balls are formed. These IMCs initially enhance the interfacial bond strength. However, with increased usage time and temperature, IMCs accumulate. Excessive IMCs lead to reduced bond strength, brittleness, and increased contact resistance. Brittle IMCs can cause fatigue failure at the bonding points under cyclic stress, ultimately resulting in open circuits or degraded electrical performance.

[0003] The reliability testing of intermetallic compounds in wire bonding is typically conducted according to the high-temperature storage life test conditions C defined by the Joint Electron Device Engineering Council (JEDEC), i.e., 150°C / 1000 hours. The semiconductor packaging industry is characterized by high production volumes, short cycle times, high requirements for process stability, and the need for rapid anomaly identification and process improvement. A 1000-hour test time is often unacceptable for both rapid Design of Experiment (DOE) verification to quickly identify anomalies and improve processes, and for rapidly predicting product lifespan. To address this issue, a new technology is needed to accelerate the reliability testing time of intermetallic compounds in wire bonding, thereby saving time and costs. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides an accelerated testing method for the reliability of intermetallic compounds in wire bonding.

[0005] To achieve the above objectives, an accelerated testing method for the reliability of intermetallic compounds in wire bonding is designed, characterized by the following steps:

[0006] S1, select multiple samples and multiple accelerated high-temperature temperatures, and conduct high-temperature tests respectively;

[0007] S2, measure the resistance value of each sample pin under different high temperature environments;

[0008] S3, set the failure condition, and the time to reach the failure condition is called the failure time;

[0009] S4, calculate the cumulative failure rate when each sample fails;

[0010] S5. Organize the test data into a table. The test data includes temperature, product failure time, and cumulative failure rate.

[0011] S6. Obtain the distribution of the cumulative failure rate of each sample with respect to the failure time of the product. Plot the data in the test data table on the log-normal distribution coordinate system and obtain the fitting linear equation for each acceleration temperature. The fitting linear equation is y=ax+b, where y is the cumulative failure rate, x is the logarithm of the failure time, a is the slope, and b is the intercept.

[0012] S7. Perform linear fitting on the data points of each acceleration temperature to confirm whether the slopes of each line are similar. If they are similar, proceed to step S8. If they are not similar, reduce the selected value of the highest temperature and adjust the interval value of each temperature to repeat steps S1 to S7.

[0013] S8, calculate the time when the cumulative failure rate is 50% at each accelerated temperature according to the linear equation, i.e., the median lifetime t(0.5);

[0014] S9. Plot the relationship between the logarithm of the median lifetime, Lnt(0.5), and the reciprocal of the temperature value in the linear coordinate system of the Arrhenius equation.

[0015] S10, perform linear fitting on each data point again to obtain the slope of the straight line, which is the activation energy value of the failure mechanism of the intermetallic compound. The fitted linear equation is m=cn+d, where m is Lnt(0.5), n is (1 / T)*10000, c is the slope, which is the activation energy value of the failure mechanism, and d is the intercept.

[0016] S11, Substitute the activation energy value, accelerated test temperature, and normal test temperature into the Arrhenius equation to obtain the acceleration coefficient at the accelerated test temperature, and thus obtain the test time at the accelerated test temperature;

[0017] In step S11, the acceleration coefficient at the accelerated test temperature is obtained according to the Arrhenius equation as follows: AF = L1 / L2 = exp[Ea / k (1 / T1 - 1 / T2)], where AF is the acceleration coefficient, L1 is the lifetime under normal conditions, L2 is the lifetime under accelerated conditions, Ea is the activation energy value of the failure mechanism, and k is the Boltzmann constant (8.62 × 10⁻⁶). -5T1 is the normal test temperature, and T2 is the accelerated test temperature;

[0018] The method for determining the test time at the accelerated test temperature based on the acceleration factor is as follows: t1 = t2 / AF, where t1 is the test time at the accelerated test temperature, t2 is the test time at the normal test temperature, and AF is the acceleration factor.

[0019] In step S1, the temperature for accelerating the high temperature is 180-300℃.

[0020] In step S2, the resistance value is measured once per hour.

[0021] In step S9, the temperature value is measured in Kelvin.

[0022] In step S3, the failure condition is the resistance change rate (Ri-R0) / R0 ≥ 10%; where R0 is the initial resistance value and Ri (i=1,2…) is the resistance value tested in the i-th hour.

[0023] In step S4, the cumulative failure rate is calculated as F(t) = i / (n+1), where F(t) is the cumulative failure rate, i is the number of failures, and n is the total number of samples.

[0024] In step S7, it is determined whether the 'a' values ​​in the linear equations of each acceleration temperature are similar. If the difference between them is ≤0.5, they are considered similar.

[0025] The specific method of step S8 is as follows: S81, substitute the cumulative failure rate = 50% into the linear equation of each acceleration temperature to obtain the logarithm of the median lifetime t(0.5) under each acceleration temperature test condition; S82, calculate the antilogarithm to obtain the median lifetime t(0.5) of the sample under each acceleration temperature test condition.

[0026] Compared with existing technologies, this invention accelerates the testing time for the reliability of intermetallic compounds in wire bonding, saving time and costs. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the experimental apparatus in an embodiment of the present invention.

[0028] Figure 2 This is a flowchart of the sample failure judgment process in an embodiment of the present invention.

[0029] Figure 3 This is a table of test data from an embodiment of the present invention.

[0030] Figure 4 This is a graph showing the relationship between accelerated failure time and cumulative failure rate of samples in the embodiments of the present invention in a log-normal distribution coordinate system.

[0031] Figure 5 This is a table showing the relationship between the median lifetime and the reciprocal of the acceleration temperature for samples under various acceleration conditions in the embodiments of the present invention.

[0032] Figure 6 This is a graph showing the relationship between the logarithm of the median lifetime and the reciprocal of the acceleration temperature of the samples under various acceleration conditions in the linear coordinate system of the Arrhenius equation in the embodiments of the present invention. Detailed Implementation

[0033] The present invention will now be further described with reference to the accompanying drawings. Example

[0034] In this embodiment, gold wire bonded BGA packaged products were selected, with 10 samples per group. The standard test procedure was 150℃ / 1000 hours, and four accelerated test temperatures were selected: 190℃, 220℃, 240℃, and 260℃.

[0035] During the experiment, if Figure 1 As shown, the sample is placed on the corresponding test plate, which is then placed in a high-temperature test chamber. The high-temperature test chamber is set to an accelerated temperature for high-temperature testing. Simultaneously, the online resistance testing system measures the resistance value of the corresponding product pins in real time.

[0036] In this embodiment, the sample failure condition is set as resistance change rate (Ri-R0) / R0 ≥ 10%. Here, R0 is the initial resistance value, and Ri (i=1,2…) is the resistance value measured in the i-th hour. The experiment continues until all samples in each accelerated temperature group fail, during which the data acquisition system records the failure time of each sample.

[0037] The cumulative failure rate for each sample is obtained using the following formula: F(t) = i / (n+1), where F(t) is the cumulative failure rate, i is the number of failures, and n is the total number of samples.

[0038] Next, the test data on temperature, product failure time, and cumulative failure rate were compiled into a table, such as... Figure 3 As shown.

[0039] Obtain the distribution of failure time as a function of the product's cumulative failure rate for each sample, and plot the data from the test data table on a log-normal coordinate system, such as... Figure 4 As shown, the fitted linear equations for each acceleration temperature are obtained.

[0040] y = ax + b, where y is the cumulative failure rate, x is the logarithm of the failure time, a is the slope, and b is the intercept.

[0041] Specifically: 190℃: y = 1.0175x - 8.3254 (1)

[0042] 220℃: y = 1.3289x - 9.9372 (2)

[0043] 240℃: y = 1.3603x - 9.5077 (3)

[0044] 260℃: y = 1.0369x - 6.5968 (4)

[0045] To determine whether the 'a' values ​​in the linear equations for each acceleration temperature are similar, based on the fitting results (1), (2), (3), and (4), the difference between them is ≤0.5. This indicates that the slopes of the fitted equations are similar, proving that the acceleration temperature did not change the failure mechanism of the intermetallic compound. Furthermore, it shows that the activation energy remains unchanged at each acceleration temperature. The similar slopes demonstrate that the acceleration temperature did not alter the failure mechanism of the intermetallic compound, and the fact that the activation energy remains unchanged at each acceleration temperature indicates that the experimentally selected temperatures effectively accelerated the failure mechanism.

[0046] Substituting the cumulative failure rate of 50% into the linear equation for each acceleration temperature, we obtain the logarithm of the median lifetime t(0.5) under each acceleration temperature test condition. Taking the antilogarithm yields the median lifetime of the sample under each acceleration temperature test condition. The values ​​obtained in this embodiment are as follows: Figure 5 As shown.

[0047] Specifically: at 190℃: Ln(t(0.5)) = 8.67, median lifetime t(0.5) = 5847

[0048] 220℃: Ln(t(0.5))=7.85, median lifetime t(0.5)=2576

[0049] 240℃: Ln(t(0.5))=7.36, median lifetime t(0.5)=1567

[0050] 260℃: Ln(t(0.5))=6.84, median lifetime t(0.5)=938

[0051] The logarithm of the median lifetime, i.e., Lnt(0.5), and the reciprocal of the temperature value, i.e. Figure 5 The data in the equation are plotted in the linear coordinate system of the Arrhenius equation to show the relationship between the two, such as... Figure 6 As shown.

[0052] A linear fit was performed on each data point to obtain the fitted linear equation:

[0053] y = 0.6415x - 5.1696

[0054] The slope of the straight line, 0.6415, is the activation energy value of the failure mechanism of the intermetallic compound in this sample.

[0055] The acceleration coefficient at the accelerated test temperature was obtained using the Arrhenius equation:

[0056] AF=L1 / L2=exp[Ea / k (1 / T1 - 1 / T2) ]

[0057] Where AF: acceleration factor, L1: lifetime under normal conditions, L2: lifetime under accelerated conditions, Ea: activation energy of the failure mechanism, k: Boltzmann constant (8.62 x 10⁻⁶). -5 T1: Standard test temperature; T2: Accelerated test temperature;

[0058] The acceleration coefficient from 190℃ to 150℃: AF = exp[0.6415 / 8.62x10] -5 [(1 / 150-1 / 190)]=5

[0059] The acceleration coefficient of 220℃ to 150℃: AF = exp[0.6415 / 8.62x10] -5 [(1 / 150-1 / 220)]=12

[0060] The acceleration coefficient of 240℃ to 150℃: AF = exp[0.6415 / 8.62x10] -5 [(1 / 150-1 / 240)]=22

[0061] The acceleration coefficient of 260℃ to 150℃: AF = exp[0.6415 / 8.62x10] -5 [(1 / 150-1 / 260)]=38

[0062] The test time at the accelerated test temperature is calculated based on the acceleration coefficient: t1 = t2 / AF

[0063] Where t1: test time at accelerated test temperature, t2: test time at normal test temperature, and AF: acceleration coefficient.

[0064] Accelerated test time at 190℃ = 1000 / 5 = 200 hours

[0065] Accelerated test time at 220℃ = 1000 / 12 = 83 hours

[0066] Accelerated test time at 240℃ = 1000 / 22 = 45 hours

[0067] Accelerated test time at 260℃ = 1000 / 38 = 26 hours

[0068] The final accelerated testing scheme for the intermetallic compound reliability of this BGA product was obtained:

[0069] 190℃ / 200 hours or 220℃ / 83 hours or 240℃ / 45 hours or 260℃ / 26 hours.

Claims

1. An accelerated testing method for the reliability of intermetallic compounds in wire bonding, characterized in that: Includes the following steps: S1, select multiple samples and multiple accelerated high-temperature temperatures, and conduct high-temperature tests respectively; S2, measure the resistance value of each sample pin under different high temperature environments; S3, set the failure condition, and the time to reach the failure condition is called the failure time; S4, calculate the cumulative failure rate when each sample fails; S5. Organize the test data into a table. The test data includes temperature, product failure time, and cumulative failure rate. S6. Obtain the distribution of the cumulative failure rate of each sample with respect to the failure time of the product. Plot the data in the test data table on the log-normal distribution coordinate system and obtain the fitting linear equation for each acceleration temperature. The fitting linear equation is y=ax+b, where y is the cumulative failure rate, x is the logarithm of the failure time, a is the slope, and b is the intercept. S7. Perform linear fitting on the data points of each acceleration temperature to confirm whether the slopes of each line are similar. If they are similar, proceed to step S8. If they are not similar, reduce the selected value of the highest temperature and adjust the interval value of each temperature to repeat steps S1 to S7. S8, calculate the time when the cumulative failure rate is 50% at each accelerated temperature according to the linear equation, i.e., the median lifetime t(0.5); S9. Plot the relationship between the logarithm of the median lifetime, Lnt(0.5), and the reciprocal of the temperature value in the linear coordinate system of the Arrhenius equation. S10, perform linear fitting on each data point again to obtain the slope of the straight line, which is the activation energy value of the failure mechanism of the intermetallic compound. The fitted linear equation is m=cn+d, where m is Lnt(0.5), n is (1 / T)*10000, c is the slope, which is the activation energy value of the failure mechanism, and d is the intercept. S11, Substitute the activation energy value, accelerated test temperature, and normal test temperature into the Arrhenius equation to obtain the acceleration coefficient at the accelerated test temperature, and thus obtain the test time at the accelerated test temperature; In step S11, the acceleration coefficient at the accelerated test temperature is obtained according to the Arrhenius equation as follows: AF = L1 / L2 = exp[Ea / k (1 / T1 - 1 / T2)], where AF is the acceleration coefficient, L1 is the lifetime under normal conditions, L2 is the lifetime under accelerated conditions, Ea is the activation energy value of the failure mechanism, and k is the Boltzmann constant 8.62 × 10⁻⁶. -5 T1 is the normal test temperature, and T2 is the accelerated test temperature; The method for determining the test time at the accelerated test temperature based on the acceleration factor is as follows: t1 = t2 / AF, where t1 is the test time at the accelerated test temperature, t2 is the test time at the normal test temperature, and AF is the acceleration factor.

2. The accelerated testing method for the reliability of intermetallic compounds in wire bonding according to claim 1, characterized in that: In step S1, the temperature for accelerating the high temperature is 180-300℃.

3. The accelerated testing method for the reliability of intermetallic compounds in wire bonding according to claim 1, characterized in that: In step S2, the resistance value is measured once per hour.

4. The accelerated testing method for the reliability of intermetallic compounds in wire bonding according to claim 1, characterized in that: In step S9, the temperature value is measured in Kelvin.

5. The accelerated testing method for the reliability of intermetallic compounds in wire bonding according to claim 1, characterized in that: In step S3, the failure condition is the resistance change rate (Ri-R0) / R0 ≥ 10%; where R0 is the initial resistance value, Ri is the resistance value tested in the i-th hour, i=1,2….

6. The accelerated testing method for the reliability of intermetallic compounds in wire bonding according to claim 1, characterized in that: In step S4, the cumulative failure rate is calculated as F(t) = i / (n+1), where F(t) is the cumulative failure rate, i is the number of failures, and n is the total number of samples.

7. The accelerated testing method for the reliability of intermetallic compounds in wire bonding according to claim 1, characterized in that: In step S7, it is determined whether the 'a' values ​​in the linear equations of each acceleration temperature are similar. If the difference between them is ≤0.5, they are considered similar.

8. The accelerated testing method for the reliability of intermetallic compounds in wire bonding according to claim 1, characterized in that: The specific method of step S8 is as follows: S81, substitute the cumulative failure rate = 50% into the linear equation of each acceleration temperature to obtain the logarithm of the median lifetime t(0.5) under each acceleration temperature test condition; S82, by taking the antilogarithm, the median lifetime t(0.5) of the sample under each accelerated temperature test condition can be obtained.

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