JPS61138153A - Method for measuring thermal fatigue of joining material - Google Patents

Abstract

PURPOSE:To enable the continuous recording and observation of a thermal fatigue degree by adding the temp. cycle to the measuring instrument with operating the heater for measuring sample and refrigerator and by finding the variation in the resistance value of the joining material by four terminal method with flowing a current between the joining material of each one set with the state thereof. CONSTITUTION:A sample 9 is set to the inside of a refrigerator 10, the terminals 6, 7 of each solder ball 1 provided on the ceramics substrate 4 thereof are connected to each terminal of a scanner 11 and the terminal of the resisting body pattern 8 being provided on a tip 2 is connected to the terminal of a heater electric power adjuster 12. The electrifying circuit of the solder ball 1 of one set in two pieces is switched by the scanner 11 with the state of reaching the prescribed temp. by electrifying the sample 9 by the program of a controller 15 and the electric resistance is found by four terminal method with measuring in order using an ohmmeter 16, is displayed 17 and recorded 18. Then when dropped to the prescribed temp. it is heated to the prescribed temp. by electrifying with the motion of the heater power adjuster 12 again by the instruction of the controller 15. The variation in the resistance value in the solder ball joining part can be measured automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] □ The present invention relates to a method for measuring heat waves and stress of a bonding material used to attach a circuit element such as a semiconductor RC chip to a wiring board.

IC, LSr to improve the processing capacity of information processing equipment
Semiconductor devices such as these are becoming smaller and larger in capacity, and at the same time, mounting methods are also being improved.

In other words, conventional semiconductor devices have a puff cage structure in which each chip is mounted on a ceramic substrate, sealed with resin, and then stored in a resin case. Alternatively, it has been mounted in a through hole.

However, with advances in passivation technology, mounting methods have also been improved, and a method is now being adopted in which a plurality of LSI elements are mounted on a ceramic multilayer board to create an LSI module, and this is mounted on a printed wiring board.

In such a case, the LSI element is attached to the ceramic substrate using a bonding material such as a solder pole or a solder bump.

In other words, the terminals (pads) of a conductor circuit provided around the periphery of an LSI element and the lands of a conductor line patterned on a ceramic substrate are bonded using solder balls, or the conductor line on a ceramic substrate is After aligning the pads of the LSI module with the solder bumps provided on the board, the bonding is performed by thermocompression bonding.

In this way, the semiconductor element is connected to the ceramic multilayer board, but since the semiconductor and ceramic boards have different coefficients of thermal expansion, stress is generated in the bonding material during use, and this gradually accumulates, causing the There is a problem in that the bonding material breaks.

In other words, even if the semiconductor element is kept at a low temperature, it generates heat during use and reaches a considerable temperature.When the current is turned off, the semiconductor element returns to its original temperature, but the stress due to the difference in thermal expansion is not absorbed by the bonding material. , as a result of repeating this,
This will cause cranking and disconnection problems at the joints.

The present invention relates to a method for measuring the degree of thermal fatigue of the bonded material thus generated.

[Conventional technology]

The conventional method for measuring thermal fatigue has been to prepare two constant-temperature layers, one kept at a low temperature and one at a high temperature, move the sample between them, and use a microscope to detect the presence or absence of a crank.

However, this method has the problem that simulation cannot be performed because the semiconductor substrate (hereinafter referred to as a chip) and the ceramic substrate undergo thermal expansion and contraction at the same time.

In other words, the chip actually heats up and expands when energized.
This heat is conducted to the ceramic wiring board through the bonding material, causing expansion of the board, and there is a time lag during this time.
As a result, stress is generated in the joining materials in a complex manner.

Furthermore, the detection of fracture is the result of the release of accumulated stress, and the intermediate processes leading to fracture are unclear, and there is also the problem that microscopic racks are difficult to detect by microscopic observation.

For these reasons, there is no practical method for measuring thermal fatigue of bonding materials, and there has been a desire to put such a measuring method into practical use.

[Problem that the invention seeks to solve]

As explained above, the problem is that there is no method that can measure the degree of thermal fatigue of bonding materials in a state close to the mounted state.

[Means for solving problems]

The above problem can be solved by constructing a measurement sample using upper and lower substrates that are bonded using multiple bonding materials, forming a pattern on the upper substrate with a heater and a conductor line connecting each bonding material, while bonding the lower substrate. A current terminal and a voltage measurement terminal are patterned at each material mounting position, and the heater and refrigerator are operated to apply a temperature cycle to the measuring device, and in this state, current is passed between each set of bonding materials. This problem can be solved by a method for measuring the degree of thermal fatigue of a bonding material, which is characterized by determining the change in resistance of the bonding material using a four-terminal method.

[Effect]

The present invention provides a heating element in the chip itself, turns on and off the current flowing through it, and changes the environmental temperature from the highest temperature to the lowest temperature, so that thermal fatigue occurs in a state close to the mounted state. A plurality of circuits are provided to connect two bonding materials, and changes in electrical resistance of these circuits are automatically measured using the four-terminal method, thereby making it possible to continuously record and observe the degree of thermal fatigue at the same time.

〔Example〕

There are two ways to attach a chip to a ceramic board: one using solder balls and the other using bumps.
Here, the former case will be explained.

FIG. 1 is a front view of a sample for thermal fatigue measurement of a bonding material according to the present invention, FIG. 2 is a perspective view thereof, and FIG. 3 is a block diagram of a measuring device according to the present invention.

That is, as shown in FIGS. 1 and 2, the solder ball 1 is connected to the pad 3 provided on the chip 2 and the ceramic substrate 4.
Circuit connection is made by connecting the pads 5 provided in the through-hole portions of the ceramic substrate, but in the case of this measurement sample, there are no through holes in the ceramic substrate, and instead, the resistance value change is measured using the four-terminal method. A current terminal 6 and a voltage measurement terminal 7 for measurement are formed in a pattern.

Further, a resistor pattern 8 is provided on the chip 2 by a method such as nichrome (Ni--Cr) vapor deposition.

In this embodiment, as shown in FIG. 2, the resistor pattern 8 is formed in an S-shape so that the entire area of the chip 2 can be heated evenly.

Furthermore, a pattern of conductive lines connecting a plurality of solder balls 1 is formed on the back surface of the chip 2, so that any two solder balls can be connected and energized.

Figure 3 shows a block diagram for measuring the degree of thermal fatigue by subjecting sample 9 to a temperature cycle.
is installed in the refrigerator 10, and the current terminal 6 and voltage measurement terminal 7 of each solder ball l provided on the ceramic substrate 4 are connected to each terminal of the scanner 11, and the The terminals of the resistor pattern 8 are connected to the terminals of the heater power regulator 12.

Further, the substrate temperature of the sample 9 is measured by thermometers 13 and 14 and fed back to the heater power regulator 12.

The mechanism shown in FIG. 3 according to the present invention will now be explained as follows.

After the sample 9 is energized according to the program of the controller 5 and reaches a certain temperature, the current is turned off, and when the predetermined temperature is reached, the energized circuit of the two solder balls 1 is connected by the scanner 1. Switch and use the resistance meter 16,
The potential differences of all the combinations are sequentially measured using the four-terminal method, and the electrical resistance is determined from the electrical resistance, which is displayed on the display device 17 and recorded in the recording device 18.

Next, after the temperature decreases and reaches a specified temperature, the heater power regulator 12 operates again according to instructions from the controller 5 to energize the sample 9 and heat the sample 9 to a specified temperature.

As described above, by using the sample configuration and measurement circuit according to the present invention, it is possible to automatically measure the change in resistance value at the solder ball joint during the process of repeating temperature cycles.

Figure 4 shows a 15 x 15n silicon chip (chip 1).
Alumina (α-AI203) is used as the ceramic substrate 4, and the conductor pattern and pad 3.5 are each made of nichrome (Ni-C) with a thickness of 0.05 μm.
r) and 1 μm gold (Au), while lead (Pb)-63 tin (300 μm in diameter) is used as the solder pole 1.
2 shows the change in electrical resistance when a temperature cycle of 0 to 100° C. is continuously applied at a period of 5 minutes to a sample bonded using Sn) using the measuring method according to the present invention.

This characteristic curve 19 shows that the resistance value increased by about 5% due to stress around 260 times, and then broke around 320 times.

As described above, according to the present invention, the degree of thermal fatigue can be measured in a state similar to the mounting form, and the state of stress accumulation before breakage can be clearly measured.

〔Effect of the invention〕

As described above, by implementing the present invention, it becomes possible to continuously and automatically measure the degree of thermal fatigue of bonding materials due to temperature cycles, and it becomes possible to contribute to the improvement of bonding materials.

[Brief explanation of drawings]

Fig. 1 is a front view showing the structure of a sample for measuring thermal fatigue degree according to the present invention, Fig. 2 is a perspective view thereof, Fig. 3 is a block diagram of a measuring device according to the present invention, and Fig. 4 is a diagram of a bonding material. The measurement result is . In the figure, 1 is a solder ball, 2 is a chi knob, 3.5 is a pad, 4 is a ceramic board, 6 is a current terminal,
7 is a voltage measurement terminal, 8 is a resistor pattern,
9 is a sample, 19 is a characteristic curve. ￥ 1 Go to figure〇 Tsudo vine Z EnP 3 Genyu 4 eyes

Claims (1)

[Claims] A measurement sample is constructed using upper and lower substrates that are bonded using multiple bonding materials, and a heater and a conductor line connecting each bonding material are patterned on the upper substrate, while a pattern is formed on each of the bonding material mounting positions on the lower substrate. The device has a pattern of current terminals and voltage measurement terminals, and the heater and refrigerator are operated to give the measurement device a temperature cycle. In this state, current is passed between each pair of bonding materials, and the four-terminal method is used to measure the temperature. A method for measuring the degree of thermal fatigue of a joining material, characterized by determining a change in the resistance value of the joining material.