CN102768223A - Measurement method for thermal resistance of integrated circuit package based on electronic speckle pattern interferometry - Google Patents

Abstract

The invention discloses a method for measuring thermal resistance of integrated circuit packaging based on electronic speckle interference technology, which uses electronic speckle interference technology as a measurement means to establish a measurement system for thermal resistance of integrated circuit packaging, and performs power loading on integrated circuit test pieces , extract the response curve of the measured displacement in real time, and establish the response equation of the out-of-plane displacement through the relationship between the temperature and the out-of-plane displacement, and perform numerical deconvolution operation on the transient response equation of the out-of-plane displacement, and obtain the integrated circuit package The relationship between thermal resistance and thermal capacity. The method can quickly and effectively extract the thermal resistance of the integrated circuit package without any damage to the tested object.

Description

Measurement method of thermal resistance of integrated circuit package based on electronic speckle interferometry

technical field

The invention relates to the field of thermal resistance testing of integrated circuit test pieces, in particular to a method for measuring thermal resistance of integrated circuit packaging based on electronic speckle interference technology.

Background technique

In recent years, with the vigorous development of the electronics industry, integrated circuit test pieces are developing in the direction of high power, high complexity, small volume, and low cost, which leads to an increase in the heat flux per unit area, coupled with new materials and new With the continuous emergence of advanced packaging technology, it is more difficult to test the packaging thermal resistance of integrated circuit test pieces. At present, the measurement methods of thermal resistance mainly include chemical methods, physical methods, electrical methods, and optical methods (non-interference measurement methods). Most of these methods are experimental studies, and have certain limitations in practical applications. The chemical method is to measure the temperature of the device through chemical materials, which have a certain corrosion effect on the tested piece; It is inconvenient to open the package of the device; the electrical test method needs to lead out the leads in advance when testing the junction temperature, which is cumbersome to operate; the optical method is mainly the infrared scanning method, which needs to be unpacked during the test, and is expensive. In contrast, the measurement method using electronic speckle interferometry has the advantages of full-field, fast, non-destructive, simple operation, and no need to open the package. Some domestic scholars have carried out electronic speckle interferometry to measure the reliability of semiconductors under thermal stress, and analyzed the deformation of semiconductor packages under thermal stress. In 2009, Xiong Xianming, Huang Li and others published a research on accelerated lifetime prediction of IC chips based on electronic speckle interferometry in "Optoelectronics. Laser". Yuan Zongheng, Song Meijie and others published a paper on the rapid evaluation of semiconductor device reliability based on laser electron speckle interferometry technology in "Optoelectronics. Laser". These studies only study the reliability of integrated circuits from the perspective of thermal stress and strain, and do not study the thermal resistance of integrated circuit packages.

Contents of the invention

The technical problem solved by the present invention provides a method for measuring the thermal resistance of integrated circuit packaging based on electronic speckle interferometry, which can quickly and effectively extract the thermal resistance of integrated circuit packaging without any damage to the tested object.

In order to solve the above problems, the present invention is achieved through the following technical solutions:

A method for measuring thermal resistance of integrated circuit packaging based on electronic speckle interferometry, comprising the following steps:

(1) Establish a set of thermal resistance test platform based on speckle interference, place the test piece in the thermal resistance test platform in a static wind environment, and load the power to the test piece, and ensure that the power of the test piece is reached when the power is loaded. rated power;

(2) Measure the temperature of the surface of the tested piece in real time with a temperature measuring device;

(3) The electrical coupling device (CCD) of the thermal resistance test platform collects in real time the interference fringe pattern of the out-of-plane displacement of the tested piece under power loading, and calculates the out-of-plane displacement according to formula ①:

$\mathrm{\Δd}=\frac{\mathrm{N\λ}}{2}$ ①

In the formula, Δd is the out-of-plane displacement, N is the series of interference fringes, and λ is the laser wavelength;

(4) According to the temperature measurement result of step (2) and the out-of-plane displacement calculation result of step (3), fit the relationship between the out-of-plane displacement and temperature of the test piece, and extract the relationship factor of this relationship accordingly, wherein:

Δd(t)＝KT(t)+L ②

In the formula, Δd(t) is the out-of-plane displacement of the tested piece under power loading at different moments, T(t) is the temperature of the tested piece at different moments under power loading, K is the relationship factor, and L is a constant;

(5) Establish the transient response equation of the out-of-plane displacement of the tested piece, namely:

Δd(t)＝KP R _th [1-exp(-t/τ)]+L ③

In the formula, Δd(t) is the out-of-plane displacement of the tested piece under power loading at different moments, K is the relationship factor, P is the power loaded by the tested piece, τ=R _th C _th , τ is the time constant, R _th is the thermal resistance of the tested piece, C _th is the thermal capacitance of the tested piece;

(6) Deriving the transient response equation of the out-of-plane displacement, taking the differential to make it discretized;

(7) Numerical deconvolution is performed on the transient response equation of the differentiated out-of-plane displacement to obtain the relationship curve between the thermal resistance and the thermal capacity of the test piece.

The thermal resistance test platform described in the above step (1) is mainly composed of a laser, a beam splitter, 2 reflectors, 2 beam expanders, an imaging lens, a prism, an electrical coupling element, an image acquisition card, and an interference image acquisition software The computer is composed of; the light emitted by the laser is divided into two beams after passing through the beam splitter, one beam is used as the measurement light, and the other beam is used as the reference light; After the beam is expanded, it is irradiated on the prism; the measuring light is irradiated on the test piece after being expanded by the second beam expander; the light reflected from the surface of the test piece passes through the imaging lens and interferes with the reference light on the prism. The interference image is collected by the coupling element behind the prism, digitized by the image acquisition card and sent to the computer.

The static wind environment in the above step (1) means that the test piece is placed in a static air temperature measuring box.

In the above step (1), the way of power loading is to perform power loading on the tested piece by adjusting the clock frequency according to the proportional relationship between the clock frequency of the tested piece and the power.

In the above step (4), during the extraction process of the relationship factor, the out-of-plane displacement obtained by the temperature within the range of the tested piece not failing should be guaranteed.

The present invention uses electronic speckle interferometry technology as the measurement means to establish a set of measurement system for the thermal resistance of integrated circuit packaging, power loads the integrated circuit test piece, extracts the response curve of the measured displacement in real time, and establishes it through the relationship between temperature and out-of-plane displacement The response equation of the out-of-plane displacement, the numerical deconvolution operation is performed on the transient response equation of the out-of-plane displacement, and the relationship curve of the thermal resistance and heat capacity of the integrated circuit package is obtained.

Compared with prior art, the advantage of the present invention is:

1. It solves the problem of needing to open the package in the traditional method of measuring thermal resistance, and avoids damage to the test piece.

2. Realized by electronic speckle interferometry technology, it can measure the response process of out-of-plane displacement accurately in real time, with rapidity and accuracy.

3. The deconvolution operation of the response equation can not only extract the steady-state thermal resistance of the integrated circuit package, but also comprehensively analyze the relationship between the thermal resistance and thermal capacity of each layer of the package.

Description of drawings

Fig. 1 is a schematic diagram of the principle of the present invention.

Figure 2 is a schematic diagram of the thermal resistance testing platform.

Figure 3 is the extraction diagram of the relationship factor K between out-of-plane displacement and temperature.

Figure 4 is a graph of the transient response to out-of-plane displacement.

Fig. 5 is the time constant spectrum diagram of the out-of-plane displacement transient response deconvolution operation.

Fig. 6 is a graph of thermal resistance-heat capacity relationship.

Detailed ways

A method for measuring the thermal resistance of an integrated circuit package based on electronic speckle interferometry, as shown in Figure 1, includes the following steps:

(1) Establish a set of thermal resistance test platform based on speckle interference, place the test piece in the thermal resistance test platform in a static wind environment, and load the power to the test piece, and ensure that the power of the test piece is reached when the power is loaded. rated power.

In the present invention, the thermal resistance test platform is mainly composed of a laser, a beam splitter, 2 reflectors, 2 beam expanders, an imaging lens, a prism, an electrical coupling element, an image acquisition card, and an interferometric image acquisition software. computer composition. The light emitted by the laser is divided into two beams after passing through the beam splitter, one beam is used as the measurement beam, and the other beam is used as the reference beam. The reference light is reflected by the first reflector and the second reflector and irradiated on the prism after being expanded by the first beam expander; the measuring light is irradiated on the tested object after being expanded by the second beam expander. The light reflected from the surface of the test piece is kept perpendicular to the measuring light. The light reflected from the surface of the test piece passes through the imaging lens and interferes with the reference light on the prism. The electrical coupling element collects the interference image after the prism and converts it into an electrical signal, and then digitizes it through the image acquisition card and sends it to to a computer and render interference fringes. as shown in picture 2.

The above-mentioned static wind environment refers to that the test piece is placed in a still air temperature measuring box.

The stress loading method adopted in the present invention is power loading. The so-called power loading is to load the tested part through the dynamic aging method, so that the heat is generated from the inside of the device, which meets the thermal resistance test requirements. The power loading method of the present invention is based on the proportional relationship between the clock frequency of the integrated circuit and the power, by adjusting the clock frequency to perform power loading on the test piece, that is, the integrated circuit test piece. The magnitude of the loaded power is the rated power of the device under test.

The relationship between integrated circuit clock frequency and power:

p＝cv ² f+vi _peak t _s f

In the formula, cv ² f is the dynamic power consumption, and vi _peak t _s f is the short-circuit power consumption.

(2) Use a temperature measuring device to measure the temperature of the surface of the tested piece in real time, and wait for the surface temperature of the tested piece to reach a thermal equilibrium state. In the present invention, since the tested object is placed in a static air temperature measuring box, the temperature measuring device is the temperature measuring box.

(3) The electrical coupling element of the thermal resistance test platform collects in real time the interference fringe pattern of the out-of-plane displacement of the tested piece under power loading, and calculates the out-of-plane displacement according to formula ①:

$\mathrm{\Δd}=\frac{\mathrm{N\λ}}{2}$ ①

In the formula, Δd is the out-of-plane displacement, N is the order of interference fringes, and λ is the laser wavelength. In the present invention, the phase change of the interference fringes caused by the out-of-plane displacement of the measured surface of the object is:

In the formula, is the phase change, θ is the angle between the measuring light and the normal of the measured surface, keep θ=0 as much as possible during the measurement, that is, cosθ≈1, λ is the laser wavelength, and Δd is the out-of-plane displacement.

When dark fringes appear in the interference image, There is an approximate relationship between out-of-plane displacement and wavelength:

$\mathrm{<span\; class="notranslate">\; \&Delta;d</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; N\&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}$

In the formula, Δd is the out-of-plane displacement, N is the order of interference fringes, and λ is the laser wavelength.

(4) According to the temperature measurement results of step (2) and the out-of-plane displacement calculation results of step (3), the relationship between the out-of-plane displacement and temperature of the test piece in the non-failure range is fitted, and the relationship is extracted accordingly relationship factor, where:

Δd(t)＝KT(t)+L ②

In the formula, Δd(t) is the out-of-plane displacement of the tested piece under power loading at different moments, T(t) is the temperature of the tested piece at different moments under power loading, K is a relationship factor, and L is a constant. Figure 3.

In the present invention, extracting the relationship factor K from the relationship between the out-of-plane displacement and temperature requires the out-of-plane displacement of the tested piece within the non-failure range, and the value of the relationship factor K is obtained by fitting multiple experiments.

(5) Establish the transient response equation of the out-of-plane displacement of the tested piece (as shown in Figure 4), namely:

Δd(t)＝KPR _th [1-exp(-t/τ)]+L ③

In the formula, Δd(t) is the out-of-plane displacement of the tested piece under power loading at different moments, K is the relationship factor, P is the power loaded by the tested piece, τ=R _th C _th , τ is the time constant, R _th is the thermal resistance of the tested piece, and C _th is the thermal capacitance of the tested piece.

According to the Cauer thermal resistance model, the thermal resistance and thermal capacitance of the device are connected in parallel, and the temperature response equation when power is loaded is:

T(t)＝P R _th [1-exp(-t/τ)]

In the formula, T(t) is the temperature of the tested piece at different moments under power loading, P is the power loaded by the tested piece, τ is the time constant τ=R _th C _th , R _th is the thermal resistance of the device, C _th is the heat capacity of the device.

(6) Deriving the transient response equation of the out-of-plane displacement, taking the differential to make it discretized.

The same integrated circuit test piece may be packaged by multiple layers of materials with different time constants, and the multi-layer package structure is a thermal system with multiple different time constants. In real physical systems, thermal resistance and thermal capacity are inseparable. In the process of time discretization, it has no practical significance to obtain the FOSTER thermal model of m points, and it needs to be converted into a Causer model in the analysis. According to the Cauer thermal resistance network model, the present invention can establish a plurality of out-of-plane displacement response equations of thermal systems with different time constants by the following formula for thermal systems with multiple time constants:

$\mathrm{<span\; class="notranslate">\; \&Delta;d</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; KP</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; th</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; mL</span>}<span\; class="notranslate">\; .</span>$

In the formula, Δd(t) is the out-of-plane displacement of the tested piece under power loading at different moments, K is the relationship factor, P is the power loaded by the tested piece, τ=R _th C _th , τ is the time constant, R _th is the thermal resistance of the tested piece, C _th is the heat capacity of the tested piece, and m is the number of thermal systems with different time constants.

(7) Carry out numerical deconvolution operation to the transient response equation of the out-of-plane displacement after differentiation. The relationship curve of capacity (as shown in Figure 6). The inflection point of the peak and trough in the curve in Figure 6 represents the boundary point of the two package structures, the distance from the origin to the package shell represents the thermal resistance from the node to the shell of the test piece, and the vertical asymptotic line from the origin to the end of the curve The distance is the thermal resistance from junction to air.

Claims (5)

1. The method for measuring the thermal resistance of integrated circuit packaging based on electronic speckle interferometry is characterized in that it comprises the following steps: (1) Establish a set of thermal resistance test platform based on speckle interference, place the test piece in the thermal resistance test platform in a static wind environment, and load the power to the test piece, and ensure that the power of the test piece is reached when the power is loaded. rated power; (2) Measure the temperature on the surface of the tested piece in real time with a temperature measuring device; (3) The electrical coupling element of the thermal resistance test platform collects in real time the interference fringe pattern of the out-of-plane displacement of the tested piece under power loading, and calculates the out-of-plane displacement according to formula ①: $\mathrm{\&Delta;d}=\frac{\mathrm{N\&lambda;}}{2}$ ① In the formula, Δd is the out-of-plane displacement, N is the series of interference fringes, and λ is the laser wavelength; (4) According to the temperature measurement result of step (2) and the out-of-plane displacement calculation result of step (3), fit the relationship between the out-of-plane displacement and temperature of the test piece, and extract the relationship factor of this relationship accordingly, wherein: Δd(t)＝KT(t)+L ② In the formula, Δd(t) is the out-of-plane displacement of the tested piece under power loading at different moments, T(t) is the temperature of the tested piece at different moments under power loading, K is the relationship factor, and L is a constant; (5) Establish the transient response equation of the out-of-plane displacement of the tested piece, namely: Δd(t)＝KPR _th [1-exp(-t/τ)]+L ③ In the formula, Δd(t) is the out-of-plane displacement of the tested piece under power loading at different moments, K is the relationship factor, P is the power loaded by the tested piece, τ=R _th C _th , τ is the time constant, R _th is the thermal resistance of the tested piece, C _th is the thermal capacitance of the tested piece; (6) Deriving the transient response equation of the out-of-plane displacement, taking the differential to make it discretized; (7) Numerical deconvolution operation is performed on the transient response equation of the differentiated out-of-plane displacement to obtain the relationship curve between the thermal resistance and the thermal capacity of the test piece. 2. The method for measuring thermal resistance of integrated circuit packages based on electronic speckle interferometry according to claim 1 is characterized in that: the thermal resistance test platform described in step (1) mainly consists of a laser, a beam splitter, 2 reflectors, It consists of 2 beam expanders, imaging lens, prism, electric coupling element, image acquisition card, and computer installed with interference image acquisition software; the light emitted by the laser is divided into two beams after passing through the beam splitter, one beam is used as measuring light, and the other The beam is used as the reference light; the reference light is reflected by the first reflector and the second reflector and irradiated on the prism after being expanded by the first beam expander; the measuring light is irradiated to the tested object after being expanded by the second beam expander Above; the light reflected by the surface of the test piece passes through the imaging lens and the reference light converges on the prism for interference, and the electrical coupling element collects the interference image behind the prism, and digitizes it through the image acquisition card and sends it to the computer. 3. The method for measuring thermal resistance of integrated circuit packages based on electronic speckle interferometry according to claim 1 or 2, wherein the static wind environment in step (1) means that the test piece is placed in a static air temperature measuring box Inside. 4. The method for measuring the thermal resistance of an integrated circuit package based on electronic speckle interferometry according to claim 1 or 2, characterized in that: in step (1), the power loading mode is proportional to the clock frequency and power of the tested object The relationship between the power load on the DUT by adjusting the clock frequency. 5. The method for measuring thermal resistance of integrated circuit packages based on electronic speckle interferometry according to claim 1 or 2, characterized in that: step (4) in the process of extracting the relational factor should ensure that the temperature is within the range of the tested object. The obtained out-of-plane displacement in the range of .

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