JP5308129B2 - Electronic component lifetime measurement method, electronic component lifetime measurement device, and board design quality determination method - Google Patents

Description

The present invention relates to an electronic component lifetime measuring method, an electronic component lifetime measuring apparatus capable of measuring a vibration fatigue lifetime of a mounted electronic component, and a substrate design quality determining method.

A control unit such as an air conditioner is configured by a board in which electronic components such as an integrated circuit such as a CPU, a RAM, and a ROM, a resistor, and a capacitor are mounted on the surface of a printed circuit board (substrate) on which electronic circuits are printed and wired. ing.
Conventionally, the control unit of an air conditioner is rarely placed in a severe vibration environment except for aircraft, military equipment, and the like. However, in recent years, the digitization of automobiles has progressed, and there are an increasing number of cases in which boards are placed in severe vibration environments and thermal environments such as directly attached to an engine for convenience of arrangement.
On the other hand, the demand for smaller and lighter substrates is also increasing, and the bases (substrates, mounting portions, etc.) of electronic components are weak.

Under such circumstances, it has become important to select an electronic component from the viewpoint of vibration strength and thermal fatigue, that is, to be able to exhibit predetermined performance for a predetermined period.
As for the thermal fatigue surface of an electronic component, a technique for studying it has been proposed as disclosed in Patent Document 1, for example.
This is based on the electrical output obtained by the strain gauge during the thermal cycle test as well as performing a thermal cycle test by attaching a strain gauge to the solder joint of the electronic component mounted by soldering the leads to the board. Thus, the quality of the solder joint is determined.
On the other hand, regarding the vibration fatigue surface of electronic parts, the technology for studying it is not as advanced as the thermal fatigue surface.

JP 2006-30048 A

By the way, in order to examine the vibration strength of an electronic component, the stress applied to the electronic component is usually measured as disclosed in Patent Document 1, but the electronic component is very small and is not attached to the solder joint. Since it is extremely fine (the width is about 1 mm at most), it is difficult to directly measure the stress.
If a strain gauge is used as in Patent Document 1, the strain gauge becomes very small, so that the work of attaching it becomes difficult, and the reliability of measured data is low.
In addition, since the vibration mode of the substrate varies depending on the mounting location of the substrate, the previous data cannot be used if the mounting location changes.

In view of the above problems, there is no effect on the electronic components, conveniently lifetime measurement method of the electronic component vibrating Ru electronic components can be measured life due to fatigue of, measuring the vibration fatigue life of mounted electronic components An object of the present invention is to provide an electronic component lifetime measuring apparatus and a board design quality determination method.

In order to achieve the above object, the present invention provides the following means.
According to the electronic component lifetime measuring method of the present invention, the substrate mounted with the electronic component is used as a test piece, and the electronic component is vibrated while measuring the strain amount of the substrate in the vicinity of the electronic component until the electronic component has a vibration fatigue life. The vibration test is repeated under different conditions, the correlation between the strain amount and the vibration fatigue life is used as a database, and the strain amount of the substrate in the vicinity of the electronic component on the substrate mounted on the product is measured by a strain measuring member. The vibration fatigue life is estimated from the database based on the measured strain amount.

According to the present invention, a vibration test is performed repeatedly while changing the vibration conditions while measuring the strain amount of the substrate in the vicinity of the electronic component until the electronic component reaches the vibration fatigue life using the substrate on which the electronic component is mounted as a test piece. The correlation between strain and vibration fatigue life is taken as a database. Then, the strain amount of the substrate in the vicinity of the electronic component on the substrate mounted on the product is measured by the strain measuring member, and the vibration fatigue life can be estimated from the database based on the measured strain amount.
As described above, the strain amount of the substrate in the vicinity of the electronic component on the substrate is measured by the strain measurement member, so that, for example, measurement has a direct influence on the electronic component compared to the case where a strain gauge is directly attached to the electronic component. Never do. Further, since measurement can be performed regardless of the size of the electronic component, it is not necessary to incorporate the strain measuring member in a small space, so that the assembling work of the strain measuring member can be easily performed.

Further, since the strain amount of the substrate in the vicinity of the electronic component on the substrate mounted on the product is measured by the strain measuring member, the vibration fatigue life of the electronic component can be always checked as necessary.
Furthermore, since the correlation between the strain amount and the vibration fatigue life is used as a database in advance, the vibration fatigue life can be estimated as it is even when the substrate installation location is changed and the vibration form of the substrate is different.
The vicinity position of the electronic component means a position close to the electronic component. In this case, the position that is not covered with the electronic circuit and the substrate is exposed is selected. Therefore, the position where the substrate is exposed is selected on either the mounting surface (front side surface) on which the electronic component is mounted or the surface opposite to the mounting surface (back side surface). If it is a back side surface, the distortion amount of the board | substrate in the position corresponding to an electronic component can be measured.

  In the above invention, the strain measuring member may be a strain gauge affixed to the vicinity position.

  Since the strain gauge is attached to the substrate, its size need not correspond to the size of the electronic component (ie, very small). For this reason, since a large strain gauge can be used, the pasting operation becomes easy. Moreover, since local distortion is not detected, the reliability of the measured data becomes high.

In the above invention, the strain measurement member may measure the amount of strain of the substrate in the vicinity without contact.

As described above, the strain measuring member measures the amount of strain of the substrate in the vicinity without contact, and thus does not damage the electronic circuit of the substrate.
In addition, since the measurement range is diverse, a wide measurement range can be used. In this way, since the amount of strain in a wide range of the substrate can be measured, the life evaluation of a plurality of electronic components can be performed simultaneously.

  An electronic component lifetime measuring apparatus according to the present invention uses a substrate on which an electronic component is mounted as a test piece, and measures vibration while measuring the strain amount of the substrate in the vicinity of the electronic component until the electronic component reaches a vibration fatigue life. The vibration test is repeated under different conditions, the correlation between the strain amount and the vibration fatigue life is used as a database, and the strain amount of the substrate in the vicinity of the electronic component on the substrate mounted on the product is measured by a strain measuring member. The vibration fatigue life is estimated from the database based on the measured strain amount.

According to the present invention, a vibration test is performed repeatedly while changing the vibration conditions while measuring the strain amount of the substrate in the vicinity of the electronic component until the electronic component reaches the vibration fatigue life using the substrate on which the electronic component is mounted as a test piece. , the database a correlation of the strain amount and vibration fatigue life. Then, it is possible to a distortion amount of the substrate in the vicinity position of the electronic component in the substrate mounted on the product measured by the strain measuring member, to estimate the vibration fatigue life from the database based on the measured strain amount.
As described above, the strain amount of the substrate in the vicinity of the electronic component on the substrate is measured by the strain measurement member, so that, for example, measurement has a direct influence on the electronic component compared to the case where a strain gauge is directly attached to the electronic component. Never do. Further, since measurement can be performed regardless of the size of the electronic component, it is not necessary to incorporate the strain measuring member in a small space, so that the assembling work of the strain measuring member can be easily performed.

Further, since the strain amount of the substrate in the vicinity position of the electronic component in the substrate mounted product is measured by the strain measuring member, always can check vibration fatigue life of the electronic components as needed.
Furthermore, since the correlation between the strain amount and the vibration fatigue life is used as a database in advance, the vibration fatigue life can be estimated as it is even when the substrate installation location is changed and the vibration form of the substrate is different.
The vicinity position of the electronic component means a position close to the electronic component. In this case, the position that is not covered with the electronic circuit and the substrate is exposed is selected. Therefore, the position where the substrate is exposed is selected on either the mounting surface (front side surface) on which the electronic component is mounted or the surface opposite to the mounting surface (back side surface). If it is a back side surface, the distortion amount of the board | substrate in the position corresponding to an electronic component can be measured.

According to the substrate design quality determination method of the present invention, the substrate on which the electronic component is mounted is used as a test piece, and the vibration is measured while measuring the strain amount of the substrate in the vicinity of the electronic component until the electronic component has a vibration fatigue life. A vibration test is repeatedly performed under different conditions, and the correlation between the strain amount and the vibration fatigue life is used as a database, and the substrate in the vicinity of the electronic component on the substrate mounted on the product based on the vibration condition of the product is used . A strain amount is simulated by a finite element method, the vibration fatigue life of the electronic component is estimated from the database based on the simulated strain amount, and it is determined whether or not it satisfies a design condition.

According to the present invention, a vibration test is performed repeatedly while changing the vibration conditions while measuring the strain amount of the substrate in the vicinity of the electronic component until the electronic component reaches the vibration fatigue life using the substrate on which the electronic component is mounted as a test piece. The correlation between strain and vibration fatigue life is taken as a database.
On the other hand, based on the vibration conditions of the product, simulation is performed by the finite element method to calculate the amount of strain of the substrate in the vicinity of the electronic component on the substrate .
Based on the simulated strain amount, the vibration fatigue life of the electronic component is estimated from the database, and it is determined whether it satisfies the life of the electronic component as a design condition.
In this way, it is possible to determine whether the life of the electronic component meets the design conditions based on the simulated strain, so before starting full-scale production of the substrate with the electronic component, design the substrate with the electronic component mounted. Can be judged.

According to the present invention, since the strain amount of the substrate in the vicinity of the electronic component on the substrate is measured by the strain measuring member, for example, the measurement is applied to the electronic component as compared with the case where the strain gauge is directly attached to the electronic component. There is no direct impact. Further, since measurement can be performed regardless of the size of the electronic component, it is not necessary to incorporate the strain measuring member in a small space, so that the assembling work of the strain measuring member can be easily performed.
Further, since the strain amount of the substrate in the vicinity of the electronic component on the substrate mounted on the product is measured by the strain measuring member, the vibration fatigue life of the electronic component can be always checked as necessary.
Furthermore, since the correlation between the strain amount and the vibration fatigue life is used as a database in advance, the vibration fatigue life can be estimated as it is even when the substrate installation location is changed and the vibration form of the substrate is different.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 5.
FIG. 1 is a block diagram illustrating a schematic configuration of a vibration test apparatus that performs a vibration test according to the present embodiment.
The vibration test apparatus 1 includes a pair of clamps 3 that vibrate in the vertical direction H, a strain gauge 5 that measures a strain amount, and a life determination unit 7 that determines a vibration fatigue life.
The pair of clamps 3 holds both end portions of the substrate 11 having the electronic component 9 mounted on the surface.
The strain gauge 5 is a strain gauge (strain) attached to a position (near position) corresponding to the electronic component 9 on the surface (back side surface) opposite to the surface (front side surface) to which the electronic component 9 of the substrate 11 is attached. A measurement member) 13 is electrically connected to measure the amount of strain of the substrate 11 from the change in electrical resistance of the strain gauge 13.

The life determination unit 7 includes a power source 15 and an ammeter 17. The life determination unit 7 forms a circuit passing through the power source 15 and the electronic component 9 and supplies a minute current to the electronic component 9.
The life determination unit 7 measures a minute current flowing through the electronic component 9 with an ammeter 17. When the current changes from the initial magnitude (disturbance), the life determination unit 7 determines that the life of the electronic component 9 has reached because the state of the electronic component has changed.
This disturbance varies depending on the electronic component 9 as a target, but is, for example, 1 to 10% of the initial current magnitude.

FIG. 3 is a plan view showing an example of the board 10 according to the present embodiment. 4 is a cross-sectional view taken along line XX in FIG.
The board 10 is configured by mounting, for example, a CPU 19, a ROM 21, a RAM 23, a capacitor 25, a resistor 27, and the like as electronic components 9 on the surface of a substrate 11 on which electronic circuits are printed and wired.
Strain gauges 13 as strain measuring members are affixed to positions near the respective electronic components 9 mounted on the substrate.
About ROM21, RAM23, capacitor | condenser 25, and resistance 27, the strain gauge 13 is affixed on the surface (mounting surface) in which they are mounted | worn. On the other hand, as shown in FIG. 4, the CPU 19 is affixed to the back surface (the surface opposite to the mounting surface).

The position where the strain gauge 13 is affixed is basically a position near the electronic component 9 that is not covered by the electronic circuit and the surface of the substrate 11 is exposed. Therefore, these strain gauges 13 are installed as described above because there is no electronic circuit at the attachment position.
Considering that the strain amount of the substrate 11 at a position corresponding to the electronic component 9 can be measured, it is desirable that the strain gauge 13 is attached to the back surface like the CPU 19.
On the other hand, in consideration of the mounting operation, it is desirable that the strain gauge 13 is attached to the surface. For example, the signal extraction line of the strain gauge 13 can be wired in advance as an electronic circuit of the substrate 11.

Thus, since the strain gauge 13 is attached to the board | substrate 11, the magnitude | size does not need to respond | correspond to the magnitude | size (namely, very small) of the electronic component 9. FIG.
For this reason, since the strain gauge 13 having a large size, for example, 5 mm or more can be used, the pasting work is facilitated. Further, since the relatively large strain gauge 13 does not detect the local strain of the substrate 11, the reliability of the measured data can be increased.
The strain gauge 13 is electrically connected to the strain gauge 29. The strain gauge 29 measures the strain amount of the portion of the substrate 11, that is, the substrate near the electronic component 9 from the change in the electrical resistance of the strain gauge 13.

This board 10 is basically a mass-produced product. Before starting mass production, a vibration test is performed by the vibration test apparatus 1 shown in FIG. This vibration test will be described.
Both ends of the substrate 11 to which the electronic component 9 and the strain gauge 13 are attached are held by the clamp 3. The signal line of the strain gauge 13 is connected to the strain gauge 5. A circuit passing through the power supply 15 and the electronic component 9 is connected to the electronic component 9 and a minute current is supplied to the electronic component 9.

In this state, the clamp 3 is vibrated with a constant amplitude in the vertical direction H. At this time, the strain gauge 5 measures the strain amount of the substrate 11 from the resistance change of the strain gauge 13.
The life determination unit 7 measures a minute current flowing through the electronic component 9 with an ammeter 17.
The life determination unit 7 checks the current detected by the ammeter 17 and determines whether it changes by a predetermined amount from the initial magnitude. This predetermined amount varies depending on the target electronic component 9, but is, for example, 1 to 10% of the magnitude of the initial current.
When the current changes by a predetermined amount, the life determination unit 7 determines that the state of the electronic component has changed, and determines that the life of the electronic component 9 has reached.
Then, the number of vibrations up to that time and the strain amount measured by the strain gauge 5 are stored.

Next, the vibration test is performed in the same manner as described above by changing the amplitude of the clamp 3, and at that time, the number of vibrations when it is determined as the life and the strain amount measured by the strain gauge 5 are stored.
This is repeated, and the number of vibrations when it is determined to be the life and the amount of strain measured by the strain gauge 5 are stored and stored in a database.
FIG. 2 is a graph showing the correlation between the amount of strain and the number of vibrations up to the lifetime in the database for one electronic component 9.

Since the database is constructed by the test before mass production, the pass / fail of the mass-produced product can be judged only by strain measurement.
In addition, once data has been collected, it is possible to make a pass / fail judgment only by strain measurement even with substrates having different specifications (shapes) by referring to the database.
That is, it is not necessary to check whether or not the electronic component is broken, and the durability test time which generally takes 50 hours or more can be saved to several hours.

This database can also be used to determine, for example, whether the board 10 meets the design requirements of the product to which it is attached. This will be described.
Based on the vibration condition of the product to which the board 10 is attached, simulation is performed by the finite element method to calculate the amount of distortion of the substrate in the vicinity of the electronic component 9 in the substrate 11.
Based on the simulated strain amount, the vibration fatigue life of the electronic component 9 is estimated from the database, and it is determined whether it satisfies the design condition of the board 10. The design condition is, for example, the lifetime of the electronic component 9.

If the board 10 does not satisfy the design conditions, make necessary design changes, such as replacing the electronic component 9 with another, changing the arrangement of the electronic component 9, or changing the mounting method of the electronic component. Can do.
In other words, since it can be determined whether or not the board 10 satisfies the design conditions based on the simulated distortion amount, it is possible to determine whether the design of the board 10 is good or bad before the board 10 is fully manufactured. it can.
The quality determination of this design is performed as necessary.

If the design sufficiently satisfies the design conditions of the board 10, the board 10 will enter mass production.
In this case, depending on the conditions, it may be possible not to implement a method for measuring the lifetime of the electronic component 9 described later. That is, the strain gauge 13 can be not attached to the board 10 that is mass-produced.

Next, a method for measuring the lifetime of the electronic component 9 when the board 10 is mounted on a product will be described.
The strain gauge 29 measures the amount of strain of the substrate 11 at each position in response to a change in the electrical resistance of the strain gauge 13 attached to the vicinity of each electronic component 9.
The vibration fatigue life of the electronic component 9, that is, the allowable number of vibrations can be estimated by hitting the database of the corresponding electronic component 9 based on the measured strain amount.
Therefore, the remaining life of the electronic component 9 can be estimated by separately measuring or estimating the number of vibrations since operation. Thereby, the maintenance time, the replacement time of the electronic component 9, the replacement time of the board 10, etc. can be easily determined.

As described above, since the strain amount of the substrate in the vicinity of the electronic component 9 on the substrate 11 mounted on the product is measured by the strain gauge 13, the vibration fatigue life of the electronic component 9 is always checked as necessary. be able to.
Furthermore, since the correlation between the amount of strain and the vibration fatigue life is used as a database in advance, the vibration fatigue life can be estimated as it is even if the substrate 11, that is, the installation location of the board 10 is changed and the vibration form of the substrate is different. it can.

In the present embodiment, the strain gauge 13 attached to the substrate 11 is used as the measurement member, but a non-contact member can be used as the measurement member, for example, as shown in FIG.
FIG. 5 is a cross-sectional view showing the same parts as in FIG.
A holographic interferometer (measuring member) 31 is attached to the installation position of the board 10 on the back side thereof.
The holographic interference measuring instrument 31 includes a main body 33, an imaging member 35, and an illuminator 37.
The main body 33 processes the image captured by the imaging member 35, forms moire interference fringes, and measures the distortion amount of the target portion.
In this case, the strain gauge 7 of the vibration test apparatus 1 may measure the amount of strain by replacing it with the holographic interferometer 31.

The holographic interferometer 31 measures the amount of strain of the substrate 11 in the vicinity of each electronic component 9.
The vibration fatigue life of the electronic component 9, that is, the allowable number of vibrations can be estimated by hitting the database of the corresponding electronic component 9 based on the measured strain amount.
Therefore, the remaining life of the electronic component 9 can be estimated by separately measuring or estimating the number of vibrations since operation. Thereby, the maintenance time, the replacement time of the electronic component 9, the replacement time of the board 10, etc. can be easily determined.

As described above, since the holographic interferometer 31 measures the amount of distortion of the substrate in the vicinity of the electronic component 9 in the substrate 11 mounted on the product, the vibration fatigue life of the electronic component 9 is always increased as necessary. Can be checked.
Furthermore, since the correlation between the amount of strain and the vibration fatigue life is used as a database in advance, the vibration fatigue life can be estimated as it is even if the substrate 11, that is, the installation location of the board 10 is changed and the vibration form of the substrate is different. it can.

Since the holographic interferometer 31 measures the amount of distortion of the substrate in the vicinity without contact, there is no possibility of damaging the electronic circuit of the substrate 11.
Further, since the holographic interferometer 31 can have various measurement ranges, the measurement range can be expanded.
In this way, since each strain amount in a wide range of the substrate 11 can be measured, the life evaluation of the plurality of electronic components 9 can be performed simultaneously.

  In addition to the holographic interferometer 31, for example, an appropriate member such as a method using a laser displacement meter or a video stroboscope or a speckle interferometer can be used as the measurement member that performs the distortion amount in a non-contact manner.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

1 is a block diagram illustrating a schematic configuration of a vibration test apparatus that performs a vibration test according to an embodiment of the present invention. It is a graph which shows the correlation with the distortion amount measured with the vibration test apparatus concerning one Embodiment of this invention, and the frequency | count of a vibration (life). It is a top view which shows an example of the board concerning one Embodiment of this invention. It is XX sectional drawing of FIG. It is sectional drawing which shows the part similar to FIG. 4 of the other embodiment of the measurement member concerning one Embodiment of this invention.

Explanation of symbols

9 Electronic component 11 Substrate 13 Strain gauge 31 Holographic interferometer

Claims (5)

Performing a vibration test repeatedly while changing the vibration conditions while measuring the amount of strain of the substrate at a position near the electronic component until the electronic component has a vibration fatigue life using a substrate on which the electronic component is mounted as a test piece,
The correlation between the amount of strain and the vibration fatigue life as a database,
Measuring a strain amount of the substrate in the vicinity of the electronic component on a substrate mounted on a product by a strain measuring member, and estimating the vibration fatigue life from the database based on the measured strain amount. A method for measuring the lifetime of electronic components.   The lifetime measurement method for an electronic component according to claim 1, wherein the strain measurement member is a strain gauge attached to the vicinity. 2. The method for measuring the lifetime of an electronic component according to claim 1, wherein the strain measuring member measures a strain amount of the substrate in the vicinity position in a non-contact manner. Obtained by repeatedly performing a vibration test while changing the vibration conditions while measuring the strain amount of the substrate at a position near the electronic component until the electronic component has a vibration fatigue life using a substrate on which the electronic component is mounted as a test piece. A database showing a correlation between the strain amount and the vibration fatigue life,
  Measuring a strain amount of the substrate in the vicinity of the electronic component on a substrate mounted on a product by a strain measuring member, and estimating the vibration fatigue life from the database based on the measured strain amount. To measure the lifetime of electronic components. Performing a vibration test repeatedly while changing the vibration conditions while measuring the amount of strain of the substrate at a position near the electronic component until the electronic component has a vibration fatigue life using a substrate on which the electronic component is mounted as a test piece,
The correlation between the amount of strain and the vibration fatigue life as a database,
Based on the vibration conditions of the product, the amount of distortion of the substrate in the vicinity of the electronic component on the substrate mounted on the product is simulated by a finite element method,
A substrate design quality determination method characterized by estimating the vibration fatigue life of the electronic component from the database based on a simulated strain amount and determining whether or not the vibration fatigue life satisfies a design condition.

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