CN103033553A - Detection method for mechanical property degradation of capacitive structural material - Google Patents

Abstract

The invention discloses a detection method for mechanical property degradation of a capacitive structural material. The detection method is characterized in that the detection method comprises the following steps of placing the capacitive structural material in a constant-temperature environment, measuring and recording environmental temperature, keeping the environmental temperature, air pressure and other conditions constant, confirming pull-down voltage between a fixed electrode and a movable electrode, recording the pull-down voltage, and analyzing and converting the pull-down voltage into relevant parameters of a mechanical property of the capacitive structural material. The detection method for the mechanical property degradation of the capacitive structural material is high in measuring efficiency and accuracy.

Description

Capacitance type structure mechanical property of materials deterioration detecting

Technical field

The present invention relates to capacitance type structure material tests field, particularly relate to a kind of capacitance type structure mechanical property of materials deterioration detecting.

Background technology

At present, because fatigue or unrelieved stress change the Young modulus of capacitance type structure material, cause that the resonance frequency of device changes.Therefore for the test of the frequency characteristic of capacitance type structure material, the common method of proportion scanning.But the resonance frequency of capacitance type structure material, quality factor may be very high, if the method for proportion scanning is tested, just require with very little frequency sweeping stepping, wider frequency sweeping scope accelerometer to be carried out stable state scanning.On measuring accuracy, the frequency sweeping step-length is less, the stable state time is longer, and measuring accuracy is just higher; And from measuring on the efficient, then on the contrary, thereby this method is difficult to satisfy simultaneously the requirement of measuring accuracy and measurement efficient two aspects.

Summary of the invention

Based on this, be necessary for the prior art defective, a kind of capacitance type structure mechanical property of materials deterioration detecting that efficient is high, measuring accuracy is high of measuring is provided.

Its technical scheme is as follows.

A kind of capacitance type structure mechanical property of materials deterioration detecting may further comprise the steps,

The capacitance type structure material is placed in the isoperibol, and environment temperature is carried out survey record;

Keep other conditions such as environment temperature, air pressure constant, the actuation voltage between fixed electorde and the traveling electrode is determined, and actuation voltage is carried out record;

The actuation voltage analysis is converted into capacitance type structure mechanical property of materials correlation parameter.

Further, capacitance type structure mechanical property of materials deterioration detecting is further comprising the steps of,

After standing vibration at the capacitance type structure material, impacting or carry out shuttling movement, redefine the actuation voltage between fixed electorde and the traveling electrode;

Repeat above-mentioned steps, relatively actuation voltage can obtain the change information of fatigue state or the unrelieved stress of capacitance type structure material.

Further, the measuring process of described actuation voltage is as follows,

Carry out voltage scanning between traveling electrode and fixed electorde, detect simultaneously the resistance between traveling electrode and the fixed electorde, when suddenly falling appearred in resistance, then corresponding voltage was actuation voltage.

Further, actuation voltage is V _p

$V_p=\sqrt{\frac{8k_m}{27\mathrm{\ϵ}{\mathrm{\ϵ}}_{0}A}{d}_0^3}$

Wherein, ε ₀Be permittivity of vacuum, ε is the relative dielectric constant of medium, and A is the capacitor plate area, d ₀Be the initial separation of capacitor plate, k _mElasticity coefficient for the capacitance type structure material.

A kind of capacitance type structure mechanical property of materials degeneration pick-up unit, comprise the actuation voltage detecting device, fixed electorde interface and traveling electrode interface are set respectively on the described actuation voltage detecting device, described fixed electorde interface is connected to fixed electorde, and described traveling electrode interface is connected with described traveling electrode.

The below describes advantage or the principle of technical solution of the present invention.

Actuation voltage between fixed electorde and the traveling electrode is a parameter with the mechanical property sensitivity of device architecture material, and when the fatigue state of capacitance type structure material or unrelieved stress changed, actuation voltage also can be along with variation.Variation by actuation voltage in the monitoring capacitance type structure material, can obtain the change information of fatigue state or the unrelieved stress of device architecture material, the method of monitoring actuation voltage is simple, efficient is high, and can with the variation of very high precision monitoring actuation voltage, can satisfy simultaneously efficient and high-precision requirement.

Description of drawings

Fig. 1 is the structural representation of the application example one described RF mems switch in the embodiment of the invention;

Fig. 2 is the structural representation of the application example two described parallel plate capacitor accelerometers in the embodiment of the invention;

Description of reference numerals:

10, input electrode, 20, output electrode, 30, bias electrode, 40, the sensitive-mass piece, 50, semi-girder, the 60, first movable electrode, the 70, second movable electrode, the 80, first fixed electorde, the 90, second fixed electorde.

Embodiment

Below in conjunction with accompanying drawing the embodiment of the invention is described in detail.

A kind of capacitance type structure mechanical property of materials deterioration detecting may further comprise the steps,

The capacitance type structure material is placed in the isoperibol, and environment temperature is carried out survey record;

Keep other conditions such as environment temperature, air pressure constant, the actuation voltage between fixed electorde and the traveling electrode is determined, and actuation voltage is carried out record;

Actuation voltage can be measured with following methods, carries out voltage scanning between traveling electrode and fixed electorde, detects simultaneously the resistance between traveling electrode and the fixed electorde, and when suddenly falling appearred in resistance, then corresponding voltage was actuation voltage.

Or actuation voltage is V _p

Existing electric contact type RF mems switch schematic diagram such as Fig. 1 comprise an input electrode 10, output electrode 20 and bias electrode 30.The contact that can control input electrode 10 and output electrode 30 by bias electrode 30 and the voltage between the input electrode 10 with separate, realize switch and closure.

When between input electrode 10 and bias electrode 30, applying voltage, will between input electrode 10 and bias electrode 30, produce electrostatic field, therefore just have electrostatic attraction and act on the input electrode 10.If the voltage that applies is V, input electrode 10 consists of capacitance structure with bias electrode 30, and electric capacity is C, and the electric field energy W that then stores in the electric capacity is:

$W=\frac{1}{2}{V}^{2}C$

The electrostatic force F that be applied on the input electrode 10 this moment is

$F=\frac{\∂W}{\∂d}=\frac{1}{2}{V}^2\frac{\∂C}{\∂d}=-\frac{1}{2}{V}^2\frac{\mathrm{\ϵ}{\mathrm{\ϵ}}_{0}A}{d_0^2}$

In the formula, ε ₀Be permittivity of vacuum, ε is the relative dielectric constant of medium, and A is the capacitance structure polar plate area, d ₀For the initial separation of input electrode 10 with bias electrode 30, establish electrostatic force F and equate with the caused mechanical return force of the rigidity of input electrode 10, then can obtain:

$\frac{1}{2}{V}^2\frac{\mathrm{\ϵ}{\mathrm{\ϵ}}_{0}A}{d^2}=k_m(d_0-d)$

In the formula, d be input electrode 10 under electrostatic forcing, stable after and the spacing between the bias electrode 30.

Finding the solution this equation can get:

$V=\sqrt{\frac{2k_m}{\mathrm{\ϵ}{\mathrm{\ϵ}}_{0}A}{d}^2(d_0-d)}---\left(1\right)$

In the formula, k _mBe the elasticity coefficient of element, to the spacing d differentiate in the formula (1) and make that derivative is zero, can obtain: when electrostatic force makes the moving displacement of input electrode 10 greater than 1/3d ₀The time, can cause output electrode 20 and input electrode 10 under electrostatic forcing, to come in contact and be bonded together.Until remove dc offset voltage V between input electrode 10 and the bias electrode 30 _Ref, just may make output electrode 20 and input electrode 10 separately.By above analysis, get d=2/3d ₀, can get actuation voltage:

$V_p=\sqrt{\frac{8k_m}{27\mathrm{\ϵ}{\mathrm{\ϵ}}_{0}A}{d}_0^3}---\left(2\right)$

The actuation voltage analysis is converted into capacitance type structure mechanical property of materials correlation parameter.

After standing vibration at the capacitance type structure material, impacting or carry out shuttling movement, redefine the actuation voltage between fixed electorde and the traveling electrode;

Repeat above-mentioned steps, relatively actuation voltage can obtain the change information of fatigue state or the unrelieved stress of capacitance type structure material.

In practical service environment, mechanical stress and because the impacts of the thermal stress that the coefficient of thermal expansion mismatch of different materials is brought in the electric contact type RF mems switch such as electric contact type RF mems switch unavoidably can be vibrated, impact.Mechanical stress and thermal stress can cause the device architecture material production tired, or produce unrelieved stress in structure, thereby cause electric contact type RF mems switch performance degradation.

On the other hand, the elasticity coefficient k in the formula (2) _mComprise two-part content, a part is that the rigidity by beam causes, and the rigidity of beam is an amount relevant with moment of inertia with material behavior such as Young modulus; Elasticity coefficient k _mAnother part be to be caused by the twin shaft unrelieved stress in the beam.Therefore, actuation voltage is relevant with material behavior and unrelieved stress in the structure, therefore, if the fatigue state in traveling electrode or unrelieved stress change, will cause actuation voltage to change.By the change information of monitoring actuation voltage, then can obtain the change information of the unrelieved stress in capacitance type structure fatigue of materials state or the device.

A kind of capacitance type structure mechanical property of materials degeneration pick-up unit, comprise the actuation voltage detecting device, fixed electorde interface and traveling electrode interface are set respectively on the described actuation voltage detecting device, described fixed electorde interface is connected to fixed electorde, and described traveling electrode interface is connected with described traveling electrode.

The present embodiment method is applicable to utilize electrostatic force to carry out the MEMS device of sensor, driving, by the traveling electrode in the MEMS micro mechanical structure and the actuation voltage between the fixed electorde are detected, realizes the monitoring to device architecture mechanical property degree of degeneration.

Lower mask body is used with the measurement of the present embodiment method in RF mems switch, parallel plate capacitor accelerometer and is elaborated.

Application example one

Carry out voltage scanning between input electrode 10 and bias electrode 20, monitor simultaneously the resistance between input electrode 10 and the output electrode 30, when then suddenly falling appearred in resistance, corresponding input electrode 10 and the bias voltage between the bias electrode 30 were actuation voltage.

After structure stands vibration, impact, or movable electrode carries out after the shuttling movement, the latter is after structure stands temperature stress, the variation of unrelieved stress can cause the variation of actuation voltage in the variation of structural-mechanical property or the structure, detect the variation of actuation voltage, can obtain the change information of unrelieved stress in structural-mechanical property or the structure.

In order to distinguish analysis of material fatigue and unrelieved stress to the impact of actuation voltage, can keep first one of them parameter is constant, change the another one parameter, monitor the variation of corresponding actuation voltage, then can distinguish analysis of material fatigue and unrelieved stress to the impact of actuation voltage.

If keep other condition constant, only change the environment temperature of RF mems switch, monitor simultaneously the variation of RF mems switch actuation voltage, then can obtain the change information of thermal stress.

Concrete steps when the below tests with the example explanation in this example implementation process, keep environment temperature and air pressure constant, by the variation of monitoring RF mems switch actuation voltage, obtain the change information of structural fatigue state or unrelieved stress:

1. keep environment temperature-resistant;

2. determine V _pV _pObtain by test method: carry out voltage scanning between input electrode 10 and bias electrode 30, monitor simultaneously the resistance between input electrode 10 and the output electrode 20, when suddenly falling appearred in resistance, corresponding input electrode 10 and the voltage between the bias electrode 30 were V _p

3. after structure stands vibration, impacts, or input electrode 10 carries out after the shuttling movement, and 2. repeating step obtains actuation voltage V _P2, V _P3, V _P4... V _Pn

By contrast V _P2, V _P3, V _P4... V _PnCan obtain the change information of fatigue state in the structure or unrelieved stress.

Application example two

Parallel plate capacitor accelerometer as shown in Figure 2, this accelerometer comprises a sensitive-mass piece 40, semi-girder 50, the first movable electrode 60, the second movable electrode 70, the first fixed electorde 80 and the second fixed electorde 90, wherein, the first movable electrode 60, the second movable electrode 70, the first fixed electorde 80 and the second fixed electorde 90 have consisted of two differential capacitances.When the acceleration perpendicular to support substrates acts on the sensitive-mass piece, the sensitive-mass piece will along movement in vertical direction, cause two differential capacitances to change, and variable quantity be just opposite.By the variation of electric capacity, can obtain the information of input acceleration.

Keep between the first movable electrode 60 and the first fixed electorde 80 voltage be zero, by monitoring the actuation voltage between the second movable electrode 70 and the second fixed electorde 90, then can obtain the change information of fatigue state in the semi-girder or unrelieved stress.

The below describes advantage or the principle of the embodiment of the invention.

Actuation voltage between fixed electorde and the traveling electrode is a parameter with the mechanical property sensitivity of device architecture material, and when the fatigue state of capacitance type structure material or unrelieved stress changed, actuation voltage also can be along with variation.Variation by actuation voltage in the monitoring capacitance type structure material, can obtain the change information of fatigue state or the unrelieved stress of device architecture material, the method of monitoring actuation voltage is simple, efficient is high, and can with the variation of very high precision monitoring actuation voltage, can satisfy simultaneously efficient and high-precision requirement.

The above embodiment has only expressed several embodiment of the present invention, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to claim of the present invention.Should be pointed out that for the person of ordinary skill of the art, without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.

Claims (5)

1. a capacitance type structure mechanical property of materials deterioration detecting is characterized in that, may further comprise the steps,

The capacitance type structure material is placed in the isoperibol, and environment temperature is carried out survey record;

Keep other conditions such as environment temperature, air pressure constant, the actuation voltage between fixed electorde and the traveling electrode is determined, and actuation voltage is carried out record;

The actuation voltage analysis is converted into capacitance type structure mechanical property of materials correlation parameter.

2. capacitance type structure mechanical property of materials deterioration detecting according to claim 1 is characterized in that, and is further comprising the steps of,

After standing vibration at the capacitance type structure material, impacting or carry out shuttling movement, redefine the actuation voltage between fixed electorde and the traveling electrode;

Repeat above-mentioned steps, relatively actuation voltage can obtain the change information of fatigue state or the unrelieved stress of capacitance type structure material.

3. capacitance type structure mechanical property of materials deterioration detecting according to claim 1 is characterized in that, the measuring process of described actuation voltage is as follows,

Carry out voltage scanning between traveling electrode and fixed electorde, detect simultaneously the resistance between traveling electrode and the fixed electorde, when suddenly falling appearred in resistance, then corresponding voltage was actuation voltage.

4. capacitance type structure mechanical property of materials deterioration detecting according to claim 1 is characterized in that, described actuation voltage is V _p

$V_p=\sqrt{\frac{8k_m}{27\mathrm{\ϵ}{\mathrm{\ϵ}}_{0}A}{d}_0^3}$

Wherein, ε ₀Be permittivity of vacuum, ε is the relative dielectric constant of medium, and A is the capacitor plate area, d ₀Be the initial separation of capacitor plate, k _mElasticity coefficient for the capacitance type structure material.

5. capacitance type structure mechanical property of materials degeneration pick-up unit, it is characterized in that, comprise the actuation voltage detecting device, fixed electorde interface and traveling electrode interface are set respectively on the described actuation voltage detecting device, described fixed electorde interface is connected to fixed electorde, and described traveling electrode interface is connected with described traveling electrode.

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