KR20250010171A - Defect inspection method for micro speaker - Google Patents

Abstract

The present invention relates to a defect inspection method for a micro speaker, which can improve the accuracy of a good/bad judgment while performing an easy and simple inspection. The defect inspection method for a micro speaker of the present embodiment includes: (a) a step of measuring inductance for a plurality of good speakers selected through a listening test, (b) a step of extracting an average value of the inductance for a plurality of measured good speakers, (c) a step of setting a reference inductance range for the extracted average inductance value, (d) a step of measuring the inductance for a speaker as a target of inspection, and (e) a step of comparing whether the inductance for the speaker as a target of inspection falls within the reference inductance range to determine good/bad.

Description

{Defect inspection method for micro speaker}

The present invention relates to a method for inspecting micro speakers, and more specifically, to a method for inspecting defects in micro speakers that can improve the accuracy of good/defect judgment while performing inspection easily and conveniently.

In general, a speaker is a device that converts an electrical signal into an audio signal. There are medium-sized and large speakers that are connected to an audio or amplifier to greatly amplify the volume, and there are also small speakers for small audio devices, such as portable electronic devices such as smartphones, which are called micro speakers.

Most portable electronic devices have built-in micro speakers, and as electronic devices become smaller, the micro speakers used in electronic devices also need to become smaller. If the quality of the micro speakers is not guaranteed, it will result in a decline in the performance and value of the entire finished electronic device product.

Therefore, it is very important for companies manufacturing micro speakers to filter out defective products through quality testing of the micro speakers being produced and ensure that only good products are supplied as components for finished electronic devices.

In general, methods such as SPL (Sound Press Level), THD (Total Harmonic Distortion), HOHD (High Order Harmonic Distortion), Rub & Buzz, and listening are used to determine the performance or quality/defect of micro speakers. However, evaluation methods using SPL, THD, HOHD, and Rub & Buzz cannot determine defects such as speaker foreign sound (Touch sound), so the inspector must directly listen to the sound of the speaker and determine quality/defect.

Meanwhile, Korean Patent No. 10-1752655 introduces a ‘speaker enclosure defect detection method’ as a method for detecting defects in micro speakers. The enclosure defect detection method of the above prior patent document is characterized by including "a step A for setting a first upper limit and a first lower limit of a certain range for determining a qualified product based on a first impedance measured from a speaker enclosure designated as a qualified product, a step B for setting a certain frequency point of the first impedance measured in step A as a reference point, a step C for measuring a second impedance to a speaker enclosure to be inspected and measuring a difference in size between the first impedance and the second impedance at the reference point, a step D for setting a second upper limit and a second lower limit by moving the first upper limit and the first lower limit by the amount of the difference in size between the first impedance and the second impedance, and a step E for determining whether the second impedance is out of the range of at least one of the second upper limit and the second lower limit to determine whether there is a defect."

The speaker defect detection method of the above patent document has a limitation in that it can only detect defects occurring in the enclosure. The micro speaker is composed of a frame, a yoke, a permanent magnet, a plate, a voice coil, a diaphragm, etc., and defects occurring in the micro speaker are caused not only by the housing (enclosure) but also by the frame, yoke, permanent magnet, plate, voice coil, diaphragm, etc., and in particular, in the case of heterogeneous noise, it is mainly caused by defects in the diaphragm or plate. Therefore, the speaker defect detection method of the patent document has a disadvantage in that it cannot detect defects such as heterogeneous noise caused by defects in the diaphragm or plate.

In addition, the speaker defect detection method of the above patent document has a disadvantage in that the 'step C of measuring the second impedance to the speaker enclosure to be inspected and measuring the difference in size between the first impedance and the second impedance at the reference point' and the 'step D of moving the first upper limit and the first lower limit by the amount of the difference in size between the first impedance and the second impedance to set the second upper limit and the second lower limit' must be performed repeatedly each time. In other words, there is the inconvenience of having to compare the size difference of the second impedance for the speaker to be inspected with the first impedance each time, and then moving the first upper limit and the first lower limit by the amount of the difference to newly set the second upper limit and the second lower limit.

Korean Patent Registration No. 10-1752655

The present invention has been proposed to solve the above problems, and has as its object the provision of a method for detecting a defect in a micro speaker, which can detect the defect in a simple manner while improving the accuracy of detection.

In addition, the present invention aims to provide a method for detecting a defect in a micro speaker by measuring the inductance measured in the speaker and the output characteristics according to frequency to detect the defect.

The defect inspection method of the micro speaker of the present embodiment for solving the above-mentioned problem includes (a) a step of measuring inductance of a plurality of good speakers selected through a listening test, (b) a step of extracting an average value of the inductance of the plurality of good speakers measured, (c) a step of setting a reference inductance range for the extracted average inductance value, (d) a step of measuring the inductance of the speaker to be inspected, and (e) a step of comparing whether the inductance of the speaker to be inspected falls within the reference inductance range to determine good/bad.

In addition, the defect inspection method of the micro speaker of the present embodiment may further include (f) a step of measuring FFT characteristics of primary good speakers determined through an inductance inspection to select a plurality of speakers having good FFT characteristics, (g) a step of extracting an average FFT characteristic of a plurality of speakers selected as having good FFT characteristics, (h) a step of setting an FFT mask that raises the extracted average FFT characteristic to a predetermined level, (i) a step of measuring FFT characteristics of other primary good speakers as inspection targets, and (j) a step of comparing the measured FFT characteristics with the FFT mask to determine good/bad.

In addition, the FFT characteristics can be measured for the entire frequency range that is arbitrarily set, and can be judged to be good when the measured FFT characteristics belong to the FFT mask in the entire frequency range.

Additionally, the FFT mask of the step (h) can be set to a level that accommodates all FFT characteristics of the mask determined to be a good product.

In the micro-speaker defect inspection method of this embodiment, the inductance and FFT characteristics of a good speaker judged through a listening test are set, and the inductance and FFT characteristics of the speaker to be inspected are sequentially measured according to the set inductance and FFT criteria, so that the accuracy of judging whether a product is good or bad is greatly improved and the measurement time can be shortened.

In addition, the inspection method of the present embodiment can efficiently detect positive/bad heterogeneous sounds in a specific frequency range by measuring and inspecting the output characteristics in the FFT manner for the entire frequency range.

Figure 1 is a process diagram schematically showing the shipping process of a micro speaker according to the present embodiment.
FIG. 2 is a flowchart showing one embodiment of a defect inspection process of a micro speaker according to the present embodiment.
FIG. 3 is a flowchart showing another embodiment of a defect inspection process of a micro speaker according to the present embodiment.
Fig. 4 is a diagram showing an example of output characteristics measured from a micro speaker according to the present embodiment.
FIG. 5 is a diagram showing an example of frequency and voltage characteristics applied for measuring micro speaker output characteristics according to the present embodiment.

The technical problems achieved by the present invention and its implementation will be made clear by the preferred embodiments described below. Hereinafter, preferred embodiments of the present invention will be examined in detail with reference to the attached drawings.

It should be understood that the differences in the embodiments described below are not mutually exclusive. That is, it should be understood that specific shapes, structures, and characteristics described in one embodiment may be implemented in another embodiment without departing from the spirit and scope of the present invention, and that the positions or arrangements of individual components within each disclosed embodiment may be changed, and that similar reference numerals in the drawings indicate the same or similar functions throughout.

Figure 1 is a process diagram schematically showing the shipping process of a micro speaker according to the present embodiment.

The shipment of the micro speaker of this embodiment is made after defect inspection of each component and defect inspection of the assembled micro speaker, and only good speakers without defects are shipped.

That is, referring to Fig. 1, a defect inspection is performed on each part (S11), and a micro speaker is assembled using parts without defects (S12). Then, a defect inspection is performed again on the micro speaker assembly (S13), and the micro speaker assembly without defects is finally shipped (S14). The inspection of the micro speaker assembly according to the present embodiment is performed by measuring inductance and output characteristics.

FIG. 2 is a flowchart showing one embodiment of a defect inspection process of a micro speaker according to the present embodiment, FIG. 3 is a flowchart showing another embodiment of a defect inspection process of a micro speaker according to the present embodiment, FIG. 4 is a diagram showing an example of output characteristics measured from a micro speaker according to the present embodiment, and FIG. 5 is a diagram showing an example of frequency and voltage characteristics applied for measuring the output characteristics of a micro speaker according to the present embodiment.

The method for inspecting a defect in a micro speaker according to the embodiment of Fig. 2 is configured to detect by measuring the inductance of the speaker. If a defect occurs in any component constituting the speaker, the inductance of the coil changes significantly, so that this can be detected to determine whether there is a defect.

Referring to Fig. 2, the defect inspection process of the micro speaker according to the present embodiment is examined. First, good and defective speakers are selected through a listening test by an inspector (S21). At this time, it is desirable to conduct a listening test on as many speakers as possible, but approximately 20 good speakers are selected.

Then, the inductance of a number of selected good and bad speakers is measured and recorded respectively (S22), and the average inductance value for the inductance values measured for a number of speakers is extracted (S23).

In this example, 20 good and defective speakers were selected through a listening test, and each inductance value and its average value for the good speakers, and each inductance value and its average value for the defective speakers were measured and extracted, as shown in Table 1. The voltage and frequency applied to measure the inductance can be arbitrarily set according to the output capacity of the speaker, and the listening test and inductance measurement are performed by dividing them into units of the output capacity of the speaker. For the micro speaker of this example, the impedance was measured for a voltage of 0.1 V and a frequency of 1 kHz.

division Good quality speaker inductance (Ls(uH)) Bad speaker inductance (Ls(uH)) 1 83.4 89.7 2 82.4 91.8 3 84.1 92 4 83 90.3 5 84.2 88.9 6 83.7 92.6 7 82.8 90.5 8 86.6 92.6 9 83.3 89.5 10 85.2 89.3 11 85.5 91.2 12 85 92.3 13 84.7 91.2 14 83.2 92.4 15 85.7 88.6 16 83.5 92.1 17 84.4 90.8 18 85.9 89.3 19 86.8 94.4 20 85.3 90 medium 84.4 91.0

According to this example, the inductance of 20 good speakers was measured, and an average inductance value of 84.4 uH was extracted. In addition, an average value of 91.0 uH was extracted based on the inductance values of 20 defective speakers.

Then, a reference inductance range for the extracted average inductance value is set (S24). That is, a reference inductance range that can be judged as a good speaker is set based on 20 inductance values and their average value, and according to the present embodiment, a value between 82uH and 87uH can be set as the reference inductance range. Similarly, the reference inductance range that can be judged as a defective speaker can be set to 89uH or more.

Next, the inductance of the speaker to be inspected is measured under the same conditions (S25), and the speaker is judged to be good depending on whether the measured inductance value is within the standard inductance range of the good speaker (S26).

The method of inspecting for defects by measuring the inductance of a speaker, as in this embodiment, has the advantage of being able to measure even with low-level signals (e.g., voltage and frequency), so that thermal damage due to overvoltage does not occur to the diaphragm or voice coil, and accurate inspection and measurement is possible in a short measurement time.

A defect inspection method of a micro speaker according to the embodiment of Fig. 3 is configured to inspect by measuring output characteristics in addition to a process of inspecting by measuring the inductance of the speaker.

Referring to FIG. 3, the defect inspection process of the micro speaker according to the present embodiment is examined. Good and defective speakers are selected through a listening test by an inspector (S31), and the inductance of a plurality of selected good and defective speakers is measured and recorded (S32). In addition, an average inductance value for the inductance values measured for a plurality of speakers is extracted (S33), and a reference inductance range is set for the extracted average inductance value (S34). Then, the inductance is measured under the same conditions for the speaker to be inspected (S35), and a good product is initially determined based on whether the measured inductance value is within the reference inductance range of the good speaker (S36).

The process of measuring and inspecting the inductance of a speaker in this way is the same as the embodiment of Fig. 2, and a further process of inspecting by measuring the FFT (Fast Fourier Transform) characteristics of the initially judged speaker is performed.

Specifically, by measuring the FFT characteristics of the first-judged good speakers through the inductance test, a plurality of good speakers with good FFT characteristics are selected (S37). It is desirable to measure the FFT characteristics of as many as possible among the first-judged good speakers to select good speakers, but approximately 10 to 20 good speakers are selected. According to this embodiment, the FFT characteristics can be measured for a plurality of speakers judged as good products in the first stage, as shown in Fig. 4. At this time, the FFT characteristics are measured for the entire frequency range that is arbitrarily set, rather than the harmonic frequency detection method for the input frequency.

The voltage and frequency applied for FFT characteristic measurement can be set according to the output capacity of the micro speaker, and in this embodiment, the input frequency and voltage as shown in Fig. 5 are applied. In addition, the frequency range applied is a frequency for an area below the resonance frequency.

Next, an average FFT characteristic is extracted for a plurality of measured FFT characteristics (S38).

Next, a reference FFT mask for the extracted average FFT characteristic is set (S39). The reference FFT mask can be set as a process of leveling up the signal size to a predetermined range as a range of FFT characteristics that can be judged as good. The FFT mask can be set to a level that accommodates all FFT characteristics of the mask judged as good, and the FFT mask of the present embodiment can be set at a level that is raised by 6 dB with respect to the extracted average FFT characteristic. Therefore, as illustrated in FIG. 4, the FFT mask maintains a level that is raised by 6 dB on average with respect to a plurality of measured FFT characteristics.

Then, for the remaining good speakers to be inspected, the FFT characteristics are measured under the same conditions (S40), and the good product is judged a second time based on whether the measured FFT characteristics fall within the reference level, i.e., the FFT mask, in the entire frequency range (S41). For example, as shown in Fig. 4, if the measured FFT characteristics fall within the level below the FFT mask within all frequency ranges, the speaker can be judged as good, and if it deviates from the FFT mask at any one frequency, the speaker is judged as defective. Here, the speakers to be inspected are the primary good speakers, excluding the speakers selected for FFT mask setting among the speakers judged as good in the first stage based on the inductance measurement.

In this way, the inspection method of this embodiment measures the inductance and FFT characteristics of some good speakers selected by the listening test, and sequentially measures the inductance and FFT characteristics of other speakers to be inspected based on these, thereby greatly improving the accuracy of judging whether a product is good or bad, and shortening the measurement time. In addition, the inspection method of this embodiment has the advantage of efficiently detecting good/bad for heterogeneous sounds in a specific frequency range by measuring the output characteristics in the FFT method for the entire frequency range and inspecting them.

While exemplary embodiments of the present invention have been illustrated and described above, it will be apparent to those skilled in the art that various modifications and other embodiments may be made thereto. It is intended that all such modifications and other embodiments be considered and encompassed by the appended claims and do not depart from the true spirit and scope of the present invention.

Claims (4)

(a) a step of measuring inductance for a number of quality speakers selected through listening tests;
(b) a step of extracting an average value of inductance for a plurality of measured good speakers;
(c) a step of setting a reference inductance range for the extracted average inductance value;
(d) a step of measuring the inductance of the speaker of the inspection subject; and
(e) A method for inspecting a defect in a micro speaker, comprising: a step of comparing whether the inductance of the speaker to be inspected falls within a standard inductance range to determine good/bad; In paragraph 1,
(f) a step of measuring FFT characteristics of first-quality speakers judged through inductance inspection and selecting a number of speakers with good FFT characteristics;
(g) a step of extracting average FFT characteristics for a plurality of speakers selected as having good FFT characteristics;
(h) a step of setting an FFT mask that raises the extracted average FFT characteristics to a predetermined level;
(i) a step of measuring FFT characteristics of other primary good speakers of the inspection subject; and,
(j) A method for inspecting a defect in a micro speaker, further comprising a step of comparing the measured FFT characteristics with the FFT mask to determine good/bad. In the second paragraph,
A method for inspecting a defect in a microspeaker, wherein the above FFT characteristics are measured for an arbitrarily set entire frequency range, and the measured FFT characteristics are judged to be good when they fall within the FFT mask in the entire frequency range. In the third paragraph,
A method for inspecting a defect in a microspeaker, wherein the FFT mask of the step (h) is set to a level that accepts all FFT characteristics of a mask determined to be a good product.