JP2009287943A - Board inspection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a board inspection method which can accurately determine the quality of a board, even when a reflected waveform is influenced by temperature, when a board in which a component having a connecting part with a board on the lower surface of a package is installed, such as, a BGA IC is inspected using TDR. <P>SOLUTION: Standard waveforms by temperature are stored in a control calculating section 2 in advance. A standard waveform according to the temperature measured by a temperature-measuring section 5 and a reflected waveform from a board 200 measured by an oscilloscope 12 are compared to each other in the control calculation section 2 to perform waveform analysis, thereby determining the quality of the board 200. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a substrate inspection method for inspecting a component mounting state or the like of a substrate on which a component such as a BGA (ball grid array) where it is difficult to visually check a connection portion.

  When an integrated circuit of a BGA package (hereinafter referred to as a BGA IC) is mounted on a substrate, the connecting portion with the substrate is located on the lower surface of the package, so the state of solder connection between the substrate and the BGA IC can be visually checked. It cannot be confirmed. For this reason, substrate inspection by boundary scan or X-ray is performed. Boundary scan requires a scanning circuit inside the BGA IC, leading to an increase in size and cost of the BGA IC. Further, the boundary scan cannot be used in a high frequency circuit or the like. On the other hand, X-ray inspection has low scanning accuracy, and connection failure due to minute cracks to be actually confirmed cannot be confirmed.

  In order to solve the above problem, substrate inspection using TDR (Time Domain Reflectometry) is performed. In the substrate inspection using TDR, a probe is brought into contact with a pad provided on the substrate and an electric pulse is input, and the connection state between the BGA IC and the substrate is inspected from the reflection characteristics (see Patent Document 1). .

JP-A-9-61486

  In substrate inspection using TDR, the reflected waveform from the substrate greatly affects the quality determination of the substrate. Since the reflected waveform has temperature dependence, there is a problem that the substrate quality is erroneously determined due to the influence of temperature.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a substrate inspection method capable of accurately determining the quality of a substrate without depending on temperature in substrate inspection using TDR. And

  The substrate inspection method of the present invention includes a temperature measurement step and a standard waveform selection step, selects a standard waveform corresponding to the temperature measured in the temperature measurement step in the standard waveform selection step, and the standard waveform and the reflected waveform from the substrate. And the quality of the substrate is determined.

  In the present invention, a standard waveform for each temperature is stored in advance, and the standard waveform corresponding to the measured temperature is compared with the reflected waveform from the substrate. Therefore, the influence of temperature can be reduced, and the accuracy of the substrate quality determination can be improved. it can.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a substrate inspection apparatus according to Embodiment 1 of the present invention. The substrate inspection apparatus includes a TDR measurement unit 1, a control calculation unit 2, an interface substrate 3, and a temperature measurement unit 5. The TDR measurement unit 1 includes a pulse oscillator 11 that outputs a high-frequency pulse and an oscilloscope 12 that measures the waveform of the line, and is connected to the substrate to be measured via the interface substrate 3. The interface board 3 is mounted with a re-stable 31 for fixing the probe 4, a switch 32, and a connector 33. The switch 32 sequentially switches the plurality of probes 4 according to the control signal s _k (k = 1 to n) from the control calculation unit 2. The connector 33 and the TDR measurement unit 1 are electrically connected. The temperature measurement unit 5 measures the ambient temperature or the measured substrate or the temperature of the TDR measurement unit 1 and transmits the measured temperature to the control calculation unit 2.

  FIG. 2 is a cross-sectional view showing substrate 200 and interface substrate 3 according to the first embodiment of the present invention. FIG. 3 is an enlarged view of a portion X in FIG. The BGA IC 100 has a solder ball 101 which is a connection portion with the substrate 200 on the lower surface of the package. The solder ball 101 is electrically connected to the land 211 via the pad 212 and the pattern 213 of the substrate 200. Further, the solder ball 101 is electrically connected to the land 214 on the non-mounting surface of the BGA IC 100 through the through hole 210.

  FIG. 4 is a plan view showing a connection portion between substrate 200 and BGA IC 100 in Embodiment 1 of the present invention. A pad 212 which is a connection portion with the BGA IC 100 is connected to the land 211 via a pattern 213. A through hole 210 is provided in the center of the land 211.

  The probe 4 is used for measuring the electrical characteristics of the land 214. The probe 4 is electrically connected to a connector 33 mounted on the interface board 3 through a microstrip line 34. Since the TDR is measured by passing a high-frequency pulse through the line, the line of the interface substrate 3 is preferably composed of a 50Ω distributed constant circuit such as a microstrip line 34 or a strip line. Thereby, the impedance of the line part between the TDR measurement part 1 and the board | substrate 200 is decided, and the measurement precision of TDR improves.

  The re-stable 31 is made such that a plurality of probes 4 are arranged in accordance with the positions of a plurality of measurement points (that is, lands 214) on the substrate 200. The plurality of probes 4 fixed to the re-sectorable 31 are physically connected to the corresponding measurement locations, but only the probe 4 selected by the switch 32 is electrically connected to the TDR measurement unit 1. is there. In this way, since the plurality of probes 4 are physically connected to each measurement location collectively, it is unnecessary to spend time for raising and lowering the probe and bringing the probe into contact with the predetermined measurement location, as in the prior art. As a result, the substrate inspection time can be greatly reduced.

  The probe 4 can be removed from the re-sectorable 31 and has versatility, but the interface substrate 3 is not versatile because it needs to be manufactured according to the pattern of the substrate 200 and the like.

The switch 32 (not shown in FIGS. 2 and 3) is constituted by, for example, a relay. The switch 32 selects the probe 4 to be connected to the TDR measurement unit 1 based on the control signal s _k (k = 1 to n) from the control calculation unit 2. By switching the probe 4 with the switch 32, the TDR measurement unit 1 can sequentially measure the waveforms of reflected waves from all the connection parts between the solder balls 101 of the BGA IC 100 and the substrate 200. The measurement waveform measured by the TDR measurement unit 1 is transmitted to the control calculation unit 2. The control calculation unit 2 determines whether the connection state between the BGA IC 100 and the substrate 200 is good based on the reflection waveform measured by the TDR measurement unit 1. In addition, since it is a board | substrate test | inspection using TDR, not only the connection state of BGA IC100 and the board | substrate 200 but the quality of the circuit wiring state in the board | substrate 200 can also be determined.

  Next, an inspection method for the substrate 200 will be described. FIG. 5 is a diagram for explaining an inspection method for the substrate 200 according to the first embodiment of the present invention. FIG. 6 is a waveform diagram for explaining the TDR measurement in the first embodiment of the present invention. 6A shows the incident waveform, FIG. 6B shows the reflected waveform when the probe 4 is not in contact with the substrate 200, and FIG. 6C shows the reflected waveform when the probe 4 is in contact with the substrate 200. Yes.

  First, in the reflected waveform measurement step, an incident wave is applied to the substrate 200 from the pulse oscillator 11 of the TDR measurement unit 1, and the reflected waveform from the substrate 200 is measured with the oscilloscope 12. An incident wave having a step waveform as shown in FIG. 6A is generated by the pulse oscillator 11 and transmitted to the probe 4 via the microstrip line 34. A portion corresponding to the rising edge of the step waveform is defined as a pulse rising point (time A in FIG. 6). When the probe 4 is not in contact with the substrate 200, the incident wave transmitted to the probe 4 is totally reflected at the tip of the probe 4. The oscilloscope 12 measures a wave in which the incident wave shown in FIG. 6A and the wave totally reflected at the tip of the probe 4 are superimposed (FIG. 6B). Since the impedance is constant by the microstrip line 34 from the pulse oscillator 11 to the connection point between the substrate 200 and the probe 4, a waveform with a constant voltage is obtained (from time A to time B). A time T1 shown in FIG. 6B is a time until the incident wave reaches the probe 4 and the reflected wave returns to the oscilloscope. In the waveform shown in FIG. 6B, the voltage rises because the reflected wave that is returned overlaps the incident wave after time T1 from the rising of the incident wave.

  A reflected waveform when the probe 4 is connected to the substrate 200 will be described. When the substrate 200 is normal, for example, the waveform shown in FIG. 6C is measured by the oscilloscope 12 as a reflected waveform. Usually, in TDR, an incident wave having a step waveform of about 400 mV is input to the substrate 200. Hereinafter, a voltage value of 400 mV is referred to as a standard voltage. Not only the solder ball 101 but also other circuits having a capacitive component and an inductive component are electrically connected to the land 214 which is a contact point with the probe 4. For this reason, the waveform measured by the oscilloscope 12 has a complicated shape in which the reflected wave generated by the complex load impedance is superimposed (the waveform after time B in FIG. 6C).

  7 and 8 are explanatory diagrams of waveform analysis in the control calculation unit 2 according to Embodiment 1 of the present invention. 7 and 8, the standard waveform is indicated by a solid line, and the reflected waveform when the substrate 200 is an abnormal substrate is indicated by a broken line. Note that time B in FIGS. 7 and 8 corresponds to time B in FIG. In the following explanation diagrams or waveform diagrams of waveform analysis, the time indicated by the same symbol as in FIG. 6 corresponds to the time shown in FIG.

  In the substrate quality determination step, the control calculation unit 2 performs waveform analysis and determines the quality of the substrate 200 based on the analysis result. A method for determining the quality of the substrate 200 will be described in detail below. First, a standard waveform as a reference for waveform analysis can be obtained using the following method. For example, a normal substrate is subjected to TDR measurement, and the reflected waveform measured by the oscilloscope 12 is held in the control calculation unit 2 in advance as a standard waveform. Alternatively, a plurality of normal substrates may be measured by TDR, and a plurality of acquired reflected waveforms may be averaged to obtain a standard waveform.

The standard waveform is different for each pin of the BGA IC100. The control calculation unit 2 stores standard waveforms corresponding to all pins of the BGA IC 100. The control calculation unit 2 compares the standard waveform with the reflected waveform transmitted from the oscilloscope 12 to determine whether the substrate 200 is good or bad. Here, the method of waveform analysis in the control calculation unit 2 will be described by taking as an example a case where the reflected waveform transmitted from the oscilloscope 12 is a broken line shown in FIG. When the potential difference ΔV between the standard waveform held in advance and the reflected waveform is equal to or greater than a first threshold value ΔV _th1 (for example, 50 mV) even for a moment, the control calculation unit 2 determines that the substrate 200 is an abnormal substrate.

  Furthermore, the control calculation unit 2 determines that there is an abnormality on the circuit connected to the pin of the BGA IC 100 that was the analysis target, and can also specify the abnormal part of the substrate 200 using the TDR measurement result. For example, in FIG. 7, T, which is the time difference between time C and time B at which ΔV is maximum, corresponds to the time when the incident wave passes through the probe 4 to propagate to the abnormal location and returns from the abnormal location to the probe 4. Therefore, the abnormal part can be specified using the time T.

Further, as shown in FIG. 8, even if the potential difference ΔV between the standard waveform and the reflected waveform is not equal to or greater than the first threshold value ΔV _th1 , ΔV is equal to or greater than the second threshold value ΔV _{th2 that is} smaller than the first threshold value ΔV _th1 . The substrate 200 is determined to be an abnormal substrate even when the time T _E continues for a predetermined time (several hundred pS, for example, 200 to 400 pS) or longer. In the determination at the time of mass production, fluctuations are expected in the TDR measurement results for each substrate. It is desirable to obtain a voltage deviation for the reflected waveforms of a plurality of normal substrates in advance and obtain the first threshold value ΔV _th1 , the second threshold value ΔV _th2 , and a predetermined time based on the values.

  Next, the case where the solder ball 101 is cracked will be described. FIG. 9 is a cross-sectional view showing substrate 200 and interface substrate 3 when crack 102 is generated in solder ball 101 according to the first embodiment of the present invention. FIG. 10 is a waveform diagram for explaining the TDR measurement in the case where the crack 102 is generated in the solder ball 101 according to the first embodiment of the present invention. The standard waveform is indicated by a solid line, and the reflected waveform when the crack 102 is generated is indicated by a broken line.

When the crack 102 is generated in the solder ball 101, for example, a reflected waveform as shown in FIG. 10 is measured. Since the impedance is constant by the microstrip line 34 from the pulse oscillator 11 to the connection point between the substrate 200 and the probe 4, the waveform is constant until time B. The line from the pulse oscillator 11 through the interface substrate 3 is finally opened at the crack 102. The incident wave that has propagated to the crack 102 is reflected by the crack 102. For this reason, as compared with the standard waveform, the voltage of the reflected waveform of the substrate in which the crack 102 is generated rapidly increases at time D as shown in FIG. T _CR is the time difference between the time B and time D is, the incident wave is propagated to the crack 102 and passes through the probe 4, it corresponds to the time returning from the crack 102 to the probe 4.

  When the inspection location of the substrate 200 is only the connection portion between the BGA IC 100 and the substrate 200, the reflected waveform when the substrate 200 is an abnormal substrate is a simple waveform. Therefore, it is possible to determine whether the substrate 200 is good or bad by analyzing the change in the waveform voltage measured by the oscilloscope 12 using the control calculation unit 2. The complicated waveform analysis performed by obtaining the potential difference between the standard waveform and the reflected waveform described above is not necessary, and the quality determination of the substrate 200 can be realized in a short time.

  As an error factor of TDR measurement, there is an influence by temperature. This is because, as the temperature changes, the microstrip line 34 expands and contracts and the load impedance of the circuit of the substrate 200 changes, so that even if the same substrate is measured, the reflected waveform changes due to the temperature change. Further, even when the temperature of the TDR measurement unit 1 changes, for example, when the temperature of the TDR measurement unit 1 rises due to continuous operation, the reflection obtained even on the same substrate due to the temperature dependence of the TDR measurement unit 1 itself. It is conceivable that the waveforms are different.

  FIG. 11 is a waveform diagram for explaining the influence of the temperature of the TDR measurement in Embodiment 1 of the present invention. 11A shows the incident waveform, FIG. 11B shows the reflected waveform when the probe 4 is not in contact with the substrate 200, and FIG. 11C shows the reflected waveform when the probe 4 is in contact with the substrate 200. Yes. In the figure, a measurement waveform obtained by measuring a normal substrate at room temperature is indicated by a solid line, and a measurement waveform obtained by measuring the same normal substrate at + 50 ° C. is indicated by a broken line. In addition, the solid line and the broken line substantially overlap in FIG. 11 (a), from time 0 to time B in FIG. 11 (b), and after time B1, from time 0 to time B in FIG. 11 (c). .

  An incident wave having a step waveform shown in FIG. 11A is generated by the pulse oscillator 11 and transmitted to the probe 4 through the microstrip line 34. When the probe 4 is not in contact with the substrate 200, the incident wave transmitted to the probe 4 is totally reflected. At normal temperature, as shown by a solid line in FIG. 11B, a reflected wave having a waveform in which the voltage increases after T1 from the generation of the pulse by the pulse oscillator 11 is measured by the oscilloscope 11. T1 is the time until the incident wave reaches the probe 4 and the reflected wave returns to the oscilloscope 12 at room temperature.

  As the temperature changes, the line from the TDR measurement unit 1 to the probe 4 expands and contracts. For example, when TDR measurement is performed at + 50 ° C., the line until the incident wave reaches the probe 4 and the reflected wave returns to the oscilloscope 12 extends more than when it is at room temperature. ΔT1 shown in FIG. 10 (b) is the time required for the radio wave to reciprocate along the portion extending on the line from the TDR measurement unit 1 to the probe 4. When the probe 4 is not in contact with the substrate 200 at + 50 ° C., as shown by a broken line in FIG. 10B, a reflected wave having a waveform in which the voltage increases after the pulse generation by the pulse oscillator 11 (T1 + ΔT1) 12 is measured.

  When the probe 4 is brought into contact with the substrate 200, for example, a waveform indicated by a solid line in FIG. 11C is measured at room temperature. From time A to time B, since the impedance of the microstrip line 34 is constant, the voltage is constant. After time B, the waveform depends on the load impedance of the circuit of the substrate 200.

  On the other hand, when the TDR measurement is performed at + 50 ° C., the voltage is constant from time A to time B1, and the time at which the voltage is constant is longer by ΔT1 compared to room temperature. After time B1, that is, after (T1 + ΔT1) from the generation of the pulse by the pulse oscillator 11, the waveform depends on the load impedance of the circuit of the substrate 200.

  Note that the waveform after time B at room temperature and the waveform after time B1 at + 50 ° C. are different because the load impedance of the circuit of the substrate 200 changes depending on the temperature.

  As described above, even when the same normal substrate is measured by TDR, if the measurement temperature is different, the reflected waveform measured by the oscilloscope 12 has a different shape. Therefore, in the first embodiment, waveform analysis is performed using a standard waveform corresponding to the measured temperature, and the quality of the substrate 200 is determined.

  First, in the temperature measurement step, the temperature is measured by the temperature measurement unit 5. The temperature measurement unit 5 measures the ambient temperature, the temperature of the substrate 200 or the TDR measurement unit 1. For example, when the ambient temperature is measured by the temperature measurement unit 5, a standard waveform for each temperature is held in advance in the control calculation unit 2 in steps of 10 ° C. from 0 ° C. to 80 ° C. in consideration of environmental conditions.

  Next, in the standard waveform selection step, the control calculation unit 2 selects a temperature-specific standard waveform that is closest to the temperature measured in the temperature measurement step from among the temperature-specific standard waveforms held in advance. The standard waveform selected in the standard waveform selection step and the measurement waveform transmitted from the oscilloscope 12 are compared, the waveform analysis in the above-described substrate quality determination step is performed, and the quality of the substrate 200 is determined.

  According to the first embodiment, a standard waveform for each temperature is held in advance, a standard waveform corresponding to the temperature measured in the temperature measurement process is selected in the standard waveform selection process, and the standard waveform and the measured reflected waveform are obtained. Compare and analyze the waveform. For this reason, the influence of the temperature in TDR measurement is reduced, and the accuracy of the quality determination of the substrate 200 can be increased.

  Further, the plurality of probes 4 are brought into contact with each measurement point at once, and the TDR measurement is performed by sequentially switching from the control calculation unit 2 by switching. For this reason, the time for raising and lowering the probe 4 to make contact with a predetermined land becomes unnecessary, and the inspection time can be greatly shortened.

Embodiment 2. FIG.
In the first embodiment, the influence of temperature is considered as an error factor in TDR measurement. In the second embodiment, the displacement of the contact position of the probe 4 is considered. Since the configuration of the second embodiment is the same as that of the first embodiment, the description thereof will be omitted, and only the method for inspecting the substrate 200 will be described.

  As an error factor of the TDR measurement, there is a shift of the contact position of the probe 4 in addition to the influence of the temperature. FIG. 12 is a diagram for explaining the displacement of the contact position of the probe 4 in the second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 3 denote the same or corresponding components. FIG. 12A shows a case where there is no deviation in the contact position between the probe 4 and the land 214, and FIG. 12B shows a case where there is a deviation in the contact position. When comparing FIG. 12A and FIG. 12B, the contact position between the probe tip 41 and the land 214 is displaced by ΔX indicated by the arrow in FIG. The distance to be increased by ΔX.

  FIG. 13 is a waveform diagram for explaining the TDR measurement when the connection position between the probe 4 and the land 214 is displaced in the second embodiment of the present invention. In FIG. 13, the reflection waveform in the connection state (the state without contact position deviation) shown in FIG. 12A is a solid line, and the reflection waveform in the connection state (the state with contact position deviation) shown in FIG. Is shown. Black circles in the figure indicate measurement data with the oscilloscope 12 in a state without contact position deviation, and white circles indicate measurement data with the oscilloscope 12 in a state with contact position deviation. Regardless of the reflection waveform obtained by measuring the same substrate, the solid line waveform and the broken line waveform shown in FIG. This is because the line becomes longer by the positional deviation ΔX of the probe 4 and it is necessary to correct this positional deviation.

The relationship between the positional deviation ΔX of the probe 4 and the reflected waveform will be described with reference to FIG. Until time B, since the impedance of the microstrip line 34 is constant, the voltage is substantially constant at the standard voltage (400 mV) as described above. After time B, since the incident wave propagates on the circuit of the substrate 200, the voltage value is determined depending on the load impedance of the circuit of the substrate 200. For example, in FIG. 12A, the incident wave that has passed through the probe tip 41 first propagates through the land 214. While the incident wave propagates through the land 214, the reflected waveform becomes substantially constant at a voltage value depending on the impedance of the land 214. Since the impedance of the land 214 is known in advance from the material to be used, the voltage value V ₁ can be calculated. In the state shown in FIG. 12B, compared with the state shown in FIG. 12A, the distance that the radio wave propagates through the land 214 is increased by the contact position deviation ΔX of the probe 4. For this reason, the broken line shown in FIG. 13 is longer by ΔT2 when the voltage value is V ₁ than the solid line. Due to this time difference ΔT2, all subsequent waveforms are shifted by ΔT2.

Next, the incident wave that has passed through the land 214 propagates through the through hole 210. While the incident wave propagates through the through hole 210, the reflected waveform becomes substantially constant at a voltage value depending on the impedance of the through hole 210. Impedance of the through hole 210 of a material such as that used for known in advance, it is possible to calculate the voltage value V _2.

  The correction of the positional deviation is performed by the control calculation unit 2 and includes an error calculation process and a waveform correction process. The control calculation unit 2 calculates the time error ΔT2 in the error calculation step, and shifts the measurement waveform by the time error ΔT2 in the waveform correction step to obtain a correction waveform. The control calculation unit 2 compares the correction waveform with the standard waveform, performs the same processing as the substrate quality determination step described in Embodiment 1, and determines the quality of the substrate 200.

  A method for calculating the time error ΔT2 in the error calculation step will be described. In the following, the reflection waveform (solid line) in the state without contact position deviation shown in FIG. 13 will be described as a standard waveform, and the reflection waveform (broken line) in the state with contact position deviation will be described as a measurement waveform.

  In the control calculation unit 2, first, a voltage change point shown in FIG. 13 (P1 point for the standard waveform and P2 point for the measurement waveform) is extracted. The voltage change point is a point at which the incident wave that has passed through the probe tip 41 passes through the material that propagates first (here, the land 214) and enters the material that propagates second (here, the through hole 210). is there. Various methods can be considered as the method for extracting the voltage change point. For example, the voltage change point can be extracted as follows.

After the pulse rising point (after time A not shown in FIG. 13), the first point where the absolute value of the voltage deviation with respect to the standard voltage becomes αV or more is detected and set as a voltage change point. The alpha, than the absolute value of the deviation of the voltage value V ₁ for at least the standard voltage value larger. Further, it determined based on the deviation between the standard voltage and the voltage value V _2. In the control calculation unit 2, the voltage change point P1 of the standard waveform and the voltage change point P2 of the measurement waveform are extracted, and a time difference ΔT2 of P2 with respect to P1 is obtained. This time difference ΔT2 is caused by the displacement of the contact of the probe 4 and is defined as a time error.

As another example, since the voltage satisfies (V ₁ ± β) V after the pulse rising point (after time A not shown in FIG. 13), the absolute value of the voltage change rate is γ. It is also possible to detect the first point that is at least% and use it as the voltage change point. β is determined based on the deviation of the voltage value V _{1 from} the standard voltage and the deviation of the voltage value V _{2 from} the voltage value V ₁ . Γ is determined based on the ratio between the voltage values V ₁ and V ₂ . In the control calculation unit 2, the voltage change point P1 of the standard waveform and the voltage change point P2 of the measurement waveform are extracted, a time difference ΔT2 of P2 with respect to P1 is obtained, and defined as a time error.

  In the waveform correction step, the control calculation unit 2 performs a process of correcting the measurement waveform. In the waveform correction step, the control calculation unit 2 shifts the measurement waveform by the time error ΔT2 in the time axis direction to obtain a correction waveform. In the error calculation step and the waveform correction step, after the positional deviation of the measurement waveform is corrected, in the substrate quality determination step, the corrected waveform and the standard waveform are compared and a waveform analysis is performed to determine the quality of the substrate 200.

  When a plurality of probes 4 are brought into contact with the substrate 200 at once, the positional deviation of each probe 4 has the same tendency. Therefore, it is possible to calculate a time error at a specific measurement location and use it for waveform analysis at other measurement locations, instead of correcting the displacement for each measurement location.

  FIG. 14 is a bottom view showing the substrate 200 according to Embodiment 2 of the present invention. For example, when TDR measurement is performed for all the lands 214 shown in FIG. 14, the lands 214 a, 214 b, 214 c and 214 d at the four corners of the BGA IC 100 are determined as specific measurement locations in the control calculation unit 2.

  In the error calculation step, the control calculation unit 2 obtains a time difference due to the positional deviation of the contact between the land 214a, which is a specific measurement location, and the probe 4. Similarly, the control calculation unit 2 also obtains a time difference due to the positional deviation of the contact between the lands 214b, 214c, 214d and the probe 4. The average value of the calculated time differences is defined as a time error ΔT2 for all measurement points. Here, a plurality of specific measurement points are provided, but one measurement point may be used. In that case, it is not necessary to obtain an average value of time differences.

  In the waveform correction step, all the reflected waveforms measured in the reflected waveform measuring step are shifted in the time axis direction by a time error ΔT2 to obtain corrected waveforms. When TDR measurement is performed at a location other than a specific measurement location, it is not necessary to calculate the time error ΔT2 due to misalignment, and the error calculation process can be omitted, so that the time required for substrate inspection can be shortened.

  According to the second embodiment of the present invention, since the waveform analysis is performed by correcting the positional deviation of the contact between the probe 4 and the substrate 200, the influence on the measurement waveform due to the positional deviation is reduced, and the quality of the substrate 200 by the TDR measurement is determined. The accuracy of determination can be increased.

  In addition, since the waveform analysis of all the measurement points is performed using the time error of the specific measurement point, the error calculation process other than the specific measurement point can be omitted, and the time required for the substrate inspection can be shortened. it can.

It is a block diagram which shows the board | substrate inspection apparatus in Embodiment 1 of this invention. It is sectional drawing which shows the board | substrate 200 and the interface board 3 in Embodiment 1 of this invention. It is an enlarged view of the X section of FIG. It is a top view which shows the connection part with BGA IC100 of the board | substrate 200 in Embodiment 1 of this invention. It is a figure explaining the test | inspection method of the board | substrate 200 in Embodiment 1 of this invention. It is a wave form diagram explaining the measurement of TDR in Embodiment 1 of this invention. It is explanatory drawing of the waveform analysis in the control calculating part 2 in Embodiment 1 of this invention. It is explanatory drawing of the waveform analysis in the control calculating part 2 in Embodiment 1 of this invention. It is sectional drawing which shows the board | substrate 200 and the interface board | substrate 300 in case the crack 102 has arisen in the solder ball 101 in Embodiment 1 of this invention. It is a wave form diagram explaining the measurement of TDR in case the crack 102 has arisen in the solder ball 101 in Embodiment 1 of this invention. It is a wave form diagram explaining the influence by the temperature of the TDR measurement in Embodiment 1 of this invention. It is a figure explaining the shift | offset | difference of the contact position of the probe 4 in Embodiment 2 of this invention. It is a wave form diagram explaining the TDR measurement when the shift | offset | difference arises in the connection position of the probe 4 and land 214 in Embodiment 2 of this invention. It is a bottom view which shows the board | substrate 200 in Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 TDR measurement part 2 Control operation part 5 Temperature measurement part 200 Board | substrate

Claims (8)

A reflected waveform measuring step of applying a predetermined incident wave to the measured substrate and measuring a reflected waveform from the measured substrate;
A temperature measuring step for measuring temperature;
A standard waveform selection step for selecting a standard waveform corresponding to the temperature measured in the temperature measurement step from the standard waveforms for each temperature held in advance;
A substrate inspection method comprising: a substrate pass / fail judgment step for judging pass / fail of the substrate to be measured based on a result of comparing the reflected waveform measured in the reflected waveform measurement step and the standard waveform selected in the standard waveform selection step. The substrate pass / fail determination step determines that the substrate to be measured is NO when the potential difference between the reflected waveform measured in the reflected waveform measurement step and the standard waveform selected in the standard waveform selection step is equal to or greater than a predetermined threshold. The substrate inspection method according to claim 1. The substrate pass / fail judgment step is performed when the state in which the potential difference between the reflected waveform measured in the reflected waveform measurement step and the standard waveform selected in the standard waveform selection step is a predetermined threshold or more continues for a predetermined time or longer. The substrate inspection method according to claim 1, wherein the determination is made as NO. A reflected waveform measuring step of applying a predetermined incident wave to the measured substrate and measuring a reflected waveform from the measured substrate;
An error calculating step for calculating a time error of the reflected waveform measured in the reflected waveform measuring step with respect to the standard waveform held in advance;
A waveform correction step of shifting the reflected waveform in the time axis direction by the time error;
A substrate inspection method comprising: a substrate pass / fail judgment step for judging pass / fail of the substrate to be measured based on a result of comparing the reflected waveform shifted in the waveform correction step and the standard waveform. 5. The substrate pass / fail judgment step, when the potential difference between the reflected waveform shifted in the waveform correction step and the standard waveform is equal to or greater than a predetermined threshold value, judges that the substrate to be measured is no. Board inspection method. The substrate pass / fail determination step determines that the substrate to be measured is NO when a state where the potential difference between the reflected waveform shifted in the waveform correction step and the standard waveform is equal to or greater than a predetermined threshold continues for a predetermined time or longer. The substrate inspection method according to claim 4. The error calculation process changes the voltage at the first point where the absolute value of the deviation of the voltage from the standard voltage exceeds the specified value after the pulse rising point for each of the standard waveform held in advance and the reflected waveform measured in the reflected waveform measurement process. 5. The substrate inspection method according to claim 4, wherein a point difference is extracted, and a time difference between the voltage change point of the reflected waveform and the voltage change point of the standard waveform is calculated as a time error. In the reflected waveform measuring step, a predetermined incident wave is applied to a plurality of measurement locations of the substrate to be measured, and the reflected waveforms from the plurality of measurement locations are respectively measured,
The error calculation step calculates the time error of the reflected waveform from the specific measurement location measured in the reflected waveform measurement step with respect to the standard waveform corresponding to the specific measurement location held in advance,
In the waveform correction step, the reflected waveforms from the plurality of measurement points measured in the reflected waveform measurement step are each shifted in the time axis direction by the time error,
The substrate pass / fail determination step determines pass / fail of the measured substrate based on a result of comparing the reflected waveform shifted in the waveform correction step with a standard waveform held in advance for each of the plurality of measurement locations. The substrate inspection method according to claim 4.

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