JP5437935B2 - INSPECTION METHOD AND INSPECTION DEVICE USED TO IMPLEMENT THE SAME - Google Patents

Description

The present invention relates to an inspection method for inspecting terminal floating when an electronic component such as an IC package is mounted on a printed board, and an inspection apparatus used for carrying out this inspection method.

As a method for inspecting whether or not an electronic component is securely soldered to a printed circuit board, there is an inspection method in which a protection diode of the electronic component is turned on, and terminal floating is determined based on an electrical parameter indicating the conduction state. It is used.
For example, in Patent Document 1, a current value is measured by applying a voltage slightly higher than a forward threshold voltage of a protection diode (or a parasitic diode, hereinafter collectively referred to as a protection diode). If there is no terminal floating or if the bonding state is good, the detected current falls within a predetermined range determined by the forward characteristics of the protection diode. Moreover, if it is a disconnection state, the detected electric current will be far below a predetermined range, and terminal floating can be discriminated.

Further, in Patent Document 2, there are bypass capacitors and stray capacitances on the pattern of the printed circuit board, and in order to prevent the inspection time from extending due to the time constants due to these, time constants such as stray capacitance with respect to the DC voltage are provided. An inspection method is disclosed in which AC voltage having a sufficiently smaller period is superimposed and terminal floating is discriminated in a short time without being affected by stray capacitance or the like.

Japanese Patent Laid-Open No. 2001-4709 JP-A-11-248781

However, the conventional terminal floating inspection method has the following problems. In other words, in order to prevent the current from being excessively large and causing the electronic component to be broken due to the current flowing in the forward direction with respect to the protective diode, the voltage value that can be applied cannot be increased. According to Patent Document 2, an AC voltage of 0.1 volts (1 KHz) is used for a DC voltage of 0.7 volts. The diode has a minimum voltage (potential barrier) necessary for carrier movement. When the diode is used with forward bias, a voltage drop corresponding to the forward voltage occurs. Therefore, the voltage that can be used for the inspection is further smaller than the applied voltage. Further, the protection diode is guaranteed with respect to the Zener characteristic, but there is no guarantee as to what characteristic the forward diode exhibits with respect to the forward bias. Therefore, a large current may flow. In order to measure the current value, the voltage at both ends is measured using a small resistance of about 1 ohm, but it is difficult to obtain meaningful detection data with such a small voltage.

In addition, the terminal float is not only in a state where it is actually floating and there is no conduction, but also when the solder is not melted and the printed circuit board and the electronic component are not connected in a wet state by the solder, In some cases, it is connected but cracked. In such a case, the connection resistance between the terminal of the electronic component and the printed circuit board pattern shows a higher resistance value than normal, but since it is conductive for the time being, if the connection resistance is not meticulously measured, the terminal floating will occur. It cannot be detected.

The present invention has been made in view of such a problem, and provides an inspection method and an inspection apparatus capable of inspecting a terminal floating of an electronic component after applying a large voltage to a protective diode. Objective.

In order to achieve the above object, according to the present invention, a probe is brought into contact with a circuit pattern appearing on the surface of a printed circuit board on which a signal terminal is mounted with an electronic component having a protection diode inside, and the signal terminal is interposed between the probe and the circuit pattern. In the inspection method of applying a forward voltage to the protection diode to obtain an electrical characteristic value, and performing a terminal floating inspection using the obtained electrical characteristic value, an electron mounted on the printed circuit board A voltage exceeding the potential barrier of the protection diode with respect to the protection diode a plurality of times when vibration is alternately applied in the direction of separating or pushing up the component and the vibration is in the direction of separating the electronic component in synchronization with the vibration. The pulse signal is applied through the probe, and the electrical characteristics flowing through the probe are measured.

Since a large voltage is applied to the protection diode and the connection resistance between the electronic component terminal and the printed circuit board pattern can be measured with a large current value, it is possible to more accurately inspect the terminal floating of the electronic component. There is an effect that can be done.

It is a figure which shows a mode that an electronic component is tested. It is a figure which shows a measurement waveform. It is a figure which shows a probe apparatus. It is a figure which shows a vibration mechanism. It is a figure which shows an inspection apparatus. It is a figure which shows the time relationship between a pulse waveform and vibration. It is a figure which shows a setting and a test | inspection routine. It is a figure which shows the determination routine. It is a figure which shows a measurement waveform.

FIG. 1 shows an electronic component 100 in which a protective diode 101 is provided inside an input, output, or input / output terminal 102 (signal terminal). The protection diode 101 is a diode specialized for this function by actively utilizing the phenomenon of avalanche breakdown. Unlike the signal diode, the response performance to the forward voltage is not guaranteed, but it is on the order of about 0.1 msec and is low speed.

FIG. 1B shows how the protection diode 101 is tested. In the figure, the probe 105 is pressed against a pattern (pad or land or the like) 10104 on the printed circuit board 103 connected to the terminal 102, and is forward with respect to the protective diode 101 via a resistor (1.3 ohm) 106. The voltage V (2.8 volts) is applied to the voltage supply terminal xy. FIG. 2 shows the result of measuring the voltage drop at the resistor 106 at this time.

In FIG. 2, a waveform α (FIG. 2B) is a waveform of the voltage V, a waveform a is an observation waveform of the voltage V, and a waveform b is an observation waveform of both ends of the resistor. The waveform a rises with a time constant with respect to the waveform α. This is due to the influence of the circuit inside the electronic component 100, the resistance in the middle of the path, and the capacitance existing between the voltage supply terminals xy. In the rising period p1 of the waveform a, the waveform b follows this. This is because the protection diode 101 does not conduct and functions like a capacitor. Thereafter, the protection diode becomes conductive at time t1. In the period p2, since the electric charge accumulated in the protection diode 101 during the period p1 is discharged, the waveform b falls below the 0 level and swings in the reverse direction. After that, after the transition period of the period p3, the steady-state voltage value is shown after the time point t3 (250 msec). In this example, it is 0.03 volts, and the resistance 106 is 1.3 ohms, so a current of 390 mA flows. Although it depends on the electronic component, a current value of about several tens to several hundreds of mA may damage the electronic component and cannot be kept flowing for a long time.

In this embodiment, a pulse signal c (FIG. 2C) having a shorter pulse width than that used to reach the steady state of the protection diode 101 is used as the waveform a. Further, the disconnection state is confirmed by applying vibration to the printed circuit board 103 and jumping up the terminal floating from the pattern of the printed circuit board by the vibration. At this time, the vibration applied to the printed circuit board 103 is the vibration having the same wavelength as the pulse signal c or several times the wavelength. Since the resonance frequency of the printed circuit board 103 is on the order of several hundred MHz (glass substrate), it can be expected that the vibration applied to the printed circuit board is in substantially the same vibration amplitude state at almost any point.

FIG. 3 shows the probe apparatus 1 according to the present embodiment. The probe device 1 includes rectangular tables 2a and 2b arranged vertically, guides 3 provided at the four corners of the tables 2a and 2b, an upper jig mounting plate 4a that slides along the guides 3, and a lower jig And a jig mounting plate 4b. In order to be able to move up and down along the guide 3 with respect to the upper jig mounting plate 4a and the lower jig mounting plate 4b, motors 5a and 5b and ball screws 6a and 6b that are rotationally driven by the motors 5a and 5b are provided. Is provided. When the motors 5a and 5b are driven, the ball screws 6a and 6b are rotated, and the upper jig attaching plate 4a and the lower jig attaching plate 4b which are screwed into the screws are raised and lowered. The jigs 7a and 7b attached to the upper jig attachment plate 4a and the lower jig attachment plate 4b are respectively input, output, input / output terminals, ground terminals, and power supply terminals in the electronic component 100 mounted on the printed circuit board 103 to be inspected. A number of probes 105 that are connected to each other and come into contact with patterns (pads or lands) appearing on the surface of the printed circuit board 103 are attached. A vibration mechanism 9 is further attached to the jigs 7 a and 7, and in parallel with the probe 105 being pressed against the printed board 103, the jig 7 a and 7 come into contact with the printed board 103 to give vibration. The vibration mechanism 9 is disposed above and below the printed circuit board 103 because the electronic components 100 are disposed on both surfaces of the printed circuit board 103.

FIG. 4 is an enlarged cross-sectional view of the vibration mechanism 9. The vibration mechanism 9 is configured by connecting a vibrating body 11 to a fixed jig 8 (fixed to the jigs 7a and 7 in FIG. 3) via positive and negative spring terminals 10a and 10b. Is attached with a holding material 12 for holding the printed circuit board 103. When a voltage is applied to the vibration mechanism 9, the printed circuit board 103 is pushed in a direction in which the electronic component 100 is pulled away from the printed circuit board 103. When the voltage application stops, the terminals 10a and 10b return. Thereby, one vibration is generated.

Next, the circuit configuration of the inspection apparatus 20 will be described with reference to FIG. The inspection device 20 includes a probe device 1, a calculator 30, and a tester 20. The computer 30 includes a CPU 31, a RAM 32, a ROM 33, and various external interfaces 35, 36, and 37. The first interface 35 is an interface for external connection, and is connected to another computer, a display screen, and an input device (not shown). The second interface 36 is an interface that controls the vibration mechanism 9, and the third interface 37 is an interface that controls the tester 40. The ROM 33 stores a program which will be described later, and the RAM 32 has a pattern position on the printed circuit board to be inspected and whether the pattern is a power source or a ground (ground), or an electronic component. Data 37 indicating which of the input, output or input / output terminal is connected is stored. The tester 40 applies a pulsed voltage at a designated timing and application time to the probe 105 corresponding to the position of the printed circuit board 103 designated from the third interface 36, and on the probe via the resistor 104. The signal is read as a voltage signal. The vibration mechanism 9 applies vibration to the printed circuit board 103 at the timing and time interval specified by the second interface 35.

FIG. 6 is a diagram illustrating a time relationship between a pulse waveform and vibration. FIG. 6A shows a vibration pattern, and shows the control voltage d applied from the second interface 35 to the vibration mechanism 9. FIG. 6B shows the timing, application time, and voltage value of the pulse c instructed from the third interface 36 to the tester 40. These are given in synchronization with the control voltage d to the vibration mechanism 9. In the figure, r0 to r5 are parameters specified from an external computer or input device (not shown) via the first interface 34, and indicate the elapsed time from the control voltage application start time T0 by the vibration mechanism 9. Yes. r0 is a parameter for adjusting a mechanical response delay by the vibration mechanism 9, and r1 to r5 indicate a pulse period and a duty.

When the control voltage is applied (ON state), the vibration mechanism 9 operates downward in FIG. 4 to cause the electronic component 100 to be pulled away from the printed circuit board 103. When the application of the control voltage is stopped (OFF state), the printed circuit board 103 acts to push up the electronic component 100 from below.

V0 is also a parameter given from the first interface 34, and indicates the voltage value of the pulse c. In addition, whether or not to measure the voltage value obtained by the resistor 105 within the range of the period during which the pulse c is applied (r1, r3, r5) is given as a parameter G via the first interface, Set to tester. Specifically, the elapsed time from the rise of the pulse c is the parameter G.

The timing of the parameter G is the timing within the period p3 in FIG. 2C (immediately before the fall of the waveform c). Based on the parameter G, the tester 40 performs a test using the probe 105 corresponding to the designated pattern position of the printed circuit board 103.

FIG. 7 is a diagram showing a flow of the computer 30. FIG. 7A is a setting routine for the tester 40. The computer 30 inputs each parameter from the first interface 34 and sets it in the memory 41 of the tester 40 together with position information (data 37, FIG. 5) of the printed circuit board 103 to be inspected.

FIG. 7B shows an inspection flow. First, the control voltage to the vibration mechanism 9 is turned on and off to start the vibration of the printed circuit board 103. After a while, when the control voltage to the vibration mechanism 9 is turned on, a measurement instruction is given to the tester 40 in synchronization with this (the instruction processing time of the computer 30 is several hundred nsec, so steps s1 and s2 are considered to be simultaneous. Good). The instruction to the tester 40 is for one probe 105. The tester 40 starts measurement using parameters preset by the setting routine. After measuring several times (three times in the embodiment) for one vibration, the printed circuit board 103 is returned to the original state, and this is repeated several times (three times in the embodiment).

This operation is performed for all terminals 102 to be inspected of the electronic component 100. When the inspection is completed, an electrical characteristic value is obtained from the tester 40 as a measurement result. Then, the voltage obtained by the resistor 105 is obtained as the electrical characteristics representing the connection resistance of the terminal 102, and the maximum value, the minimum value, and the average value thereof are obtained and output to the outside through the first interface. In this embodiment, the period of vibration by the vibration mechanism is 1.5 msec, and the period (t1 + t2) of the pulse signal c is 0.4 msec.

  FIG. 8 shows a determination flow for determining whether the printed circuit board 103 is good or bad. First, the inspection substrate shown in FIG. 7 is inspected with respect to the printed circuit board having no defect on which the electronic component is mounted, and then the inspection target printed circuit board 103 is inspected in the same manner according to the inspection flow in FIG. Then, by comparing the obtained maximum value, minimum value, and average value, the quality of the printed circuit board 103 to be tested is determined.

The values detected as the maximum value, the minimum value, and the average value correspond to the value of the connection resistance between the terminal 102 of the electronic component 100 and the pattern of the printed circuit board 103, and therefore are acceptable for a printed circuit board having no defect. The printed circuit board 103 showing a small value below the range is determined to be defective as the connection resistance is higher than normal and the terminal floats.

In this embodiment, the protection diode 101 is energized only within a short time of the order of 0.1 msec using the pulse waveform c, so that there is an effect that the load on the electronic component is small. Since a large detection value appears in the resistor 104 as compared with the conventional case, there is an effect that the detection system is improved.

Further, since the pulse signal c is also given in synchronization with the vibration mechanism 9, the conduction state is acquired by capturing the moment when the printed circuit board 103 is moved away from the electronic component 100, and the terminal floating occurs. There is an effect that the detection accuracy in a certain case is increased.

In the above embodiment, the measurement was performed with the protection diode 101 in a steady state, but an embodiment in which the protection diode 101 is inspected in a transient state is shown below.
In FIG. 9, FIG. 9B shows a waveform β having a shorter pulse period than that for reaching the steady state with respect to the protection diode 101 provided between the voltage supply terminals xy, and FIG. 9A applied the pulse signal β. The observed waveform e at the time is an observed waveform f at both ends of the resistor 104. In the period pa immediately after the rising edge of the pulse signal e, the protection diode 101 functions as a capacitor as in the period p1 shown in FIG. Thereafter, at time tb, the protection diode 101 is turned on. Thereafter, a transient response is shown in the period pb. When the pulse signal e falls at the time point tc, a waveform that is significantly lower than 0 volt than the carrier accumulated in the protection diode 101 is observed in the period pc. Thereafter, a waveform gradually dropping to 0 volt is seen in the period pd. During this period, the protection diode is in a non-energized state, and the capacitance between the voltage supply terminals xy (FIG. 1) is discharged. From the time te when the pulse signal e rises, the waveforms from pa to pd are repeated. Here, in the second and subsequent pulses rather than the first pulse, the waveform when the protective diode 101 is turned on stably shows the same waveform.

The voltage on the waveform when the pulse signal e is applied in such a short time period is sampled to obtain a detection result. Specifically, a positive peak voltage in the period pa and a negative peak in the period pc are acquired. Alternatively, a positive peak value in the period pd or a negative peak in the period pb may be acquired.

In order to acquire the positive and negative peak voltages, in the setting routine (FIG. 7A) of the tester 40 in the previous embodiment, a period (pa to pd) is set for the tester 40 instead of specifying the measurement timing (parameter G). And set to measure either positive or negative peak value. In order to obtain the peak value, it is only necessary to employ a circuit configuration in which the measurement values sampled in a short cycle in the tester 40 are sequentially compared to leave only those having a large absolute value. Other parameters such as timing are the same as in the previous embodiment. As a result, in the inspection routine (FIG. 7B), as in the previous embodiment, the pulse signal e is given to the vibration mechanism 9 and several pulses are applied during the period in which the printed circuit board 103 is pushed away from the electronic component 100. The positive / negative peak voltage is measured at both ends of the resistor 106. From the tester 40, the maximum value, the minimum value, and the average value in the period pa (or pd) and the maximum value, the minimum value, and the average value in the period pc (or pb) are calculated by the calculator 20 as in the previous embodiment. Desired. Then, the quality of the printed circuit board 103 is determined according to the determination flow (FIG. 8).

According to the present embodiment, the protection diode 101 is in a state where a high voltage is applied, and the transient response is used. Therefore, the signal value that appears in the resistor 104 is large, but the protection diode 101 is deep. There is an effect that the conductive state is not reached and the load on the electronic component 100 is small.

In the above embodiment, the maximum value, the minimum value, the average value in the period pa (or pd), the maximum value, the minimum value, and the average value in the period pc (or pb) are obtained. The maximum value, minimum value, and average value for the voltage value may be output. In addition, the tester does not specify the periods P1 to pd but instead of measuring the maximum value in each of the periods P1 to pd, and simply determines the maximum value on the positive side of the sample measured values in one period of the pulse. Alternatively, the measurement may be performed while leaving the maximum value on the negative side.

DESCRIPTION OF SYMBOLS 1 Probe apparatus 9 Vibration mechanism 20 Inspection apparatus 30 Computer 40 Tester 100 Electronic component 101 Protection diode 103 Printed circuit board 105 Probe 106 Resistance

Claims (4)

A probe is brought into contact with a circuit pattern appearing on the surface of the printed circuit board on a printed circuit board on which an electronic component having a protective diode inside is mounted on a signal terminal, and a forward voltage is applied to the protective diode through the signal terminal. In the inspection method of applying and acquiring the electrical characteristic value, and performing the terminal floating inspection using the acquired electrical characteristic value,
Vibration is alternately applied in the direction of separating or pushing up the electronic components mounted on the printed circuit board,
In synchronization with the vibration, a pulse signal having a voltage exceeding the potential barrier of the protection diode is applied to the protection diode a plurality of times when the vibration is in a direction to separate the electronic component, through the probe,
An inspection method characterized by measuring electrical characteristics flowing through the probe.
2. The inspection according to claim 1, wherein the measurement of electrical characteristics flowing through the probe is performed by specifying in advance a timing at which a current value flowing through the probe reaches a steady value after the pulse signal rises. Method.
2. The inspection method according to claim 1, wherein the measurement of electrical characteristics flowing through the probe measures a maximum value of positive and negative values within a range of one period of the pulse signal.
A probe is brought into contact with a circuit pattern appearing on the surface of the printed circuit board on a printed circuit board on which an electronic component having a protective diode inside is mounted on a signal terminal, and a forward voltage is applied to the protective diode through the signal terminal. In the inspection device that acquires the electrical characteristic value by applying the terminal floating inspection using the acquired electrical characteristic value,
A vibration mechanism that alternately vibrates in a direction to pull away or push up an electronic component mounted on the printed circuit board;
A tester for applying, via the probe, a pulse signal having a voltage exceeding the potential barrier of the protection diode to the protection diode a plurality of times when the vibration is in a direction to separate the electronic component in synchronization with the vibration; Have
The tester is characterized by measuring an electrical characteristic flowing through the probe.