JP2865046B2 - Method and apparatus for inspecting solder connection of electronic components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for inspecting solder connection, and more particularly to a method and an apparatus for inspecting solder connection of leads of electronic components.

[0002]

2. Description of the Related Art Lead Flat QFP (Quad Flat Pack)
age), for example, a continuity test is performed using two probes using an in-circuit tester (for example, manufactured by Hioki Electric Co., Ltd.) as a method for inspecting the solder connection of the leads of a semiconductor package such as a semiconductor device. There is an electrical inspection method.

A conventional example of a lead connection inspection method for an electronic component such as a semiconductor package will be described below in detail with reference to the drawings.

FIG. 6 is a diagram for explaining a conventional method for inspecting lead connection of electronic components by an electrical inspection method for conducting a continuity test using two probes.

Referring to FIG. 6, a conventional inspection method uses two coaxial probes 56 and 56 'for four-terminal measurement, and uses a pad 55 on a circuit board 50 and a lead shoulder of a lead 53 of a semiconductor package 51. A current is caused to flow between the unit 54 and the unit 54 by the current source 57, and the two probes 56, 5
The voltage between 6 'and 6' is measured by a voltmeter 58, the resistance between the probes 56 and 56 'is determined from the current value and the measured voltage according to Ohm's law, and the solder connection between the lead 53 and the pad 55 is inspected. Things.

In the case of the four-terminal measurement method, measurement is generally performed with four probes. However, as the pitch of the semiconductor package is reduced, it becomes difficult to perform probing by contacting the leads 53 with two probes. Therefore, a coaxial probe is used for this purpose.

[0007] As the pitch becomes narrower, the lead width and the lead thickness of the semiconductor package both become smaller, and damage (damage) to the lead caused by the contact of the probe becomes larger. There is a limit to the response.

[0008]

The above-described conventional method for inspecting lead solder connection of electronic components is a contact type measurement by a four-terminal measurement method. By pressing by the probe,
The lead comes into contact with the pad 55 of the circuit board 50, whereby the lead is electrically connected at the time of probing, and is erroneously determined as a non-defective product, and a connection failure (defective product) may be missed.

Further, the conventional method for inspecting lead solder connection of electronic parts has a problem that the lead 53 is damaged due to a contact (contact with the tip of the probe), and furthermore, a soft touch is performed at the time of flowing. (It takes time for contact), and thus it is difficult to realize high-speed flowing.

[0010] Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a solder connection inspection method and an inspection apparatus capable of performing solder connection inspection of electronic components having a narrow pitch at high speed and reliably. To provide.

[0011]

According to the present invention, there is provided a method for inspecting a solder connection of a lead of at least an electronic component including a semiconductor package mounted on a circuit board. A signal is applied by abutting a probe on a pad portion on the circuit board to be connected, and the sum of electric fields induced in the lead and the lead adjacent thereto is separated from the solder connection side of the lead. located Te, it is disposed in proximity to the predetermined area, measured by the electric field detecting sensor, the measured field strength, the Li
A method for inspecting solder connection of an electronic component , comprising: distinguishing between opening of a lead and a short between the lead and a lead adjacent to the lead .

In the present invention, preferably, a predetermined region of the lead, in which the electric field detection sensor is disposed in proximity, is a shoulder of the lead.

Further, in the present invention, preferably, the electric field detection sensor is disposed via a space gap within a range in which the detection sensitivity is secured with respect to the lead shoulder, and the electric field detection sensor is brought into a non-contact state. It is characterized in that the intensity is detected.

Further, according to the present invention, it is preferable that a metal tip surface of the electric field detection sensor for an electric field guide close to the lead shoulder is to be inspected at least in the direction in which the leads of the electric field detection sensor are arranged. In the moving range of the amount corresponding to one lead width of the target semiconductor package, the inspection target lead has a shape in which the area facing the shoulder of the lead adjacent thereto is substantially constant.

The present invention is characterized in that the electric field detection sensor is controlled to move along a predetermined scanning direction while maintaining a predetermined space gap with respect to the lead shoulder.

Further, according to the present invention, when the output of the electric field detection sensor is fetched at a predetermined sampling cycle using a signal processing means and subjected to signal processing, the data number corresponding to one lead width of the semiconductor package to be inspected is obtained. After performing the averaging process as the maximum unit of the addition and averaging, the level of the electric field intensity after the averaging process is compared with a predetermined value to determine and determine,
It is characterized in that a solder connection state between the lead and a pad on the circuit board and a short circuit between an adjacent lead are detected.

According to another aspect of the present invention, there is provided an apparatus for inspecting a solder connection of an electronic component including a semiconductor package having at least a lead mounted on a circuit board, the pad on the circuit board to which the lead is to be solder-connected. A probe positioned and abutted on the portion, a signal generator for applying a signal to the pad portion via the probe, and a solder connection side of a lead to which a signal is to be applied by the probe and an adjacent lead. An electric field detection sensor that is disposed in the vicinity of a predetermined area that is spaced apart through a predetermined space gap and that detects a sum of electric field strengths, and receives an output of the electric field detection sensor and receives the output of the electric field detection sensor. Signal processing means for processing the detection signal of the electric field strength in a predetermined area, and compares and determines the level of the electric field strength with a predetermined value, Providing a solder connection test apparatus for electronic components, characterized by detecting a short-circuit between the solder connection state and the adjacent leads of said lead circuit pads on the substrate.

According to the present invention, a probe for applying a signal abuts only on a pad of a circuit board, and uses an EO sensor for detecting an electric field using an electro-optic effect, thereby using a lead portion of a semiconductor package such as a QFP. By measuring the electric field strength and inspecting the connection state of the solder in a non-contact manner, the unconnected state of the solder can be reliably detected without causing damage to the leads.
Further, according to the present invention, since the probing operation of the soft touch required in the contact-type inspection is not required (the EO sensor is not in contact with the lead portion in the present invention), high reliability and high speed are achieved. , And enables highly efficient inspection.

Further, according to the present invention, by devising the shape of the tip metal of the EO sensor, it is possible to simultaneously measure not only the lead to be inspected but also the electric field induced in the lead adjacent thereto. By comparing the sum of the obtained electric field strengths with a predetermined output set in advance, open and short between the lead to be inspected and the adjacent lead can be inspected by one measurement.

[0020]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram for explaining an outline of a solder connection inspection method for an electronic component according to an embodiment of the present invention.

Referring to FIG. 1, in the present embodiment,
An EO sensor 7 for detecting an electric field intensity is arranged in the lead 4 of the semiconductor package 2 mounted on the circuit board 1 and close to the lead shoulder 5 on the side of the resin mold 3 distant from the solder connection portion 11. Circuit board 1 to which lead 4 is to be connected by soldering
A signal is applied from a signal source 9 by contacting a probe 8 to the upper pad 6, a signal processing unit 10 for detecting the electric field strength of the lead shoulder 5 with an EO sensor 7 and inputting the output of the EO sensor 7.
Then, according to the magnitude of the signal level, the state of the solder connection between the lead 4 and the pad 6 on the circuit board 1 and the short-circuit with the adjacent lead are inspected.

FIG. 2 is a sectional view schematically showing an example of the configuration of the EO sensor 7 shown in FIG.

Referring to FIG. 2, EO sensor 7 includes a laser 21 as a light source and an isolator 2 for removing return light.
2, a polarization beam splitter 23 that reflects 100% of the S component of the laser beam and transmits part of the P component.
A first condenser lens 24 for condensing the laser beam, an electro-optical element (EO element) 25 whose refractive index changes by an electro-optical effect when placed in an electric field, and a Metal body 26 for guiding the arranged electric field to electro-optical element 25
And a Wollaston prism 27 that reflects the laser light reflected by the end face of the electro-optical element 25 on the metal body 26 side, undergoes a polarization change in the electro-optical element 25, and is reflected by the polarization beam splitter 23 into P and S components. , Wollaston prism 2
A second condenser lens 28 for condensing the two laser beams P and S split at 7 and a two-channel photodetector 29 for receiving the two converged laser beams and converting the amount of light into a current. Have been.

With the change in the electric field strength, the P and S components
Since the two laser light intensities change, the potential state of the DUT can be measured by detecting the difference between the two light intensities.

Referring to FIG. 1, the electric field intensity generated by the potential of the lead shoulder 5 shows an electric field intensity of a certain level or more when the pad 6 and the lead 4 are connected. Since the electric field intensity is at the zero level, the solder connection state of the lead 4 can be inspected from the detected electric field intensity.

Further, the electric field strength is determined by the E from the lead shoulder 5.
Although it decreases exponentially depending on the distance of the O sensor 7, that is, the size of the space gap, it is necessary to compare the detection level with the detection level based on a predetermined threshold value to determine the quality of the solder connection. A space gap that is acceptable within the detection sensitivity of the sensor 7 is provided.

That is, by using the EO sensor, it is possible to inspect the solder connection by the non-contact method.
In particular, in order to detect unconnected solder, the lead shoulder 5
It is better to avoid contact of the EO sensor 7 with the EO sensor as much as possible. The present embodiment is characterized in that the connection state (good / defective) of the solder is detected in a non-contact manner as described above, so that damage (damage) to the lead is avoided, and the unconnected state of the solder is surely achieved. Can be detected, and an operation and effect of realizing high-reliability, high-speed and high-efficiency inspection can be achieved.

FIG. 3 is a perspective view for explaining the probe scanning method of the electronic component solder connection inspection method according to the embodiment shown in FIG.

Referring to FIG. 3, a probe 8 applies a voltage from a signal source 9 to one pad portion 6 on a circuit board, and a lead shoulder to which a voltage is to be applied and a lead shoulder of an adjacent lead 4 '. With the EO probe 7 arranged near the parts 5, 5 ',
The sum of the electric fields induced in the two leads 4 and 4 ′ is measured via the metal body 26 attached to the tip of the EO sensor 7. The tip of the metal body 26 is moved at a constant speed in the scanning direction 30 with a predetermined space gap with respect to the lead shoulders 5 and 5 ', and the EO probe 7 is synchronized with the movement of the EO probe 7. The probe 8 for signal supply is also in the scanning direction 30.
Is moved at a constant speed while repeating the vertical probing operation.

FIGS. 4A and 4B are views for explaining a method of detecting the electric field strength in the solder connection inspection method for the electronic component shown in FIG.

FIG. 4A shows the case where the lead to be inspected is normally soldered to the pad on the circuit board.
(B) schematically shows a case where there is a short circuit with an adjacent lead.

Referring to FIG. 4 (A), an electro-optic crystal 25 whose end face provided on the upper surface of metal body 26 is grounded by transparent electrode 33 from signal source 9 via a pad on a circuit board. A lead shoulder 5 of the lead to be inspected to which the signal has been applied;
An electric field 32 having an intensity proportional to an electric field 31 generated between the metal body 26 of the EO sensor and the lead shoulder 5 is induced.

On the other hand, referring to FIG. 4B, when the lead to be inspected is short-circuited with the adjacent lead, the metal body 26 and the two lead shoulders 5 and 5 'opposed thereto are connected. In between, electric fields 31 and 31 ′ are generated in proportion to the facing areas, and an electric field 32 ′ having an intensity approximately twice that in FIG. 4A is induced in the electro-optic crystal 25.

Therefore, by simultaneously measuring the electric field induced in the adjacent lead in addition to the lead to be inspected, the measured electric field strength is used to determine the solder connection between the lead to be inspected and the pad on the circuit board. A short between the target lead and the adjacent lead can be determined at the same time.

FIG. 5 is a plan view for explaining the tip shape of the metal body 26 shown in FIG.

Referring to FIG. 5, a metal body 26 is provided so as to face the lead 4 to be inspected and the lead shoulder 5 of the adjacent lead 4 '. The probe 8 is in contact with the circuit board-side pad 6 of the lead 4 to be inspected, and the probe 8 is moved at a constant speed in the scanning direction 30 in synchronization with the metal body 26. While the probe 8 is in contact with the pad 6, a signal is supplied from the signal source to the lead 4 to be inspected.

In the actual measurement, while the probe 8 is in contact, the EO is performed at a predetermined sampling cycle.
It takes in a signal proportional to the electric field strength detected by the sensor,
The signal processing unit 10 (see FIG. 1) performs predetermined signal processing.

Generally, the output signal of the EO sensor includes a noise component of a laser light source or an electric circuit, and performs an averaging process or the like in the signal processing to improve the S / N ratio (signal-to-noise ratio). .

For this reason, it is desirable that the detection sensitivity of the EO sensor be constant while the probe 8 is in contact with the EO sensor. This requires that the facing area between the metal body 26 and the lead shoulder 5 be constant. doing.

In the present embodiment shown in FIG. 5, the planar shape of the tip of the metal body 26 has a rectangular shape, and
In the scanning direction 30 of the metal body 26, at least the lead 4 to be inspected
Therefore, a certain detection sensitivity can be assured while the probe 8 is in contact with the lead 4 to be inspected. That is, EO
The tip of the metal body 26 of the sensor is located on the shoulder of the lead 4 to be inspected and the lead 4 'adjacent to the lead 4 in an amount of movement corresponding to one lead width of the semiconductor package to be inspected in the lead arrangement direction (scanning direction 30). The shape is such that the area facing the portion is constant (the scanning direction 30 is a long side in the figure).

The signal processing section 10 averages the output signal of the EO sensor 7 using the number of data corresponding to one lead width of the semiconductor package as the maximum unit of addition and averaging, and then performs the electric field intensity level after this averaging processing. Is compared with a predetermined value.

The semiconductor package depends on the product type.
Since the pitch and lead width are different, practically the pitch +
By setting the shape of the metal body 26 according to the product having the largest lead width, the same metal body 26 can be used for other products.

[0044]

As described above, the method and apparatus for inspecting the solder connection of an electronic component according to the present invention employs an EO sensor while the conventional solder connection inspection method using a four-terminal method is a contact type. By measuring the lead voltage of the semiconductor package in a non-contact manner, it is possible to reliably detect the unconnected state of the solder without damaging the lead, and to detect the soft touch required for the contact-type inspection. Since the probing operation is not required, there is an effect that the inspection can be performed with high reliability and at high speed.

Further, according to the present invention, by devising the shape of the tip metal of the EO sensor, it is possible to simultaneously measure not only the lead to be inspected but also the electric field induced in the lead adjacent to the lead to be inspected. By comparing the sum of the obtained electric field intensities with a predetermined output set in advance, open and short can be inspected by one measurement.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of an EO sensor according to one embodiment of the present invention.

FIG. 3 is a perspective view for explaining an embodiment of the present invention.

FIG. 4 is a diagram for explaining an embodiment of the present invention. (A) schematically shows a state of an electric field when a lead to be inspected is normally soldered to a pad on a circuit board,
(B) schematically shows the state of the electric field when there is a short circuit with an adjacent lead.

FIG. 5 is a plan view for explaining an embodiment of the present invention.

FIG. 6 is a diagram for explaining a conventional example.

[Explanation of symbols]

 1, 50 Circuit board 2, 51 Semiconductor PKG 3, 52 Resin mold 4, 4 ', 4 ", 53 Lead 5, 5', 5", 54 Lead shoulder 6, 55 Pad 7 EO sensor 8, 56, 56 ' Probe 9 Signal source 10 Signal processing unit 21 Laser 22 Isolator 23 Polarizing beam splitter 24 First condenser lens 25 Electro-optical element 26 Metal body 27 Wollaston prism 28 Second condenser lens 29 Photodetector 30 Scanning direction 31, 31 ′ , 32, 32 'Electric field 33 Transparent electrode 57 Ammeter 58 Voltmeter

Claims (11)

(57) [Claims] 1. A method for inspecting a solder connection of a lead of an electronic component including at least a semiconductor package mounted on a circuit board, wherein a probe is applied to a pad portion on the circuit board to which the lead is to be solder-connected. A signal is applied in contact with the lead, and the sum of the electric fields induced in the lead and the lead adjacent thereto is arranged close to a predetermined area of the lead, which is located apart from the solder connection side. measured by the electric field detecting sensor, the measured field strength, and open the lead, before
Identifying a short with a lead adjacent to the lead ,
A method for inspecting solder connection of an electronic component, comprising: 2. The method according to claim 1, wherein the predetermined area of the lead where the electric field detection sensor is disposed in proximity is a shoulder of the lead. 3. The electric field detection sensor is disposed with respect to the lead shoulder via a space gap within a range where the detection sensitivity is ensured, and detects electric field intensity in a non-contact state. 3. The method for inspecting solder connection of an electronic component according to claim 2, wherein: 4. The electric field detection sensor according to claim 1, wherein a metal tip surface for an electric field guide proximate to the lead shoulder is provided at least in a direction in which the electric field detection sensor is arranged with the leads.
The semiconductor package to be inspected has a shape in which the area of the semiconductor package to be inspected and the area of opposition to the shoulders of the adjacent leads are substantially constant in a movement range corresponding to one lead width. Item 3. The method for inspecting solder connection of an electronic component according to Item 3. 5. The apparatus according to claim 4, wherein said electric field detection sensor is controlled to move along a predetermined scanning direction while maintaining a predetermined space gap with respect to said lead shoulder.
The method for inspecting solder connection of electronic components described in the above. 6. When the output of the electric field detection sensor is fetched at a predetermined sampling cycle using a signal processing means and subjected to signal processing, the number of data corresponding to one lead width of the semiconductor package to be inspected is averaged. After averaging as the maximum unit, the level of the electric field strength after the averaging is compared with a predetermined value, and the solder connection state between the lead and the pad on the circuit board, and at least the adjacent lead 6. The method for inspecting solder connection of an electronic component according to claim 5, wherein a short circuit with the electronic component is detected. 7. The solder connection inspection method according to claim 1, wherein said electric field detection sensor detects an electric field intensity by an electro-optic effect. 8. The method according to claim 1, wherein a voltage is applied from the probe to the pad portion. 9. An apparatus for inspecting a solder connection of an electronic component including a semiconductor package having at least a lead mounted on a circuit board, wherein the lead is positioned at a pad portion on the circuit board to be solder-connected. A probe for applying a signal to the pad portion via the probe; and a lead to which a signal is to be applied by the probe and a solder connection side of an adjacent lead. An electric field detection sensor that is arranged in the vicinity of a predetermined area located through a predetermined space gap that is predetermined and detects the sum of electric field strengths; Signal processing means for processing the detection signal of the electric field strength, and comparing and determining the level of the electric field strength with a predetermined value, Solder connection between the pads on the circuit board, and solder connection test apparatus for electronic components, characterized by detecting a short circuit between at least the adjacent lead. Wherein said electric field detecting sensor the electronic component Li
Solder connection test device according to claim 9, characterized in that it comprises means Before moving with a predetermined space gap against the shoulder portion of the lead in a direction perpendicular to the longitudinal direction of the over-de. 11. An apparatus according to claim 9, wherein said electric field detection sensor comprises an EO sensor including an element having an electro-optic effect.