JP4167689B2 - Inspection method for solder explosion of electronic parts - Google Patents

Description

  The present invention relates to an electronic component explosion inspection method, and more particularly to an electronic component explosion inspection method capable of detecting the probability of occurrence of an explosion failure when mounting an electronic component with high accuracy with a small number of samplings.

  For example, when a chip-type electronic component is mounted on a circuit board, it is often performed by a solder reflow process. In this solder reflow process, it is known that a solder explosion phenomenon may occur depending on chip-type electronic components.

  The solder explosion phenomenon is a phenomenon in which moisture enters a molten solder through a certain route to cause a steam explosion, and the molten solder is blown off to a particle size of about 20 μm. When this explosion phenomenon occurs, there is a possibility that the solder blown in a granular form may cause a short circuit phenomenon by connecting electrodes that should not be connected. In addition, solder that has been blown into particles may be connected and connected to form a bridge.

  It is thought that the cause of the solder explosion phenomenon is that moisture remaining inside the electrode of the chip-type electronic component is vaporized by heating during the reflow process and enters the molten solder.

  Therefore, Patent Document 1 proposes a method of detecting an electronic component that may cause a solder explosion phenomenon by detecting moisture contained in the electrode of the chip-type electronic component. In the method shown in Patent Document 1, an electronic component to be inspected is immersed in a hydrophobic organic solvent and heated to visually detect bubbles generated by vaporizing residual moisture in the electronic component.

  However, the method disclosed in Patent Document 1 has a problem that an electronic component having an exterior resin cannot effectively detect an electronic component that may cause a solder explosion phenomenon. Etc. That is, according to the method shown in Patent Document 1, when an electronic component having an exterior resin is immersed in a hydrophobic organic solvent and heated, even if the electronic component is a non-defective product that does not cause the explosion phenomenon, Bubbles are generated from the exterior resin and cannot be distinguished from bubbles caused by moisture that causes explosion.

Therefore, conventionally, for each production lot, a large number of electronic components that reach about 10% of the lot size are sampled, solder reflow processing is actually performed, and whether the explosion phenomenon actually occurs or not is determined. It was necessary to judge whether it was good or bad. Therefore, it is necessary to test a large number of parts, which deteriorates the manufacturing efficiency of electronic parts.
JP 2003-344329 A

  The present invention has been made in view of such a situation, and an object of the present invention is to detect the probability of occurrence of an explosion failure when mounting an electronic component with high accuracy with a small number of samplings, and to improve manufacturing efficiency. It is to provide an explosion inspection method.

In order to achieve the above object, an electronic component explosion inspection method according to the present invention includes:
A method for inspecting an explosion phenomenon that may occur when an electronic component having an electrode and an exterior resin is mounted by solder reflow,
Sampling and taking out some of the electronic components having electrodes and exterior resin;
Immersing the electronic component sampled and taken out in a liquid at 60 ° C. or higher for 20 minutes or more;
A step of performing a solder reflow process on the electrode in the electronic component taken out from the liquid and dried to detect whether an explosion phenomenon occurs; and
Have

  In the present invention, when the electronic component is immersed in a liquid at 60 ° C. or higher for 20 minutes or more, water enters the explosion-causing part such as a void formed in the electrode of the electronic component. Thereafter, by performing the solder reflow process on the electronic component after the drying process, it is possible to detect the probability of occurrence of explosion failure when mounting the electronic component with a small number of samplings and with high accuracy.

  For example, in the conventional method, it is not possible to detect a production lot including an electronic component that may cause an explosion phenomenon unless it is inspected by sampling about 10% of the lot size from the production lot of the electronic component. . On the other hand, according to the method of the present invention, even if sampling is performed from a lot of electronic parts manufactured at a number of 5% or less, further 3% or less, particularly 1% or less of the lot size, the explosion phenomenon occurs. It is possible to detect a production lot including electronic components that may cause As a result, the use of the method of the present invention makes it possible to reduce the number of electronic components to be sampled for inspection, thereby improving manufacturing efficiency and reducing the number of man-hours required for inspection.

  The drying of the electronic component after taking out from the liquid is preferably natural drying. If heat is positively applied, there is a risk that the accuracy of detecting the explosion phenomenon will be reduced in the subsequent steps.

  Preferably, the main component of the liquid is water. Although it is not specifically limited that a main component is water, For example, it means that only about 5 weight% or less is contained as a whole as components other than water.

  Preferably, the liquid includes an alcohol and / or a surfactant. These components are preferable because they reduce the surface tension.

  Preferably, if any one of the electronic parts sampled and inspected from the production lot of the electronic parts is exploded, it is determined that a defective product is mixed in the production lot.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a longitudinal sectional view of a coil chip component as a surface mount electronic component according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of main parts of a coil chip part and a mold showing an example of a manufacturing process of the coil chip part shown in FIG.
FIG. 3 is a cross-sectional view of a main part of a liquid heating device used in the method for inspecting a coil chip component according to an embodiment of the present invention.
4 (A) and 4 (B) are main part sectional views for explaining the explosion phenomenon in the solder reflow process,
FIG. 5 is a graph showing a comparison between an inspection method according to an embodiment of the present invention and a conventional inspection method;
FIG. 6 is a graph showing the relationship between the immersion temperature and the defective product occurrence rate,
FIG. 7 is a graph showing the relationship between the immersion time and the defective product incidence.
Coil chip parts

  First, a surface mount electronic component that is an object of an inspection method according to an embodiment of the present invention will be described. As shown in FIG. 1, a coil chip component 2 as a surface mount electronic component according to an embodiment of the present invention has a drum core 4 as a core portion (core material). The drum core 4 is made of a ferrite material. The drum core 4 has a core part 4 a in which a wire 10 a constituting the coil part 10 is wound along the axial direction of the core 4.

  A first flange 4b and a second flange 4c are integrally formed at the first end and the second end, which are both ends in the axial direction of the core 4a. The outer dimensions of the first flange 4b and the second flange 4c are larger than the outer diameter of the core 4a.

  The cross section of the core part 4a is not particularly limited, and may be a rectangular cross section, a circular cross section, or other cross sectional shapes. The cross-sectional shape of the first flange 4b and the second flange 4c is a square shape such as a rectangular cross section. The 1st flange 4b and the 2nd flange 4c are the same size, for example, length is about 0.82 mm and width is about 0.30 mm. Moreover, the outer diameter of the core part 4a is about 0.42 mm. The total axial length L0 of the drum core 4 (substantially the same as the total length of the component 2) L0 is about 1.637 mm.

  As shown in FIG. 1, the connecting portions 10b and 10c formed at both ends of the wire 10a constituting the coil portion 10 are connected to the base electrode layer 20 at the outer peripheral positions of the flanges 4b and 4c. The connecting portions 10b and 10c of the wire 10a are fixed to the outer circumferences of the flanges 4b and 4c by means such as thermocompression bonding after the base electrode layer 20 is formed, and these connecting connections are ensured.

  The base electrode layer 20 is an electroless Ni plating having a first layer of 1.0 to 2.0 μm and a second layer of electrolytic Ni plating having a thickness of 1.0 to 2.0 μm.

  After the base electrode layer 20 and the connecting portions 10b and 10c are connected, the outer resin portion 30 is formed by molding a resin in the outer circumferential concave portion of the core portion 4a where the coil portion 10 is formed. It does not specifically limit as resin which comprises the exterior resin part 30, An epoxy resin, a phenol resin, a diallyl phthalate resin, a polyester resin etc. are illustrated.

  The exterior resin part 30 is molded using, for example, molds 80 and 82 shown in FIG. As shown in FIG. 2, the connected drum core 4 in which the coil portion 10 is formed inside the plurality of cavities 84 formed by closing the molds 80 and 82 is connected to the first drum core 4 of the adjacent drum core 4. It arrange | positions along with an axial direction so that the end surface of the flange 4b may contact the end surface of the 2nd flange of the adjacent drum core 4. FIG.

  The molds 80 and 82 are formed with holding convex portions 86 for holding the outer periphery of the contact portion between the first flange 4b and the second flange 4c of the drum core 4 disposed adjacent to each other. A circumferential gap 88 for forming the resin flange covering portion 30a shown in FIG. The circumferential gap 88 communicates with the cavity 84, and resin is injected into the cavity 84 and molded, and the molds 80 and 82 are opened, so that the exterior resin part 30 having the flange covering part 30a shown in FIG. A plurality of integrated element bodies 5 are obtained. The four side surfaces of the exterior resin part 30 are flat surfaces.

  The outer diameter of the exterior resin portion 30 of each element body 5 is larger than the outer dimensions (the maximum outer dimensions of the core portion) of the first flange 4b and the second flange 4c, and the first flange 4b and the second flange 4c. A flange covering portion 30a having a predetermined thickness is formed on the outer periphery. The flange covering portion 30a is formed integrally with the exterior resin portion 30, and is formed so as to cover the outer periphery of the flange portions 4b and 4c from the inner side to the outer side to the middle position in the axial direction.

  The thickness of the flange covering portion 30a corresponds to the depth H1 of the step-shaped recess 50 described later. Further, the axial length of the flange covering portion 30a is determined so as to appropriately adjust the axial width (W1) of the step-shaped recess 50 described later.

  After the exterior resin portion 30 is formed, the coil chip component 2 is obtained by forming a pair of end electrodes 40 at both axial ends of the element body 5. The end electrode 40 is formed after the exterior resin part 30 is formed.

  In this embodiment, each end electrode 40 has electroless Ni plating of 1.0 to 2.0 μm for the first layer, electrolytic Ni plating of 1.0 to 2.0 μm for the second layer, and 3 for the third layer. Electrolytic Sn plating of 0.0 to 4.0 μm. The thickness of the end electrode 40 is 8 μm or less.

  Each end electrode 40 is formed in a stepped shape so as to directly cover the outer peripheral surface of the flange 4b, 4c from the end face of each flange 4b, 4c and to cover the flange covering portion 30a of the exterior resin portion 30. . Each end electrode 40 is directly connected to the base electrode layer 20 and the connecting portions 10b and 10c at the end surfaces of the flanges 4b and 4c and a part of the outer peripheral surface of the flanges 4b and 4c. Moreover, since each end electrode 40 is formed so as to cover the flange covering portion 30a of the exterior resin portion 30, a step-like recess 50 that is continuous in the circumferential direction is formed on the outer peripheral surface of each end portion 40. Is done.

  As shown in FIG. 1, the step-shaped recess 50 is formed with a predetermined width (W1) from the axial end surface of the element body 5, and the ratio (W1 / W0) to the total width (W0) of each end electrode. ) Is preferably 0.1 to 0.8, more preferably 0.3 to 0.6. By setting the ratio (W1 / W0) within the above range, the connection between the end electrode 40 and the coil connecting portions 10b and 10c is sufficiently secured, and the bonding strength between the end electrode 40 and the exterior resin portion 30 is also high. high. Moreover, the effect which suppresses a tombstone phenomenon is large by setting it as this range.

  The tombstone phenomenon means that when an electronic component is mounted on a substrate, the electronic component starts up due to an imbalance of moments generated on the solder paste surfaces of the end electrodes formed at both ends of the electronic component. This is a phenomenon that results in poor bonding.

  Further, the stepped recess 50 is formed such that the depth (H1) from the maximum outer peripheral surface dimension of each end electrode 40 is 10 to 40 μm. By setting the depth H1 within this range, the connection between the end electrode 40 and the coil connection portions 10b and 10c is sufficiently secured, and the bonding strength between the end electrode 40 and the exterior resin portion 30 is also high. Moreover, the effect which suppresses a tombstone phenomenon is large by setting it as this range. On the other hand, if the depth H1 is too deep, the maximum outer dimensions of the flange portions 4b and 4c in the drum core 4 are relatively small with a limited chip size, and the electrical performance tends to deteriorate. .

  The ratio (H1 / H0) of the depth (H1) of the stepped recess 50 to the total height (H0) of the maximum outer peripheral surface of each end electrode 40 is in the range of 0.011 to 0.045. By setting the ratio within this range, the connection between the end electrode 40 and the coil connecting portions 10b and 10c is sufficiently secured, and the bonding strength between the end electrode 40 and the exterior resin portion 30 is also high. Moreover, the effect which suppresses a tombstone phenomenon is large by setting it as this range.

  In the present embodiment, in particular, even when the chip maximum height H0 is a small coil chip part 2 having a size of 0.9 mm or less and a light weight of 5 mg or less, the end electrode 40 of the end electrode 40 is reflowed during solder reflow. Solder enters the gap between the stepped recess 50 formed on the bottom surface and the substrate 60. Since the step-shaped recess 50 is formed continuously in the circumferential direction of the end electrode 40, a sufficient amount of solder can be secured. As a result, the so-called tombstone phenomenon can be effectively prevented and mounting defects can be prevented.

  For example, in the conventional coil chip component (there is no stepped recess 50), the tombstone phenomenon occurred at a ratio of about 10 per 100,000, whereas the embodiment of the present invention (the stepped recess 50) In some cases, no tombstone phenomenon occurred.

  Further, in the present embodiment, since the solder wraps around the stepped recess 50, sufficient bonding strength can be obtained even when the size of the fillet formed by the solder is reduced, and high-density mounting is possible.

  In the present embodiment, the stepped recess 50 is formed by forming the end electrode 40 so as to cover the outer periphery of both ends of the exterior resin part 30 having an outer dimension larger than the maximum outer dimension of the flanges 4b and 4c. It is formed. For this reason, it is not necessary to process the flange itself, the volume of the flange does not decrease, and the performance as a coil chip is not affected at all. Moreover, since the stepped recess 50 can be formed by resin molding, the manufacturing process is not complicated.

  Furthermore, in this embodiment, the axial width W0 of each end electrode 40 shown in FIG. 1 is preferably 0.41 mm, so that the flat surface of the exterior resin portion 30 located between the edges of the end electrode 40 is provided. The axial width L1 of 30b can be about 0.817 mm. The axial width L1 of the flat surface 30b is 30 to 70% of the total length L0 of the component 2.

The upper flat portion 30b of the exterior resin portion 30 having such an axial length L1 can be favorably sucked and held by the suction nozzle. In addition, since the thickness of the end electrode 40 is as thin as 8 μm or less, even if the end of the suction nozzle is positioned on the end electrode 40, the suction action is not reduced so much by the suction nozzle, and the part can be mounted with sufficient suction force. Can be held.
Inspection method of coil chip parts

  In order to inspect a solder explosion phenomenon that may occur when an electronic component such as the coil chip component 2 having the exterior resin 30 described above is mounted on a circuit board or the like, in the present embodiment, the electronic Inspecting parts.

  That is, among the coil chip parts 2 manufactured by the above-described method, for each lot, for example, for a lot size of 50000 pieces, the sampling number of 500 pieces (1% with respect to the lot size), the coil chip part 2 Take out. These sampled coil chip components 2 are first heated for a predetermined time in a liquid 71 in a container 73 heated by a heating device such as a hot plate 75 as shown in FIG.

  The liquid 71 contains water as a main component, but alcohol or a surfactant may be added. The amount of alcohol or surfactant added is not particularly limited, but is preferably about 5% by weight or less. If the amount added is too large, the detection accuracy tends to decrease due to a relative decrease in moisture. By adding alcohol or a surfactant to water, the surface tension of the liquid 71 is lowered, and water easily enters the cause of the explosion described later.

  The heating temperature of the liquid 71 is preferably 60 ° C. or more, more preferably 70 to 80 ° C., and the immersion time of the coil chip component 2 in the liquid 71 is preferably 20 minutes or more, more preferably 25 to 25 ° C. 35 minutes. By immersing the coil chip part 2 in the liquid at such a heating temperature and immersion time, water is blown to the explosion-causing part such as a gap formed in the end electrode 40 of the coil chip part 2 that is to be a defective product. Enters.

  Thereafter, the coil chip component 2 is taken out from the liquid 71 and dried naturally. Next, as shown in FIG. 4A, the coil chip component 2 is installed on the land 72 of the circuit board 70. It is installed so that the bottom surface of each end electrode 40 is positioned on 74. Thereafter, as shown in FIG. 4B, when the solder reflow process is performed, the end surfaces of the end electrodes 40 are raised by the surface tension while the solder 74 is melted.

  At this time, if there is an explosion cause portion in the end electrode 40, a solder explosion phenomenon occurs in the process in which the molten solder 74 moves up the end surface of the end electrode 40 due to surface tension, and the solder particles 74a are separated. Then, it blows out toward the outside of the end electrode 40. In the inspection method of the present embodiment, the probability that an explosion failure will occur when the coil chip part 2 is mounted is detected with high accuracy with a small number of samplings by performing a solder reflow process on the coil chip part 2 after the drying process. be able to.

  For example, in the conventional inspection method, the explosive inspection is performed without immersing the coil chip component 2 in the heated liquid. Therefore, for example, 5000 (10%) sampling is performed for 50000 lot sizes, and mounting evaluation is performed. Had gone. For this reason, the number of electronic components (defective product occurrence rate) in which the solder explosion phenomenon was actually confirmed visually was 5 (0.1%).

  On the other hand, in the embodiment of the present invention, pure water is used as the liquid 71 shown in FIG. 3, the heating temperature of the coil chip component 2 is set to 75 ° C., and the coil chip component 2 is immersed for 30 minutes and then naturally dried. Then, implementation evaluation was performed.

  In the present example, when 5000 pieces (10%) are sampled with respect to a lot size of 50000 pieces in the coil chip part 2 of the same production lot, the number of electronic parts in which the solder explosion phenomenon can be visually confirmed (indefinite) The occurrence rate of non-defective products was 65 (1.3%). These results are shown in FIG. That is, in the inspection method according to the embodiment of the present invention, the sensitivity is 13 times (65/5) compared to the conventional inspection method.

  In the method of the embodiment of the present invention, since the inspection sensitivity is 13 times, the number of samplings required for the explosion inspection can be reduced to about 400, which is 1/13 compared to the conventional 5000. In this case, the number of samplings of 400 is 50,000 for the entire lot size, and is 0.8% of the lot size, which is 1% or less.

  That is, in the embodiment of the present invention, when a sample is inspected by sampling at a number of 5% or less, preferably 3% or less, more preferably 1% or less of the lot size, if any one of the explosions occurs, It can be determined that defective products are mixed in the production lot. Therefore, in this embodiment, the probability of occurrence of explosion failure when the coil chip component 2 is mounted can be detected with high accuracy with a small number of samplings.

  In another embodiment of the present invention, pure water is used as the liquid 71 shown in FIG. 3, the immersion time is fixed at 20 minutes, as shown in FIG. 6, and the relationship between the immersion temperature and the defective product occurrence rate. Asked. As shown in FIG. 6, when the immersion temperature was 60 ° C. or higher, the probability of finding a defective product (defective product occurrence rate) was increased, and it was confirmed that there was almost no change at 80 ° C. or higher. For this reason, it has confirmed that immersion temperature became like this. Preferably it is 60 degreeC or more, More preferably, it is 70-80 degreeC.

  Further, in another embodiment of the present invention, pure water is used as the liquid 71 shown in FIG. 3, and the immersion temperature is fixed at 60 ° C. as shown in FIG. Sought a relationship. As shown in FIG. 7, it was confirmed that when the immersion time was 20 minutes or longer, the probability of finding a defective product (defective product occurrence rate) was increased, and almost no change was observed after 35 minutes. For this reason, it has confirmed that immersion time became like this. Preferably it is 20 minutes or more, More preferably, it is 25-35 minutes.

Note that the present invention is not limited to the above-described embodiments and examples, and can be variously modified within the scope of the present invention.
For example, the specific cross-sectional structure of the electronic component that is the target of the inspection method according to the present invention is not limited to the embodiment shown in FIG. 1 and can have various aspects.

FIG. 1 is a longitudinal sectional view of a coil chip component as a surface mount electronic component according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a main part of a coil chip part and a mold showing an example of a manufacturing process of the coil chip part shown in FIG. FIG. 3 is a cross-sectional view of the main part of the liquid heating apparatus used in the coil chip component inspection method according to one embodiment of the present invention. 4 (A) and 4 (B) are cross-sectional views of relevant parts for explaining the explosion phenomenon in the solder reflow process. FIG. 5 is a graph showing a comparison between the inspection method according to the embodiment of the present invention and the conventional inspection method. FIG. 6 is a graph showing the relationship between the immersion temperature and the defective product occurrence rate. FIG. 7 is a graph showing the relationship between the immersion time and the defective product incidence.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Coil chip component 4 ... Drum core 4a ... Core part 4b ... 1st flange 4c ... 2nd flange 5 ... Element main body 10 ... Coil part 10a ... Wire 10b, 10c ... Connection part 20 ... Underlayer electrode layer 30 ... Exterior resin Part 30a ... Flange coating part 30b ... Flat surface 40 ... End electrode 50 ... Stepped recess 60 ... Substrate 70 ... Circuit board 71 ... Liquid 72 ... Land 73 ... Container 74 ... Solder 74a ... Solder grain 75 ... Hot plate 80, 82 ... Mold 84 ... Cavity 86 ... Holding convex part 88 ... Circumferential clearance

Claims (4)

A method for inspecting a solder explosion phenomenon that may occur when an electronic component having an electrode and an exterior resin is mounted by solder reflow,
Sampling and taking out some of the electronic components having electrodes and exterior resin;
Immersing the electronic component sampled and taken out in a liquid of 60 ° C. or higher whose main component is water for 20 minutes or more;
A step of performing a solder reflow process on the electrode in the electronic component taken out from the liquid and dried to detect whether or not a solder explosion phenomenon occurs;
I have a,
Wherein one of the electronic components the electronic components examined by sampling from the production lot, when phenomenon occurs popping even one, soldering of electronic components, characterized in that defective products in the production lot is determined to be contaminated bursting test Method. In the step of immersing the electronic component in the liquid,
If the cause partial bursting on the electrode is present, the solder popping test method for an electronic component according to claim 1, wherein the liquid is characterized in that entering the bursting due portion.   The solder explosion test method for an electronic component according to claim 1, wherein the liquid contains alcohol and / or a surfactant. 4. The electronic component solder explosion inspection method according to claim 1, wherein the electronic component manufacturing lot is sampled and inspected at a number of 5% or less of the lot size.

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