JPH083471B2 - Solder fillet inspection method - Google Patents

Description

The present invention relates to a method for inspecting a solder fillet, in which after reflow, a check area is set at a solder fillet formation position and its light reflection characteristics are observed by a camera. The presence / absence of the solder fillet is determined by.

(Prior Art) A substrate on which an electronic component is mounted by an electronic component mounting device is sent to a soldering device, where the cream solder applied to the grounded portion of the lead is heated. FIG. 4 shows the tip of the lead L after the reflow that has been subjected to such heat treatment, and the solder fillet 10 is formed at the tip of the lead L. Although the acceptance criteria for the fillet 10 are not necessarily constant, it is generally considered that the slope 10a having a gentle slope from the substrate 2 to the tip of the lead L as shown in FIG. The defective solder fillet or the defective solder fillet is sorted and removed as a defective product. Conventionally,
The visual inspection of the solder fillet has been performed by an inspector by visual inspection.

(Problems to be Solved by the Invention) However, there are problems that the inspection efficiency is not improved by the visual inspection work of the inspector, the inspection standard is likely to vary due to the individual error of the inspector, and an erroneous judgment is easily caused due to an error.

By the way, after the reflow, the inclined surface 10a of the fillet 10 is a glossy mirror surface, and has a characteristic of being strongly mirror-reflected obliquely upward when irradiated with light from above.

Therefore, it is conceivable to automatically inspect the presence or absence of the solder fillet using a camera by utilizing the light reflection characteristics of the solder fillet. In order to inspect the solder fillet with the camera, it is necessary to set a check area in the solder fillet, but in this case, it cannot be inspected if the set chuck area is displaced from the solder fillet to be inspected, so check The area must be set to properly contain the solder fillet.

By the way, in recent years, the leads of electronic parts have tended to become finer and narrower, and some leads have a width of 1 mm or less. In an electronic component having such a lead with a narrow pitch, if the position of the check area is slightly misaligned, the image of the solder fillet cannot be successfully obtained by the camera, and the solder fillet cannot be inspected. .

Therefore, it is an object of the present invention to provide a solder fillet inspection method capable of reliably setting a check area at a position including a solder fillet even with an extremely fine / narrow pitch lead.

Means for Solving the Problems For this reason, the present invention, after the reflow of the substrate on which the electronic component is mounted is subjected to heat treatment, observes the electronic component with a camera, and The step of detecting the position, the step of setting the check area at the solder fillet expected formation position of the lead tip at a predetermined distance from the position of the bent portion with the detected position of the bent portion as the start position, and the check area is illuminated with light. The method of inspecting the solder fillet is constituted by the step of irradiating and observing the light reflection characteristics with a camera to judge the presence or absence of the solder fillet.

Operation According to the above-mentioned configuration, it is possible to surely set the check area at the position including the solder fillet on the lead side and inspect the presence or absence of the solder fillet.

(Example 1) Next, an example of the present invention will be described with reference to FIG.

FIG. 1 shows a solder fillet inspection apparatus, in which reference numeral 1 denotes an electronic component mounted on a substrate 2, a camera 3 is disposed obliquely above the electronic component, and a light source 4 is disposed above the electronic component. Reference numeral 5 denotes a control device such as a computer connected to the camera 3. This electronic component 1 is an electronic component with leads, in which leads L extend to both sides of the mold body 6, and after being mounted on the cream solder of the substrate 2, it is sent to the soldering device, where The heat treatment is applied to the cream solder. The molded body 6 is made of a material having a low brightness such as black synthetic resin, but the leads L are made of a metal material having a high brightness. This lead L has a horizontal base end a.
A bent portion b, a sloped portion c having a steep downward slope, and a horizontal tip portion d that contacts the substrate 2. FIG. 2 shows the details of the vicinity of the leads, in which four leads L1 to L4 extend from one side surface of the mold body 6, and a solder fillet 10 is formed at the tip end portion thereof. As shown in FIG. 4, the normal fillet 10 after the heat treatment and the reflow is performed.
Has an inclined surface 10a that gently rises from the substrate 2 toward the tip of the lead L. Therefore, when irradiating light from above and observing the vicinity of the lead with the camera 3 obliquely above,
The light incident on the bent portion b of the lead L and the upper surface of the fillet 10 is strongly reflected toward the camera 3 and is observed as a bright and bright portion of the camera 3, and the base end portion a of the lead and the steep slope portion are observed. Since the light incident on the upper surface of c is reflected upward, it hardly enters the camera 3 and is observed by the camera 2 as a dark portion with low brightness.

 Next, a method for inspecting the presence / absence of the solder fillet 10 will be described.

Before inspecting the presence or absence of the solder fillet, in order to set the check area of the solder fillet, first, the electronic component 1
The positional deviation of is detected. To detect the displacement of the electronic component 1, check areas A1 and A4 are set on the bent portions b of the leads L1 and L4 at both ends (see FIGS. 2 and 3),
The barycentric positions G1 and G4 of the brightly shining portion of the camera 3 illuminated with light from above are determined as the positions of the bent portion b. This detection of the center of gravity can be easily obtained by obtaining the intersection point of the line that bisects the brightly shining portion in the xy direction. When the centers of gravity G1 and G4 are obtained in this way, the centers of gravity G1 'and L4' of the master leads L1 'and L4', which are preset inspection standards, are calculated.
The positional deviation of the electronic component 1 is detected by comparing with G4 '. Here, if the electronic component 1 is displaced by more than the allowable value, the line is removed as a defective product.

If the displacement of the center of gravity G1, G4 is within the allowable value, then the presence or absence of the solder fillet is inspected. In this case, the center of gravity G1, G4 detected as described above is set as the start position, and the check areas C1, C4 are set at the fillet predicted formation position a predetermined distance D from this point, and the brightness in the areas C1, C4 is set by the camera. Observe according to 3. Here, as described with reference to FIG. 4, if the fillet 10 is present, the areas C1 and C4 are observed by the camera 3 as bright and bright areas, but if the fillet 10 is not present. For example, almost no reflected light is incident on the camera 3, and it is observed dark. This inspection is also performed for the other leads L2 and L3 by similarly setting the check areas C2 and C3. In this way, if bright brightness is observed in all four check areas C1 to C4, all leads L1 to L4
It is judged that the solder fillet 10 is correctly formed on the surface, but if no bright brightness is observed in any one of them, it is judged that the fillet 10 does not exist in that part, and it is excluded from the line as a defective product. It As described above, according to the present method, the electronic parts are observed by the camera to detect the position of the bent portion which is the characteristic portion of the lead, and the check area is set at the tip of the lead based on this position. Therefore, even if the lead wire has an extremely fine and narrow pitch, the check area can be surely set at the position including the solder fillet.

(Effect of the Invention) According to the present invention, even if the lead is an ultra-fine / narrow-pitch lead, the check area is surely set at a position including the solder fillet existing ahead of the lead to inspect the presence or absence of the solder fillet. It can be carried out.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a side view of a solder fillet inspection apparatus, FIG. 2 is a perspective view of an electronic component, and FIG. 3 is a plan view near a lead under observation. FIG. 4 is a side view. 1 ... Electronic parts 2 ... Substrate 3 ... Camera 10 ... Solder fillet C1 to C4 ... Check area L ... Lead

Claims (1)

[Claims] 1. A step of detecting a position of a bent portion of a lead extending from an electronic component by observing the electronic component with a camera after a reflow process in which a substrate on which the electronic component is mounted is subjected to heat treatment, and detected. The step of setting the check area at the solder fillet expected formation position of the lead tip at a predetermined distance from the position of the bent portion and the position of the bent portion, and irradiating the check area with light to measure the light reflection characteristics of the camera. And a step of determining the presence or absence of a solder fillet by observing with a solder fillet.