JPH0794973B2 - Appearance inspection method of soldering state - Google Patents

Description

The present invention relates to a visual inspection method for a soldering state.

(Prior Art) Regarding the appearance inspection means in the soldering state by laser light,
Conventionally, various types have been proposed (for example, Japanese Patent Laid-Open No. 63-
177042, 177045).

(Problems to be Solved by the Invention) However, in all of the above-mentioned conventional means, important technical problems for the visual inspection of the soldering state by the irradiation of laser light as described below have not been solved.

That is, of the soldered states, what is particularly important is the shape of the solder fillet formed at the tip of the lead, and whether the soldered state is acceptable or not is greatly affected by the shape of the solder fillet. Therefore, in order to judge whether the soldering state is acceptable or not, it is needless to say that the laser beam must be surely applied to the solder fillet to be measured. However, since the electronic components mounted on the board have positional deviations and dimensional errors with respect to the design position or the ideal position, teaching the design position in advance,
Even if the laser light is irradiated toward this design position, the laser light does not always hit the solder fillet. Particularly in recent years, due to the demand for high density and high integration, the pitch of leads tends to be minimized, and there are some with a small pitch of 0.3 mm or less. Even if the laser beam is emitted toward the taught position, the laser beam is emitted to a point other than the solder fillet which is the measurement target, and an incorrect measurement result is obtained.

Further, since the solder fillet is a glossy metal such as tin or lead, the surface thereof has a substantially mountain-shaped cross-section with specularity, and unless the irradiation direction of the laser light or the light receiving position of the light receiving means is devised, The reflected light cannot be received reliably, and the measurement result is distorted. As described above, the means for surely irradiating the solder fillet with the laser light and the means for surely receiving the laser light reflected by the solder fillet have not been established yet.

Therefore, the present invention is a means for solving the technical problem peculiar to the visual inspection of the soldering state as described above, that is, laser light can be reliably applied to the solder fillet to be inspected,
Another object of the present invention is to provide a means that can reliably receive the reflected light.

(Means for Solving the Problem) For this purpose, the present invention sets a first start point on the side of a lead extending from a molded body of an electronic component mounted on a substrate, and the first start point is set. The center of this lead is detected by sweeping a laser beam in a direction that traverses the lead from the above and receiving the laser beam reflected by this lead, and then on the line extending in the lead direction passing through this center. The starting point of 2 is set, laser light is swept and irradiated from the second starting point in the extending direction of the lead, and the reflected light is provided obliquely above in the direction orthogonal to the extending direction of the lead. The light is received by the light receiving means and the shape of the solder fillet formed at the tip of the lead is measured.

(Operation) In the above configuration, the center of the lead is detected by sweeping and irradiating the lead with laser light in the direction crossing the lead and receiving the laser light reflected by the lead. Next, the solder fillet to be inspected is irradiated with the laser beam by sweeping the laser beam in the extending direction of the lead passing through the center. Further, the reflected light is received by a light receiving means provided obliquely above in the direction orthogonal to the extending direction of the lead, and the shape of the solder fillet is measured.

(Example) Next, the Example of this invention is described, referring drawings.

FIG. 1 is a perspective view of a visual inspection apparatus in a soldered state,
Reference numeral 1 is a substrate, on the upper surface of which electronic components (hereinafter referred to as “chip”)
2) is installed. Reference numeral 3 is a lead extending laterally from the mold body 2a of the chip 2 and reference numeral 4 is a solder fillet formed at the tip of the lead 3.

Reference numeral 5 denotes a laser device. The laser spot light emitted from the laser device 5 is reflected by the mirror 6 and applied to the solder fillet 4, and the reflected light enters the light receiving means 7. At that time, by rotating the mirror 6 in two directions, laser light is swept and irradiated in the XY directions. Reference numeral 8 is a condenser element, and 9 is a position detecting element such as PSD. In the figure, the laser light is indicated by a dashed arrow.

As shown in FIGS. 2 and 3, the laser light reflected by the mirror 6 is emitted from above the leads 3 and the solder fillet 4. Further, the light receiving means 7 is arranged in the extending direction (Y
Direction) and is disposed obliquely above in the X direction. By setting the irradiation direction of the laser light and the arrangement position of the light receiving means 7 in this way, the laser light reflected by the solder fillet 4 having a mirror-shaped cross-section and a mountain-shaped cross section can be stably and reliably received. it can. In FIG. 1, 10 is a land of a circuit pattern formed on the substrate 1, Q is a position reference mark formed at an appropriate position on the substrate 1, and the coordinate position of each land 10 with respect to this mark Q is known.

This apparatus has the above-mentioned configuration, and a method of visual inspection of the soldered state will be described next.

In FIG. 3 and FIG. 4, first, a start point A is set on the side of the lead 3, from which sweeping laser light is irradiated in the X1 direction across the lead 3, and the reflected light is received by the light receiving means 7. , The center B of the lead 3 is detected. The detection of the center B is performed for each lead 3. The start point A is set to the side of each land 10 which is a known position with respect to the position reference mark Q on the substrate 1 as described above. Next, a start point C is set on the Y-direction line passing through the center B, laser light is swept and irradiated in the extending direction of the leads 3 (Y1 direction), and the shape of the solder fillet 4 is measured.

As described above, according to this method, first, the center B of the lead 3 is detected, and then the laser beam is irradiated in the extending direction of the lead 3 passing through the center B.
Even if there is a positional shift in the direction, the solder fillet 4 can be reliably irradiated with the laser light. Further, since the light receiving means 7 is provided obliquely above the lead 3 in the extending direction, the solder fillet 4 irradiated from above and reflected by the solder fillet 4 can be reliably and stably provided. The light can be received by the light receiving means 7.

By the way, in some chips, for example, the mini-transistor 2 shown in FIG. 8, the leads 3 are bent at a steep slope along the side wall of the molded body 2a. When the shape of the solder fillet 4 is measured by sweeping and irradiating a laser beam along such a predetermined measurement area a in the Y direction, the chip 2 is displaced by the distance 1 in the Y direction. Then, the laser light is reflected by the shoulder 3a of the lead 3 and the height of the shoulder 3a is mistakenly recognized as the maximum height of the solder fillet 4. In the figure, the chain line indicates a chip with no displacement. Such misjudgment is
It is also likely to occur in chips with steep leads such as tantalum capacitors and coils, and also in chips with long lateral leads such as QFP and SOP. Therefore, next, a means for reliably irradiating the solder fillet with the laser beam even if there is such a displacement in the Y direction will be described.

In FIG. 5, even if the chip 2 is significantly displaced in the Y direction, a measurement area a1 that can sufficiently cover from the upper surface of the molded body 2a or the upper surface of the base end 3a of the lead 3 to the tip of the solder fillet 4. Is set, and the first sweeping irradiation of the laser light is performed along this area a1 to measure the appearance of the chip 2 in this area a1.
N1 is a sweep line.

FIG. 6 shows the result. In the figure, HMAX is the height of the upper surface of the chip 2, and a point S having a height 0.7HMAX of a predetermined ratio (for example, 0.7) with respect to this height HMAX is detected. Next, an offset point Soffset is set at a predetermined offset distance e from this point S toward the tip of the solder fillet 4.
To set. Next, the second measurement area a2 is set from this offset point Soffset toward the tip of the solder fillet 4, and this offset point Soffset is used as the start point of the second measurement, as indicated by the dashed arrow N2. A laser beam is irradiated at a sweep ratio to measure the shape of the solder fillet 4 in detail. FIG. 7 shows the measurement result.

As described above, according to this method, even if the chip 2 is misaligned in the Y direction, the solder fillet (the portion extending downward from the tip of the lead) that is extremely important for determining whether the soldering state is acceptable or not is surely secured. The shape can be reliably measured by irradiating a laser beam on the. Numerical values such as 0.7 and e are set in advance according to the type of chip and required shape accuracy.

Further, it is desirable that the appearance inspection of the soldering state is performed in a wide range as fast as possible, but this method has a drawback that it takes time because the laser beam sweep irradiation must be performed twice. Therefore, the first sweep irradiation, which is performed to determine the start point of the second measurement area a2, is roughly performed (for example, 2 mm / 100 points) and is performed to measure the shape of the solder fillet in detail. The second sweep irradiation,
Inspection speed can be increased by performing closely (for example, 0.5 mm / 100 points).

(Effects of the Invention) As described above, according to the present invention, even if the electronic component is displaced in the X direction or the Y direction, the solder fillet is reliably swept and irradiated with laser light, and the reflected light thereof is emitted. It is possible to reliably receive light and accurately measure the shape of the solder fillet.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a perspective view of a visual inspection apparatus in a soldering state, FIG. 2 is a front view during measurement, FIG. 3 is a partial perspective view of the same, and FIG. The figure is the same plan view, FIG. 5 is a side view, FIGS. 6 and 7 are graphs showing measurement results, and FIG. 8 is a side view. 1 ... Substrate 2 ... Electronic component 2a ... Molded body 3 ... Lead 3a ... Lead base end 4 ... Solder fillet 5 ... Laser irradiation means 7 ... Light receiving means B ... Lead center e ... … Offset distance Soffset …… Offset point

Claims (2)

[Claims] 1. A first start point is set on a side of a lead extending from a molded body of an electronic component mounted on a substrate,
The center of the lead is detected by sweeping and irradiating the laser light from the first start point in the direction crossing the lead and receiving the laser light reflected by the lead.
Next, a second start point is set on the line extending in the lead extending through the center, and laser light is swept from the second start point in the lead extending direction, and the reflected light is emitted from the lead. A visual inspection method in a soldering state, characterized in that the shape of a solder fillet formed at the tip of the lead is measured by receiving light by a light receiving means provided obliquely above in a direction orthogonal to the outgoing direction. 2. In a soldering appearance inspection method in which a laser beam is swept and irradiated toward a solder fillet and the reflected light is detected by a light receiving means, the upper surface of the mold body of the electronic part or the base of the lead Laser light is swept and irradiated from the upper surface of the end toward the tip of the solder fillet, and a point having a predetermined ratio height with respect to the height of this electronic component is detected, and the solder fillet is detected from this point. An offset point is set at a position of a predetermined offset distance toward the tip portion, and then the offset fill point is used as a start point, and the laser beam is swept again toward the tip portion of the solder fillet to form the shape of the solder fillet. A method for inspecting appearance in a soldered state, characterized by being measured.