JP3161010B2 - Solder appearance inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting the appearance of solder for bonding a lead of an electronic component to a substrate and measuring the shape of the solder while satisfactorily reflecting a laser beam toward a light receiving portion. It is.

[0002]

2. Description of the Related Art After bonding leads of electronic components such as ICs, LSIs or TAB chips to a substrate by soldering,
An appearance inspection of the solder is performed to determine the quality of the soldered state.

FIG. 8 shows a conventional appearance inspection means using a laser beam. In the figure, reference numeral 1 denotes a main body of an electronic component;
2 'is a lead extending from the main body 1, 3 is a solder for bonding the lead 2 to the circuit pattern 7 of the substrate 4, 5 is a laser irradiator, and 6 is a light receiving section.

[0004] This conventional method is performed as follows. First, the laser beam L is scanned (direction N1) so that the laser beam L completely traverses from the edge E 'on the lead 2 opposite to the light receiving section 6 to the edge E on the light receiving section 6 side.
Then, the center A of the lead 2 is obtained by receiving the reflected light L ′ in the light receiving section 6.

Then, the laser beam L is scanned in the length direction N2 of the lead 2 passing through the center A, and the reflected light L 'is received by the light receiving portion 6, so that the solder 3 along the direction N2 is formed. The shape is measured, and the quality of the shape of the solder 3 is determined based on the result.

[0006]

By the way, the cross section of the lead 2 is generally in a semicylindrical shape, and its upper surface 2a is curved in an arch shape. Moreover, the curvature is not always constant, and the shape of the upper surface 2a varies depending on the lead.

For this reason, according to the above-mentioned conventional means, when the laser beam L is scanned in the N1 direction, the laser beam radiated particularly near the edge E 'of the lead 2 on the side opposite to the light receiving section 6 is directed to the arrow a. As shown in the figure, 2
The second reflected light a is easily reflected on the light receiving section 6. Therefore, as shown in FIG. 9, the curve indicating the measured value largely fluctuates, and a large number of uneven portions are formed. Only this curve indicates which convex portion indicates the edge E on the light receiving portion 6 side, It is often difficult to judge quickly. This is a large bottleneck when a computer is used to determine the position of the edge E without manual intervention, scan the lead 2 in the longitudinal direction based on the edge E, and perform an automatic solder appearance inspection. It becomes.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the conventional means and to provide a method capable of favorably measuring the shape of solder.

[0009]

For this purpose, the present invention provides a laser irradiator for irradiating a laser beam from above toward a lead extending from a main body, and a reflected light from this lead obliquely above the lead. A light receiving unit for receiving and receiving the light, inspects the appearance of the solder, sets a start position of the laser light at the center of the upper surface of the lead, and sends the laser light from the laser irradiator to the light receiving unit side. A process of scanning in the direction of the lead to detect the edge of the lead on the light receiving portion side, a process of setting an offset point between the edge and the center of the lead, and a length of the lead passing through the offset point. A laser beam is scanned in the direction to measure the shape of the solder adhered to the tip of the lead.

[0010]

According to the above construction, the laser beam is not irradiated near the edge of the lead on the side opposite to the light receiving portion, and the secondary reflection can be avoided to reduce the flutter of the measured value. .

[0011]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a solder appearance inspection means according to the present invention. The configuration is almost the same as the conventional means shown in FIG. 8, and the description of the configuration is omitted by attaching the same reference numerals. In this means, a laser irradiator 5 is provided so that the laser beam L can be irradiated from above vertically to the lead 2, and the reflected light L ′ from this lead 2 is received obliquely above the lead 2. A light receiving unit 6 is provided.

First, the central portion C of the upper surface 2a of the lead 2
Is set to the start position S of the laser beam L (see FIG. 1 partially enlarged view). The start position S can be appropriately set in the central portion C, but the adjacent lead 2 ′
In order to surely prevent the secondary reflection due to light, it is desirable to set the position closer to the light receiving unit 6 than the center A. As described above, since the start position S is set in the central portion C, as shown in FIG. 2, a position S ′ (see a dashed line) at the time of actual measurement from the set start position S (see a solid line). ) Is slightly shifted to the opposite side (in the direction of the arrow N3) of the light receiving unit 6, the laser light L is not irradiated near the edge E 'on the opposite side of the light receiving unit 6. In addition, since the laser irradiator 5 irradiates the lead 2 with the laser light L from vertically above, there is almost no possibility that the laser light L is secondarily reflected by the adjacent lead 2 ′ and enters the light receiving section 6. Absent.

Next, the laser beam L is scanned in the direction from the laser irradiator 5 toward the light receiving section 6 (the direction of the arrow N1). That is, the laser beam L passes through the edge E from the start position S and leaves the lead 2. FIG. 3 (a)
FIG. 5 illustrates a graph of measured values obtained by this scanning. In FIG. 3A, P indicates the end point of the scanning. In this graph, the center of the start point S and the end point P is set to the position of the edge E.

Now, even if the edge E 'on the opposite side of the light receiving section 6 is excluded from the scanning and the secondary reflection from the adjacent lead 2' is avoided, the measurement is performed as illustrated in FIG. Values often have irregularities. Next, FIG.
To FIG. 4, FIG. 5, FIG.
The process of detecting the edge E on the light receiving section 6 side will be described. First, the measured values are smoothed by the moving average method (Step 4 in FIG. 7) to obtain a smooth curve from which fine irregularities are removed (FIG. 3B). Next, a convex point (△ in FIG. 3C) and a concave point (▽ in FIG. 3C) of the curve are extracted (Step 5 in FIG. 7). These convex points and concave points can be obtained by a simple calculation. Should be included in the calculation, and the calculation should be performed while averaging the gradient to some extent. If there is a convex point next to the start position S, the start point S
Is a concave point, and if there is a convex point immediately before the end point P, the end point P is a concave point. Here, in FIG.
D2 and D3 are concave points, and U1, U2, U3 and U4 are convex points.

One of the convex points U1, U2, U3, U4 is a convex point indicating the position of the edge E. next,
Advantageous means for automatically determining which of these convex points indicates the edge E using a computer or the like will be described. This means includes a plurality of parameters H (i), X as shown in steps 6 to 11 in FIG.
(I), Y (i), Z (i) are calculated, and their sum S
(I) is obtained, and an evaluation score table (FIG. 5) is created.
According to (i), it is determined which of the convex points U1, U2, U3, and U4 is the one corresponding to the edge E.

The height parameter H in step 6 of FIG.
(I) shows the reference line B. as shown in FIG. L.
(For example, the horizontal axis of the graph of measured values)
The heights H1, H2, H3, H4 of U2, U3, U4 and the height H of the edge E of the chip data (known) of the lead 2 are compared, and the height H closest to the height H of the edge E is obtained. . Specifically, H (i) = (| H−Hi | / H) × K1 (where K1 is a weighting factor, i = 1, 2, 3, 4), and H (i) is minimized. If there is any, it is evaluated that the certainty of the required convex point is large.

Similarly, as shown in FIG. 4B, the position parameter X (i) in step 7 in FIG. L. (As described above, when setting the start position S and the end point P, the edge E is positioned on this line SL.)
Distance X1, X2, X3, X to 1, U2, U3, U4
X (i) = Xi × K2 (where K2 is a weighting factor, i = 1, 2, 3, 4). If X (i) is the minimum, the above-mentioned certainty is evaluated as large.

The drop parameter Y (i) for the next concave point in step 8 in FIG. 7 is the distance Y in FIG.
1, Y2, Y3, and Y (i) = (| H−Yi | / H) × K3 (where K3 is a weighting coefficient, i = 1, 2, 3).

Further, as for the drop parameter Z (i) for the immediately preceding concave point in step 9 in FIG. 7, the distances Z1, Z2, Z3, Z4 in FIG. 4 (d) are obtained, and Z (i) = (Zi / H) × K4 (where K4 is a weighting factor, i = 1, 2, 3, 4) and is obtained. If the parameters Y (i) and Z (i) are also minimum, it is evaluated that the certainty is large.

Then, in step 10 of FIG. 7, the evaluation point S (i) = H (i) + X (i) + Y (i) + Z
(I) is calculated, and the convex point having the smallest evaluation point S (i) is set as the convex point (decision point) corresponding to the edge E (step 12 in FIG. 7). It is to be noted that some of these parameters may be omitted, and the convenience weighting factors K1, K2, K3, K
4 may be changed.

Next, an offset point B is set between the edge E (decision point) and the center A of the lead 2 (FIG. 7).
Step 13). The width of the lead 2 is included in the chip data and is known, and the offset point B can be easily set.

In FIG. 9 (graph of measured values by the conventional means), K indicates an abnormal reflection of the laser beam due to the edge E 'on the opposite side to the light receiving section 6, and due to the abnormal reflection, the lead 2 The difficulty in finding center A accurately is
As described in the section of the problem to be solved by the invention.

Next, as shown in FIG. 1, the laser beam L is scanned in the longitudinal direction N2 of the lead 2 passing through the offset point B, and the reflected light L 'is received by the light receiving section 6, whereby The shape of the solder at the tip of the lead 2 is measured (Step 14 in FIG. 7).

FIG. 6 shows the longitudinal shape of the lead 2 measured in this manner in the longitudinal direction N2. In FIG. 6, reference numeral 20 denotes the upper surface shape of the lead 2, and 30 denotes the upper surface shape of the solder 3. Yes, the shape of the solder 3 is determined from the upper surface shape 30.

As described above, according to the present method, it is possible to avoid the deviation of the measured value due to the secondary reflection of the laser beam due to the edge E 'on the opposite side of the light receiving section 6, and to easily find the position of the edge E. In addition, the position of the edge E can be detected by inspection using a computer without manual intervention, and automation of the appearance inspection of the solder can be promoted.

[0027]

According to the present invention, a laser irradiator for irradiating a laser beam from above toward a lead extending from a main body and a light receiving portion for receiving reflected light from the lead obliquely above the lead are used for soldering. It is to inspect the appearance of, the start position of the laser light is set at the center of the upper surface of the lead, scanning this laser light in the direction from the laser irradiator toward the light receiving unit side, A process of detecting the edge of the lead on the light receiving portion side, a process of setting an offset point between the edge and the center of the lead, and scanning a laser beam in a length direction of the lead passing through the offset point. Since the process for measuring the shape of the solder adhered to the tip of the lead was configured, the laser light was not irradiated near the edge of the lead opposite to the light receiving section. To avoid secondary reflection by adjacent leads, it is possible to easily detect the light receiving portion side of the edge to be obtained. In addition, the shape of the solder can be satisfactorily measured while scanning the laser beam along the length direction of the lead and reliably reflecting the reflected light toward the light receiving section.

[Brief description of the drawings]

FIG. 1 is a perspective view of a visual inspection unit according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram of a measurement example according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram of parameters according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of evaluation points according to one embodiment of the present invention.

FIG. 6 is an explanatory diagram of a measurement example according to one embodiment of the present invention.

FIG. 7 is a flowchart according to an embodiment of the present invention.

FIG. 8 is an explanatory view of a conventional means.

FIG. 9 is an explanatory diagram of a measurement example of a conventional means.

[Description of Signs] 1 Main body 2 Lead 2a Upper surface of lead 2 'Lead 3 Solder 5 Laser irradiator 6 Light receiving section A Center of lead B Offset point C Central part E Edge on light receiving section L Laser light L' Reflected light N1 Light receiving Direction toward head N2 Lead length direction S Start position

Continued on the front page (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 11/24 G01N 21/956 H05K 3/34 512 H01L 21/66

Claims (1)

(57) [Claims] 1. A solder irradiator for irradiating a laser beam from above toward a lead extending from a main body, and a light receiving portion for receiving reflected light from the lead obliquely above the lead to form an external appearance of the solder. Inspection, setting the start position of the laser beam at the center of the upper surface of the lead,
A process of scanning the laser light in a direction from the laser irradiator toward the light receiving unit to detect an edge of the lead on the light receiving unit side, and an offset point between the edge and the center of the lead. A process of setting, and a process of scanning a laser beam in a length direction of the lead passing through the offset point, and measuring a shape of the solder adhered to a tip portion of the lead. Appearance inspection method.