JP2662870B2 - Printed wiring pattern and unsolder detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention makes it easy to find defective soldering spots when soldering lead terminals of mounted components on a printed wiring pattern, especially on a printed wiring pattern by reflow soldering. The present invention relates to a printed wiring pattern and a non-solder detecting method which enable the above.

(Prior art) When mounting a component such as a flat package type IC on a printed wiring pattern on a substrate, a rectangular pattern pre-positioned to correspond to a large number of lead terminals derived from a peripheral portion of the IC or the like. A method of forming a portion and soldering each lead terminal and each pattern portion has been performed. As a soldering method, a reflow method is often used in which a predetermined amount of solder cream is printed and formed on each pattern, and then heated and melted while placing lead terminals on the solder cream, and then cooled and solidified.

However, due to various causes such as variations in the length of the lead terminal and the protruding length downward, poor adhesion between the lead terminal and the pattern portion during welding, the solder solidifies in a state where the lead terminal floats from the pattern portion and the solder. There is.

That is, FIGS. 3A and 3B are an explanatory view comparing the case where soldering is properly performed and the case where soldering is defective, and a plan view showing a mounting state.
When each of the lead terminals 4 of the IC 3 is mounted with the solder 5, the lead terminal 4 on the right side of the drawing is welded to the pattern portion 2 in a state of being in close contact with the pattern portion 2, but the lead terminal 4 on the left side of the drawing is Part 2 as well as solder 5 on it
It is in a state completely separated from.

Actually, as an intermediate form of these, there may be a case where both are slightly connected via solder, but such a connection state is insufficient, which often causes detachment of the lead terminal. .

By the way, conventionally, when such a connection failure occurs,
It was extremely difficult to find. That is, conventionally, the unsoldered portion was visually checked from the side of the board, and if the unsoldered portion was found, the work was completed through a step of re-soldering with a soldering iron or the like, but the work was completed. It is extremely difficult to accurately detect the separated state and poor connection state of the parts only by visual observation. In particular, it was impossible to find out when the distance between the two was extremely small, or when there was no or insufficient contact with, but in contact with.

If the faulty connection is overlooked, the electronic device cannot operate normally, so this check is important and it is desirable to complete it. It often appears as a malfunction of the electronic device after the product is completed.

(Object of the Invention) The present invention has been made in view of the above, and has been made in consideration of the above circumstances, and has a printed wiring that enables a defective connection between a printed pattern and a lead terminal of an IC to be easily found by visual inspection or an automatic inspection method. It is intended to provide a pattern.

(Summary of the Invention) In order to achieve the above object, an invention according to claim 1 is a printed wiring board provided with a printed wiring pattern for performing solder connection with a bottom piece of a lead terminal of a mounted component mounted thereon. Is divided into an inner region and an outer region by separating a portion located on the tip side from the tip of the bottom piece of the lead terminal by a fine slit, and the substrate surface is exposed in the fine slit, The interval between the fine slits is such that the solder on the inner area of the printed wiring pattern can be spread on the outer area to form a solder bridge, and the bottom piece of the lead terminal is connected to the solder on the inner area. It is characterized by being performed.

The invention according to claim 2 is a method for judging the quality of a soldering state in a printed wiring board provided with a printed wiring pattern to be soldered in a state where a bottom piece of a lead terminal of a mounted component is placed, wherein the printed wiring pattern is The portion located on the tip side from the tip of the bottom piece of the lead terminal is separated by a fine slit into an inner region and an outer region, and the substrate surface is exposed in the fine slit, The interval between the fine slits is such that the solder on the inner area of the printed wiring pattern can be spread on the outer area to form a solder bridge, and the bottom piece of the lead terminal is placed inside the printed wiring pattern by a reflow method. After soldering on the area, whether or not a solder bridge was formed in the fine slit portion of the printed wiring pattern Therefore, and judging the quality of the soldering state between the printed circuit pattern and the mounting component of the lead terminal.

According to a third aspect of the present invention, the quality of a soldering state between the pattern and a lead terminal of a mounted component is determined by checking whether there is electrical continuity between the regions of the printed wiring pattern divided by the fine slit. It is characterized by doing.

Hereinafter, a printed wiring pattern according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows one embodiment of the present invention, and FIG.
Parts that are the same as those in (b) are denoted by the same reference numerals, and redundant description is omitted.

In the pattern portion 2 of the present invention, the lead terminals 4
A fine slit (identifying means) 10 having a narrow width is directed in the width direction of the pattern portion 2 at a position closer to the front end by a predetermined distance 1 from the front end of the bottom piece 4B (comprising the leg 4A and the bottom piece 4B). This is a characteristic configuration in that it is penetratingly formed. As a result, regions 2a and 2b are defined with the fine slit 10 as a boundary. That is, the region 2a is an inner region with the slit 10 as a boundary, and the region 2b is an outer region with the slit 10 as a boundary.

In the above embodiment, the fine slits 10 are linear and formed in parallel with the width direction of the pattern portion 2, but this is only an example. Thus, the fine slit may be a curve, a curved line, an irregularly shaped line, etc.
Also, the line may be formed at a predetermined angle without being parallel to the width direction of the pattern portion.

Also, the fine slit 10 is formed in the pattern portion 2,
Since a part thereof is notched, the upper surface of the substrate 1 (printed wiring board) is exposed from the fine slit 10. The exposed substrate surface has a different color, pattern, etc. (identifiable difference) from the pattern portion 2, and it is necessary that the two can be easily distinguished visually or by other detecting means.

However, when an identification test described later is visually performed, the width of the fine slit 10 is set to be smaller than the width of the exposed substrate 1 for the reason described later.
It must be large enough to visually identify the surface and fine enough to allow the molten solder to flow over slit 10 to the opposite side and form a bridge. An appropriate width to meet these conditions is
For example, about 0.2 mm is preferable. The width may be narrower than this, but this is the limit with the current fine processing technology.

In the automatic continuity inspection method that is not performed visually as described later, it is preferable because the slit 10 can be further narrowed by etching using a laser beam or the like, and the slit 10 can be easily filled when soldering is not performed.

In each of the above embodiments, the position illustrated as the position where the fine slit 10 is formed (the position at a distance 1 from the tip of the bottom piece 4B of the lead terminal 4) is a connection failure between the pattern portion 2 and the lead terminal 4. Any shape can be used as long as the molten solder flowing and developing on the upper surface of the pattern portion 2 belongs to the reachable range. Of course, these slits
As will be described later, when performing a visual check operation, it is necessary to be at a position avoiding obstacles (inspection obstacles) such as the lead terminals 4 and the IC body 3.

The pattern wiring of the present invention having the above configuration is
It was created based on the discovery of the following phenomena.

That is, FIG. 2 (a) is an explanatory view showing the concentration state of the solder when the connection between the pattern portion 2 and the lead terminal is good, and the printing on the substrate 1 as shown in FIG. When the bottom piece 4B of the lead terminal 4 is properly welded by the solder 5 on the portion 2, the molten solder 5 is cooled while being concentrated on the contact portion between the bottom piece 4B of the lead terminal 4 and the pattern portion 2. Due to solidification, a small amount of solder 5a protrudes outside the peripheral edge of the contact portion. Of the protruded solder 5a, the one on the lead terminal tip side does not reach the fine slit 10 located at a position separated by a predetermined distance l. Since the color of the solder 5 and the pattern portion 2 is usually substantially the same or a color tone that is difficult to distinguish, the solder 5
As long as the substrate surface does not extend beyond 10, the substrate surface exposed from the fine slit 10 can be identified and visually recognized. Therefore, IC3
If the presence of the fine slits 10 can be confirmed in the inspection after mounting, it can be confirmed that the connection between the pattern portion 2 and the lead terminal 4 is well performed. Since solder as known can not be developed on the substrate beyond the range of the metal constituting the pattern portion was melted by setting the minimum projection amount l ₁ of the inner direction of the pattern portion 2 The solder can be caused to flow to the tip side of the pattern portion 2.

FIG. 2 (b) is an explanatory view showing the state of development of the molten solder when the connection between the pattern portion 2 and the lead terminal 4 is defective. In this case, the molten solder 5 flows and develops on the pattern portion. However, it also flows and deploys mainly in the tip direction. As described above, the width of the fine slit 10 is
The solder 5 covers a part or all of the slit, and covers the color of the substrate 1 (see the dotted line in FIG. 1).
Therefore, the inspector can properly know that the connection between the pattern portion 2 and the lead terminal is defective.

As an inspection method, the efficiency can be improved by performing a continuity inspection between the regions 2a and 2b separated by the slit using an inspection device in addition to the visual inspection. In this case, not only the width of the fine slit 10 can be reduced, but considering the advantage that the narrower the narrower, the easier the bridge is formed beyond the slit, the higher the detection accuracy is than in the case of visual observation. Can be.

As means for judging the quality of the soldering state, if the presence of the slit portion is detected by irradiating the light of the fine slit and monitoring the characteristics such as the amount of reflected light or the phase thereof, the inspection of the wiring pattern can be performed. Time can be reduced. Further, when a defect in the soldering state is detected, the portion is re-soldered, which is convenient in automating the work of correcting the unsoldered portion.

In the above embodiment, the identification means formed in the pattern portion is formed at the time of printed wiring. However, only the fine slit 10 serving as the identification means may be formed by laser beam processing in the subsequent stage.

Japanese Utility Model Application Laid-Open No. Sho 62-47171 discloses that a pad portion of a wiring pattern on a printed circuit board is divided into two portions, and a bottom piece of a lead terminal of an integrated circuit (mounting component) is mounted over the two pad portions. A technique for solder connection in a state of being placed is disclosed. In this conventional example, a configuration in which the substrate surface is exposed between two pad portions is disclosed, but the purpose of this conventional example is to use an ohmmeter. By contacting only the two pad portions without bringing the detection terminal into contact with the lead terminal, the electrical connection state between the bottom piece of the REIT terminal and the pad is checked. Therefore, the slit-shaped gap located between the two pad portions is not for confirming the occurrence of a solder bridge between the two pads as in the present invention. The use of this slit for checking the solder bridge results in a result that largely contradicts the purpose of the technique described in this publication. That is, when a solder bridge occurs between the two pads, it becomes meaningless to check the connection state of the lead terminal bottom pieces on each pad portion after dividing the pad into two. That is,
In this conventional example, it is absolutely necessary to avoid the occurrence of a solder bridge between the two pads. Therefore, the interval between the slits needs to be set wide enough to prevent the occurrence of the solder bridge. Further, positioning the slit of the present invention below the bottom piece of the lead terminal as in this conventional example results in obstruction (inspection obstacle) such as the lead terminal and the IC body obstructing visual confirmation, The meaning of the present invention is completely lost.

In other words, although the divisional structure of the pad described in this publication is similar to the divisional structure of the wiring pattern of the present invention at first glance, the purpose of use thereof is completely different, so that the configuration is substantially greatly different. The quality of the connection of the lead terminals cannot be confirmed by visually checking the connection quality using the pad structure described above or by checking the presence or absence of electrical conduction between both pad portions. Regarding the check of the presence or absence of electrical continuity, in the technology described in the publication, there should always be no electrical continuity between both pad portions, and therefore, the present invention that checks electrical continuity between both pad portions is Different technologies.

(Effect of the Invention) As described above, in the printed wiring pattern of the present invention, a defective connection between the printed pattern and the lead terminal of the IC can be easily found by visual inspection or an automatic inspection method.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a configuration of a first embodiment of the present invention, FIGS. 2 (a) and 2 (b) are explanatory views showing a method of checking good or bad connection according to the present invention, and FIGS. 3 (a) and 3 (b). 4A and 4B are an explanatory diagram and a plan view showing a mounting state in which a case where soldering is properly performed and a case where soldering is defective are compared. 1 ... printed circuit board, 2 ... pattern part, 3 ... IC,
4 ... lead terminal, 10 ... fine slit (identification means)

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Tomoyuki Sawada 2-1-1 Kotani, Samukawa-cho, Koza-gun, Kanagawa Prefecture Toyo Tsushinki Co., Ltd.

Claims (3)

(57) [Claims] In a printed wiring board provided with a printed wiring pattern for soldering with a bottom piece of a lead terminal of a mounted component mounted thereon, the printed wiring pattern is located closer to the tip than the tip of the bottom piece of the lead terminal. The portion located is cut off by the fine slit to be divided into an inner region and an outer region, and the substrate surface is exposed in the fine slit. The interval between the fine slits is on the inner region of the printed wiring pattern. The printed wiring pattern has such an interval that the solder can be spread on the outer region to form a solder bridge, and the bottom piece of the lead terminal is soldered on the inner region. 2. A method for judging whether a soldering state is good or not in a printed wiring board provided with a printed wiring pattern to be soldered in a state where a bottom piece of a lead terminal of a mounted component is mounted, wherein the printed wiring pattern comprises The portion located closer to the tip side than the tip of the bottom piece of the terminal is separated by a fine slit into an inner region and an outer region, and the substrate surface is exposed in the fine slit. Is an interval at which the solder on the inner area of the printed wiring pattern can be spread on the outer area to form a solder bridge, and the bottom piece of the lead terminal is placed on the inner area of the printed wiring pattern by a reflow method. After the solder connection, whether or not a solder bridge is formed in the fine slit portion of the printed wiring pattern is determined. Te, non solder detection method characterized by determining the quality of the soldering state between the printed circuit pattern and the mounting component of the lead terminal. 3. The method according to claim 1, further comprising the step of checking whether or not there is electrical continuity between the respective regions of the printed wiring pattern divided by the fine slit to determine whether or not the soldering state between the pattern and the lead terminals of the mounted component is good. 3. The method for detecting unsolder according to claim 2, wherein: