JP3284758B2 - IC package - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IC package capable of easily confirming a soldered state on a printed circuit board.

[0002]

2. Description of the Related Art There are various types of IC packages. From the viewpoint of automatic mounting on a printed circuit board, a QFP type IC package has been often used so far.
However, in recent years, BGA (Ball Grid Ar
ray) type IC packages are starting to attract attention. An example of the BGA type IC package will be described with reference to FIG. A sealed IC body 2 such as an IC chip or an IC module is mounted on an upper surface of a base plate 1 made of a multilayer substrate.
Many ball-shaped connection terminals 3 are provided on the lower surface of the base plate 1. When this IC package is bonded to a printed board, cream solder is applied to the electrode portions (lands) 4a of the printed board 4 by screen printing or the like as shown in the figure, and the connection terminals 3 are placed thereon, and then reflowed. Solder through the furnace. However, in such an IC package, due to various factors, the base plate 1 warps or the formation of the connection terminals 3 varies, so that it is difficult to align all the tips of the connection terminals 3 on the same plane. In addition, warping of the base plate 1 may occur in a reflow furnace. Further, in some cases, the printed circuit board 4 may be warped, causing variations in the height of the electrode portions 4a. Therefore, when connecting the IC package to the printed circuit board, it may not be possible to completely solder all the connection terminals.

[0003]

Conventionally, when the soldering is insufficient as described above, the connection terminals are located below the base plate, and it is extremely difficult to detect them from the appearance. . For this reason, a soft X-ray device had to be used to ensure confirmation, but such a device is expensive, and in the case of a soft X-ray device, X-rays are harmful to the human body. Therefore, there is a problem that sufficient care must be taken in handling the device.

The present invention has been made in view of the above problems, and has as its object to dispose a plurality of connection terminals on one surface of a base member on which an IC is mounted as described above. An object of the present invention is to provide an IC package in which soldering with a printed circuit board can be easily confirmed from the appearance in the IC package.

[0005]

In order to achieve the above object, according to the present invention, a plurality of connection terminals for connecting an external circuit or the like to one surface of a base member on which an IC chip or an IC module is mounted. In an IC package in which a tubular connection terminal filled with solder is passed through the base member from the other surface at a position where the IC chip or IC module or the like is not mounted on the base member, Are mounted so that they protrude from the one surface of the base member .

[0006]

The cream solder is applied to the electrode portion of the printed circuit board, and the IC package having the above configuration is placed so that the ends of the connection terminals are in contact with the cream solder.
When the solder is put into the reflow furnace in this state, the cream solder and the solder filled in the connection terminals are melted. When the cream solder melts, it rises to the outside of the tip of the connection terminal. At this time, a part of the solder inside the connection terminal flows out to the outside. Therefore, on the opposite side of the connection terminal, the end face of the solder moves and a gap is generated between the end face of the connection terminal and the solder. After taking out from the reflow furnace, the gap is visually checked or observed by a known visual inspection device to confirm whether the connection terminal is joined to the electrode portion of the printed board by soldering.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described with reference to the embodiments shown in FIGS. FIG. 1 is a perspective view showing an example of the IC package of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. 3A and 3B are enlarged cross-sectional views of a main part showing a joint between the IC package and the printed circuit board . FIG. 3A shows a state before heating in a reflow furnace, and FIG. 3B shows a state after heating.

An IC element 2a is provided at the center of the upper surface of the base plate 1.
Is mounted with an IC chip 2 sealed with a synthetic resin or the like. The base plate 1 is made of ceramic, silicon, glass, or a synthetic resin, and is usually provided with a single-layer or multi-layer wiring pattern. In FIGS. 2 and 3, a single-layer wiring pattern is used. 1a is shown. A connection terminal 5 serving as an input / output terminal of the IC chip 2 is attached to the base plate 1. The connection terminal 5 is made of copper or a copper alloy, has a tubular shape, and has a through hole 5 a filled with solder 6. The solder 6 may be a solder containing no flux or a solder containing flux. The connection terminal 5 has a shell-shaped outer shape and is slightly tapered.
Therefore, in order to attach the connection terminal 5 to the base plate 1, the connection terminal 5 is press-fitted from the upper surface side of the base plate 1 to bring the pattern 1 a into contact with the connection terminal 5. Gold plating may be applied to the outer peripheral surface of the connection terminal 5 in advance in order to improve the contact relationship between the two.

Next, a case where the above IC package is bonded to a printed circuit board will be described with reference to FIG.
In FIG. 3, illustration of the resist coating layer is omitted. The printed circuit board 4 has an electrode portion 4a of a wiring pattern formed of copper foil. First, cream solder 7 is applied to the electrode portion 4a by screen printing.
Is applied. Next, the above-mentioned IC package is mounted on the printed circuit board 4 by an automatic mounting machine or the like. Fig. 3
This is shown in FIG. The cream solder 7 usually has a thickness of about 0.1 mm to 0.7 mm, and in this state, the tip of the connection terminal 5 is not in contact with the electrode portion 4a. Also, since the cream solder 7 is viscous, even if the tips of all the connection terminals 5 are not aligned on the same surface when the IC package is mounted, if the difference is within the tolerance, I
When the C package is placed, all the connection terminals 5 come into contact with the cream solder 7 because the IC package slightly bites into the cream solder 7.

After placing the IC package in this manner,
The printed circuit board 4 is placed in a reflow furnace and heated. When the cream solder 7 melts, the wettability of the tip of the connection terminal 5 is improved by the action of the flux contained in the cream solder, and a fillet is formed between the electrode portion 4a and the connection terminal 5 to swell. In this process, the cream solder on the outer peripheral portion of the electrode portion 4a is drawn to the fillet portion and the through-hole 5a
Is also drawn in the same manner. Accordingly, the molten solder 6 in the through hole 5a moves downward, and a difference is generated between the upper end surface 6a and the upper end surface of the connection terminal 5. This state is shown in FIG.

On the other hand, IC packages and printed circuit boards
The solder may be deformed by heat or force from the outside after manufacturing, and the thickness of the cream solder may not be applied uniformly. For this reason, when the IC package is mounted on the printed circuit board, the ends of some of the connection terminals 5 may not contact the surface of the cream solder 7 in some cases. In such a case, it is needless to say that the connection between the electrode portion 4a and the connection terminal 5 is not performed. In this case, the through hole 5a
The inner solder 6 is melted when heated in the reflow furnace, but since the diameter of the through hole 5a is small, the melted solder 6 does not hang down below the connection terminal 5. Therefore, in that case, the upper end surface 6a of the solder 6 is on the same plane as the upper end surface of the connection terminal 5, and does not descend.

After the soldering in the reflow furnace in this way, the printed circuit board is taken out of the reflow furnace and inspected. As described above, a difference occurs between the upper end surface of the connection terminal 5 and the upper end surface 6a of the solder 6 when joining is performed, and a difference occurs between them when joining is not performed. Therefore, the bonding state can be easily confirmed by visually observing the IC package from above. When this inspection is performed automatically, it can be easily confirmed by a well-known visual inspection device using an image processing technique.

Further, if the above-mentioned bonding state can be confirmed by color, the effect is further enhanced. As an example of such a case, the connection terminal 5 in FIG.
May be gold-plated, including the upper end surface 6 a of the solder 6. In this way, when the joining is performed and the upper end surface 6a of the solder 6 descends, the gold melts into the solder 6 and diffuses. Therefore, the upper end surface of the connection terminal 5 is gold, and the upper end surface 6a of the solder 6 is solder color, which can be clearly confirmed. On the other hand, when the joining is not performed, on the upper end surface 6a of the solder 6, the gold does not dissolve in the solder, and the gold remains as a whole except for the trace of bubbles from inside the solder. Even if it is a substance other than gold, if it has a property of reacting with the solder and melting into the solder and having a color completely different from that of the solder, the connection terminal 5
And the upper end surface 6a of the solder 6 is thinly coated, whereby the same effect as in the case of gold can be obtained.

If a slip-like paste-like substance, such as wax, is applied to the interface between the solder 6 and the connection terminal 5, the upper end surface 6a of the solder can be smoothly lowered at the time of joining, and the outside of the through hole 5a can be formed. The amount of the solder 6 flowing out to the upper surface also increases, and the detection of the upper end surface 6a becomes easy.

In the above embodiment, the outer shape of the connection terminal 5 is a shell shape. However, the connection terminal of the present invention may be cylindrical or rectangular, and in other words, even if it is tubular. I just need to be. Further, the attachment to the base plate 1 may be performed by a conductive adhesive or solder plating instead of press-fitting. Furthermore,
The present invention can be implemented as an IC package (MCM type package) in which a plurality of IC chips 2 are mounted as in the second embodiment shown in FIG. 4, or as in the third embodiment shown in FIG. In order to obtain the heat radiation effect of the IC package, the length of the connection terminal 5 may be increased.

FIG. 6 is a side view showing a case where the IC chip 2 is mounted at the center of the lower surface of the base member 1. A large number of connection terminals 5 are arranged around the IC chip 2. As described above, the IC chip 2 and the connection terminal 5 may be arranged on the same surface of the base member 1. In some cases, the IC chips 2 may be mounted on both sides of the base member 1.

[0017]

As described above, according to the present invention, the soldering to the printed circuit board is confirmed in spite of an IC package in which a plurality of connection terminals are arranged on one surface of a base member on which the IC is mounted. Can be easily performed from the appearance. In addition, by preliminarily applying gold plating or the like to the end surfaces of the connection terminals filled with the solder, it is possible to confirm even by the color difference.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an IC package of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an enlarged sectional view of a main part showing a joint between the IC package shown in FIGS. 1 and 2 and a printed board;
Shows a state before heating in a reflow furnace, and (b) shows a state after heating.

FIG. 4 is a perspective view of a second embodiment.

FIG. 5 is a partially sectional explanatory view of a third embodiment.

FIG. 6 is a partially sectional explanatory view of a fourth embodiment.

FIG. 7 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base plate 1a Wiring pattern 2 IC chip 2a IC element 4 Printed circuit board 4a Electrode part 5 Connection terminal 5a Through hole 6 Solder 7 Cream solder

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 23/12

Claims (7)

(57) [Claims] 1. An IC package in which a plurality of connection terminals for connecting to an external circuit or the like are arranged on one surface of a base member on which the IC is mounted.
At a position where is not attached, a tubular connection terminal filled with solder inside, penetrates the base member from the other surface ,
An IC package , wherein a tip of the IC package is mounted so as to protrude to the one surface of the base member . 2. The IC package according to claim 1, wherein a tip of the connection terminal is formed so as to be gradually thinned. 3. The IC package according to claim 1, wherein the connection terminal is mounted on the base member with a conductive adhesive. 4. The IC package according to claim 1, wherein the connection terminal is provided with conductive plating on an outer peripheral surface thereof before being attached to the base member. 5. The IC according to claim 1, wherein a slip-like paste substance is applied to an interface between the connection terminal and the solder inside the connection terminal. package. 6. The method according to claim 1, wherein the solder is a solder containing a flux.
C package. 7. The method of claim 1, characterized in that it has the the end surface opposite to the side where it is connected to an external circuit or the like, coated with a substance that dissolves in the solder and has a color different from that of solder of the connecting terminal 7. The IC package according to any one of claims 1 to 6 .