JPS5832785B2 - electronic parts container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in electronic component containers, particularly containers referred to as chip carriers for semiconductor integrated circuits (ICs).

Conventionally, containers for housing electronic component elements, especially ICs, and mounting them on circuit boards have used containers with connection leads to the circuit board attached to the container body, as typified by so-called dual-in-line packages. It has been.

However, from the standpoint of reducing costs and increasing packaging density, containers called chip carriers have recently begun to be adopted.

As shown in FIG. 1a, the cross-sectional structure of the IC
A chip 1 is housed in a container body 2 made of ceramic or the like,
After connecting the conductor layer 4 with the wire 3, it is hermetically sealed with the lid 5, while the conductor layer 4 is connected via the side wall of the ceramic container body 2 or through a through hole formed through the body 2. It extends to the back surface of the main body 2, and a connection pad 6 is provided there.

The connection pins are usually arranged along the outer periphery of the back surface of the container body.

This chip carrier is immersed in a solder bath to apply preliminary solder 7 to the band 6, and then, when mounting on a circuit board, the chip carrier is placed in a predetermined position and subjected to a reflow treatment to complete the mounting.

Solder flow is performed by applying flux and heating it with a heater block or infrared lamp, or if flux is not used, heating it in a reducing atmosphere furnace.

During this reflow process, even if the mounting position of the chip carrier is slightly shifted, the surface tension of the molten solder moves the chip carrier to the proper position and fixes it, which not only facilitates the mounting position but also There is also a margin in the positional accuracy of the chip carrier and the conductor layer pattern of the circuit board.

Also, the elimination of the need for a conventional container has the advantage of lowering costs.

The circuit board on which the above chip carrier is mounted is as follows:
A circuit board called a motherboard, which carries several chip carriers in addition to a regular printed circuit board, is commonly used.

Figure 1 shows four chip carriers 8 and a motherboard 9.
This is a side view of the device mounted on a PC board, which is handled as one module that is connected to and mounted on an ordinary printed circuit board via a connection lead to the printed circuit board.

In electronic component containers such as those mentioned above, which are called chip carriers, it is difficult to expect the adhesion strength of connection leads that are inserted and fixed into through holes of printed circuit boards as in the past. Improvement in this area is desired.

Furthermore, as ICs become more highly integrated and their packaging density increases, there is an urgent need to improve heat dissipation, that is, to lower the thermal resistance of the container. If you try to install it, you may lose the low price feature.

Therefore, it is an object of the present invention to improve the heat dissipation properties of the above-mentioned chip carrier and the strength of its adhesion to a circuit board with an extremely simple structure.

The electronic component container according to the present invention includes a container body that houses an element, a signal terminal electrically connected to the element, and a plurality of solder pads provided along the outer periphery on one surface of the container body. In the electronic component container, the solder for the signal terminal on the - side has a pad in the area inside the band that does not function as a signal terminal, and the pad for the double solder has a pad after the molten solder is attached. This feature is characterized in that the heights of the two are formed in a pattern that is approximately equal to each other, and this will be explained in detail below.

In the present invention, the above object is achieved by providing a band for soldering signal terminals and a band for soldering to reduce thermal resistance and improve bonding strength on the surface of the container (chip carrier) body that is fixed to the circuit board. It is something.

The amount of solder adhering to the band is influenced by the surface tension of the molten solder, and the solder adheres to a height proportional to the size of the band.

For example, in a square band with a side of 0.25wIt, even if the solder adhesion height is 15 to 20μ, Q, 35wIt
Solder adheres to a height of 30 to 40 μm for a band of 0.5 wIt angle, and 50 to 65 μm for a band of 0.5 wIt angle.

Needless to say, if the amount of solder adhered to each band is different in this way, the band with a smaller amount of solder adhered will be unstable in contact with the circuit board.

The present invention is characterized in that, in order to avoid such unstable connection, the signal terminal pad and the band for improving thermal resistance and strength are patterned so that the solder adhesion heights are approximately the same.

In order to achieve this, it is convenient to make all the bands substantially the same shape, or to make the band for improving thermal resistance and strength into a band shape, and to make the width of the band the same as one side of the signal terminal pad.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2a is a cross-sectional view of an electronic component container (chip carrier) according to an embodiment of the present invention, in which 11 is an IC element, 12 is a container body, 13 is a connecting wire, 14 is a conductor layer, and 15 is an airtight seal. 16 is a signal terminal band, 17 is solder, 1
8 indicates pads for improving thermal resistance and strength, respectively.

The structure of this container is such that the conductor layer 14 passes through the IC element 11 through a through hole formed by penetrating the periphery of the container body 12.
The basic structure is the same as that of the conventional chip carrier shown in FIG. 1, except for the connection between the chip carrier and the pad 16.

However, according to the present invention, a pad 18 for improving thermal resistance and strength is provided on the back surface of the chip carrier main body 12 in a region inside the signal terminal pad 16.

FIG. 2 is a plan view showing the pattern of each pad on the back surface of the chip carrier according to this embodiment, and each pad 16 and 18 has the same size and shape.

FIG. 2C shows another example of a pin soldering pattern, in which the heat dissipation and strength improvement pad 18 according to the present invention is strip-shaped, and its width is equal to one side of the signal terminal pad 16. It is approximately the same as the length.

Regardless of the pattern, the height of the molten solder deposited on each pin is approximately the same, and each band is evenly fixed to the conductor pattern of the circuit board.

FIG. 3 shows an example of the cross-sectional structure of a chip carrier according to the present invention fixed onto a circuit board by solder reflow.

In this figure, the same parts as in FIG. 2 are given the same numbers.

A conductor pattern 22 is also provided on the circuit board 21 at a position corresponding to the heat dissipation and strength improving band 18 on the back surface of the chip carrier 12, and both are bonded by solder 17.

Since this pad 18 is located directly below or close to the IC element 11 which is a heat generation source, it is possible to
This has a remarkable effect on reducing the thermal resistance of the heat dissipation path via 1.

In order to further enhance this effect, it is effective to use a ceramic material such as alumina as the insulating material constituting the circuit board 21, but of course other types of printed circuit boards are also applicable.

Furthermore, in terms of adhesion strength, soldering significantly increases the area, so a remarkable effect can be obtained.

The reason why the signal terminal pads 16 are arranged along the periphery of the back surface of the chip carrier 12 is that, as can be seen from FIG. This is because, as shown in FIG. 3, when the solder 17 climbs up and is fixed to the side wall of the chip carrier 12, its strength is significantly improved.

In contrast, the pad 18 formed at the center of the back surface of the chip carrier 12 does not have the function of a signal terminal.
Even if the electrical contact between the circuit board 21 and the conductor pattern 22 is incomplete or unstable, no serious trouble will occur, so there is no need for repeated inspection, correction, or replacement.

The pattern of the band for heat dissipation and strength improvement provided according to the present invention can be changed in various ways depending on the purpose.

FIG. 4 is a plan view of the back surface of a chip carrier showing an example of this.

In this example, all of the bands 32 for heat dissipation and strength improvement provided on the back surface of the chip carrier 31 are electrically interconnected and connected to a power supply terminal 33/.

33 is a band for signal terminals. This results in band 3
2 can also have the function of an electrical shield.

That is, noise is likely to be induced between horizontally or vertically adjacent signal lines, but by interposing the conductor of the power supply system, a shielding effect can be obtained to block such noise.

Furthermore, the above-mentioned pattern produces effects in terms of manufacturing.

That is, the conductor pattern constituting each band is made by printing a conductor paste such as molybdenum-manganese on the surface of the ceramic container body, baking it, and then soldering it to the surface with a nickel layer to obtain properties and oxidation of the nickel layer. It is formed by sequentially electroplating metals that prevent the problem and facilitate hermetic sealing, but if the pattern shown in FIG. 4 is used, the connection of the plating electrodes during electroplating can be done in exactly the same way as in the past.

Further, with the pattern shown in FIG. 4, the height of molten solder adhering to each pad is approximately equal, so that each pad can be uniformly soldered to the corresponding conductor pattern on the circuit board.

Although it is effective to connect the pad 33 for heat dissipation and strength improvement to the power supply terminal (including the ground terminal) as in the above example, connecting it to another signal terminal 33 adds a parasitic element. This should be avoided, as it will cause problems and the shielding effect cannot be expected.

The reason why the semicircular recess 34 is formed in the side wall of the main body 31 in the chip carrier example shown in FIG. 4 is due to the manufacturing process thereof, as is well known.

That is, this type of chip carrier is made by, for example, forming through-holes arranged in a pattern on a relatively large ceramic plate, and then filling the through-holes with a conductive paste.
After firing, a process of cutting the ceramic plate along the through-holes allows a large number of chip carrier bodies 31 to be made at once, and a conductor layer in the through-holes is used to separate each pad 33 on the back side and the conductor on the element mounting side. It connects the layers.

The semicircular recess 34 corresponds to the through hole.

As is clear from the above explanation, according to the present invention, the heat dissipation performance and mechanical adhesion strength of the so-called chip carrier can be significantly improved without adding any particularly complicated manufacturing process or structure. The effect of providing this service is significant.

[Brief explanation of drawings]

FIG. 1a shows the structure of a conventional chip carrier, FIG. 1 shows its mounting state, and FIGS. 2a, b, and c show the cross-sectional structure and solder band pattern of a chip carrier according to an embodiment of the present invention. 3 is a diagram showing a mounting state of a chip carrier according to an embodiment of the present invention, and FIG. 4 is a diagram showing a solder pin pattern according to another embodiment of the present invention. 11...IC terminal, 14...conductor layer,
16.33...Soldering for signal terminal is band, 1
7...Solder, 18.32...Soldering for heat dissipation and strength improvement is a band, 21...Circuit board.

Claims (1)

[Claims] 1. An electronic component container having a container body that houses an element, and a plurality of solder pads that are signal terminals electrically connected to the element and are provided along the outer periphery on one surface of the container body. , the solder for the signal terminal on the - side has a band in addition to the band, the solder that does not function as a signal terminal has a band, and the height of the solder in both solders is almost the same after the molten solder is attached. An electronic component container characterized by being formed into a pattern.