The present invention relates to a package construction of a semiconductor device. More particularly, the present invention relates to a package construction of a semiconductor having a BGA (Ball Grid Array) construction where soldering balls to be used for a soldering operation in the embodying of the semiconductor device into the product are provided in a matrix on the reverse face of a substrate.
The conventional semiconductor device comprises a BGA substrate, a semiconductor chip to be arranged on the BGA substrate, a heat spreader for dispersing externally the heat generated in the semiconductor chip, and a ring in a space between the BGA substrate and the heat spreader for splicing both of them. The BGA substrate has a multi-layer construction with a plurality of insulation layers being superposed on each other. A plurality of lines and via holes are provided in each of the insulation layers. The BGA substrates are mutually combined with a predetermined line through the via holes when a plurality of lines are superposed. A plurality of lines can be crossed through an insulation layer, thus realizing a smaller size of the semiconductor device.
FIG. 6 is a partially cut-away perspective illustrating view showing one example of the conventional semiconductor device. Referring to FIG. 6, reference numeral 1 denotes a BGA substrate, numeral 2 denotes a semiconductor chip, numeral 3 denotes a heat spreader, numeral 4 denotes a ring, numeral 6 denotes a soldering ball, and numeral 8 denotes a sealing member.
Each line (not shown) provided in the BGA substrate 1 is electrically connected with the external electrode (not shown) of the semiconductor device. The soldering ball 6, made of a soldering material, is electrically connected with the external electrode of the semiconductor device. A plurality of electrodes (not shown) of the semiconductor chip 2 are electrically connected respectively with the predetermined line of the BGA substrate 1. For example, a soldering bump is provided beforehand on the surface of the external electrode connected with each electrode surface of the semiconductor chip 2 and each line of the BGA substrate 1. The connection is realized through the soldering operation by using the solder bump. The sealing member 8, made of sealing resin, is provided for adhering the semiconductor chip 2 to the BGA substrate 1. That is, sealing member 8 prevents breaking in the connecting portion between the wiring of the BGA substrate 1 and the electrode of the semiconductor chip 2 caused due to the camber or the like of the BGA substrate 1.
In the ring 4, an opening is provided in the center of the plate-shaped member. The shape of the opening portion is determined in accordance with the shape of the semiconductor chip 2. The shape of the heat spreader 3 is a thin plate which is similar to that of the BGA substrate 1. The semiconductor chip 2 and the heat spreader 3, the BGA substrate 1 and the ring 4, and the heat spreader 3 and the ring 4 are bonded respectively with adhesives. Adhesives for bonding the semiconductor chip 2 with the heat spreader 3 is, for example, a thermally conductive silicon adhesives. Adhesives for bonding the BGA substrate 1 with the ring 4, and the heat spreader with the ring 4 is, for example, a taper shaped thermosetting adhesive or thermoplastic adhesives.
Then, a method of manufacturing the semiconductor device will be described. FIGS. 7(a) to 7(d) and FIGS. 8(a) to 8(c) respectively depict a process sectional illustrating view showing one example of the method of manufacturing the conventional semiconductor device. Referring to FIGS. 7(a) to 7(d) and FIGS. 8(a) to 8(c), the same reference numerals are used as the same components as those of FIG. 6. Reference numeral 5a denotes a first solder bump electrically connected with an electrode (not shown) to be included in the semiconductor chip 2. Numeral 5b denotes a second solder bump electrically connected with each one-end portion (not shown) of a plurality of lines provided in the BGA substrate. Numeral 7a shows a first adhesives layer composed of adhesives for bonding the BGA substrate 1 with the ring 4, and the heat spreader 3 with the ring 4. Numeral number 7b denotes a second bonding layer comprising a bonding agent for bonding the semiconductor chip 2 with the heat spreader 3.
The first soldering bump 5a is provided on the electrode included in the semiconductor chip 2. Similarly, the second soldering bump 5b is provided (see FIG. 7(a)) on each one end portion of a plurality of lines of the BGA substrate 1. A flux material is applied on the area, where the second soldering bump 5b is formed, of the surface of the BGA substrate 1. A semiconductor chip 2 is placed on the BGA substrate 1, and the BGA substrate 1 and the semiconductor chip 2 are charged into a thermally processing furnace (so-called reflow furnace) with the first soldering bump 5a and the second soldering bump 5b being in contact with each other. As a result, the first soldering bump 5a and the second soldering bump 5b are melted. Thereafter, the first soldering bump 5a and the second soldering bump 5b in contact with each other are integrated. In FIGS. 7(a) to 7(b), the first soldering bump and the second soldering bump which are integrated with each other serve as a soldering bump 5. The electrode to be included in the semiconductor chip 2 is electrically connected (see FIG. 7(b)) with a plurality of lines of the BGA substrate 1. After the flux material has been washed, the ring 4 is bonded (see FIG. 7(c)) with the BGA substrate 1 by the first adhesives layer 7a.
After synthetic resin for sealing has been injected into a gap portion between the BGA substrate 1 and the semiconductor chip 2, and subjected to thermosetting to form a sealing member 8, so as to fix the semiconductor chip 2 with the semiconductor chip 2 being adhered on the BGA substrate through the sealing member 8. A second bonding layer 7b is provided (FIG. 8 (a)) by applying the adhesives on the surface of the semiconductor chip 2. The first bonding layer 7a is provided by applying the adhesives on the surface of the ring 4. Then, the heat spreader 3 is placed on the semiconductor chip 2 and the ring 4, so as to bond the heat spreader 3 on the semiconductor chip 2 and the ring 4 (see FIG. 8(b)). Finally, a soldering ball 6 is provided on the external electrode of the semiconductor device connected with the other terminal portion of a plurality of lines of the BGA substrate, so as to obtain the semiconductor device (see FIG. 8(c)).
In a process of manufacturing the conventional semiconductor device is a process including a thermal processing for connecting a plurality of lines of the BGA substrate with the semiconductor chip electrode by using, for example, a first soldering bump and a second soldering bump. Generally, the BGA substrate and the semiconductor chip are different in thermal expansion coefficient, so that camber is sometimes caused in the BGA substrate during the thermal processing. Therefore, the first soldering bump and the second soldering bump which have been opposed to each other before the thermal processing step are opposed to each other no more during the thermal processing process. As a result, there is caused such a problem that electric connection is not connected between a plurality of lines of the BGA substrate and the electrode of the semiconductor chip.
On the other hand, some unevenness exists on the BGA substrate surface and the semiconductor chip surface. When a soldering material is printed on a plurality of lines of the BGA substrate or the electrode of the semiconductor chip through the mask, so as to form the first soldering bump or the second soldering bump, the mask is not sometimes adhered with the lines or the electrodes. As a result, the size of the first soldering bump or the second soldering bump becomes unequal, thereby causing such a problem that the electric connection is not retained, between the line of the BGA substrate and the electrode of the semiconductor chip.
Accordingly, an object of the present invention is to provide a semiconductor device which can retain the electric connection, even after the thermal processing process, between the line of the BGA substrate and the electrode of the semiconductor chip.