JP2740917B2 - Ceramic substrate - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic substrate, and more particularly to a ceramic substrate used for a package substrate or a printed wiring board for housing semiconductor elements.

[Conventional technology]

Ceramic substrates are susceptible to cracking and chipping by colliding with each other in the transport process and the assembly process.
A device has been devised to prevent these cracks and chips.

For example, according to Japanese Patent Application Laid-Open No. 57-62546, as shown in the cross section in FIG.
At the boundary between the upper surface 41 where the cavity 40 is not formed and the outer peripheral end surface 43, two rounded portions having a radius of curvature of about 0.04 to 0.06 mm
By forming 44 and 45, cracking and chipping of this portion were prevented.

[Problems of the prior art]

However, the conventional ceramic substrate 40 as described above has an upper surface.
The rounded portions 44 and 45 were formed only on the 41 side, and the boundary between the lower surface 42 where the cavity was formed and the outer peripheral end surface 43 was an edge 46. For this reason, the edge portion is required during the process of transporting the ceramic substrate 40 until assembly as a semiconductor package.
Cracking and chipping were easy to occur in 46.

If a rounded portion is similarly formed on the lower surface 42 side, cracks and chips can be prevented.
There was a problem that the rounded portion on the 42 side caught the lower punch, making it difficult to remove.

Also, the radius of curvature of the rounded portions 44 and 45 on the upper surface 41 side is 0.04 to 0.04.
Since it was as small as 0.06 mm, the effect of preventing chipping and cracking was poor.

[Means for solving the problem]

In view of the above, the present invention, in a substrate made of ceramic, while having a small step on both the ridge between the upper surface and the outer peripheral surface, and the ridge between the lower surface and the outer peripheral surface, the radius of curvature is 0.2 to 1.0 mm By forming the rounded portion so as to be continuous with the upper and lower surfaces, enhancing the effect of preventing cracking and chipping, and by setting the radius of curvature of the rounded portion continuous to the lower surface which is the lower punch side during press molding to 0.5 mm or more This facilitates removal during press molding.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an exploded perspective view showing a plug-in type semiconductor package.
Are combined.

The ceramic substrate 10 has a die attach surface D,
At the time of press molding, there are a lower surface 12 serving as a lower punch side, an upper surface 11 serving as an upper punch side, and an outer peripheral surface 13, and a minute step and a rounded portion are formed at each ridge. That is, the second
As shown in the figure in an enlarged cross section, the upper surface 11 of the ceramic substrate 10
A step 14 is formed at the ridge between the outer peripheral surface 13 and the step 14.
A rounded portion 15 having a curvature radius of 0.2 to 1 mm is formed on the upper surface 11 side, and a minute rounded portion 16 having a curvature radius of 0.03 to 0.2 mm is formed on the outer peripheral surface 13 side. Similarly, a step 17 is also formed on the ridge between the lower surface 12 and the outer peripheral surface 13, and a relatively large rounded portion 18 having a radius of curvature of 0.5 to 1 mm is formed on the lower surface 12 side of the step 17, On the 13th side, a minute rounded portion 19 having a curvature radius of 0.03 to 0.2 mm is formed.

By forming the rounded portions 15 and 18 and the minute rounded portions 16 and 19 on the ridges in this manner, even when the ceramic substrates 10 collide with each other, the effect of preventing chipping and cracking can be enhanced. In addition, in order to prevent chipping and cracking, the rounded portions 15 and 18 are more important, and the minute rounded portions 16 and 19 do not particularly need to have a large radius of curvature, so that processing is facilitated. There is a slight roundness.

Further, the rounded portion 18 on the lower surface 12 has a larger radius of curvature than the rounded portion 15 on the upper surface, but this facilitates removal after press molding during the manufacturing process as described later. To do that.

Furthermore, the formation of steps 14, 17 is necessary to easily form the rounded parts 15, 18 by press molding, and disperses the impact even in the case of collision, preventing the occurrence of large chips To do that. For that purpose, the widths t ₁ , t ₃ of these steps 14, 17 need to be 0.08 mm or more, especially 0.3
Those having a thickness of ~ 0.35 mm were excellent in the effect of preventing chipping. Further, the heights t ₂ and t ₄ of the steps 14 and 17 of 0.1 to 0.3 mm were excellent.

Here, a method for manufacturing the ceramic substrate 10 will be described. First, a ceramic raw material powder prepared by adding a predetermined sintering aid and a binder to a ceramic powder such as alumina is prepared, and is formed into a substrate shape by a press forming machine. As shown in FIG. 3, this press molding machine has a die 31,
An upper punch 32 and a lower punch 33 are formed.A protrusion 32a and a round forming portion 32b are formed on the outer periphery of the upper punch 32, and a protrusion 33a and a round forming portion 33b are formed on the outer periphery of the lower punch 33, respectively. The raw material powder 34 can be formed into a shape having the steps 14, 17 and the rounded portions 15, 18 only by press forming.

When removing the compact after pressing, use the lower punch 33
The molded body is raised on the die 31 and extruded from the side, but since the rounded portion 18 on the lower surface 12 has a large radius of curvature as described above, this portion is easy to take out without getting caught. It has become.

Next, the formed body is fired under predetermined conditions, and finally, barrel polishing is performed to form the fine round portions 16, 19, whereby the ceramic substrate 10 is completed.

Experimental Example In the ceramic substrate 10 of the present invention, as described above, the radius of curvature of the round portions 15 and 18 is a very important problem. Therefore, as shown in Table 1 below, prototypes were manufactured with variously changed radii of curvature of the rounded portions 15 and 18, and the occurrence rate of chips when an impact test was performed and the ease of removal after press molding were examined. Was. The results are shown in Table 1.

The ceramic substrate was made of alumina ceramic and had a size of 19 mm × 6 mm × 2 mm.

Furthermore, in the impact test, 200 samples were prepared, and 6 samples were stored in a hollow plastic semiconductor package holding tube having a length of 60 cm.
After 25 rotations at an angular speed of 90 degrees / second, the incidence was examined for each crack size. Further, the ease of removal after press molding was evaluated as ○ when smooth removal was possible without any problem, × when it was difficult to remove due to snagging, and Δ when intermediate between these.

As shown in Table 1, Sample 1 had no step or rounded portion at all, and had a high incidence of large chips.

Next, in Sample 2, the rounded portions 15 and 18 had a radius of curvature of 0.07 mm, but the chipping rate was high, and it was difficult to remove after press molding. Further, the sample 3 has a rounded portion on the upper surface side.
Only 15 had a radius of curvature of 0.2 mm, and although the incidence of chipping was slightly lower, it was still insufficient.

On the other hand, in Sample 4, both the upper and lower rounded portions 15, 18 had a radius of curvature of 0.2 mm, and in particular, 0.6 mm.
Since the above-mentioned chipping rate was very low, the level reached no problem in practical use. However, even with this sample 4, it was somewhat difficult to take out after press molding. Therefore, when the radius of curvature of only the rounded portion 18 on the lower surface was increased to 0.5 mm or more as in Samples 5 and 6, removal after press molding could be facilitated while maintaining a low chip generation rate.

Summarizing the above results, in order to reduce the chip generation rate of the ceramic substrate 10 and make it a practically sufficient level, the radius of curvature of the rounded portions 15, 18 on the upper surface side and the lower surface side should be 0.2 mm or more. In addition, in order to facilitate removal after press molding, it is better to use a rounded portion 18 on the lower surface side with a radius of curvature of 0.5 mm or more, which is larger than the rounded portion 15 on the upper surface side.

Furthermore, increasing the radius of curvature of the rounded portions 15 and 18 causes a problem of adversely affecting the dimensional accuracy and the like of the ceramic substrate 10 itself. If the radius of curvature of the rounded portion 15 is in the range of 0.2 to 1 mm, there is no problem, and particularly, the radius of curvature of 0.2 to 0.4 mm is excellent. Also, the radius of curvature of the rounded portion 18 on the lower surface side was set to 0.5 to 1 mm, which was excellent.

Further, in the above embodiments, only the ceramic substrate for the plug-in type semiconductor package has been described, but the same applies to the ceramic substrate for other semiconductor packages and the printed wiring board.

〔The invention's effect〕

As described above, according to the present invention, in a substrate made of ceramic, a ridge portion between the upper surface and the outer peripheral surface that are the upper punch side during press molding has a minute step and a radius of curvature continuous with the upper surface of 0.2 to 1.0. By forming a rounded portion of mm, and at the ridge of the lower surface and the outer peripheral surface on the lower punch side, by forming a rounded portion with a small step and a radius of curvature continuous with the lower surface of 0.5 to 1.0 mm, respectively, The effect of preventing chipping and cracking during the transportation and assembly processes can be greatly increased, and the radius of curvature of the rounded portion on the lower side is 0.5 mm or more, which is larger than that on the upper side, so press molding The subsequent removal is also facilitated, the yield can be improved, and a ceramic substrate excellent in quality and reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a ceramic substrate for a semiconductor package according to an embodiment of the present invention, and FIG.
It is an X-ray sectional view. FIG. 3 is a sectional view showing a pressing device for forming the ceramic substrate of the present invention. FIG. 4 is a sectional view showing a conventional ceramic substrate for a semiconductor package. 10: ceramic substrate, 11: upper surface 12: lower surface, 13: outer peripheral surface 14, 17: step, 15, 18, ... rounded portion

Claims (1)

(57) [Claims] In a substrate made of ceramics, a ridge between an upper surface and an outer peripheral surface which is an upper punch side at the time of press molding is provided.
The radius of curvature continuing from the minute step and the upper surface is 0.2 to 1.0 mm
In addition to forming the rounded portion, the ridge portion between the lower surface and the outer peripheral surface on the side of the lower punch, a minute step and a rounded portion having a radius of curvature continuous with the lower surface of 0.5 to 1.0 mm are formed. Ceramic substrate.