Package for semiconductors, and semiconductor module that...

Details Package for semiconductors, and semiconductor module that... Package for semiconductors, and semiconductor module that...

1999-01-12

2002-01-01

Picard, Leo P. (Department: 2835)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C361S710000, C361S714000, C257S717000, C165S080300

Reexamination Certificate

active

06335863

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a package for semiconductors, and more specifically to a highly heat-dissipating package for semiconductors that is used to mount high-output, highly heat-generative elements such as high-output transistors and microwave monolithic ICs (MMICs). The present invention further relates to a semiconductor module that mounts a semiconductor element or semiconductor elements on the package.
2. Description of the Background Art
As the output of semiconductor elements and operating frequencies increases, the heat generated by these elements increases. Great market demands for the miniaturization and reduction of weight of electronic devices cause the continual increase in the density of semiconductor elements. The increase in the heat generated by semiconductor elements combined with the mounting density further intensifies the need requirement for improving the heat dissipating characteristic of modules that mount these semiconductor elements.
Modules required to have such a high heat dissipation have a substrate comprising highly heat-conductive materials as the heat sink to mount semiconductor elements and effectively dissipate the heat from the elements, so as to prevent overheating of the elements. (See U.S. Pat. No. 4,788,627 and unexamined Japanese patent application Tokukaihei 7-99268.) The substrate is then bonded onto a metallic member, and sealed hermetically as required.
A typical example of a semiconductor for package which is used for such a conventional semiconductor module is shown in
FIGS. 3 and 4
.
FIG. 3
shows a perspective view of the package for semiconductors. FIG.
4
(
a
) is a sectional view of the package shown in
FIG. 3
, and FIG.
4
(
b
) a plan view. Mounted on a metallic member
11
, a substrate
12
has an area
15
for mounting semiconductor elements on the top thereof. The area
15
is surrounded by via holes
14
that are electrically connected to the metallic member
11
below. Lead frames
13
are attached to edge portions opposite each other on the substrate
12
through metallized layers
16
.
In conventional semiconductor modules, beryllia (BeO) has been widely used as a substrate for mounting high-output transistors, MMICs, or other high-output semiconductor elements that generate a large amount of heat, because BeO has superior heat conductivity and dielectric characteristics.
However, the above-described circumstances, the continual increase in the heat generated by semiconductor elements and in mounting density, cause even semiconductor modules employing highly heat-conductive BeO as the substrate to become insufficient in heat dissipation. Although an attempt is made to lower the thermal resistance by reducing the thickness of the BeO substrate, the thickness has already reached its lower limit considering that BeO itself has poor machinability as well as toxicity.
Diamond, on the other hand, has a higher thermal conductivity than any other substances and is an ultimate material for reducing the heat resistance of the semiconductor modules described above. It also has a comparable dielectric characteristic to that of conventional substrate materials such as BeO, alumina, and AlN. (See unexamined Japanese patent application Tokukaihei 4-343232.) Diamond, however, is too expensive to meet the requirement that these modules must employ components at minimal cost.
Diamond has another drawback in that it has a smaller coefficient of thermal expansion than a semiconductor element, so that cracks tend to develop in a semiconductor element during the soldering process for mounting the element on a diamond substrate. When an MMIC is to be mounted, via holes are provided in the substrate to reduce the inductance of the grounding circuit of the device. Due to diamond's poor machinability, machining cost increases drastically. In addition, when lead frames are attached to diamond directly, the lead frames are easily detached due to weak bonding between the lead frames and diamond.
SUMMARY OF THE INVENTION
In consideration of the foregoing circumstances, it is an object of the present invention to provide a low-cost package for semiconductors and a semiconductor module employing the package that is free from toxicity, safe in production, superior in heat dissipation, and able to prevent the cracking of semiconductor elements at the time of mounting.
In order to fulfill the above object, the present invention provides a package for semiconductors that comprises a chemical vapor-deposition (CVD) diamond substrate for mounting semiconductor elements on top of it and a highly heat-conductive metallic member bonded with the diamond substrate at the substrate's surface opposite to that for mounting semiconductor elements, the metallic member having protuberances around the diamond substrate, with the protuberances reaching the top of the diamond substrate.
The present invention further provides another package for semiconductors that comprises a base material, having thermal conductivity of 100 W/m·K or more, for mounting semiconductor elements; a CVD diamond layer formed on a part or the whole of the base material's surface at the side for mounting semiconductor elements; and a highly heat-conductive metallic member bonded with the base material at the base material's surface opposite to that for mounting semiconductor elements, the metallic member having protuberances around the base material provided with the diamond layer, with the protuberances reaching the top of the diamond layer. In this case, it is desirable that the base material comprise at least one kind selected from the group consisting of Si, AlN, SiC, Cu—W alloy, Cu—Mo alloy, and Cu—W—Mo alloy.
In either of the foregoing packages for semiconductors, a ceramic member made of or mainly consisting of alumina (Al
2
O
3
) may be provided at the bonding places of the lead frames for the package. On the surface for mounting semiconductor elements of the CVD diamond substrate or layer, laminated wiring layers comprising a plurality of combinations of an insulating layer having a dielectric constant of 5 or less and a metallic wiring layer may be formed.
The semiconductor module offered by the present invention mounts a high-output semiconductor element or high-output semiconductor elements on the surface for mounting semiconductor elements of the CVD diamond substrate or the CVD diamond layer formed on the top of the base material of the above-described packages for semiconductors.
The present invention, employing the CVD diamond substrate or the highly heat-conductive base material having the CVD diamond layer on it as the substrate for mounting semiconductor elements, provides a package for semiconductors that is safe in production due to the exclusion of toxic BeO, superior in heat dissipation with low thermal resistance, and able to prevent the cracking of a semiconductor element at the time of mounting.
Particularly, the substrate for mounting semiconductor elements that has a thin CVD diamond layer on the highly heat-conductive base material causes the effective coefficient of thermal expansion of the top region to increase, more reliably preventing the cracking of semiconductor elements mounted on the same.
The provision of protuberances on the metallic member facilitates the extension of the ground potential with low inductance, and enables the production of semiconductor modules free from leakage of microwaves and millimeter waves, providing an environment where even high-output, highly heat-generating semiconductor elements such as MMICs operate stably.
DETAILED DESCRIPTION OF THE INVENTION
For a substrate for mounting semiconductor elements, the present invention employs either a CVD diamond substrate made of an independent diamond lamina formed by vapor-phase synthesis or a base material, having thermal conductivity of 100 W/m·K or more, with a CVD diamond layer formed on the surface thereof. The CVD diamond, which has been specially developed in recent years, can be synthesized wit

Affiliated with

Also associated with

Rating

Package for semiconductors, and semiconductor module that... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Package for semiconductors, and semiconductor module that..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Package for semiconductors, and semiconductor module that... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2832702