Substrate for mounting element and process for its production

Abstract

To provide a substrate for mounting element having sulfurization resistance improved by increasing planarity of the surface of a thick conductor layer.The substrate 10 for mounting element of the present invention has such a structure that on a surface of a LTCC substrate or ceramics substrate as an inorganic insulating substrate 1, a thick conductor layer 2 is formed as an element connection terminal. The thick conductor layer 2 is made of a metal composed mainly of silver (Ag) or copper (Cu) and formed by printing and firing a metal paste. This thick conductor layer has its surface planarized by wet blast treatment to a surface roughness Ra of at most 0.02 μm. A Ni / Au-plated layer 3 is formed on the thick conductor layer 2, so that the surface of the thick conductor layer 2 is completely covered without any space.

Description

TECHNICAL FIELD[0001]The present invention relates to a substrate for mounting element and a process for its production, particularly to a substrate for mounting element excellent in sulfurization resistance, wherein planarity of a surface of a thick conductor layer formed on the substrate surface is good, and a process for producing such a substrate.BACKGROUND ART[0002]In recent years, along with a tendency to a high brightness and whitening of a light-emitting diode (hereinafter referred to as LED) element, a light-emitting device employing a LED element has been used for backlights of mobile phones or liquid crystal TVs or liquid crystal displays, generic illumination, etc. Accordingly, peripheral components of a LED element are also required to have higher performance. For example, as a substrate to mount a LED element, one made of a resin material is used. However, such a resin substrate is likely to be deteriorated by a heat or light accompanying higher brightness of a LED ele...

AI Technical Summary

Benefits of technology

[0019]According to the present invention, the thick conductor layer made of a metal such as silver (Ag) or copper (Cu) formed on the surface of the inorganic insulating substrate, is planarized (smoothed) by the wet blast treatment, and spaces among the thick conductor (Ag) particles are filled and the surface roughness Ra is adjusted to be at most 0.02 μm, whereby the plating property is good, and the thick conductor surface can be completely covered even by a Au-plated layer having a usual thickness. Thus, it is possible to obtain a substrate for mounting element, which is excellent in sulfurization resistance.

Problems solved by technology

However, such a resin substrate is likely to be deteriorated by a heat or light accompanying higher brightness of a LED element.

However, in recent years, a substrate to mount a LED element or the like, is required to have sulfurization resistance, and with conventional plated thicknesses (Ni-plated thickness of from 3 to 5 μm / Au-plated thickness of from 0.1 to 0.3 μm) required for the wiring bonding portions, there has been a problem that a color change to black is observed at the Ni / Au-plated portion in a sulfurization test in accordance with JIS-C-60068-2-43, thus failing to pass the sulfurization test.

However, the method of forming a thick Au layer or increasing the thickness of the Au-plated layer has had a problem that the production cost increases substantially.

Further, in the case of the LTCC substrate, there has been a problem such that if the sintering property is improved by reducing the particle size of the Ag powder, timing in shrinkage by firing will not meet with the substrate whereby the substrate is likely to undergo warpage.

However, by this method, it was not possible to increase the sulfurization resistance by removing the grain boundary void spaces or surface irregularities of the thick conductor (Ag) layer.

That is, although Patent Document 1 does not disclose the conditions for the wet blast treatment in detail, the blast treatment to remove glass is one to break and remove glass as a hard substance in a short time by blasting.

Under blast treatment conditions for such a purpose, it has been difficult to fill spaces among the conductor (Ag) particles.

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