Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Solder wettable contact – lead – or bond
Reexamination Certificate
2001-08-20
2003-02-04
Lam, Cathy (Department: 1775)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Solder wettable contact, lead, or bond
C257S736000, C257S772000, C257S774000, C257S776000, C257S781000, C257S786000, C257S792000
Reexamination Certificate
active
06515372
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a structure of a wiring board (or a circuit board), a producing method thereof, a semiconductor device, a producing method thereof, which are used i n common electronic apparatuses each comprising a board(s) carrying an LSI(s), and an electronic apparatus, especially the same as above and a semiconductor device package structure which are suitable for such electronic apparatuses which are required to meet the compatibility between high reliability and a lower manufacturing cost.
BACKGROUND ART
Such a conventional wiring board c an be seen in JP-A-62-263661.
According to the prior art, the multi-layered metal structure of which layers are interconnected with one another on a board and which comprises a bond layer consisting of an element selected from the group of Ti, Ba, Cr a nd Ta, which is deposited on the board, a stress relaxation layer consisting of an element selected from the group of Cu, Fe, Al, Ag, Ni and Au, which is deposited on the bond layer, a barrier layer consisting of Ti or Zr and a wettable surface layer.
In the case where a solder is brought into direct contact with a wiring layer in order to connect a wiring board with an outer circuit, there will occur a phenomenon that composition elements of the solder and the wiring layer migrate each other between them during soldering or by a change with the passage of time after soldering resulting in loss of component elements of a wiring material (so called “solder damage”). Since an alloy layer is produced from the elements derived from the solder and the wiring layer under the phenomenon, there will arise a problem of harmful effects that the bonding part becomes brittle and of high electric resistance. If the “solder damage” further develops, the solder reaches the bottom face of the wiring material to deteriorate adhesion between the wiring material and an under layer so that the bonding part is delaminated from the under layer resulting in a defective product.
Therefore, in order to prevent occurrence of the above defect at the bending portion by soldering, the following two countermeasures have been usually adopted.
One method thereof is to prevent the solder from reaching the bottom face of the wiring material during the producing method and operation of the apparatus by making the wiring material thick.
Another method is to protect the wiring from the solder by providing a protective coating onto the wiring, which has high resistance against the solder damage, and by stopping the migration due to the solder within the protective coating.
The former method of making the wiring material thick does not solve the problem of strength reduction due to the formation of the alloy layer produced at the bonding part and causes some technical difficulties in other processes including a process of forming an insulation layer and another forming process because of an increase of the thickness of the wiring material.
In case of forming the protective coating layer with high resistance against the solder, namely the solder diffusion barrier layer called the UBM (Under Bump Material) or BLM (Ball Limiting Metallurgy) according to the latter method, a metal layer which is not usually used for wiring materials, for example, Ni, Ni—Cr, Ni—Cu, Pt, etc. must be additionally formed and processed so that the process steps increase and a higher level technology will be required.
On the other hand, because of demands for higher performance and more multi-function of electronic apparatuses, the total length of the wiring to be accommodated in the wiring board used for them is rapidly increasing so that the wiring becomes further finer and a further advanced multi-layer is required. Furthermore, in view of transfer quality of signals in a wiring board, requirements for the form of wiring and the positional accuracy of wiring, etc. become more strict and severer so that, for keeping the function at connecting portions with outside as stated in the above, it becomes difficult to change specifications for wiring. Therefore, in case of advanced electronic apparatuses, specifications for wiring are determined on the basis of electrical characteristics so that a structure, in which connecting electrodes with a material having higher resistance against the solder damage are provided to another layer, is becoming the main current.But, such a structure has a problem that process steps increase and a higher level technology is required leading to a remarkably higher production cost.
Further, with regard to the fine wiring on wiring boards hereafter, it will be necessary to apply soldering to a wiring board with solder-connecting electrodes each having a small surface area, which is called “micro-soldering”. Especially, for a metal composition and a thickness of the UBM and forming thereof, a much higher level technology will be required in the future.
DISCLOSURE OF INVENTION
An object of the invention is to provide a wiring board and a semiconductor device having a high density and high reliability in solder-connecting.
Another object of the invention is to provide methods of producing a wiring board and a semiconductor device in which the wiring board and the semiconductor device each having a high density and high reliability in solder-connecting can be produced at a low cost.
A still further object of the invention is to provide an electronic apparatus and a semiconductor device package structure which have a wiring board and a semiconductor device each having a high density and high reliability in solder-connecting and being capable of a low cost production.
Under the objects, according to the present invention, there is provided a wiring board which comprises:
an insulation layer formed on the wiring board; and
a wiring consisting of a Cu layer and a Cr or Ti layer which is arranged between the Cu layer and the insulation layer under the Cu layer in order to closely connect the Cu layer with the insulation layer, wherein
a solder for the outer connection is provided on the Cu layer and brought to diffuse into the Cu layer to produce an alloy, and brought to reach the Cr or Ti layer thereby connecting the solder to the Cr or Ti layer.
According to the present invention, there is provided also a wiring board which comprises:
a board having an electrode and being coated with an insulation layer with a hole for exposing the electrode;
a wiring consisting of a Cr or Ti layer, which is connected to the electrode and closely contacts with the insulation layer, and a Cu layer which is closely contacts with the Cr or Ti layer;
a protective film which covers the wiring and is provided with another hole for soldering; and
a solder for the outer connection which is mounted in the both holes and brought to diffuse into the Cu layer to produce an alloy, and which reaches the Cr or Ti layer thereby connecting the solder to the Cr or Ti layer.
The followings are preferable embodiments of the invention:
The solder for the outer connection used in the wiring board may comprise Sn.
The Cu layer in the wiring board may have a thickness of from about 0.1 &mgr;m to about 10 ∞m.
In the wiring board, the Cr layer may be provided between the Cu layer and the insulation layer.
The insulation layer in the wiring board may comprise an organic resin layer.
The solder for the outer connection used in the wiring board may be directly connected to the wiring layer which is connected to the electrode on the wiring board.
An Au layer, an Ni—Au layer or a rust prevention layer such as preflux may be provided between the solder for the outer connection and the Cu layer in the wiring board in order to improve wettability of the solder.
According to the invention, there is provided also an electronic apparatus in which a solder for the outer connection in a wiring board is connected to electronic components.
According to the invention, there is provided also a method of producing a wiring board, which comprises the following steps:
a step of forming an insulation layer on a wiring board;
a step of forming a wiring, in wh
Itou Mitsuko
Narizuka Yasumori
Tenmei Hiroyuki
Yamaguchi Yoshihide
Lam Cathy
Townsend and Townsend / and Crew LLP
LandOfFree
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