Wiring substrate using embedding resin

Details Wiring substrate using embedding resin Wiring substrate using embedding resin

2001-12-27

2004-08-03

Williams, Alexander Oscar (Department: 2826)

Active solid-state devices (e.g., transistors, solid-state diode

Housing or package

With contact or lead

C257S701000, C257S758000, C257S774000, C257S668000, C257S680000, C257S698000, C428S209000, C523S427000, C523S428000, C523S429000, C523S434000, C525S526000, C525S109000, C525S113000, C525S423000, C525S438000

Reexamination Certificate

active

06770965

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an embedding resin for embedding electronic parts such as chip capacitors, chip inductors, chip resistances, etc., in the inside of a substrate and to a wiring substrate (wiring board) having electronic parts embedded in the inside of the substrate using the resin. Particularly, the invention is suitable for a multilayer wiring substrate, a package for containing (receiving) a semiconductor element, etc.
2. Description of the Related Art
Recently a multichip module (MCM) mounting many semiconductor elements on a build-up wiring substrate has been investigated. In the case of mounting electronic parts such as chip capacitors, chip inductors, chip resistances, etc., it is general to surface-mounting the electronic parts on a wiring layer for mounting formed on the surface of a wiring substrate using a solder.
However, when electronic parts are surface-mounted on the surface of a build-up wiring substrate, definite mounting area for various electronic parts is required, whereby there is, as a matter of course, a limit for the miniaturization. Also, by treating a wiring in the case of carrying out surface mounting, the occurrence of a parasitic inductance, which is undesirable for characteristics, is increased and there is a problem that the correspondence of electronic instruments to high frequency becomes difficult.
For solving these various problems, various methods or embedding electronic parts in the inside of a substrate have been investigated. For example, Japanese Patent Laid-Open No. 126978/1999 discloses a method of, after previously solder-mounting electronic parts to a wiring substrate having a transfer sheet made of a metal foil, transferring the electronic parts, but there remains a problem in the position precision, etc., at mounting. Also, Japanese Patent Laid-Open No. 124352/2000 disclosed a multilayer wiring substrate obtained by build-upping an insulating layer on electronic parts embedded in the inside of a core substrate.
In the method of embedding electronic parts in the inside of an insulating substrate such as a core substrate, etc., it is necessary that the gaps between the insulating substrate and the electronic parts are embedded with an embedding resin, and further a wiring layer formed on the insulating layer built-up thereon is electrically connected to the electrodes of the electronic parts by electroless plating, etc. In this case, for insuring the reliability of the connection, it is necessary to fill also fine gaps between the electrodes of the electronic parts with the embedding resin. For the purpose, it is necessary that the embedding resin has a low viscosity. Moreover, when the using environment is considered, it is necessary to prolong the usable time (the time of maintaining the good treating property of the embedding resin even when the curing reaction proceeds to some extent).
As a method of controlling the viscosity of the embedding resin, there are largely two methods. Practically, there are a method of controlling the addition amount of a filler and a method of using a curing agent having a slow curing rate.
In general, when the addition amount of a filler is reduced, the viscosity of the resin can be lowered. However, for preventing the occurrence of a trouble caused by the difference of the thermal expansion coefficient between materials, it is necessary to match the thermal expansion coefficient of the embedding resin with the expansion coefficient of a material, which becomes the core substrate or the build-up material to some extent. For the purpose, the addition of at least a definite amount of a filler is necessary. As described above, by only controlling the addition amount of filler, it was difficult to obtain both lowering the viscosity and obtaining the reliability.
SUMMARY OF THE INVENTION
An object of the invention is to provide an embedding resin capable of realizing both lowering of the viscosity and obtaining a high reliability by matching of thermal expansion coefficients.
Another object of the invention is to provide a wiring substrate wherein electronic parts disposed in the inside of an opening formed in an insulating substrate embedded therein using the embedding resin.
That is, the embedding resin of the invention is an embedding resin containing a thermoplastic resin, an acid anhydride curing agent, a curing accelerator, and a filler, wherein the viscosity thereof after allowing to stand for 24 hours at 25° C.±1° C. can be maintained at not higher 85 Pa·s in a shear rate of 8.4 s
−1
.
Then, the invention is explained in detail.
About the embedding resin, when the using method thereof is considered, it is necessary to lower the viscosity thereof in one part liquid state of the mixture of the resin component, the acid anhydride curing agent, the curing accelerator, and the filler. In this case, when the workability such as filling property, etc., is considered, the embedding resin, which can maintain the viscosity thereof after allowing to stand for 24 hours at 25° C.±1° C. at not higher than 85 Pa·s, preferably not higher than 60 Pa·s, and more preferably not higher than 45 Pa·s in a shear rate of 8.4 s
−1
, is preferred. More preferably, the embedding resin, which can maintain the viscosity thereof after allowing to stand for 48 hours at 25° C.±1° C. at not higher than 85 Pa·s, preferably not higher than 60 Pa·s, and more preferably not higher than 45 Pa·s in a shear rate of 8.4 s
−1
, is preferred. By selecting the material, which can maintain the low viscosity for a long time, the increase of the viscosity during working at normal temperature can be restrained, whereby the occurrence of troubles such as inferior filling, etc., can be prevented and the yield can be improved.
The amount of the resin component (thermoplastic resin) is preferably 10 to 45 wt %, more preferably 10 to 23 wt %, based on the embedding resin.
As the curing agent, it is preferred to use the acid anhydride curing agent the viscosity of which at 25° C.±1° C. is not higher than 170 mPa·s, preferably not higher than 100 mPa·s, and more preferably not higher than 60 mPa·s. The acid anhydride curing agent is a material contributing to lower the viscosity of the embedding resin. By using the curing agent having the viscosity as low as possible, the viscosity of the embedding resin itself can be lowered. In addition, since the acid anhydride curing agent having a viscosity of not higher than 170 mPa·s shows the behavior as Newtonian flow different from the embedding resin, the viscosity is not largely fluctuated by the change of a shear rate. Accordingly, the viscosity of the curing agent may be measured by a shear rate different from the shear rate (8.4 s
−1
) at measuring the embedding resin.
Also, by using the curing agent having a very low viscosity, even when the curing reaction of the embedding resin proceed to some extent, the curing agent can be used at the low viscosity. (that is, the usable time is long). As the result thereof, the effects of improving the workability and capable of preventing the entrance of bubbles at filling the embedding resin are obtained. Also, since by using the curing agent having a low viscosity, the viscosity of the embedding resin can be lowered, it is desirable to use the curing agent having a low viscosity.
As the acid anhydride curing agent, phthalic anhydride-base curing agents are preferred. Particularly, methyltetrahydrophthalic anhydride or methylhexahydrophthallic anhydride is preferred because of the high storage stability.
The amount of the curing agent is preferably 10 to 45 wt %, more preferably 10 to 26.5 wt %, based on the embedding resin.
The amount of the curing accelerator is preferably 0.02 to 3.5 wt %, based on the embedding resin.
In the embedding resin of the invention, by appropriately controlling the content of the filler, the filling property thereof can be more effectively improved. The preferred content of the filler is from 45 to 90% by weight,

Affiliated with

Also associated with

Rating

Wiring substrate using embedding resin does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Wiring substrate using embedding resin, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wiring substrate using embedding resin will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3277267