Electricity: conductors and insulators – Boxes and housings – Hermetic sealed envelope type
Reexamination Certificate
2000-02-07
2001-08-28
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Boxes and housings
Hermetic sealed envelope type
C174S050510, C174S262000, C174S266000, C216S017000, C216S018000, C438S667000
Reexamination Certificate
active
06281436
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an improvement in the air-tightness of an electronic part in which an electronic part element is air-tightly encapsulated with a resin wiring substrate and a resin material, particularly to an encapsulation structure of an encapsulated surface-mounting electronic part, suitable for hermetically encapsulating a piezoelectric element such as a surface acoustic wave device in a cavity. That is, the encapsulated surface-mounting electronic part of the present invention has an encapsulated cavity region (vacuum or gas region) and comes under a technical field different from that of resin molding or resin casting for simply shielding an electronic part element from atmosphere.
TECHNICAL BACKGROUND
For shielding an electronic part which performs mechanical vibration (e.g., a piezoelectric element, a magnetostrictor or other movable part) from atmosphere and electrically connecting it to an external circuit to utilize the function thereof, generally, a so-called cavity encapsulation in which a space (vacuum or gas) is formed around the part is required instead of an encapsulation called molding, resin encapsulation or resin casting.
Conventionally, the cavity encapsulation is mainly carried out by means of hermetical sealing with a ceramic case, and recently, from the viewpoint of economic performances, the method of hermetical sealing with a resin material is also proposed in JP-A-9-148477, and the like.
As one example,
FIGS. 4 and 5
show the outline of the structure of hermetical sealing with a conventional resin material, carried out by the present inventor. In these Figures,
1
indicates a resin wiring substrate, and an electronic part element
5
is spliced and fixed onto the resin wiring substrate
1
through a junction member (e.g., gold)
6
. The electronic part element
5
is connected to an outside with a conductor on the wiring substrate
1
and via a through hole
4
formed in the wiring substrate
1
as an electrically conductive through hole.
2
indicates a resin frame substrate, a space necessary for housing the electronic part element
5
is made, a resin cover substrate
3
is placed thereon, and the wiring substrate
1
and the frame substrate
2
, and the frame substrate
2
and the cover substrate
3
, are hermetically bonded to each other with an adhesive. Then, the resultant set is cut in cutting positions Z to obtain individual electronic parts as shown in FIG.
5
. With the conductor on the wiring substrate
1
, the through hole
4
is connected to the electronic part element
5
housed in a cavity
7
surrounded by the wiring substrate
1
, the frame substrate
2
and the cover substrate
3
, whereby a surface-mounting electronic part using a semi-cylindrically cut through hole surface
4
a
as a side electrode for external connection can be constituted, and the function of the electronic part element
5
housed inside can be worked by connecting the through hole surface
4
a
to an external circuit.
FIGS. 6 and 7
show enlarged views of a through hole portion of the hermetical sealing structure formed of a resin material shown in
FIGS. 4 and 5
. In the through hole
4
, a Cu plating layer
12
is coated on an inner circumferential surface by Cu plating, and an Au plating layer
13
as an uppermost layer is coated thereon through an Ni plating layer (not shown) by Au plating, for the purpose of electrically connecting conductors
10
and
11
(e.g., Cu copper foil patterns attached to the substrate) on upper and lower surfaces of the resin wiring substrate
1
.
The purpose in the Au plating is to form a chemically stable surface so that the soldering performance is not degraded when the above surface mounting electronic part is exposed to atmosphere for a long period of time, since the inner surface of the through hole
4
and the external connection surface (lower side in Figure) of the wiring substrate
1
constitute soldering surfaces when the part is used. In this case, land pads l
0
a
and
11
a
are provided on both sides of the through hole
4
for easy plating on the interior of the through hole and securing the reliability of connection to the patterns on the wiring substrate
1
. These land pads lO
a
and
11
a
are constituted as annular portions integrally formed on end portions of the conductors
10
and
11
on the upper and lower surfaces of the resin wiring substrate
1
so as to surround the entire circumferences of peripheries of the above through hole
4
. Further, the above Cu plating layer
12
to the above Au plating layer
13
as an uppermost layer are laminate-formed by the above plating procedures.
In
FIGS. 6 and 7
, those portions which are the same as those in
FIGS. 4 and 5
are indicated by the same symbols.
DISCLOSURE OF THE INVENTION
Meanwhile, when the resin wiring substrate
1
and the resin frame substrate
2
are bonded to each other, each bonding surface is roughened by chemical treatment for improving adhesion. However, the Au land pad surface P which is a bonding surface on the upper surface side of the wiring substrate
1
(A surface formed by coating the Au plating layer
13
on the uppermost layer of the land pad
10
a
) is chemically stable and is not roughened so that it is a surface having decreased bonding reliability. When the wiring substrate
1
having the above Au land pad surface P and the frame substrate
2
are bonded, the minimum bonding surface distance having air-tightness reliability in shielding the cavity
7
from atmosphere is L
1
which is considerably smaller than the entire width L
0
of the bonding surface.
For the above reason, in the structure of cavity sealing according to prior art, it is required to dimensionally increase a product by width dimensions of the Au land pad surface P for securing a necessary L
1
dimension, and when the dimensions of the product are limited, there is a problem that the reliability with regard to air-tightness decreases.
It is also thinkable to employ a method of intra-through-hole plating called a land-less through hole as shown in
FIGS. 8 and 9
for narrowing a through hole pitch. Since, however, the contact area of a wiring pattern (conductor)
15
on each surface of the substrate and a conductor
16
a
on the inner circumference of the through hole
16
is small, the reliability of connection decreases to that degree. For example, the difference thereof is confirmed by a thermal shock test between −40° C. and 85 C. Further, when the through hole
16
is cut in a semi-cylindrical form and used as a side electrode of the above electronic part, there is caused a problem that the intra-through-hole conductor
16
a
may peel off due to a mechanical stress caused during the cutting, or that the terminal strength at the time of soldering to an external circuit decreases, and particularly when the through hole is cut in a semi-cylindrical form to be used as a side electrode for connecting the above part to an outside, the above method is improper.
It is an object of the present invention to improve the reliability of bonding of a resin wiring substrate and a cover member constituting an encapsulated region which surrounds an electronic part element and has a cavity inside, and to subsequently provide an encapsulated surface-mounting electronic part which can be improved in the reliability of air-tight encapsulation.
Other objects and novel characteristic features of the present invention will be made apparent in the mode of practice to be described later.
For achieving the above object, in an encapsulated surface-mounting electronic part in which an electronic part element is mounted on a resin wiring substrate, a cover member is bonded to the above wiring substrate so as to cover said electronic part element thereby to constitute an encapsulation region housing the above electronic part element and having a cavity inside, and a connection conductor path to an external circuit is formed of an electrically conductive through hole or groove made in a cover-member-bonding surface on the above wiring substrate
Gotoh Masashi
Kanazawa Jitsuo
Yamamoto Shuichiro
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Oliva Carmelo
Reichard Dean A.
TDK Corporation
LandOfFree
Encapsulated surface mounting electronic part does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Encapsulated surface mounting electronic part, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Encapsulated surface mounting electronic part will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2539901