JP2001244783A - Surface acoustic wave device and circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave device, provided with a sound absorption member that provides ease of flip-chip connection at a low cost. SOLUTION: A surface acoustic wave element 1 is arranged in such a way that the face of the element 1 toward a transducer 2 is arranged counterposed to a wiring pattern forming face of a base board 6 and is structured such that the surface acoustic wave element 1 is covered and sealed by a cap member 9. The base board is a copper clad circuit board, and a wiring pattern 10 is formed by patterning the copper clad circuit board. The connection part of the wiring pattern with a bump of the surface acoustic wave element 1 is copper-plated after patterning, nickel plating is applied to the copper plating and gold plating is applied to the nickel plating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device used for, for example, a television, and more particularly to a surface acoustic wave device having a sound absorbing material for absorbing surface acoustic waves and an internal connection structure thereof.

[0002]

2. Description of the Related Art A method of connecting a transducer surface of a surface acoustic wave element to a circuit board having a wiring pattern opposed thereto by flip-chip bonding has been known in order to reduce the size and surface mounting of a surface acoustic wave device. I have. The flip chip connection method is a method in which terminals provided on the element surface and terminals provided on the substrate are directly joined to each other without using wires.
A ceramic material is generally used as a substrate material connected to the surface acoustic wave element, and a metal pattern such as tungsten is formed on the surface of the substrate.

For example, in a surface acoustic wave device used for a specific application such as a television, a sound absorbing material is formed on a transducer surface of a surface acoustic wave element and / or a back surface of the element in order to absorb unnecessary surface acoustic waves. . However, if a sound absorbing material is provided on the surface of the surface acoustic wave element on the side facing the substrate, when flip-chip connection is performed, the thickness of the sound absorbing material disturbs the connection between the two terminals, or In some cases, a sufficient connection weight may not be applied. For this reason, a part of the substrate surface facing the sound absorbing material must be cut off or a concave portion must be provided. As described above, a hard material such as a ceramic is used as a material of the substrate, so that processing is troublesome.

[0004]

As described above, when a convex portion such as a sound absorbing material is provided on a surface acoustic wave element so as to face a substrate, it is necessary to process a relatively hard substrate. There is a disadvantage that the manufacturing cost of the surface acoustic wave device increases.

The present invention solves the above problems and provides a low-cost surface acoustic wave device which can be easily flip-chip connected even with a surface acoustic wave device provided with a sound absorbing material, and an internal connection structure thereof. The purpose is to do.

[0006]

A surface acoustic wave device according to the present invention comprises a transducer, a wiring pattern connected to the transducer, a pad provided on a part of the wiring pattern, and a pad formed on the pad. A surface acoustic wave element having a bump;
A base substrate provided with a terminal for connection to the outside on one surface and a wiring pattern connected to the terminal on the other surface, and a concave portion provided on the base substrate and larger than the thickness of the surface acoustic wave element. A cap member having a connection member that electrically and mechanically connects the surface acoustic wave element and the base substrate, and a sealing member that mechanically connects and seals the cap member and the base substrate, The surface of the surface acoustic wave element on the transducer side is disposed so as to face the other surface of the base substrate on which the wiring pattern is formed, and the surface acoustic wave element is covered and sealed by the cap member. Wherein the base substrate is a copper-clad circuit board, and the wiring pattern is formed by patterning the copper-clad circuit board.

In the surface acoustic wave device according to the present invention, a sound absorbing material for absorbing surface acoustic waves is formed on at least the surface of the surface acoustic wave element on which the transducer is formed.

In the surface acoustic wave device according to the present invention, at least a portion of the base substrate connected to the bump portion of the surface acoustic wave element is plated with copper after the patterning.
Further, it has a structure in which nickel plating is performed thereon and gold plating is further performed thereon.

In the surface acoustic wave device of the present invention, copper plating is 15 to 40 μm and nickel plating is 1 to 10 μm.
m, and preferably, gold plating is formed in a thickness of 0.03 to 2 μm.

In the surface acoustic wave device of the present invention, the thickness of the copper foil on the base substrate is A1, the thickness of the Cu plating is A2, and
When the thickness of the i-plate is A3, the thickness of the Au plating is A4, the thickness of the bump is A5, the thickness of the wiring pattern of the surface acoustic wave element is A6, and the maximum thickness of the sound absorbing material is B, A1
+ A2 + A3 + A4 + A5 + A6> B.

Further, in the surface acoustic wave device according to the present invention, there is no wiring pattern on the base substrate in a region facing the sound absorbing material of the surface acoustic wave element.

Further, the surface acoustic wave device according to the present invention is characterized in that there is no wiring pattern on the base substrate in an area facing the transducer of the surface acoustic wave element.

Further, in the surface acoustic wave device according to the present invention, the conductor pattern is arranged in the base substrate region facing the transducer of the surface acoustic wave element.

The internal connection structure of the surface acoustic wave device according to the present invention includes a pad portion connected to a transducer of the surface acoustic wave element, a gold bump formed on the pad portion, and at least a pattern on a base substrate. Copper plating formed on the plated copper wiring portion and nickel plating formed thereon and gold plating formed thereon, electrically connecting the gold bumps and the gold plating and mechanically A conductive adhesive to be fixed.

By using a copper-clad circuit board as the base substrate, patterning of the base substrate can be facilitated, and the thickness can be further increased by plating while maintaining this patterning. Since the upper surface of the base substrate is sealed by the cap member, there is no need to form a coating on the copper foil wiring pattern.

The increase in thickness due to multiple plating can be arbitrarily set by adjusting processing conditions such as plating time.

By forming a pattern having a predetermined thickness that is thicker than the thickness of the sound absorbing material and that includes the multiple plating layers, the sound absorbing material on the surface acoustic wave element comes into contact with the base substrate even in the case of flip-chip connection. Sufficient characteristics as a surface acoustic wave device can be obtained without deterioration.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a surface acoustic wave device according to one embodiment of the present invention. A transducer 2 is formed on the chip surface of the surface acoustic wave element 1, and a wiring pattern 3 and a sound absorbing material 4 are formed on this surface. The wiring pattern 3 is connected to the base substrate 6 via the connection section 5. A plurality of terminals 7 are arranged at an end of the base substrate 6. Further, the surface acoustic wave element 1 includes a transducer 2
Are flip-chip connected to the base substrate 6 so that the wiring pattern is opposed to the wiring pattern on the substrate surface of the base substrate 6. The surface acoustic wave element 1 is surrounded and sealed with the substrate 6 by the cap material 9 and the sealing material 8.

Next, the structure of the connecting portion 5 of the surface acoustic wave device according to the present invention will be described in detail. FIG. 2 is an enlarged sectional view of the connecting portion 5 of FIG.

A Cu (copper) layer 5f is formed by plating on the copper foil wiring pattern 5g of the base substrate 6, a Ni (nickel) layer 5e is formed thereon by plating, and further thereon. An Au (gold) layer 5d is formed.

On the other hand, the surface acoustic wave element 1 has a wiring pad portion 5a electrically connected to the transducer 2. This wiring pad 5a is formed of, for example, aluminum. An Au bump 5b is formed on the wiring pad 5a by a bump bonding method. The bump bonding method is a method of heating a bonding portion and connecting metals by ultrasonic waves and pressure. A conductive adhesive 5c is applied on the Au plating 5d on the base substrate side, and the Au bumps 5b are in contact therewith and are electrically connected.

FIG. 3A is a plan view of the base substrate 6 and FIG.
(B) is a bottom view and a side view. As shown in FIG. 3A, a wiring pattern 10 including a connection portion 5g is formed on the front surface of the base substrate 6, and as shown in FIG.
Are formed. The terminal 7a and the wiring pattern 10 are connected by a through-hole plating 7b. Terminal 7a
Is connected to a pad portion on a circuit board (not shown) to which the surface acoustic wave device is applied. In FIG. 1, for convenience of explanation, the two terminals 7 face each other in the same direction as the left and right sound absorbing members 3, but are actually arranged above the position indicated by the dotted line 4a in FIG. .

The copper-clad base substrate 6 used in the present invention is, for example, a substrate having a thickness of 0.4 mm and copper foil having a thickness of 18 μm on each side. As the material of the substrate, for example, a glass epoxy substrate FR-4 or FR-5, BT resin (bismaleimide triazine resin), or the like is preferable. Although the thickness of this copper foil was 18 μm here,
It may be arbitrarily adjusted in the range of 9 to 100 μm. However,
When a fine wiring pattern is to be formed on the base substrate, a thinner one is preferable in terms of accuracy. 18 μm when used with a surface acoustic wave element having a sound absorbing material
About m is appropriate.

A resist is applied to both sides of the substrate, and only the necessary portions are exposed to pattern the resist. Then, the resist is stripped by dipping in a Cu etching solution to remove a portion of the copper foil. The wiring pattern 10 including the pattern 5g can be formed on a circuit board as shown in FIG. Usually, the width of the pattern is at least about 100 μm.

Subsequently, Cu plating 5f is performed on the formed Cu wiring pattern by about 15 to 35 μm. Further, Ni plating 5e is performed thereon at 5 to 10 μm, and Au plating 5d is further performed thereon at about 0.03 to 2 μm. These may be electrolytic plating or electroless plating. The Au plating on the surface also serves to improve the corrosion resistance.

By doing so, the step "A" between the substrate surface and the patterned metal surface is about 40 to 80 μm in total. At this time, the base substrate 6
It is necessary that a coating such as a solder resist does not exist on the wiring pattern 5g in order to obtain good electrical connection.

FIG. 4 is a cross section showing the relative relationship between the sound absorbing material 4 and the joint 5 of the surface acoustic wave device according to the embodiment of the present invention.
The sound absorbing material 4 prevents the surface acoustic wave generated by the transducer 2 from being reflected at the end of the surface acoustic wave element 1. The sound absorbing material 4 is provided at both ends of the surface acoustic wave element, but may be provided so as to surround the transducer 2. The thickness “B” of the sound absorbing material 4 is different from that of the surface acoustic wave element 1.
Is smaller than the distance “C” between the circuit board 6 and the circuit board 6.

Transducer section 2 of surface acoustic wave element 1
Since the thickness of the sound absorbing material formed on the surface provided with is approximately 40 μm when formed by a normal screen printing method, as shown in FIG.
By making the sound absorbing material 4 of the surface acoustic wave element face the other, the sound absorbing material 4 and the base substrate 6 are both maintained without contact as shown in FIG. If they come into contact with each other, the performance of the surface acoustic wave device 1 may be degraded, and the strength of the contact portion may be reduced to cause damage.

The case where there is no wiring pattern in the region of the base substrate 6 facing the transducer 2 of the surface acoustic wave element 1 and the case where the conductor pattern is arranged are as follows.
Although there is a difference in the performance of the surface acoustic wave device, one of them may be selected with a configuration with less performance degradation.

[0031]

As described above, according to the internal connection structure of a surface acoustic wave device according to the present invention, a surface acoustic wave device having a structure in which a surface acoustic wave element on which a sound absorbing material is formed is flip-chip connected to a base substrate. The wave device can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a surface acoustic wave device according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view of the surface acoustic wave device of FIG.

FIG. 3 shows a wiring pattern and a terminal pattern formed on a base substrate.

FIG. 4 is a sectional view showing the relationship between the thickness of the sound absorbing material and the internal connection structure of the surface acoustic wave device according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 surface acoustic wave element 2 transducer 3 routing wiring pattern 4 sound absorbing material 5 internal connection structure 5a wiring pad 5b Au bump 5c conductive adhesive 5d Au plating layer 5e Ni plating layer 5f Cu plating layer 5g Cu foil 6 base substrate ( (Circuit board) 7 terminal 8 sealing material 9 cap material

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E336 AA04 BB02 BC34 BC36 CC34 CC38 CC58 DD22 DD28 DD35 GG30 5J097 AA04 AA24 AA33 EE07 HA04 HA09 JJ01 JJ09 KK10

Claims (9)

[Claims] 1. A transducer, a wiring pattern connected thereto, a pad portion provided on a part of the wiring pattern, and a surface acoustic wave device having a bump formed on the pad portion. A base substrate provided with a terminal for connection to the outside on one surface, and a wiring pattern connected to the terminal on the other surface; and a concave portion provided on the base substrate and having a thickness larger than the thickness of the surface acoustic wave element. And a connection member for electrically and mechanically connecting the surface acoustic wave element and the base substrate, and a sealing member for mechanically connecting and sealing the cap member and the base substrate. A surface of the surface acoustic wave element on the transducer side is arranged to face the other surface of the base substrate on which the wiring pattern is formed, and the surface acoustic wave element is provided with the cap. Having a structure covered and sealed with a material, wherein the base substrate is a copper-clad circuit board, and the wiring pattern is formed by patterning a copper foil of the circuit board. Surface acoustic wave device. 2. The surface acoustic wave device according to claim 1, wherein a sound absorbing material for absorbing surface acoustic waves is formed on at least a surface of the surface acoustic wave element on which the transducer is formed. 3. The wiring pattern of the base substrate, wherein at least a connection portion between the surface acoustic wave element and the bump portion has a multiple plating layer formed on the copper foil. 3. The surface acoustic wave device according to 1 or 2. 4. The surface acoustic wave device according to claim 1, wherein the multiple plating layer is composed of a copper, nickel, and gold plating layer in order from a lower layer on the copper foil. 5. The copper plating is 15 to 40 μm, the nickel plating is 1 to 10 μm, and the gold plating is
5. The semiconductor device according to claim 4, wherein the thickness is 3 to 2 μm.
The surface acoustic wave device according to claim 1. 6. The surface acoustic wave device according to claim 1, wherein the base substrate is a copper-clad base substrate having no covering on the wiring pattern. 7. The thickness of the copper foil of the base substrate is A1,
The thickness of the copper plating is A2, the thickness of the nickel plating is A3,
4. A1 + A2 + A3 + A4 + A5 + A6> B, where A4 is the thickness of the gold plating, A5 is the thickness of the bump, A6 is the thickness of the wiring pattern of the surface acoustic wave element, and B is the maximum thickness of the sound absorbing material. The surface acoustic wave device according to claim 1. 8. A pad connected to a transducer of a surface acoustic wave element, a gold bump formed on the pad, and a multiplex formed on at least a patterned copper wiring on a base substrate. A surface acoustic wave device comprising: a plating layer; and a conductive adhesive for electrically connecting and mechanically fixing the multiple plating layers and the gold bumps. 9. A circuit board, comprising: an insulating substrate; a metal wiring pattern formed on the insulating substrate; and a multiple plating layer partially provided on the metal wiring pattern.