JPH1117308A - Electronic component packaging structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent crackings around a terminal electrode of an electronic component surface-packaged on a circuit board, and to prevent the breakage of the electronic component and degradation of electric characteristics, even if thermal history such as heating and cooling or an extraneous force is applied to the electronic component, while being used. SOLUTION: In a packaging structure, an electronic component 1 is constructed by packaging terminal electrodes 5 provided on the both ends of a ceramic sintered body 4 on a pair of wiring patterns 3 on an external circuit board 2, by using solders 6. If the line width of the wiring patterns 3 in a solder- packaging portion is Wh, the width of the ceramic sintered body 4 is Ws, the interval between the pair of wiring patterns 3 is Dh, and the interval between the terminal electrodes 5 is De, the relations 1.0<=Wh/Ws<=1.2 and 0.8<=Dh/De<=1.0 is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the mounting of an electronic component such as a multilayer ceramic capacitor having terminal electrodes formed at both ends thereof on the surface of a wiring pattern of an external circuit board by soldering. The present invention relates to a structure having improved strength and durability against thermal stress such as thermal shock.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view of a conventional mounting structure of an electronic component 11 such as a multilayer ceramic capacitor. As shown in FIG. 1, terminal electrodes 12, 12 of an electronic component 11 are conductively connected by solder 15 to wiring patterns 14, 14 of an external electric circuit board or an electronic circuit board (hereinafter, referred to as a circuit board) 13. Was composed. In FIG. 1, reference numeral 16 denotes a dielectric ceramic sintered body. For example, a laminated body is formed by embedding internal electrodes 17 in layers between a plurality of plate-shaped ceramics, and the inside of both ends of the laminated body is formed. Terminal electrodes 12 and 12 mainly composed of silver or the like are formed on the exposed surface of the electrode 17.

[0003] In the conventional mounting structure, the circuit board 13,
Ceramic sintered body 16, terminal electrodes 12, 12, and solder 1
5 have different thermal expansion coefficients, the ceramic sintered body 1 has a difference in thermal expansion and thermal contraction due to thermal shock during heating and cooling by soldering or the like during surface mounting.
6, tensile stress was generated, and cracks were generated near the terminal electrodes 12, 12 of the ceramic sintered body 16. The cracks may be minute at first, in which case the electrical characteristics do not matter at the time of surface mounting on the circuit board 13, but the ambient temperature changes repeatedly apply during use, and the minute cracks gradually grow. The electrical characteristics were degraded.

Therefore, in order to solve the above-mentioned problem, it is proposed to set the length of the terminal electrode to a certain range or less with respect to the entire length of the ceramic sintered body constituting the main body of the ceramic electronic component. (Conventional Example 1: Japanese Patent Laid-Open No.
-294512). Further, a chip-type ceramic electronic component element having external electrodes at both ends of an element body, wherein a metal clip is provided so as to sandwich two opposing surfaces of the chip-type ceramic electronic component element with a spring property in the external electrode portion. A device provided with the same has been proposed (conventional example 2: see Japanese Patent Application Laid-Open No. 7-22269).

[0005]

However, in the above-mentioned conventional example 1, although the electronic components can be firmly surface-mounted on the circuit board by soldering, due to the heat history during use for a long period of time, the electronic parts are formed on the lower side surface of the ceramic sintered body. The generated stress may cause a crack in the vicinity of the terminal electrode portion of the electronic component, and when an external force is applied, the electronic component is broken or the electrical characteristics are deteriorated.

Further, in the conventional example 2, although the expansion and contraction of the circuit board is absorbed by the metal clip and the stress generated in the electronic component element can be reduced, the conductive adhesive for joining the external electrode of the electronic component element and the metal clip is used. There has been a problem that the film is peeled off due to heat history during use for a long period of time, and electrical characteristics are deteriorated.

SUMMARY OF THE INVENTION The present invention has been completed in view of the above circumstances, and an object of the present invention is to enable an electronic component to be firmly surface-mounted on a circuit board by soldering, and to provide a terminal electrode of a ceramic sintered body of the electronic component surface-mounted. Even if a heat history such as heating and cooling or external force is applied to the electronic component during use without cracking near the part, the electronic component will not be damaged or the electrical characteristics will not be deteriorated. To provide.

[0008]

According to the present invention, there is provided a mounting structure of an electronic component comprising terminal electrodes provided at both ends of a ceramic sintered body formed by alternately laminating a plurality of ceramic plates and a plurality of internal electrodes. An electronic component mounting structure mounted on a pair of wiring patterns of an external circuit board by soldering, wherein the line width of the wiring pattern in the solder mounting portion is Wh, and the width of the ceramic sintered body is Ws, when the distance between the pair of wiring patterns is Dh and the distance between the terminal electrodes is De, 1.0 ≦ Wh / Ws ≦ 1.2 and 0.8 ≦ Dh / D
e <1.0, wherein the relationship between the line width of the wiring pattern and the width of the ceramic sintered body constituting the main body of the electronic component, and the distance between the pair of wiring patterns and the terminal electrode By setting the relationship with the distance to the specific range, stress concentration on the ceramic sintered body can be reduced,
The purpose of the present invention is to suppress or prevent crack generation and crack growth under severe thermal conditions during use.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A mounting structure of an electronic component according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view of an electronic component of the present invention, which has a mounting structure in which an electronic component such as a multilayer ceramic capacitor is surface-mounted on a circuit board.

In FIG. 1, reference numeral 1 denotes a plurality of ceramic plates 4.
b and a plurality of internal electrodes 4a alternately laminated, and electronic components such as a ceramic capacitor having a ceramic sintered body 4 as a main body, a multilayer ceramic capacitor, a chip resistor element, and the like.
2 is an external circuit board for surface mounting the electronic component 1,
Reference numerals 3 and 3 denote a pair of wiring patterns formed of Cu, Ag, Au or the like and formed on the circuit board 2 to electrically connect the electronic components 1 to each other. Reference numeral 4 denotes barium titanate (BaTiO ₃ ) and lead titanate (PbTiO ₃ ). , Lead zirconate titanate (PbZr
A ceramic sintered body 4 made of a dielectric ceramic mainly composed of TiO ₃ ) or the like, 4a is a layered Ag, Pd, Ag-Pd alloy, Ni, C
u, etc., 5 and 5 are terminal electrodes provided on both ends of the ceramic sintered body 4 and made of Ag, Cu, Ni, Ag-Pd, etc., and 6 is a terminal pattern
For conductive connection to the wiring, Wh is the wiring pattern 3,3
, Ws is the width of the ceramic sintered body 4, De is the distance between the terminal electrodes 5 and 5, and Dh is the distance between the pair of wiring patterns 3 and 3.

As described above, the electronic component 1 has the terminal electrodes 5 and 5 at both ends of the ceramic sintered body 4, and the terminal electrodes 5 and 5 are conductively connected to the wiring patterns 3 and 3 by the solder 6. , Is surface-mounted on the circuit board 2.

In the present invention, 1.0 ≦ Wh / Ws ≦
1.2 and 0.8 ≦ Dh / De <1.0. When Wh / Ws <1.0, the ceramic sintered body 4 is twisted with respect to the wiring patterns 3 and 3 during surface mounting. It is easy to be connected, and at this time, there is a possibility that a mounting failure such as peeling of the electronic component 1 from the wiring patterns 3 and 3 may occur, and there is a problem in durability. Conversely, when Wh / Ws> 1.2, remarkable stress concentration occurs in the ceramic sintered body 4 and cracks are likely to be generated near the terminal electrodes 5 and 5. Also, Dh / De
If <0.8, the wiring patterns 3 and 3 are likely to be short-circuited. Conversely, if Dh / De ≧ 1.0, significant stress concentration occurs in the ceramic sintered body 4 and 5
Cracks are likely to occur in the vicinity.

More preferably, 1.05 ≦ Wh / Ws ≦
It is preferable that 1.15 and 0.8 ≦ Dh / De ≦ 0.95.

Further, according to the present invention, in the solder mounting portion,
Solder enters between the surface of the wiring patterns 3 and 3 and the terminal electrodes 5 and 5, and the minimum thickness t of the solder is preferably 90 μm or more.
Stress concentration on the substrate can be further reduced. More preferably 95μ
m or more. The upper limit of t is not particularly limited, but is preferably 500 μm or less in order to reduce the amount of solder and prevent displacement during mounting.

The terminal electrodes 5 and 5 preferably have a laminated structure in which a Ni layer, a Sn layer and the like are laminated on an underlayer made of Ag. In this case, the wettability with the solder 6 is improved, and Adhesion to the ceramic sintered bodies 4 of 5, 5 can be enhanced.

As the solder 6, a solder such as a Sn-Pb eutectic solder is suitable in terms of good conductivity, easy mounting process, and the like. In the present invention, any material other than the solder 6 can be used as the solder 6 as long as it is a conductive material that melts when heated to a predetermined temperature and solidifies when the temperature is lowered.

In the ceramic sintered body 4 constituting the main body of the electronic component 1 of the present invention, the corners and ridges of the end faces on which the terminal electrodes 5 and 5 are provided are formed by curved surfaces, so that the stress concentration at the corners is increased. This is desirable in that the generation of cracks can be suppressed by reducing the amount of cracks, which can be easily processed by a known barrel polishing method or the like.

Further, the mounting structure of the electronic component 1 according to the present invention is such that the terminal electrodes 5, 5
Can be applied to not only the above-described multilayer ceramic capacitor but also, for example, a multilayer coil or an LC composite filter having a ceramic sintered body as a constituent member.

Thus, the present invention provides a method for heating and
The circuit board 2, due to thermal stress such as thermal shock during cooling,
Due to the difference in thermal expansion and contraction between the electronic component 1 and the solder 6, stress concentration occurring in the ceramic sintered body 4 can be reduced. As a result, cracks do not occur in the ceramic sintered body 4 and severe conditions in which a large heat history such as heating and cooling is applied during use, or the electronic component 1
Even if an external force is applied, the crack does not develop or the electrical characteristics do not deteriorate, so that the mounting yield and long-term reliability of the electronic component 1 are improved.

It should be noted that the present invention is not limited to the above embodiment, and various changes may be made without departing from the scope of the present invention.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the electronic component mounting structure of the present invention will be described below. Further, the operation and effect of the present invention were confirmed by computer simulation accompanying the present embodiment.

(Embodiment) The mounting structure of the electronic component 1 of FIG. 1 was constructed as follows. A plurality of ceramic plates 4b mainly composed of BaTiO ₃ and a plurality of internal electrodes 4a made of Ag are alternately laminated and sintered (length = 2.0 mm).
× (width Ws = 1.0 mm) × (thickness = 1.0 mm) rectangular ceramic sintered body 4 was produced. This was used as the main body of the multilayer ceramic capacitor. Thereafter, Ag, Ni, and Sn were sequentially baked on both end surfaces to form terminal electrodes 5 and 5, thereby producing a multilayer ceramic capacitor. At this time, the distance De between the terminal electrodes 5 and 5 is 1.0 mm.

The multilayer ceramic capacitor as the electronic component 1 is formed on a pair of wiring patterns 3 and 3 formed on an alumina substrate as a circuit board 2 and made of Sn.
Terminal electrodes 5 and 5 were conductively connected at 230 ° C. and surface-mounted using eutectic solder composed of 63 wt% -Pd 37 wt%.

At this time, Wh / Ws, Dh / De, and t were set to various values, and the results of tests for their reliability are shown in Table 1. Specifically, each structure was subjected to a thermal shock test in which 50 samples of each sample were prepared, and each of the samples was alternately immersed in Galden's solution at -40 ° C and 130 ° C for 5 minutes for one cycle. For up to 2000 cycles. Then, after 500 cycles, 1000 cycles, and 2000 cycles, the number of cracked multilayer ceramic capacitors in the ceramic sintered body 4 was examined by visual inspection using a stereoscopic microscope and penetrant inspection. still,
Numbers 500, 1000, and 20 in the column of the number of cracks in Table 1
00 indicates the number of cycles, and the capacitor in the remarks column means a multilayer ceramic capacitor.

[0025]

[Table 1]

As is clear from the results in Table 1, Wh / W
s <1.0 sample NO. In Examples 1 and 2, although there was no major problem in the thermal shock test, the multilayer ceramic capacitor was peeled off from the wiring patterns 3 and 3. This is probably because the multilayer ceramic capacitor was mounted by being twisted.

Sample No. Wh / Ws> 1.2 In 7,
Cracking was already observed after 500 cycles.

Sample No. Dh / De <0.8 10,1
In No. 5, a short circuit occurred between the wiring patterns after 2,000 cycles.

Sample No. Dh / De ≧ 1.0 14,1
In No. 9, 10 or more defective products were generated after 2000 cycles, and the reliability was poor.

The sample No. having t less than 90 μm. 24
Then, after 2000 cycles, 10 defective products occurred.

Here, after 2,000 cycles of the thermal shock test, a ceramic sintered body in which the cumulative number of cracked ceramic sintered bodies is within 10% of the initial number (50 in this embodiment) has good reliability. When the determination criterion is adopted, the above sample NO. 1,2,7,9,10,14,1
None of the mounting structures 5, 19, 24 and 25 are practical.

On the other hand, the sample No. 3-6,8,1
In Nos. 1 to 13, 16 to 18, and 20 to 23, no electrical short-circuit occurred, and the number of ceramic sintered bodies that had cracks after 2000 cycles of the thermal shock test was within 10% of the initial number. , Proved to be sufficiently reliable.

On the other hand, the present inventor performed a computer simulation for stress analysis by the finite element method in order to confirm the operation and effect of this embodiment.

FIG. 2 shows an example of the 1/4 cut model used for the stress analysis, and the reference numerals in the figure correspond to those in FIG.
In this analysis, in order to carry out the analysis in detail, the following four types of three-dimensional models were created that reproduced the shape of the mounting structure of the multilayer ceramic capacitor used in the example, and the ceramic sintered body 4, the terminal electrodes 5, 5 , Solder 6, wiring patterns 3, 3,
The physical property values of the alumina substrate were input as parameters for each element. In particular, elasto-plastic thermal stress analysis was performed for the solder 6 in consideration of plasticity.

As representative examples of the analysis results, FIGS. 3 to 6 show stress distributions when the ceramic sintered body 4 is viewed from the direction A (obliquely downward rightward) in FIG. FIG. 3 shows Wh / Ws = 1.
0 and Dh / De = 0.9, t = 98 μm, FIG.
/Ws=1.3 and Dh / De = 0.9 and t = 98μ
m, FIG. 5 shows that Wh / Ws = 1.0 and Dh / De = 0.8
T = 104 μm, and FIG. 6 shows that Wh / Ws = 1.0 and Dh
/De=1.2 and t = 79 μm.
This is a 4-cut model. 3 to FIG.
The width of 1/2 of s is illustrated.

As a result of the analysis, the maximum tensile stress 22 generated at the lower part of the side surface of the ceramic sintered body 4 is 5.5 in FIG.
kgf / mm ² , whereas in the case of FIG.
gf / mm ² , which was found to be about 1.6 times. Therefore, it was found that as Wh becomes larger than Ws, the stress generated in the ceramic sintered body 4 becomes larger, and the possibility of cracking increases.

Further, the maximum tensile stress 22 is that of Figure 5 whereas a 5.4kgf / mm ^2, was ^2, and about 1.56 times 8.4kgf / mm in the case of FIG.

[0038]

According to the present invention, the line width of the wiring pattern is set to Wh,
The width of the ceramic sintered body is Ws, and the distance between the wiring patterns is D.
h, and when the distance between the terminal electrodes is De, 1.0 ≦ Wh / W
By satisfying the relationship of s ≦ 1.2 and 0.8 ≦ Dh / De <1.0, and setting the minimum thickness t of the solder from the surface of the wiring pattern to the terminal electrode in the solder mounting portion to 90 μm or more, the temperature change Cracks do not occur in the ceramic sintered body even under severe conditions where it is repeatedly applied, and there is no deterioration of the electrical characteristics as an electronic component.As a result, the yield after surface mounting of the electronic component is high, and long-term It has the effect of being excellent in reliability.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a mounting structure in which a multilayer ceramic capacitor as an electronic component of the present invention is surface-mounted on a circuit board.

FIG. 2 is a perspective view showing an example of a カ ッ ト cut model used for stress analysis by the finite element method.

3 is a stress distribution diagram of a 1/4 cut model when a ceramic sintered body of Wh / Ws = 1.0 and Dh / De = 0.9 and t = 98 μm is viewed from a direction A in FIG. 2; .

FIG. 4 is a stress distribution diagram of a ceramic sintered body with Wh / Ws = 1.3 and Dh / De = 0.9 and t = 98 μm.

FIG. 5 is a stress distribution diagram of a ceramic sintered body where Wh / Ws = 1.0, Dh / De = 0.8, and t = 104 μm.

FIG. 6 is a stress distribution diagram of a ceramic sintered body where Wh / Ws = 1.0, Dh / De = 1.2, and t = 79 μm.

FIG. 7 is a sectional view of a conventional electronic component mounting structure.

[Explanation of symbols]

 1: electronic component 2: circuit board 3: wiring pattern 4: ceramic sintered body 5: terminal electrode 6: solder 22: maximum tensile stress

Claims (1)

[Claims] 1. A terminal electrode provided at both ends of a ceramic sintered body formed by alternately laminating a plurality of ceramic plates and a plurality of internal electrodes on a pair of wiring patterns of an external circuit board. Wherein the line width of the wiring pattern in the solder mounting portion is Wh, the width of the ceramic sintered body is Ws, the interval between the pair of wiring patterns is Dh, and the terminal electrode is Assuming that the distance is De, 1.0 ≦ Wh / Ws ≦ 1.2 and 0.8 ≦ Dh
An electronic component mounting structure characterized by satisfying a relationship of /De<1.0.