JP2000223814A - Mounting board for wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold a secure and tight electric connection for a long period by eliminating a defect in connection between a wiring board and an external electric circuit board. SOLUTION: When a package A which has a container for storing a semiconductor element 5 on an insulating substrate 1 made of ceramic and connection terminals 4 formed on the reverse surface is mounted on a circuit board B, a wiring conductor 9 between wiring conductors 8 and 9 adhered onto the top surface of an insulator 7 made of a composite material of glass and synthetic resin is arranged in a recessed part 10 of the circuit board B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a case where a wiring board, especially a large surface-mounting wiring board is brazed and mounted on an external electric circuit board made of an insulating plate made of a composite material of glass and synthetic resin. The present invention relates to a mounting structure of a wiring board suitable for the above.

[0002]

2. Description of the Related Art A wiring board has a structure in which a metallized wiring layer is disposed on the surface or inside of an insulating substrate. A typical example is a semiconductor element, particularly an LSI (Large Scale Integrated Circuit Element).
There is a semiconductor device housing package for housing a semiconductor integrated circuit device such as the above.

[0003] In this package for housing a semiconductor element, a hole for accommodating a semiconductor element is formed on the surface of an insulating substrate generally made of alumina ceramics, and the surface and the inside of the insulating substrate are made of tungsten, molybdenum or the like. A plurality of metallized wiring layers made of a melting metal powder are provided, and are electrically connected to a semiconductor element housed in the hole. In addition, a connection terminal for electrically connecting to an external electric circuit board is provided on a lower surface or a side surface of the insulating substrate, and the connection terminal is electrically connected to the metallized wiring layer.

[0004] Such a semiconductor element storage package (hereinafter, the semiconductor element storage package is abbreviated as a package) includes connection terminals provided on the lower surface or side surfaces of the insulating substrate and wiring conductors formed on the surface of the external electric circuit substrate. Are mounted by soldering with solder or the like and electrically connecting them.

In general, as the degree of integration of a semiconductor device increases, the number of electrodes formed on the semiconductor device also increases, and accordingly, the number of terminals in a package also increases. Further, the dimensions of the package itself must be increased. However, since miniaturization is also required, the density of connection terminals is increased.

The most common connection structure in a conventional package is a pin grid array (PGA) in which metal pins such as Kovar are connected to the lower surface of the package. Quad flat package (QF) in which an L-shaped metal member is brazed to the derived metallized wiring layer
P), leadless leadless chip carrier (LCC) with electrode pads on four sides of the package,
Further, there is a ball grid array (BGA) or the like in which a spherical terminal made of solder is arranged on the lower surface of the insulating substrate. Among these, the BGA can achieve the highest density.

This BGA has a structure in which a spherical body made of a brazing material such as solder is brazed to a connection terminal, and this spherical body is brought into contact with a wiring conductor of an external electric circuit board, and then about 250 mm. It is mounted on an external electric circuit board by heating and melting at a temperature of about 400 ° C. and joining the spherical body to a wiring conductor.

In such a mounting structure, each electrode of the semiconductor element housed in the package is electrically connected to an external electric circuit via the metallized wiring layer and the connection terminal.

[0009] Further, there has been proposed a technology for forming an insulating substrate of a package using a glass ceramic sintered body from the viewpoint of low-temperature firing, low dielectric constant, and high electrical conductivity copper wiring.

[0010]

Alumina, mullite, and the like are frequently used as ceramics constituting the insulating substrate. As a result, a high strength of 200 MPa or more is achieved, and high reliability is obtained with respect to the technology of forming a multilayer with a metallized wiring layer. Property is obtained.

However, when this insulating substrate is mounted on an external electric circuit board such as a printed circuit board containing an organic resin such as a glass-epoxy resin composite material or a glass-polyimide resin composite material, the external electric circuit board and the insulating substrate Is larger than 10 × 10 ⁻⁶ / ° C., and the heat generated during the operation of the semiconductor element is repeatedly applied to both the insulating substrate and the external electric circuit board, thereby reducing the thermal stress. Occurs.

When the number of connection terminals provided on the package is relatively small, such as less than about 300, the thermal stress is small. However, when the number of connection terminals is increased to about 300 or more, the thermal stress increases. Due to the cycle of operation / stop of the semiconductor element, stress concentrates on the outer peripheral portion of the connection terminal of the package and the bonding interface between the connection terminal and the wiring conductor of the external electric circuit board, and the connection terminal peels from the insulating substrate,
The connection terminal peels off from the wiring conductor of the external electric circuit board, and as a result, there is a problem that the connection terminal of the package cannot be stably and electrically connected to the wiring conductor of the external electrode circuit for a long time.

Accordingly, an object of the present invention is to provide a reliable and stable connection for a long period of time when a wiring board such as a package is surface-mounted by brazing to an external electric circuit board. The object of the present invention is to provide a mounting structure.

[0014]

SUMMARY OF THE INVENTION The present invention is directed to a method of forming a wiring board having a connection terminal group formed on one surface of a ceramic insulating substrate provided with a metallized wiring layer on an insulating plate made of a composite material of glass and synthetic resin. In mounting the wiring conductors on the external electric circuit board on which the wiring conductors are attached, the connection terminals on the wiring board are individually brazed to the wiring conductors on the external electric circuit board. A part is provided in a concave portion formed in the insulating plate, and a distance between the connection terminal and the wiring conductor is made longer than other wiring conductors.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to FIGS. FIG. 1 is a cross-sectional view of a structure in which a BGA type semiconductor element housing package A as the wiring board is mounted on an external electric circuit board B, and FIG. 2 is a plan view showing an arrangement of wiring conductor groups of the external electric circuit board B. . 3 to 5 are plan views showing the arrangement of the wiring conductor groups of the other external electric circuit boards B1, B2, B3.

BGA type semiconductor element storage package A
(Hereinafter, abbreviated as package A) is provided by forming a large hole on an insulating substrate 1 made of ceramics to form a container 6 in which a semiconductor element 5 is housed, and disposing a lid 2 thereon. Hermetically seal. Further, a metallized wiring layer 3 is formed inside or on the surface of the insulating substrate 1, and one end thereof is electrically connected to a substantially circular connection terminal 4 formed on the lower surface of the insulating substrate 1. The connection terminal 4 is made of Cu, Au, Al, Ni, Pb-S
n. a and b are brazing materials such as high-melting solders in the form of a ball or a football. The hole forms a container 6 in which the semiconductor element 5 is housed, and is hermetically sealed by the lid 2.

The external electric circuit board B (hereinafter abbreviated as circuit board B) is constituted by a printed board or the like.
That is, Cu, Au, Al, Ni, Pb-Sn are formed on the surface of the insulator 7 made of a composite material of glass and a synthetic resin such as a glass-epoxy resin or a glass-polyimide resin composite.
A substantially disk-shaped wiring conductor 8, 9 made of a metal such as a metal is adhered and formed, and the wiring conductor 9 is disposed in a substantially cylindrical concave portion 10 located near the periphery of the circuit board B. The arrangement portion is lower than the other wiring conductors 8. The brazing material a is arranged on the wiring conductor 8, and the brazing material b is arranged on the wiring conductor 9.

The inner diameter of the recess 10 is 60% to 160% of the outer diameter (pad diameter) of the connection terminal 4, and more preferably 80% to 1%.
It may be configured to have a ratio of 40%, preferably 9%.
It is good to be 0-130%, optimally 100-120%, so that the connection strength by brazing becomes the largest. If this ratio is less than 60%, the contact areas of the brazing materials a and b with the wiring conductors 8 and 9 become small, and disconnection due to a difference in thermal expansion coefficient between the two tends to occur. On the other hand, if it exceeds 160%, the adjacent wiring conductors 8
Since the space between the wiring conductors or between the wiring conductor 8 and the wiring conductor 9 is reduced and narrowed, it is likely to be difficult to route the wiring.

The depth of the recess 10 may be set in the range of 5% to 125%, more preferably 10% to 100%, preferably 20% to 90%, and most preferably 30% to 100% of the pad diameter of the connection terminal 4. 70% is preferable, whereby the connection strength by brazing is maximized.

Next, a method of mounting the package A on the circuit board B will be described. Wiring conductors 8 and 9 are formed in the recess 10 of the circuit board B and further on predetermined portions of the insulator 7, and cream-like low melting point solder is applied on these wiring conductors 8 and 9 by printing. Also in the package A, the connection terminals 4 are formed on the insulating substrate 1, cream-like low melting point solder is applied thereon by printing, and a spherical solder made of high melting point solder is placed thereon. Heating is performed at a temperature of 250 ° C. to fix the spherical solder on the package A.
Next, the package A is mounted on the circuit board B. At this time, the individual connection terminals 4 are connected to the corresponding wiring conductors 8 and 9.
, While being in contact with each other, are disposed to face each other with the brazing materials a and b interposed therebetween. Thereafter, by heating at a temperature of about 250 to 400 ° C., the brazing material such as solder is melted to form brazing materials a and b. The package A is mounted on the circuit board B by such a brazing process.

Thus, in the mounting structure of the present invention, since the wiring conductors 9 are disposed in the recesses 10 as described above, the size of the brazing material b is increased, and the brazing material b is easily bent near the brazing material b. Therefore, the insulating substrate 1 and the circuit board B
The thermal stress caused by the difference in thermal expansion between the package A and the circuit board B is reduced. As a result, a poor connection does not occur between the package A and the circuit board B, and a reliable and strong electrical connection is maintained for a long time. You.

As a preferred embodiment of the present invention, the thermal expansion coefficient of the insulating substrate 1 made of ceramics at 40 to 400 ° C. is 7 to 25 ppm / ° C., optimally 8 to 25 ppm / ° C.
It is good to That is, the coefficient of thermal expansion of the semiconductor element 5 is usually 1 to 3 ppm / ° C., the coefficient of thermal expansion of the circuit board B is 10 to 40 ppm / ° C., and the coefficient of thermal expansion of the insulating substrate 1 is It is good to define between both, and when the range is 7 to 25 ppm / ° C,
The semiconductor element 5 can be stably fixed on the package A, and the thermal stress generated due to the difference in the thermal expansion coefficient between the package A and the circuit board B is alleviated. As a result, a highly reliable mounting structure can be realized.

The metallized wiring layer 3 of the package A
May be formed of gold or copper, and may be simultaneously fired with the insulating substrate 1 (a firing temperature: 1000 ° C. or less). As a suitable insulating substrate material therefor, crystalline lithium silicate glass, borosilicate glass or the like at a ratio of 20 to 80% by volume, and a filler such as SiO ₂ (quartz, cristobalite), Al ₂ O ₃ , enstatite, etc. The components are mixed at a ratio of 80 to 20% by volume, the mixture is shaped and fired to obtain a glass ceramic sintered body. With such a mixing ratio, firing can be performed at a temperature of 1000 ° C. or less.

When crystalline lithium silicate glass is used, Li ₂ O is contained at a ratio of 5 to 30% by weight and SiO ₂ is used.
₂ comprises 60 to 85 wt%, the total amount of Li ₂ O and SiO ₂ is a 65 to 95 wt%, the balance being Al ₂ O _3, alkaline earth oxides, alkali metal oxides, ZnO, P ₂ O
Those composed of ₅ or the like are preferred.

When quartz, forsterite, enstatite, and cristobalite are contained as filler components in lithium silicate glass, the coefficient of thermal expansion can be easily controlled to 7 to 25 ppm / ° C. In addition, as other filler components, tridymite, spinel, wollastonite, montiselanite, nephein, lithium silicate, diopside, merbinite, akermite, magnesia, alumina, carnegieite, magnesium borate, celsian, garnite, petalite, etc. You may.

An organic resin binder for molding is added to the mixture of the crystalline glass and the filler as described above, and then formed into a sheet by a desired molding means, for example, a doctor blade, a rolling method, a die press or the like. To get a green sheet. A metallizing paste such as copper or gold is printed on the surface of the green sheet by a screen printing method or the like, and furthermore, an appropriate punching process is performed to form a through hole, and the metallizing paste is filled in the through hole. Are laminated and fired.

In this firing, the binder component blended for molding is removed in an atmosphere at about 700 ° C. When the wiring conductors 8 and 9 are formed of copper (Cu), the wiring conductors 8 and 9 are formed in a nitrogen atmosphere containing water vapor at 100 to 700 ° C. Further, the shrinkage start temperature of the molded body is preferably set to about 700 to 850 ° C. If the temperature is lower than 700 ° C., it becomes difficult to remove the binder.

The firing is preferably performed in an oxidizing atmosphere at 850 ° C. to 1050 ° C., whereby the relative density is 90%.
It is densified up to the above. If the firing temperature is lower than 850 ° C., the metallized layer is not densified, and if it exceeds 1050 ° C., the metallized layer is melted by simultaneous firing with the metallized wiring layer.

According to the glass ceramic sintered body constituting the insulating substrate of the wiring board thus manufactured, the crystalline phase of forsterite, quartz, cristobalite or the like added as a filler, enstatite or the like based on these filler components, or the like is used. , And a lithium silicate crystal phase precipitated from crystalline glass. In addition, there may be a crystal phase generated by the reaction between the crystalline glass and the filler. Furthermore, a small amount of a glass phase may be present at the grain boundaries of these crystal phases. By precipitating these crystal phases with a large coefficient of thermal expansion,
A glass ceramic sintered body having a high coefficient of thermal expansion is obtained.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements may be made without departing from the scope of the present invention. For example, in the above example, the concave portions 10 (wiring conductors 9) of the circuit board B are provided all around the group of wiring conductors. Thus, the wiring conductors 9 may be arranged, or may be provided at four corners where the stress is greatest as in the circuit board B2 in FIG.
The wiring conductors 9 may be provided at the corners or three corners, or the wiring conductors 9 may be discontinuously arranged around the wiring conductor group as in the circuit board B3 in FIG.

In the above case, the recesses 10 (wiring conductors 9) are arranged around the group of wiring conductors.
9 may be provided inside the wiring conductor group.

[0032]

(Example 1) 92% by volume of alumina and the balance (Si
(O, CaO, MgO) molded with raw materials having a mixing ratio of 8% by volume, a through hole is formed using a tungsten (W) material for a metallized wiring layer, and a connection terminal formed of metallized W is also formed. Then, they were simultaneously fired in a nitrogen atmosphere at 1600 ° C. to produce an insulating substrate (wiring substrate) having a size of 5 × 4 × 40 mm.

When the coefficient of thermal expansion of this insulating substrate at 40 to 400 ° C. was measured, it was 7.0 ppm / ° C. Then, after the connection terminal is plated with Ni, a high melting point solder (Pb 90% by weight-Sn 10% by weight) is applied to the terminal.
The ball-shaped brazing materials a and b having a diameter of 0.8 mm were attached with low melting point solder (Pb 37% by weight-Sn 63% by weight). The pitch of the connection terminals is 1.27 mm, the number of terminals is 1225, the length of one side of the package is 45 mm, and the thickness of the wiring board is 2 mm.

On the other hand, as a circuit board B, a glass-epoxy board (coefficient of thermal expansion at 40 to 400 ° C .: 13 ppm)
/ ° C) on a surface of an insulator on which a wiring conductor made of a copper foil was formed. The length of one side of the printed circuit board was 80 mm, and the thickness was 1.6 mm. In the wiring conductor group arranged in a matrix,
The wiring conductors in the columns were arranged in recesses provided in the insulator. This concave portion was machined to a diameter ratio and a depth ratio as shown in Table 1 with a required diameter and depth using a drill and a laser. The diameter ratio is a ratio of the inner diameter of the recess to the outer diameter (pad diameter) of the connection terminal, and the depth ratio is the ratio of the depth of the recess to the outer diameter (pad diameter) of the connection terminal.

Then, a low-melting-point solder paste (Pb 37% by weight) is formed on the wiring conductor (pad) of the printed circuit board.
Sn 63% by weight) is applied by a printing method, the connection terminal is superimposed thereon, and the connection is hardened and connected using a reflow furnace having a peak temperature of 230 ° C. to obtain a conventional sample N having no concave portion.
o. No. 1 and various sample Nos. With various diameter ratios and depth ratios. 2 to 8 were produced.

[0036]

[Table 1]

Next, each sample was subjected to a heat cycle test. The sample was held in a thermostat controlled at -40 ° C. and 125 ° C. in an atmosphere of air at 30 ° C./30 min. Then, the electrical resistance between the wiring conductor of the printed circuit board and the package substrate was measured for each cycle, and the number of endurance cycles until the electrical resistance changed was shown in Table 1.

As is clear from this table, the sample of the present invention provided with a concave portion. If it is 2 to 8, good results can be obtained for the heat cycle test, and as a result, it can be seen that a strong and stable connection can be obtained for a long period of time.

(Example 2) In this example, an insulating substrate was manufactured using 80% by volume of lithium silicate glass and 20% by volume of quartz as a filler component as raw materials. In this case, the metallized wiring layer and the through-hole were formed of a copper material and fired simultaneously in a nitrogen atmosphere at 900 ° C. Others are the same as (Example 1). 40 to 4 of this insulating substrate
The coefficient of thermal expansion at 00 ° C. was determined to be 10.0
ppm / ° C. Then, the concave portion was processed into a diameter ratio and a depth ratio as shown in Tables 2 to 7.

When the diameter ratio was changed to 60% and the depth ratio was changed variously within the range of 5 to 125%, the results shown in Table 2 were obtained.

[0041]

[Table 2]

When the diameter ratio was changed to 80% and the depth ratio was changed in various ways, the results shown in Table 3 were obtained.

[0043]

[Table 3]

When the diameter ratio was 100%, the results shown in Table 4 were obtained.

[0045]

[Table 4]

When the diameter ratio was 120%, the results shown in Table 5 were obtained.

[0047]

[Table 5]

When the diameter ratio was 140%, the results shown in Table 6 were obtained.

[0049]

[Table 6]

When the diameter ratio was 160%, the results shown in Table 7 were obtained.

[0051]

[Table 7]

As is clear from these tables, since the wiring conductors provided near the periphery of the circuit board B are provided in the recesses formed in the insulating plate, the distance between the package A and the circuit board B can be extended. Thus, the connection structure was firmly and stably connected over a wide range, thereby providing a highly reliable wiring board mounting structure.
In particular, when the diameter ratio was 60% or 160%, by setting the depth ratio to 30 to 75%, no change in resistance was observed at all up to 1000 cycles, and an extremely good electrical connection state could be maintained. In addition, the diameter ratio is 80 to 140
%, By setting the depth ratio to 10 to 100%,
Similarly, no change in resistance was observed up to 1000 cycles.

[0053]

As described above, according to the present invention, in the mounting structure in which the connection terminal group of the wiring board is individually brazed to the wiring conductor group of the external electric circuit board, the wiring conductor provided on the external electric circuit board is provided. By providing a part in the recess formed in the insulating plate, the size of the brazing material in the recess becomes longer, and it becomes easier to bend near the brazing material. The thermal stress caused by the difference in thermal expansion at the substrate is reduced, thereby preventing poor connection between the wiring board and the external electric circuit board, and reliably and firmly maintaining the electrical connection for a long time. result,
A highly reliable wiring board mounting structure that is firmly and stably connected for a long time can be provided. In particular, a highly reliable mounting structure can be provided for a multi-terminal wiring board accompanying an increase in the size of a semiconductor circuit element.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a structure in which a package for storing a BGA type semiconductor element which is a wiring board of the present invention is mounted on an external electric circuit board.

FIG. 2 is a plan view showing an arrangement of wiring conductor groups of the external electric circuit board of the present invention.

FIG. 3 is a plan view showing an arrangement of wiring conductor groups of another external electric circuit board of the present invention.

FIG. 4 is a plan view showing an arrangement of wiring conductor groups of another external electric circuit board of the present invention.

FIG. 5 is a plan view showing an arrangement of wiring conductor groups of another external electric circuit board of the present invention.

FIG. 6 is a plan view showing an arrangement of wiring conductor groups of another external electric circuit board of the present invention.

FIG. 7 is a plan view showing an arrangement of wiring conductor groups of another external electric circuit board of the present invention.

FIG. 8 is a plan view showing an arrangement of wiring conductor groups of another external electric circuit board of the present invention.

FIG. 9 is a plan view showing an arrangement of wiring conductor groups of another external electric circuit board of the present invention.

[Explanation of symbols]

A BGA type semiconductor element storage package (package) B, B1, B2, B3 External electric circuit board (circuit board) 1 Insulating substrate 5 Semiconductor element 2 Lid 6 Container 4 Connection terminal a, b Brazing material 7 Insulator 8, 9 wiring conductor 10 recess

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E319 AA03 AA07 AA10 AB05 AC02 AC04 AC15 BB04 CC58 CD29 GG03 GG11 GG20 5E336 AA04 AA08 AA09 AA16 BB01 BB16 BB18 BC25 BC34 CC33 CC34 CC36 CC43 CC58 DD01 EE01 GG11

Claims (1)

[Claims] 1. A wiring substrate having a connection terminal group formed on one surface of a ceramic insulating substrate provided with a metallized wiring layer, and a wiring conductor group formed on an insulating plate made of a composite material of glass and synthetic resin. In the mounting structure in which the connection terminal group of the wiring board is individually brazed to the wiring conductor group of the external electric circuit board, the wiring conductor is partially placed on an insulating plate. A wiring board mounting structure characterized in that the distance between the connection terminal and the wiring conductor is longer than that of the other wiring conductors by being provided in the recess formed in the wiring board.