JPH0635341B2 - Multilayer wiring board - Google Patents

Description

TECHNICAL FIELD The present invention mainly relates to a multilayer wiring board for a hybrid IC, and more specifically, a ceramic insulating layer and a conductor of W or Mo are formed on a ceramic green sheet and fired in a reducing atmosphere. The present invention relates to a multilayer wiring board made of alumina porcelain.

(Prior art and its problems) With the recent increase in the integration of semiconductor chips, high density wiring and high dimensional accuracy are required for ceramic multilayer wiring boards and IC packages on which they are mounted. . Among the dimensional accuracy, the warp of the substrate made of alumina porcelain has a great influence on the mounting of IC chips, the connection of I / O pins, the hermetic sealing, and the like.

By the way, in the conventional firing operation in this technical field, since the warpage of the substrate and the package made of alumina porcelain is large, the purpose is to reduce such warpage,
Techniques such as (a) changing the shape of the metallized printing pattern, (b) applying a load to the substrate during firing, and (c) increasing the internal pressure of the firing furnace have been adopted.

Further, the conventional substrate has an inherent problem that the resistance of the W conductor and the Mo conductor formed on the substrate is large, and a plurality of packages and the like are formed on one substrate,
A groove (snap line) is provided in advance for each section,
There is also a problem in that when the groove is bent after firing and divided into individual pieces, snapping failure that does not work well, and many plating failures when plating on the conductor are caused. Further, in the conventional substrate having an alumina content of about 90% by weight, a W conductor and a Mo conductor are co-fired with a substrate (green sheet) in a reducing atmosphere, and an Ag-Pd-based conductor is further air-treated thereon. For printed multilayer wiring boards, A
The alumina porcelain surface around the g-Pd-based conductor is discolored yellow, and the appearance is not good.

(Object of the Invention) Here, the first object of the present invention is to reduce the warpage that occurs during firing of the alumina porcelain used for the ceramic multilayer wire substrate, reduce the conduction resistance of the W conductor and Mo conductor, and perform firing. The second purpose is to improve the snapping property of the porcelain afterwards, and the second purpose is to reduce the glass phase in the alumina porcelain of the ceramic multilayer wiring board, and to prevent plating defects caused in the manufacturing process due to the large amount of glass phase. The third object of the present invention is to eliminate
This is to eliminate the phenomenon that the surface of the porcelain becomes yellow when the Ag—Pd-based conductor is baked in air on the alumina porcelain fired in the reducing atmosphere.

(Structure of the Invention) The present invention provides a special technical structure of an alumina porcelain for achieving the above-mentioned object, and further, a special technical structure of a multilayer wiring board, which is the gist of the invention. Is Al ₂ O ₃ : 85 to 96% by weight, SiO ₂ :
2.5 to 12% by weight, MgO: 0.5 to 4% by weight, and CaO: 2% by weight or less, and MgO / Ca
A multilayer wiring board characterized by forming a W or Mo conductor on an alumina porcelain having an O weight ratio of 2 or more, and Al ₂ O ₃ : 85-96 wt%,
SiO ₂ : 2.5 to 1% by weight, MgO: 0.5 to 4% by weight, and CaO: 2% by weight or less, and Mg
In an alumina porcelain having an O / CaO weight ratio of 2 or more, W
Alternatively, the gist of the present invention is also a multi-layer wiring board characterized in that a Mo conductor is formed by simultaneous firing, and an Ag-Pd-based conductor is baked and provided on the alumina porcelain.

The alumina porcelain in such a multilayer wiring board preferably contains mullite and / or spinel crystal phase in addition to corundum, and more preferably has a relative density of 95% or more.

By the way, according to the present invention as described above, the warpage mechanism of the alumina porcelain by the green sheet molding method, which is mainly used for the alumina substrate or the alumina IC package, the W conductor or Mo conductor formed on the green sheet and the alumina substrate or the alumina IC is used. It was completed as a result of intensive research and analysis of the relationship with the package and the mechanism of discoloration of the substrate when the Ag-Pd-based conductor is baked.

In short, according to the research conducted by the present inventors, the warp of the porcelain by the green sheet forming method is mainly M of alumina porcelain.
It became clear that they were easily affected by the gO / CaO weight ratio.

That is, in the alumina porcelain containing about 90% by weight of Al ₂ O ₃ , which was often used in the conventional multilayer wiring board or IC package, the MgO / CaO weight ratio was about 1. Thus, compared to CaO, Mg
With a composition containing a small amount of O, the flux component added as a sintering aid becomes a liquid phase at the time of sintering and causes liquid phase sintering to form a sintered body. However, since the wettability of the liquid phase to the alumina powder is too large, the flow of the sintered body is easily induced during firing, and the flow of the sintering atmosphere, the humidity distribution, etc. are affected, and the warp is extremely warped. It will be easier. The present inventors have found that in order to prevent this, the MgO / CaO weight ratio should be increased to reduce the wettability of the liquid phase. Then, the fluidity of the fired body at the time of firing is reduced, and it is less likely to be affected by external factors and warpage is less likely to occur.

By the way, as shown in FIG. 1, the warp of the porcelain after firing changes depending on the weight ratio of MgO / CaO.
When the aO weight ratio is 2 or more, it becomes small, and when it is 3 or more, it becomes smaller, and when it becomes 4 or more, the warp becomes negligible. The curve in Fig. 1 is
MgO / Ca regardless of the amounts of Al ₂ O ₃ and SiO _2.
It depends only on the O weight ratio. The warp of the substrate is a warp value in a size of 50 mm square.

In addition, by setting the weight ratio of MgO / CaO to 2 or more, W and M in the substrate or the IC package can be
It was found that the conduction resistance of the o conductor was small. This is also because, as described above, by increasing the MgO / CaO weight ratio, the wettability of the liquid phase in the alumina calcined body at the time of calcining became small, so that the liquid phase between the W and Mo metal powders became excessive. Infiltration of W and Mo powders is largely suppressed by sintering of the metal, and as a result, the glass phase filling the gaps between the metal powders is reduced more than necessary and the conduction resistance is reduced. is there.

Further, as shown in FIG. 2, when the MgO / CaO weight ratio is 2 or more, the conduction resistance is reduced by about 10%, and when it is 3 or more, it is reduced by about 20%.
The curves in FIG. ₂ are Al ₂ O ₃ and Si.
It depends only on the MgO / CaO weight ratio, regardless of the amount of O ₂ .

In FIG. 3 showing the form of snap lines, FIG. 3 (a) is a perspective view of an alumina green sheet with snap lines, and A in FIG. 3 (a).
In the (b) diagram which is an enlarged cross-sectional view of the portion, the snap groove 2 put in the green sheet 1 has a MgO / CaO weight ratio of less than 2 in the porcelain after firing.
(C) Like the porcelain 3 shown in FIG.
Becomes a cause of snap failure, whereas Mg
When the weight ratio of O / CaO is 2 or more, (d)
As shown in the figure, in the alumina porcelain 5 obtained by firing, the groove 6 does not adhere to each other and shows a good snap property.

Since the wettability of the liquid phase during baking was reduced in this way, as shown in FIG. 4, when a plurality of IC packages were simultaneously baked in a single plate-like form, and then each of them was subjected to a chocolate break. The snap failure has decreased. The snap failure rate is halved when the MgO / CaO weight ratio is 2 or more, and becomes ⅕ of the conventional rate when the MgO / CaO weight ratio is 4 or more. The curve in FIG. 4 changes only with the MgO / CaO weight ratio, regardless of the amounts of Al ₂ O ₃ and SiO ₂ .

Further, in the conventional alumina porcelain for a substrate or IC package in which the amount of Al ₂ O ₃ is about 90%, the crystal phase of the sintered body is different from the corundum phase composed of alumina which is the main component. There was no flux, and all the flux was a glass phase. On the other hand, it was found that in the alumina porcelain of the present invention, a mullite phase or a spinel phase was precipitated in addition to the corundum phase, and the glass phase in the porcelain was reduced. The precipitation phenomenon of such a crystal phase is
This is because the CaO weight ratio is increased. By virtue of such precipitation of the crystal phase, the glass phase in the porcelain was reduced, and the plating failure, which was a problem of conventional alumina porcelain, could be effectively eliminated or alleviated. The mullite phase and / or the spinel phase, which are precipitated and coexist with the corundum phase, are generally 1% of the total crystal phase.
It is made to exist so that it may become a ratio of about 15% by weight.

In addition, as shown in FIG. 5, as the MgO / CaO weight ratio increases and the glass phase decreases, the plating failure decreases, and the plating failure rate of about 15% in the past is It was revealed that the / CaO weight ratio was 9% at 2 or more, and 7% at 4 or more.

Furthermore, the yellow discoloration of the porcelain surface that occurs when an Ag-Pd-based conductor is baked on the multilayer wiring board in air is also
It became clear that the O / CaO weight ratio was greatly affected. This discoloration phenomenon is caused by Ag in the Ag-Pd system conductor
It is presumed that it occurs by reacting with Ca in the glass phase on the surface of the alumina porcelain. More specifically, as shown in FIG. 6, when the yellowness of the substrate is expressed by the b value of the Lab method using a color difference meter, the MgO / CaO weight ratio is 2, and the MgO / CaO weight ratio is 1. When it is 3 or more, it is 40 to 45%, and the whiteness is improved to such a degree that the yellow color cannot be visually judged.

If the amount of Al ₂ O ₃ in the alumina porcelain is less than 85% by weight, the amount of flux will be too large and the porcelain will adhere to the setter such as Mo plate or alumina during firing, and the relative density will also be 92. There is a problem that it only goes up to%. On the contrary, when the amount of Al ₂ O ₃ is more than 96% by weight, the flux content is insufficient and a sufficiently dense porcelain cannot be obtained. Therefore, in the present invention, the amount of Al ₂ O ₃ in the alumina porcelain is selected within the range of 85 to 96 wt% where the relative density is 95% or more, and more preferably the relative density of the porcelain is 96. 88 to 94 that is more than%
Weight percent is recommended. In particular, the alumina porcelain according to the present invention is required to have a relative density of 95% or more, preferably 96% or more, in order to improve its airtightness when it is used as a substrate or an IC package. Of.

Further, if the amount of SiO ₂ in the alumina porcelain is less than 2.5% by weight, it will not sinter sufficiently, and if it exceeds 12% by weight, the melting point of the flux will be too low and the sintering will be above the binder combustion temperature. Since it starts at a low temperature, the binder removal does not occur sufficiently when firing in a reducing atmosphere. Therefore, it is necessary to adjust the blending amount within the range of 2.5 to 12% by weight.

Further, if the amount of MgO in the alumina porcelain is less than 0.5% by weight, the effect of suppressing abnormal grain growth of alumina particles is lost, and coarse grains are generated in the porcelain to reduce the strength of the porcelain, while If it exceeds%, the melting point of the flux becomes too high and it becomes difficult to sinter. Therefore, the amount of MgO in the alumina porcelain will be 0.5 to 4% by weight.

Furthermore, if the CaO content in the alumina porcelain is more than 2% by weight, the glass phase in the porcelain will increase, causing plating failure and snap failure. Therefore, the content of CaO should be 2% by weight or less. Will be decided.

In addition, in the present invention, in general, Al ₂ within the above range is used.
Substantially composed of O ₃ , SiO ₂ , MgO and CaO, in other words their total amount is substantially 100.
Alumina porcelain will be constructed in the composition of wt%, and if necessary, in addition to the four essential components, other additives will be further compounded to construct the desired alumina porcelain. It is also possible. For example, as the additive, TiO ₂ for coloring alumina porcelain,
Examples include Cr ₂ O ₃ and Fe ₂ O ₃ . However, the additive as the third component is compounded within the limit that does not adversely affect the properties of the obtained alumina porcelain, and generally in a ratio of about 5% by weight or less (therefore, the total amount of the above four components is 95 to 100). It will be blended by weight).

By the way, the alumina porcelain according to the present invention as described above can be advantageously manufactured, for example, by the following method.

First, mix the raw material powder of the alumina porcelain flux,
It is calcined and the calcined product is crushed. Next, the obtained calcined flux (pulverized product) and alumina powder are mixed so as to have the alumina porcelain composition of the present invention, and then shaped into a desired shape by a conventional method and fired. In this alumina porcelain manufacturing method, the composition of the flux is preferably ₂₀ to 75% by weight of Al ₂ O _{3, 20} to 75% by weight of SiO ₂ , 5 to 30% by weight of MgO, and 15% by weight or less of CaO. And the calcination temperature of this flux is 1000 to 1450 ° C., while the firing temperature of the porcelain is preferably 1450 to 1650 ° C., which makes it possible to use an alumina porcelain having a relative density of 95% or more. You can get it.

(Examples) Hereinafter, some examples of the present invention will be shown to clarify the present invention more specifically, but the present invention is construed to be limited to the description of the examples. Needless to say, it is not a thing. It should be noted that the present invention is, in addition to the following embodiments, and in addition to the above specific description, various changes, modifications, and improvements within the scope not departing from the spirit of the present invention based on the knowledge of those skilled in the art. It should be understood that it can be implemented in addition to the above.

First, a mixture of alumina porcelain flux raw materials (Al ₂
O ₃ + SiO ₂ + MgO + CaO), 1300-14
It is calcined at 00 ° C, and the resulting calcined product has an average particle size of 4
Dry pulverization was performed so that the size was about μm. Then, using this calcined flux powder and alumina powder as a porcelain raw material, alumina porcelain No. of various chemical compositions shown in Table 1 below.
1-20 were produced. Firing temperature is 1550 to 1600 ° C
And Table 1 also shows the MgO / CaO weight ratio, relative density, and warpage of each of the various alumina porcelains obtained.
Also, with respect to these alumina porcelain Nos. 1 to 20, various porcelain characteristics and W conductor characteristics were measured, and the results were
Shown in the table.

In this example, the relative density was determined from the porosity of the mirror-polished porcelain cross section observed by a microscope. The warpage of the porcelain after firing was determined by measuring "waviness" using a surface roughness meter using a 50 mm square sample. Further, the W conductor paste was printed on the green sheet so that the conductor thickness after firing was 20 μm, and after firing, the conduction resistance was measured.
Furthermore, Ag-P is applied to the surface of the alumina porcelain fired in a reducing atmosphere.
The d conductor paste was printed in a predetermined pattern, baked in air at 850 ° C., and the yellowness of the alumina porcelain surface around the pattern was measured using a color difference meter. In this case, the b value of the Lab method was used for the yellowness.

As is clear from the results of Tables 1 and 2, the characteristics of the alumina porcelain Nos. 1 to 3, 5 to 8 and 11 to 18 having the porcelain composition and the MgO / CaO ratio according to the present invention have a relative density of 95% or more, warpage of porcelain is 90 μm or less, snap failure rate is 0.4% or less, conduction resistance is 10 mΩ / □ or less, plating failure rate is 9% or less, and yellowness of porcelain after baking Ag-Pd conductor is 3 No. 4, which is less than 3 and other than the porcelain composition and MgO / CaO specified in the present invention,
Compared with 9, 10, 19 and 20, the characteristic values are remarkably excellent.

Further, among these characteristics, the characteristics other than the relative density tend to improve as the MgO / CaO weight ratio in the porcelain increases. For example, the plating failure rate is 9.0 when the MgO / CaO weight ratio is 2.3.
%, But when the MgO / CaO weight ratio is 19, 6.
It has decreased to 5%. When the porcelain composition is out of the range of the present invention, the sinterability is poor and the relative density is 91 to 9
It is recognized that it can only go up to 3%. On the other hand, when the MgO / CaO weight ratio is large, the warp of the porcelain, the snap failure rate, the conduction resistance, the plating failure rate, and the yellowness of the porcelain all show good values, which are as described above. Is. In addition, in the samples 19 and 20 in which the weight ratio of MgO / CaO is smaller than 2, all the characteristics such as the relative density of the porcelain, the warp of the porcelain, the defective snap rate, the conduction resistance, the defective plating rate, and the yellowness of the porcelain were obtained. , Is inferior to the alumina porcelain according to the present invention. For example, the yellowness is 6.2 to 6.7,
The warp of the porcelain is 190 to 220 μm.

(Effects of the Invention) As is apparent from the above description, according to the present invention, the warpage of the porcelain after firing is reduced, and plating defects, snap defects, and the like in the manufacturing process of the IC package are improved.
It is possible to manufacture a multilayer wiring board and an IC package in which the conduction resistance of the o conductor is small. Furthermore, Ag on the multilayer wiring board
Thick film HIC by baking Pd-based conductor in air
When used as a substrate, the phenomenon that the substrate surface around the Ag-Pd-based conductor pattern develops yellow can be effectively suppressed or prevented.

[Brief description of drawings]

FIG. 1 is a graph showing changes in warpage of alumina porcelain with respect to MgO / CaO weight ratio, and FIG. 2 is MgO.
It is the graph which showed the change of the conduction resistance of the W conductor on the alumina porcelain with respect to the / CaO weight ratio. FIG. 3 shows changes in the snapping grooves formed on the alumina green sheet during firing. (A) is a perspective view of the green sheet having the snapping grooves,
(B) is an enlarged groove section explanatory drawing of A part of (a), (c)
And (d) are views corresponding to (b) showing different shapes of the groove portion of the alumina porcelain (fired body). FIG. 4 is a graph showing the change in snap failure rate of alumina porcelain with respect to MgO / CaO weight ratio, and FIG. 5 is the change of plating failure rate of W conductor on alumina porcelain with respect to MgO / CaO weight ratio. Is a graph showing
Further, FIG. 6 is a graph showing the change in yellowness of the surface of the porcelain when the Ag—Pd conductor was baked on the alumina porcelain in air against the MgO / CaO weight ratio. 1: Green sheet 2: Snap groove (snap line) 3, 5: Alumina porcelain 4, 6: Snap groove after firing

Claims (2)

[Claims] 1. Al ₂ O ₃ : 85-96% by weight, Si
O ₂ : 2.5 to 12% by weight, MgO: 0.5 to 4% by weight, and CaO: 2% by weight or less, and Mg
A multi-layer wiring board comprising an alumina porcelain having an O / CaO weight ratio of 2 or more and W or Mo conductors formed thereon. 2. Al ₂ O ₃ : 85-96% by weight, Si
O ₂ : 2.5 to 12% by weight, MgO: 0.5 to 4% by weight, and CaO: 2% by weight or less, and Mg
In an alumina porcelain having an O / CaO weight ratio of 2 or more, W
Alternatively, a multi-layer wiring board is characterized in that a Mo conductor is formed by simultaneous firing, and an Ag—Pd-based conductor is baked and provided on the alumina porcelain.