JPH0290551A - Manufacture of ceramic package - Google Patents

Abstract

PURPOSE:To eliminate a plating process, to contrive the formation of a fine pattern due to a reduction in the resistance of an internal layer conductor and to decrease the number of laminated layers and the number of manufacturing processes by a method wherein, after a conductor is printed with a metal paste on a ceramic green sheet for low-temperature firing use, a low-temperature simultaneous firing is performed. CONSTITUTION:A conductor printing is performed on a green sheet 1 and conductor layers 21 and 22 consisting of a gold paste, a conductor layer 3 consisting of a copper or silver paste and a conductor layer 4 consisting of a nickel paste are respectively formed on a die bonding part and wire bonding parts, plane and vertical circuit parts and pin soldering parts. After these are laminated to perform a cutting of the external shape of the laminated material, a low- temperature removal of the binder and baking are performed at low temperature, pins 5 are soldered and a package is completed via an inspection. Thus, in the case of an alumina PGA package, the package is formed into a 6-layer constitution with the amount of a pattern formation layer for plating use added thereto, but according to this manufacturing method, a two-stage wire bonding package of a 4-layer constitution can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a ceramic package (ceramic container and wiring board) on which chips such as ICs and LSIs are mounted.

[Conventional technology]

Traditionally, ceramics for ceramic packages include:
Alumina is mainly used. Typical PGA
Taking a (pin grid array) package as an example, the manufacturing process of a ceramic package using this alumina green sheet is basically as follows.

That is, a predetermined organic binder, plasticizer, etc. are added to raw material alumina powder to form a green sheet, which is punched into a predetermined size and through-hole processed. Next, as the cross section is schematically shown in FIG.
~8m) are laminated and co-fired (approximately 1500°C, 142°C in a reducing atmosphere). After that, Ni and Au plating are performed on the pin soldering parts, wire bonding parts, and wire bonding parts for connection with external electrodes, and finally the terminal parts for plating (
This method involves cutting the dotted line in Figure 2).

[Problem to be solved by the invention]

However, the conventional ceramic package described above still has the following problems.

First, the firing temperature of alumina ceramic is 1500 to 16
Because the temperature is as high as 00°C, it is necessary to use a high melting point metal such as W or Mo in the conductor paste for the conductor circuit printed on the green sheet. However, these metals have high sheet resistance, so the conductor line width becomes thick.
Planar circuit patterns cannot be made fine.

In addition, for wire bonding and gui bonding using gold wire, as mentioned above, it is necessary to perform surface treatment of the wiring conductor (Mo, W, etc.) by plating Ni and Au after firing, but this plating is usually Since this is done by plating, a plating electrode is required, and a circuit to take this plating terminal out to the outside is essential. Furthermore, as a post-baking process, when attaching pins, it was necessary to apply Ni plating to the soldered parts, and in the case of leadless packages, it was necessary to apply Au plating to the connection parts with external electrodes.

As described above, since it is difficult to thin the wires and a plating circuit is also required, the number of laminated layers inevitably increases.For example, as shown in Figure 2, in the case of a two-stage wire bonded alumina PGA package, It had a six-layer structure including two pattern forming layers for plating. In addition, the manufacturing process is complicated because there are many plating steps after simultaneous firing.

In view of these circumstances, this invention reduces the number of laminated layers and manufacturing steps by eliminating the plating process and creating a fine pattern by lowering the resistance of the inner layer conductor.
An object of the present invention is to provide a method for easily manufacturing a ceramic package.

[Means to solve the problem]

For fine patterning, Au and A are used for conductor circuits.
It is necessary to use low-resistance metals such as G, Cu, etc., but since the melting points of these low-resistance metals are around 1000°C, they cannot be used in combination with the above alumina ceramics, which have a high firing temperature. There is a problem. Therefore, the development of so-called ceramic substrate materials for low-temperature regulation, which can be fired at a temperature below the melting point of this low-resistance metal, is progressing, and attempts are being made to combine the above-mentioned low-resistance metal as a conductor metal.

In the production of ceramic packages, the inventors used such low-temperature firing ceramics to lower the resistance of the inner layer conductor, and by printing conductors on the bonding parts as well as the circuit parts before firing, the inventors succeeded in reducing the resistance after firing. It was discovered that the plating process could be omitted, and this invention was completed.

Therefore, the method for manufacturing a ceramic package according to the present invention includes printing a conductor using a metal paste on at least the Gui bonding part, the wire bonding part, and the circuit part on a ceramic green sheet for low-temperature firing.
Make sure to simultaneously fire at a low temperature.

Gold paste is applied to the wire bonding parts and wire bonding parts, metal paste containing at least one of copper, copper oxide and silver is applied to the circuit parts, and nickel and nickel oxide are used to the pin connection parts when soldering pins. It is preferable to use a metal paste containing at least one of these metal pastes.

In addition, the glass composition that serves as a raw material for the ceramic green sheet for low-temperature firing includes 48 to 63% by weight of SiO2, 10 to 25% by weight of A1201, 10 to 25% by weight of MgO, and 4 to 10% by weight of BtOs. , respectively, and 20% of the market weight of the MgO
The following are substituted with at least one of Bad, SrO, and CaO, and T is used as a nucleating agent.
i 02 , Z r Ox , M o OxPg
0%, ASt'Os, and 5nOz may be added in an amount of 5% by weight or less.

[For production]

Since a ceramic green sheet for low-temperature firing is used, conductor printing can be performed using a low-resistance metal with a low melting point such as ALL Ag or Cu, and then simultaneous firing can be performed at a low temperature. In other words, the circuit pattern can be refined. Furthermore, since necessary conductor printing is performed on the bonding portions and the like as well as the circuit portions before firing, the plating step after firing can be omitted, and a circuit pattern for plating is also unnecessary. From the above, it is possible to reduce the number of laminated layers in the package. At the same time, the manufacturing process
For example, in the case of a low-temperature fired ceramic PGA package,
After the binder and firing process, it is only necessary to braze the pins, which is much simpler than conventional methods.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the drawings showing one embodiment thereof.

First of all, regarding the ceramic green sheet for low temperature firing,
There is no particular limitation as long as it can be fired at a temperature lower than the melting point of the metal for conductor printing. Usually, a low resistance metal such as Au (melting point 1063°C), Cu (melting point 1083°C), Ni (melting point 1455°C), which can be fired below its melting point, is selected. This green sheet is made by adding a sintering aid to any low-temperature firing ceramic, thoroughly mixing it, and then adding an organic binder, additives, solvent, etc., and casting the resulting mixed slip using a conventional method. can get.

Regarding the above-mentioned sintering aid, organic binder, binder, etc., commonly used ones can be arbitrarily selected as required. Further, typical examples of the raw material ceramics for low-temperature firing include a mixture of alumina and glass (borosilicate glass, etc.), crystallized glass (glass ceramics), and the like. More specifically, it is preferable to use the powder of the glass composition according to claim 3 as a raw material because it takes on a cordierite crystal structure with a low dielectric constant after firing.

In this glass composition, the composition ratio of 5ift is 48
~63% by weight (hereinafter simply referred to as "%"). If this exceeds 63%, a dense sintered body cannot be obtained, and on the other hand, if it falls below 48%, the crystallization rate increases and the temperature reaches 950°C.
If the firing temperature is lower than that, sufficient crystallization may not be achieved or densification may become difficult.

The composition ratio of AItos is set at 10 to 25%, and when this upper limit is exceeded, the temperature at which sintering can be performed increases, and sufficient sintering cannot be performed at a firing temperature of 950°C or less. -SiO□ due to fewer crystals
- Since many MgO-based crystals precipitate, the relative permittivity increases.

The composition ratio of MgO is also set at 10 to 25%,
If it exceeds 25%, deformation becomes large, probably due to the precipitation of magnesium silicate, which is impractical, and if it falls below 10%, it is difficult to form a dense sintered body.

B20. The composition ratio of 4 to 10% is selected. If this exceeds 10%, the glass phase will be large and foaming will occur easily, and the firing temperature range will also be narrowed. In addition, the mechanical strength becomes weak, making it impractical. On the contrary 4
%, the surface layer of the glass powder crystallizes too rapidly, making it difficult to obtain a dense sintered body.

In addition, Bad, SrO and Ca to replace the above MgO
The substitution rate of O is set to 20% or less, and if it exceeds this, M
Since the gO component decreases, precipitation of α-cordierite crystals becomes worse. Note that, in order to lower the dielectric constant, the substitution rate is preferably 3% or more.

Furthermore, in order to more reliably form the crystals of the sintered body into α-cordierite, a nucleating agent is used at a composition ratio of 5% or less. If the content of the nucleating agent exceeds 5%, the crystallization rate becomes extremely high, resulting in a sintered body that is not sufficiently densified.

The above-mentioned glass composition is obtained by melting each raw material component and then rapidly cooling it, which is then ground into powder and used as a green sheet raw material. In addition, since the above is the composition at the glass composition stage, it is also possible to use materials other than the listed oxides as starting materials, that is, materials that can eventually become each of the above oxides. It is possible.

The obtained green sheet is subjected to external cutting and drilling for through holes (via holes) as necessary. Next, the following parts 0 to 0: ■ Die bonding section where the chip is mounted, and wire bonding section, ■ Planar circuit (routing circuit) section and vertical circuit (through hole) section, ■ PGA, DIP (circuit dip) type, etc. For packages that require soldering of pins, use any metal paste for the pin connection part, and for packages that do not require pin soldering, such as LCC (leadless chip carrier), use the external connection terminal part. Perform conductor printing in accordance with the law.

The metal paste used may be any metal (especially low-resistance metal for circuit parts) as a conductive material, and may be made into a paste by adding the necessary organic binder, solvent, etc., and there are no particular limitations. Not done. If necessary, one or more of these may be used in combination for printing 0 to 0 copies.

For example, it is preferable to use gold paste for the bonding part (2) above. However, it is equally preferable to replace the die bonding part with a hole (oxidized T14 paste), but as for the wire bonding part, since wire bonding is usually performed using a gold wire,
Most preferably, the conductor layer is formed of gold paste. In this wire bonding, it is required to ensure adhesion to the ceramic substrate as well as wire bondability. In this case, the purity of gold is important for wire bonding properties, and the type and amount of glass frit added to the paste plays a major role in terms of adhesion to the substrate. Therefore, in order to satisfy both of these requirements, 100 parts by weight (hereinafter simply referred to as "parts") of glass flint with a softening temperature equal to or lower than that of the glass used in ceramics for substrates must be added. It is recommended to add about 0.5 to 5 parts.

It is preferable to use a metal paste containing at least one of copper, copper oxide, and silver for the circuit section (2) above. In this copper, copper oxide paste, etc., in terms of sheet resistance and adhesion to the substrate, as mentioned above, glass frit with a softening temperature equal to or lower than the glass used for ceramics for substrates is added to 100 parts of copper. It is appropriate to add about 0 to 10 parts. For circuit use, this copper, copper oxide paste, etc. may be fritless, but
When used in another part (for example, a die bonding part, etc.), it is preferable to contain a frit.

Furthermore, it is preferable to use nickel paste for the pin connection portions of the PGA package, etc. in the above item (2). Since silver solder is usually used for soldering these pins, compatibility with the silver solder and adhesion with the substrate are required.

Therefore, nickel paste 1 is prepared by adding 0.65 to 10 parts of glass frit similar to the above to 100 parts of nickel.
- is preferred. On the other hand, it is preferable to use copper or gold paste for the external connection terminal portion of the LCC package, etc. in the item (2) above.

If necessary, a plurality of green sheets with conductor printing applied thereto are laminated and pressed to be bonded and integrated with each other. Then, as in the usual manufacturing method, the green sheet and the conductor paste are sintered at the same time by firing at a low temperature using an appropriate heating furnace or the like.

The firing schedule, such as the atmosphere and temperature for 1 hour in the firing process, is not particularly limited, but it is preferable to divide the firing process into three stages and perform them sequentially, as shown below, for easy management of the firing process.

First, the organic binder, solvent, etc. in the green sheet are completely burned off by heating in an oxidizing atmosphere (for example, air). The heating temperature at this time may be relatively low. At this stage, depending on the type of metal conductor in the conductor paste, part or most of it is oxidized to become a metal oxide such as copper oxide.

Next, a five-component atmosphere (e.g. II2 gas, N2+14z
(mixed gas, etc.), but prior to this, it is preferable to expel the atmosphere and combustion gas from the previous stage with N2 gas, etc., and then introduce the gas. In this reduction stage, the conductive metal that has become oxidized in the previous stage is reduced back to its metallic state. The temperature at this time, that is, the reduction temperature, is set at a temperature at which the reduction reaction is carried out well and at a temperature at which sintering of the metal conductor and the ceramic material of the green sheet begins. Specifically, the temperature is usually preferably about 300 to 600°C.

Finally, the green sheet and the conductor paste are simultaneously sintered and integrated in a non-oxidizing atmosphere (for example, N2 gas, etc.). The sintering temperature at this time varies depending on the ceramic material for low-temperature firing used, but is usually 800 to 1000.
It is carried out at around ℃.

Note that the metal conductor reduced in the previous step is not oxidized again by heating in a non-oxidizing atmosphere in this step, and a metal conductor layer that remains in a reduced state is obtained after sintering.

Here, as described above, in a package (such as an LCC) that uses a connection method that does not use pins, it is preferable to perform conductor printing using copper (copper oxide) or gold paste on the external connection terminal portion. Therefore, when copper/copper oxide paste is used in the circuit part, it is preferable to select the same three-step firing process as above, since the entire conductor layer will be a combination of gold paste and copper/copper oxide paste. When silver paste is used for the circuit portion, by selecting gold paste for the terminal portion, a conductor layer consisting of only the gold paste and the TA base 1 can be formed. In the case of the combination U of gold and ↑V, firing can be performed only in an oxidizing atmosphere, which greatly simplifies the firing process and facilitates manufacturing.

In addition, when forming a copper conductor layer and a nickel conductor layer,
It is preferable to use copper oxide powder or nickel oxide powder for the paste I, rather than using metallic copper powder or nickel powder, and to perform the three-step firing process as described above. This is because the material cost of oxides is lower than that of metals in a reduced state, which makes them more economical, and metals in a reduced state are oxidized once during the binder removal process in the firing process, but at that time they expand. However, metal oxides do not cause such problems. When using copper oxide and nickel oxide, the formulation should be made in terms of metallic copper and metallic nickel.

Summarizing the above, an example of the manufacturing process and configuration of a low temperature firing ceramic PGA package will be shown below. First, a green sheet is produced using ceramics for low-temperature firing, and then punched. Next, as the cross section is schematically shown in Fig. 1, a conductor is printed on the green sheet 1, and conductors i21 and 22 made of gold paste are applied to the bonding part and the wire bonding part.
A conductor layer 3 made of copper (I'm copper oxide) or silver paste is formed on the plane and vertical circuit parts, and a conductor layer 4 made of nickel (nickel oxide) paste is formed on the pin soldering part. Then, after stacking these and cutting the outline, low-temperature binder removal and firing are performed, and finally,
Pin 5 is soldered and the ceramic package is completed after inspection. In this way, even in the same two-stage wire bonding PGA package, in the case of an alumina PGA package, it has a six-layer structure including a pattern forming layer for plating, but according to the manufacturing method of this invention, four layers can be formed. Two-stage wire-bonded low-temperature fired ceramic PGA
package can be realized. As shown in FIG. 1, a copper/nickel conductor layer 6 for a sealing member such as a metal cover (cap) may be formed on the top layer of the stack.

Further detailed embodiments of the present invention will be described below with reference to the drawings.

Example 1 - ■ Production of ceramic green sheet for low temperature firing Si0
．． 57 parts, A1.0224 parts, M[014 parts and B,
After melting 0.5 parts at 1450° C., a uniform glass lift was obtained by rapidly cooling. Next, this was ground in an alumina bot mill to obtain a glass powder with an average particle size of 1.6 am.

An organic binder, a plasticizer, a dispersant, and a solvent were respectively added to the above glass powder according to a conventional method, and these were thoroughly mixed in an alumina pot mill. The obtained mixed slip was cast by a doctor blade method to produce a green sheet having a thickness of about 0.6 Ill after drying. Furthermore, using this, a punched sheet with through holes was produced using a punching press.

(2) Preparation of Gold Paste To 100 parts of gold powder with an average particle size of 0.9 μm, 2 parts of glass frit with a softening temperature of 700° C. and an average particle size of 1.5 pm were added. Here, ethylcellulose (-binder)
A binder solution, which had been previously dissolved with butylcarbyl acetate, was added to form a paste to obtain a gold paste.

■ Preparation of copper oxide paste 100 parts of copper oxide powder with an average particle size of 1.2 am (copper equivalent: 8
0 parts), 3 parts of glass frit powder similar to the above (■) and ethyl cellulose binder. g Add H substance, 3
It was made into a paste using this roll.

■ Preparation of nickel oxide paste For 100 parts of nickel oxide powder with an average particle size of 1.0 μm and 79 parts of sokel equivalent), add glass frisol similar to the above
-4.5 parts and ethyl cellulose binder melt were added to form a paste.

■ Conductor printing Gui bonding part and wire bonding part (inner lead pad) of the green sheet made in above ■
Then, screen printing was performed using the gold paste prepared in ① above. Next, the circuit routing section (planar circuit section)
Print the 214 oxide paste prepared in step ``-'' on the through-hole section (vertical circuit section), print the nickel oxide paste prepared in step ① above on the connecting pin soldering land, and apply the above conductor paste. Dry thoroughly.

■ The green sheet with conductor paste prepared in step 2 of ``Lamination and firing'' was
The sheets were stacked and thermocompression bonded under the conditions of 70°C and 60 kg/cn.

After removing the binder from this laminate in an oxidizing atmosphere (atmosphere) according to the profile shown in Figure 5, it was then treated in a reducing atmosphere (NZ + 10% Hz) according to the profile shown in Figure 6.
A ceramic package was produced by firing in a mixed gas (mixed gas) and a neutral atmosphere (N2 gas).

■ Pin brazing Using BAg-7 brazing material, a 42 alloy pin was brazed (700°C, 3 minutes) to the nickel land of the ceramic package obtained above to produce the low-temperature fired ceramic l) shown in Figure 3. An A package (180 pin two-stage wire bonding type) was manufactured. In addition, in the same figure, W3. W
2, Wx and W4 are 40.0, 16.0 in this order
, 14.0, 12.0 (unit s*), H= 2
．． 0 + u.

Example 2 The same green sheet, gold, copper oxide, and nickel oxide paste as in Example 1 were used, and the procedure was the same as in Example 1, except that the copper oxide paste was printed on the die bonding area. Low-temperature fired ceramic PGA shown in Figure 3
A package was created.

Example 3 A low-temperature-fired ceramic PGA package shown in FIG. 3 was produced in the same manner as in Example 1 above, except that the following was used as the raw material glass powder for the low-temperature-fired ceramic green sheet. .

[Preparation of glass powder]

310!57.1 parts, Al20123.8 parts, Mg01
2.4 parts of CaO, 1.9 parts of CaO, 1.8 parts of B,O, and 52.0 parts of P,O were dissolved in the same manner as in Example 1 above.
+? 1! , quenched, and pulverized to obtain glass powder with an average particle size of 2.2 μm.

Example 4 - LCC chain...
- Gui bonding part using the same green sheet gold and copper oxide paste as in Example 1 above.

Circuit section and external connection terminal section (outer lead pad)
After printing the same oxidized paste and the gold paste on the inner lead part, it was fired in the same manner as in Example 1, and the fourth
The 44-terminal LCC package shown in the figure was manufactured. In addition, in the same figure, W=16.0 fins and W$=6.8 fins.

Example 5 - *4 Construction of LCC page 4 A green sheet was made using the same glass powder as in Example 3 above, except that gold paste was used in the bonding part. 4 in the same manner as in Example 4 above.
A 4-terminal LCC package was manufactured.

Example 6 ★4 LCC page I Akira'iL
A CC package with 44 terminals was manufactured in the same manner as in Example 5, except that gold paste was also used for the outer lead portion and copper oxide paste was used only for the circuit portion.

Example 7 - ★, Difference in the construction of LO shearing CC package (Take 4 Akira) ■ Preparation of ceramic green sheet for low temperature firing 5iO
z54.5 parts, A+, ot18.2 parts, Mg014, 5
part, B20, 9.1 parts, PzOsl, 8 parts and 8.1 parts
101.8 parts were melted, rapidly cooled, and pulverized in the same manner as in Example 1 above to obtain 17 glass powders with an average particle size of 2.5 μm.

Using the above glass powder, a green sheet was produced in the same manner as in Example 1, and this was processed into a perforated sheet with through holes.

■ Preparation of gold paste For 100 parts of gold powder with an average particle size of 0.9μ, softened 1M
Two parts of glass frit having an average particle size of 1.4 μm were added at 4° C. at 680° C. The same ethyl cellulose binder melt as in Example 1 was added thereto to form a paste to obtain a gold paste.

(2) Preparation of silver paste To 100 parts of silver powder with an average particle size of 1.5 parts, 2 parts of glass frit with a softening temperature of 700° C. and an average particle size of 1.5 μm was added. The same ethyl cellulose binder melt as in Example 1 was added thereto to form a paste to obtain a silver paste.

After printing the gold paste obtained in step (1) above on the die bonding part, inner lead part, and outer lead part of the green sheet in step (2) above, and the silver paste obtained in step (2) above on the circuit part, Lamination was carried out in the same manner as in 4. Thereafter, it was fired in an oxidizing atmosphere according to the profile shown in FIG. 7 to produce a 44-terminal LCC puff cage.

The above examples are summarized in Table 1.

〔Effect of the invention〕

As described above, according to the terminology of the ceramic package according to the present invention, by using a ceramic green sheet for low-temperature firing, it is possible to form a circuit using a low-resistance metal and refine the circuit pattern. moreover,
Since the necessary conductor printing is performed on the bonding portion and the like as well as the circuit portion before firing, the plating step after firing can be omitted, and a circuit pattern for plating is also unnecessary. I-L
Therefore, it is possible to reduce the number of layers in the package.

[Brief explanation of the drawing]

FIGS. 1 and 3 show low-temperature fired ceramic PGA obtained by the method for manufacturing a ceramic package according to the present invention.
An example of a package; FIG. 2 is an example of an alumina PGA pancake manufactured by a conventional method; FIG. 4 is an example of a low-temperature fired ceramic LCC package obtained by the ceramic package manufacturing method of the present invention; Both FIG. 6 and FIG. 7 are graphs showing firing (including binder removal) profiles in one embodiment of the present invention. l... Ceramic green sheet for low temperature firing 21.
・Gui bonding part metal conductor Jfj 22...
Wire bonding department metal conductor problem 3...Circuit section 1
．． 1 Conductor layer agent Patent attorney Takehiko Matsumoto

Claims (1)

[Claims] 1. A ceramic package in which a ceramic package is obtained by printing a conductor using a metal paste on at least a die bonding part, a wire bonding part, and a circuit part on a ceramic green sheet for low-temperature firing, and then simultaneously firing it at a low temperature. manufacturing method. 2. Gold paste for the die bonding part and wire bonding part, metal paste containing at least one of copper, copper oxide, and silver for the circuit part, and at least nickel and nickel oxide for the pin connection part when soldering pins. 2. The method for manufacturing a ceramic package according to claim 1, wherein each metal paste contains one kind of metal paste. 3 A glass composition that is a raw material for a ceramic green sheet for low-temperature firing contains 48 to 63% by weight of SiO_2, 10 to 25% by weight of Al_2O_3, 10 to 25% by weight of MgO, and 4 to 10% by weight of B_2O_3. and 20% by weight of the MgO
The following are substituted with at least one of BaO, SrO and CaO, and Ti is used as a nucleating agent.
O_2, ZrO_2, MoO_3, P_2O_5, As
3. The method for manufacturing a ceramic package according to claim 1, wherein at least one of _2O_3 and SnO_2 is added in an amount of 5% by weight or less.