JPH08316641A - Multilayer wiring board manufactured by collective connection method - Google Patents

Abstract

PURPOSE: To join the laminated sheets of a multilayer wiring board to each other at a temperature capable of the heat resistance of the sheet being secured and obtain a junction organization with a larger heat resistance than solders, by bonding to each other with resin the portions other than the Au-Sn junctions of the electrode portions of the sheets. CONSTITUTION: Onto the copper conductor of the junction portion of one side of a board, an Sn plating of 1-3μm, preferably 3μm, in thickness is applied, and onto the copper conductor of the other side of the board, an Au plating of 0.3μm in thickness is applied, and double-sided conductor forming films are superimposed on each other in multilayer. Then, in either of the atmosphere, an inert gas atmosphere and a reducing gas atmosphere of 300-350 deg.C in maximum temperature and 10-20MPa in pressure, the junction portions of the double-sided conductor films are joined with metal to each other by a thermo-compression bonding, and the portions other than these Au-Sn junction portions are bonded with resin to each other to be hardened. In the interlayer connective bonding of this multilayer wiring board, when a liquid phase is formed in case of the Au-Sn joining, it is apt to generate bridging faults because of the flowings of alloys into its electrodes. Therefore, by so using bonding resins 5 in the bonding portions other than the metallic junction portions as for them to be bonded to each other and be hardened, the bridging faults are prevented.

Description

Detailed Description of the Invention

[0001]

[Field of Industrial Application] A multilayer wiring board is one in which a conductor circuit is formed in three or more layers by combining an inner conductor circuit of a substrate material and a surface layer conductor circuit, and is mainly used in industrial electronic devices. Recently, it has also been used in highly functional consumer electronic devices. The present invention relates to an interlayer connection adhesion method for a multilayer wiring board suitable for high-density mounting, a multilayer wiring board using the same, and a mounted product.

[0002]

2. Description of the Related Art With the miniaturization, thinning, high integration, and speeding up of electronic components, in multi-layer wiring boards, there are demands for higher wiring density, thinner boards, heat resistance of connecting portions, and lower wiring resistance. Is getting more and more severe. Recently, a method has been adopted in which a polyimide sheet is used as a wiring board, and a laminated board having a pattern formed by etching or the like is laminated by hot pressing. In addition, the connection between layers is mainly solder,
Au-Au is used.

As a method for laminating sheets, Japanese Patent Laid-Open No. 04-1
In the method described in Japanese Patent No. 62589, as the sheet material,
Although it is stated that polyimide is applied to an Au film and Au plating is applied on the Au film, Au-Au is used for connection and lamination is performed, but detailed bonding conditions are unknown.
Au-Au bonding is generally performed in a high temperature region of 350 ° C. or higher, which is a problem because it exceeds the heat resistant temperature of the polyimide sheet. If the connecting material is solder, the temperature can be lowered, but since it is necessary to join without using flux, the material composition, conditions, etc. are limited, and it is not easy to join, and the heat resistant temperature of the joint is low.

[0004]

In view of the above problems, an object of the present invention is to bond sheets at a temperature of about 300 to 350 ° C., which can secure the heat resistance of the sheets, and has a heat resistance higher than that of solder. (EN) It is intended to provide a collective connection method for obtaining a joint structure having high property and a multilayer wiring board using the same.

[0005]

In the case of Au—Sn plating bonding, a brittle intermetallic compound layer of Au—Sn is easily formed in the bonding portion, and the bonding strength is determined by the thickness of this compound layer.
The structure and composition of the joint vary greatly depending on the process conditions such as joint temperature, pressure and time and the plating thickness. Therefore, in the present invention, the relationship between the process conditions and the Au and Sn plating thickness and the bonding strength is experimentally investigated, and Au-
The bonding conditions (process, member) that minimize the formation of the Sn compound layer have been found. Note that Au-Sn is a liquid phase bonding that forms an Au-Sn molten alloy at the time of bonding.
Therefore, when the joints have a narrow pitch, the melted alloy flows into another electrode, and a defect called a bridge in which the distance between the electrodes is short is likely to occur. Therefore, in the present invention, A of the electrode portion is
By bonding the parts other than the u-Sn junction with resin,
Prevented bridge failure. Also, Au-Ag bonding using Ag plating instead of Sn plating is solid phase bonding,
Compared with Au-Sn joining, a higher pressure is required at the time of joining, but since a liquid phase is not formed at the time of joining, there is no need for resin bonding. Furthermore, since Au-Ag is a system that does not form an intermetallic compound, high bonding strength can be obtained. Since Au plating is expensive, Sn-Ag bonding using Sn plating is used instead of Au plating when cost reduction is required.

[0006]

[Operation] Au-Sn, Au-
By adopting collective bonding by plating Ag or Sn-Ag, it is possible to bond at a relatively low temperature. Au-
In the Sn junction, a heat-resistant junction can be obtained by controlling the junction conditions to thin the Au—Sn compound layer formed in the junction and make the composition Au-rich.
Since Au-Ag junction does not form an intermetallic compound, high strength can be expected. Further, the joining by plating does not require flux unlike the joining by soldering. Therefore, the cleaning process is not necessary and cost-effective, and since CFCs that destroy ozone are not used, the method is considered to be environmentally friendly.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An interlayer connection bonding method for a multilayer wiring board and a multilayer wiring board product using the method according to an embodiment of the present invention will be described below.

FIG. 1 shows a multilayer wiring board which is an embodiment of the present invention. This is a polyimide tape 1 with a Cu sheet 2
After drilling a via hole in the sheet where
Is used as a cathode to perform electroplating of Cu to fill the via 3 with the conductive metal 3. Then, the via metal tip is electroplated with a bonding metal. On the other hand, Ni is formed on the Cu foil 2 pattern formed by applying the resist 5 and etching.
The plating 7 of the joining metal is applied via the base plating 6. The diameter of the via hole 3 is about 0.03 mm. Therefore, the area of the connection part is about 0.3 × 10-2mm2 and the pitch is 0.1mm.
And is very fine. The thickness of one layer of the substrate is 0.1
mm.

Generally, the joint is evaluated by measuring the strength by a peel test. The multilayer wiring board of the present invention can be evaluated collectively, but since it is fine bonding, it is not possible to evaluate the bonding portions one by one and it is not possible to select an appropriate bonding condition and plating thickness.

Therefore, in the present invention, a model sample was used to experimentally examine the combination of the joining metals and the appropriate joining conditions when the substrates (sheets) are laminated by thermocompression bonding.

FIG. 2 is a side view of a bonding model sample and a heating head for experimentally examining the optimum bonding conditions of the interlayer connection bonding method for a multilayer wiring board. The joining was performed using the upper and lower heating heads 8 and 9 heated to the same temperature for the purpose of uniformly heating the joined portion. Actually, the upper tool 8 descends to heat and press the sheet. The bonding material is 0.1mm thick, 3mm wide, and 20mm long, and is a polyimide film 9.
A Cu tape 10 having a thickness of 35 μm was used.
The upper tool side 8 has a polyimide film 9 as a joining member.
After forming a via hole 11 from the side, Cu 10 is used as a cathode to perform electroplating of Cu to form a conductor metal 11 in the via 11.
Filling, and finally bonding metal plating to the tip of the via 1
The member subjected to 2 was arranged. The diameter of the via hole 3 is
0.1 mm, and the plated portion 12 at the tip has a width of 0.2 mm. On the lower joining tool 9 side, a member having Au or Sn plating 12 applied to the entire surface of the Cu tape 10 through a 0.5 μm Ni undercoat 11 is arranged. The bonding atmosphere was air, an inert atmosphere, or a reducing atmosphere. Regarding joint strength, per connection point of laminated sheet with actual connection width of 0.03 mm (actual via hole diameter of multilayer wiring board)
Assuming a strength of 10 g is required, which corresponds to a peel strength of about 30 N / cm, this strength was determined to be the required strength when evaluated with a model sample.

FIG. 3 shows the temperature / pressure dependence of the bonding strength when the upper tool side member is plated with 3 um Sn and the lower tool side member is plated with 1.2 um Au on the Cu lead via the Ni underlayer. Indicates. Other joining conditions are a pressure of 20 MPa and a time of 20 seconds. From this result, the joining temperature is 250 ℃.
Although the strength was low at the temperature below, the strength increased at a temperature higher than this, and the strength exceeding 30 N / cm on average could be obtained at 300 ° C. or higher. The bonding atmosphere may be air, an inert atmosphere, or a reducing atmosphere.

When the joining temperature must be lowered, this plating thickness combination has low strength. In such a case, the Sn plating can be thickened and the Au plating can be thinned to make the composition of the bonding portion Sn-rich and lower the melting point to bond at a low temperature of 250 ° C. or lower.
A value close to the required strength (30 N / cm) was obtained when the Sn plating was 10 μm and the Au plating was 0.3 μm, and the joining was performed under the conditions of 220 ° C., 20 seconds and 20 MPa.

FIG. 4 shows that the Au plating thickness is kept constant at 1.2 μm,
The Sn plating thickness dependency of the strength when bonded under the conditions of a temperature of 300 ° C., a time of 20 seconds and a pressure of 20 MPa is shown. As a result, the bonding strength is highest when the Sn plating is 3 μm, and the strength tends to be low when the Sn plating is thick or thin.

FIG. 5 shows an example of the sectional structure of the Au--Sn junction. In the case of Au-Sn, it is considered that when the joint portion is heated, the Sn-plated portion having a low melting point is first melted, and Au is melted into this Sn to be joined. In Au-Sn system, Sn plating is thick and Au plating is thin to lower the bonding temperature.
A joining method is often used in which a Sn-rich molten alloy is formed into a fillet and this maintains the strength of the joint. However, this joint has no heat resistance because the joint structure is Sn-rich. To increase the heat resistance, it is necessary to raise the bonding temperature, but in this case, since the weak compound layer of Au-Sn is formed thickly over the entire bonding layer in the bonding part,
The strength is greatly reduced. Therefore, in the present invention, the Au plating is thick, the Sn plating is thin, the joining temperature is set to be slightly high, and the time is set to be long, so that the joining layer is mainly composed of the Au-rich alloy layer 14 as shown in FIG. By suppressing the formation of the Au—Sn compound layer 15, it was possible to obtain a sound and strong joint.

FIG. 6 shows the temperature / pressure dependence of the strength of the Au—Ag joint using Ag plating instead of Sn plating. The bonding time is 10 seconds and the Au plating thickness is 0.6um.
Is. Bond strength depends on temperature and pressure. Pressure is
When it is as low as 20 MPa, 18 has low strength regardless of temperature. On the other hand, when the joining pressure is 50MPa 19 or more, the strength rises as the temperature rises, and when joining at 50MPa, it is 350 ℃ or more at 19 and 100MPa at 20 ℃ at 300 ℃.
A strength exceeding 40 N / cm could be obtained. Note that A
Compared with the case of u-Sn junction, higher temperature and pressure are required, but the joining strength is much higher.

FIG. 7 shows a joining temperature of 350 ° C., a time of 10 seconds and a pressure of 5
It is an example of a cross-sectional structure of an Au-Ag joint when they are joined at 0 MPa. It is known from the phase diagram that the Au-Ag system is a system that does not form an intermetallic compound.
It was confirmed from the interface with the g-plating 19 that the compound layer was not formed at the joint. Further, the Au-Ag system is solid-phase bonding that does not form a liquid phase. In such joining, it is considered that the joining portion is brought into contact by heating and pressurizing the joining portion with a heating tool to destroy the oxide film on the plating surface to expose a new surface of Au and Ag and to bring them into contact with each other. In addition, since the temperature and pressure are low, the oxide film on the plating surface is destroyed and Au, A
When the contact between g plating is insufficient, they are not joined and remain as unjoined portions. In the case of FIG. 7, since the joining temperature and pressure are high, the joining is sound and there is no unjoined portion. In addition,
The unbonded portion tends to increase as the temperature becomes lower and the pressure becomes lower, so that the strength becomes low. The bonding strength depends on the Ag plating thickness, and stable strength can be obtained at 5um or more.
The newly formed surface is insufficiently formed due to the plastic deformation of the plating, resulting in low strength. The thickness of Ag plating is preferably 5um or more.

FIG. 8 shows that the member on the upper tool side has Ag of 7 μm.
When the plating and the member on the lower tool side are plated with 0.6 μm of Sn on the Cu lead, that is, the temperature dependence of the strength of the Sn—Ag bond is shown. The joining pressure is 20 MPa and the joining time is 20 seconds. As a result, the strength increased sharply at 300 ° C and above, and the strength of 40 N / cm and above could be obtained at 330 ° C and above. This method is a cost-effective combination because it does not include Au plating and the thickness of Sn plating can be made thinner than that of Au-Sn system, but when Sn plating is thin, bonding is performed. Since the strength is easily affected by the surface condition of the plating such as the formation of an oxide film, it is necessary to exercise caution in managing the members.

FIG. 9 shows an example of an interlayer connection adhesion method for a multilayer wiring board according to the present invention. The multilayer wiring board of the present invention is made of Au--Sn,
When forming a liquid phase at the time of joining such as Sn-Ag, the melted alloy easily flows into the adjacent electrodes, which easily causes a bridge failure. Therefore, in the present invention, the bonding resin 5 is used for the bonding portion other than the metal bonding, and the bonding resin 5 is bonded and cured to prevent the bridge. As the resin used, an organic adhesive such as epoxy is used. Note that Au-Ag
In the case of solid-phase bonding that does not form a liquid phase as described above, no resin bonding is necessary because no bridging failure occurs. However,
We believe that resin bonding is necessary to reinforce the strength of the joint.

The multilayer wiring board of the present invention is joined by thermocompression bonding. Therefore, the area of the substrate is determined by the area of the thermocompression bonding tool. Currently, up to 50 x 50 mm is possible.

10 and 11 show an example of a mounted product using a multilayer wiring board assembled by the interlayer connection bonding method of the present invention. In FIG. 10, a plurality of QFPs 23 each having a built-in LSI are mounted, and input / output pins 25 are provided on the back surface of the multilayer wiring board 24 of the present invention.
It is the perspective view which showed the structure of the multichip module which attached. FIG. 11 shows a multilayer wiring board of the present invention 100-200.
This is also an example applied to a narrow pitch mounting of um pitch, and an LSI is applied to the multilayer wiring board 24 manufactured by the interlayer connection bonding method of the present invention.
This is an example in which the chip 26 is mounted as a bare chip by flip chip (COB). Further, the multilayer wiring board of the present invention may have one or more elements such as LSI, resistors, capacitors, etc. built therein. FIG. 12 shows an example in which the LSI 30 is built in the multilayer wiring board of the present invention. As described above, by mounting the LSI inside, the mounting density can be improved, and the present invention can be applied to a field such as a card, which is required to be thin. In this case, the wiring board 33, 34 of the present invention is processed to produce the LSI 30.
After securing a space for housing the LSI, the bump 31 of the LSI and the plated portion of the substrate 32 are aligned and joined. Next, the substrates 32 and 33 are laminated. After that, a resin is filled in the space 36 in which the LSI is stored, and finally the substrate 34 is laminated. When the LSI is housed in the multilayer wiring board of the present invention, a space is provided to the LSI chip to some extent. Therefore, the number of layers of the substrate is determined by the thickness of the polyimide film of the substrate and the height of the LSI. It should be noted that other electronic components can be incorporated, and the components can be mounted on the surface of the substrate 35 and can be combined depending on the application.

[0022]

EFFECT OF THE INVENTION A method of stacking multi-layer wiring boards is described in Au-Sn,
By using a thermocompression-bonding heating tool, it is possible to carry out batch bonding by Au-Ag and Sn-Ag plating at a low temperature in a relatively short time. In addition, both have excellent heat resistance as compared with soldering. In particular, Au-Sn
In the case of joining, by optimizing the combination of joining conditions and plating thickness, the heat resistance of the joined part could be greatly improved.

[Brief description of drawings]

FIG. 1 is a joint structure of a multilayer wiring board according to an embodiment of the present invention.

FIG. 2 is a joining model sample for investigating the optimal joining conditions of the interlayer connection adhesion method.

FIG. 3 is a graph showing the temperature / pressure dependence of the bonding strength in an Au—Sn junction.

FIG. 4 is a graph showing the Sn plating thickness dependence of the bonding strength in Au—Sn bonding.

FIG. 5 is an example of a cross-sectional structure of Au—Sn junction.

FIG. 6 is a graph showing temperature-pressure dependency of strength of Au—Ag junction.

FIG. 7 is an example of a sectional structure of an Au—Ag joint.

FIG. 8 is a graph showing temperature / pressure dependence of strength of Sn—Ag junction.

FIG. 9 is an example of an interlayer connection adhesion method for a multilayer wiring board according to the present invention.

FIG. 10 is a perspective view showing the structure of a multi-chip module assembled by the interlayer connection bonding method of the present invention.

FIG. 11 is a front view of an example in which an LSI is mounted on a multilayer wiring board manufactured by an interlayer connection bonding method of the present invention by a flip chip (COB) as a bare chip.

FIG. 12 is a cross-sectional view of an example in which an LSI is built in the multilayer wiring board of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Polyimide tape, 2 ... Cu sheet, 3 ... Via hole and conductor metal, 4 ... Bonding metal plating layer, 5 ... Adhesive resin, 6 ... Ni underlayer plating, 7 ... Bonding metal plating layer, 8 ... Upper heating head, 9 ... Lower heating head, 10 ... Cu sheet, 11 ... Ni base plating, 12 ... Bonding metal plating, 13 ... Cu layer, 14 ... Au rich layer, 15 ... Au-Sn compound layer, 16 ... Au line analysis result, 17 ... Sn line analysis result, 18 ... Bonding pressure of 20 MPa strength result, 19 ... Bonding pressure of 50 MPa strength result, 20 ... Bonding pressure of 100 MPa strength result, 21 ... Au plating layer, 22 ... Ag plating layer, 23 ... LSI Built-in QFP package, 24 ... Multilayer wiring board manufactured by the interlayer connection adhesion method of the present invention, 25 ... Input / output pins, 26 ... LSI chip, 27 ... Bump, 28 ... Resin, 29 ... Heat shield 30 ... LSI chip, 31 ... Bump, 32 ... Wiring board of the present invention, 33 ... Wiring board of the present invention, 34 ... Wiring board of the present invention, 35 ... Wiring board of the present invention, 36 ... For accommodating LSI Space portion (filled with resin), 37 ... Via hole (conductive portion).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masayuki Kyoi, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd., Institute of Industrial Science, Hitachi, Ltd. (72) Inventor Hideo Togawa, 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd., Production Engineering Laboratory

Claims (6)

[Claims] 1. A through-hole is formed in a heat-resistant insulating film such as polyimide, copper conductors connected to the through-hole are formed on both sides of the film, and an adhesive is applied or applied to at least one side of the film, and a joint is formed by etching. In a double-sided conductor forming film formed by opening a window, Sn plating is applied to the copper conductor on one side on one side to 1 to 3 μm, preferably 3 μm.
Applying 0.3um Au plating on the copper conductor on the other side, stacking double-sided conductor forming films in multiple layers
~ 350 ° C, pressure 10 ~ 20MPa in air, in inert atmosphere or in reducing atmosphere by thermocompression bonding to bond metal parts between the double-sided conductor forming films and resin bond other parts. A method for bonding interlayer connection of a multilayer wiring board, which is characterized by curing, a multilayer wiring board using the same, and a mounted product using the same. 2. The double-sided conductor forming film according to claim 1, wherein Sn plating is applied on the copper conductor at one side of the joint by 10 ± 3 μm,
0.3 ± 0.1um of Au plating is applied on the copper conductor on the other side, and the double-sided conductor forming film is laminated in multiple layers, and the maximum temperature is 300 to 3
Thermocompression bonding is performed in the atmosphere of 50 ° C, pressure of 10 to 20 MPa, in an inert atmosphere, or in a reducing atmosphere to perform metal bonding between the joints between the double-sided conductor forming films, and resin-bond the other portions for curing. An interlayer connection adhesion method for a multilayer wiring board, a multilayer wiring board using the same, and a mounted product using the same. 3. The double-sided conductor-forming film according to claim 1, wherein the copper conductor at the joint portion on one side is Ag-plated with 5 to 10 μm,
Desirably apply 7um and Au plating on the copper conductor on the other side.
0.3 to 0.6 μm, preferably 0.6 μm, stacking double-sided conductor forming films in multiple layers, and thermocompression bonding in the atmosphere at a temperature of 350 ° C. and a pressure of 50 MPa or more, in an inert atmosphere, or in a reducing atmosphere. A method for interlayer connection and bonding of a multilayer wiring board, wherein a bonding portion between conductor forming films is metal-bonded, a multilayer wiring board using the same, and a mounted product using the same. 4. The interlayer connection bonding method for a multilayer wiring board according to claim 3, wherein in the double-sided conductor forming film and the plating combination, the bonding portions are metal-bonded and the other portions are resin-bonded and cured. And a multilayer wiring board using the same and a mounted product using the same. 5. The double-sided conductor-forming film according to claim 1, wherein the copper conductor at the joint portion on one side is Ag-plated at 5 to 10 μm,
Desirably, apply 7um, and Sn plating on the copper conductor on the other side.
0.4 to 1um, preferably 1um, stacking double-sided conductor forming films in multiple layers, maximum temperature 300 to 350 ° C, pressure 20 to
An interlayer connection bonding method for multi-layer wiring boards characterized by thermocompression bonding in the atmosphere of 50 MPa to bond the joints between the double-sided conductor forming films with each other, and then curing the other parts with a resin and using it. Multilayer wiring board and mounted products using the same. 6. The terminals according to claim 1, wherein one or more of an LSI element, an IC sensor, a module mounting the element, a resistor, a condenser, a coil, or the like is sandwiched between the double-sided conductor-forming films. A multi-layer wiring board characterized by completing connections at the same time and incorporating them.