JPH0864721A - Ball grid array package for multichip module and its manufacture - Google Patents

Abstract

PURPOSE: To enable a rework and the assembly at a low cost without the deterioration of the high speed response and the high density wiring by a method wherein outer ball electrodes made of solder and a ceramic or metallic lid which covers the MCM mounted on a single layer ceramic board are provided. CONSTITUTION: A multichip module(MCM) board 7, hereinafter referred to as MCM, on which a plurality of LSI chips 6 are mounted is bonded to a single layer ceramic board 1 having a number of through-holes 2 whose both ends are to be electrically connected. Further, the outer ball electrodes 13 of the solder filling the through-holes 2 and a ceramic or metallic lid 10 which covers the MCM mounted on the single layer ceramic board are provided. As MCM is mounted not on a multilayer ceramic board but on the single layer ceramic board 1, the cost of the ceramic board can be as low as 1/4 of the conventional cost. On the other hand, the high speed response and the high density wiring which are characteristics of MCM are not deteriorated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball grid array type package for a multi-chip module in which a plurality of LSI chips are mounted on one substrate.

[0002]

2. Description of the Related Art Conventional multi-chip module (hereinafter abbreviated as MCM) packaging technologies include those focusing on package reliability and those focusing on cost reduction. Here, MCM is M, which is a high-density wiring board.
This refers to the entire CM board on which a plurality of LSI chips are mounted.

For reliability, the MCM substrate 7 on which the LSI chip 6 is mounted, that is, the MCM and the pin grid array 22 are mounted on the laminated ceramic substrate 21 shown in FIG. A pin grid array type package that performs hermetic sealing by electrically welding metal lids one by one in an atmosphere chamber and a quad flat package that uses a lead frame instead of the above pin grid array. and so on. Further, in order to reduce the cost, the MCM and the lead frame 26 as shown in FIG. 6 are molded resin 27.
There is a plastic package that shields the MCM from the outside air by covering it with.

[0004]

However, in the packaging method as shown in FIG. 5, although rework is possible, an expensive laminated ceramic substrate 21 must be used because a pin grid array or a lead frame is used for the external terminals. There is a drawback in that the cost is inevitably increased because it is not obtained, and each is hermetically sealed by electric welding. See also FIG.
The resin encapsulation as described above has a drawback in that the package cannot be disassembled once encapsulation is performed and rework cannot be performed.

Rework is the packaged MC.
The operation test of M is performed, and when a defective LSI chip is found, the defective LSI chip is removed and replaced with a good product. Since multiple LSI chips are registered in MCM, the good product rate of MCM is
It is the product of the good product rate of each chip. Therefore, as the number of chips to be mounted increases, the non-defective rate decreases significantly, and in a configuration in which reworking is not possible, the production cost may increase even if the unit price of the package component is low. An object of the present invention is to realize a ball grid array package for MCM which can be reworked and can be assembled at low cost without impairing the features of MCM such as high-speed response and high-density wiring.

[0006]

In order to achieve the above object, the present invention provides a ball grid array package for a multi-chip module having a large number of through holes electrically connected at both ends thereof. A single-layer ceramic substrate formed with a pad electrode and a thick film wiring formed of a material that reacts with solder located around the through hole; and an external ball electrode of the solder that closes the through hole.
Multi-chip mounted on the single-layer ceramic substrate
Composed of a ceramic or metal lid that covers the module, after fixing the above components with resin or glass, melt the solder balls placed on the through holes of the single-layer ceramic substrate under vacuum or an inert gas atmosphere, The package was hermetically sealed by simultaneously reacting with the pad electrode and closing the through hole, and the solder remaining outside the through hole was used as an external ball electrode.

[0007]

The operation of the present invention will be described with reference to FIGS.

First, in the ball grid array package for MCM of the present invention, the electrical connection between the MCM and the outside is made as follows. Through-holes are formed by bonding wires 9 between the MCM substrate 7 and the single-layer ceramic substrate 1, and by thick-film wirings 4 formed between the bonding pads 5 and the through-holes 2 on the single-layer ceramic substrate 1 (see FIG. 4). Both ends of 2 are electrically connected by a process such as applying a conductive paste to the inner wall of the through hole 2. The solder remaining outside the through hole 2 when the solder ball 12 is melted and the through hole 2 is closed functions as the external ball electrode 13.

Next, the hermetic sealing is performed as follows. First, the boundary between the single-layer ceramic substrate 1 and the lid 10 is sealed with resin or glass. At this time, the inside of the package and the outside air are the through holes 2 of the single-layer ceramic substrate 1.
Only through. Next, after sealing between the single-layer ceramic substrate 1 and the lid 10, the inside of the package is evacuated or purged with an inert gas. After that, through hole 2
Airtight sealing is completed by melting the solder ball 12 placed on the upper side and closing the through hole 2. Blocking here means
This means a state in which the openings of the through holes 2 are all covered with solder and the movement of gas or the like is interrupted, and it does not matter whether the solder has entered the through holes 2 or not. Since the pad electrode 3 (see FIG. 3) formed around the through hole 2 is formed of a material that reacts with solder, the solder ball 12 firmly adheres to the through hole 2.

Next, rework is performed as follows. First, when a defective LSI chip is found, the package is heated to lower the adhesive strength of the resin or glass, and the lid 1
0 is separated from the single-layer ceramic substrate 1. Next, if the LSI chip 6 and the MCM board 7 are connected by solder, the solder is melted, and if the bonding wire is connected, the wire is cut, and then the defective LSI chip is removed from the MCM board 7 by the lid. Peel off in the same manner as when peeling off 10 and replace with a good product. After replacement of the LSI chip, rework is completed by packaging the MCM according to the manufacturing method of the present invention according to claim 2.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a sectional view of an embodiment of the present invention. According to the present invention, a plurality of L's are provided on a single-layer ceramic substrate 1 having a large number of through holes 2 electrically connected at both ends.
MCM board 7 on which SI chip 6 is mounted, that is, MCM
Are glued together. Further, the lid 10 is bonded on the single-layer ceramic substrate 1 so as to protect the MCM. Further, under the through hole 2,
The external ball electrode 13 made of solder is formed.

The manufacturing method of the present invention will be described below with reference to the flow chart of FIG. 2 showing the procedure for assembling the ball grid array package for MCM of the present invention.

The single-layer ceramic substrate 1 has a diameter of 0.4.
An alumina substrate having 224 mm through holes 2 was used (see FIGS. 3 and 4). A pad electrode 3 is formed on one surface of the single-layer ceramic substrate 1 around the through hole 2 by Ag-Pd paste (see FIG. 3). Further, on the surface other than the above-mentioned surface of the single-layer ceramic substrate 1, the pressure film wiring 4 made of Ag-Pd paste and the Au film are formed.
A bonding pad 5 made of paste is applied (see FIG. 4), and Ag-Pd paste is applied to the inner wall of the through hole 2 to improve wettability with solder, and electrical connection between both ends of the through hole 2 is made. Has been taken.

First, an MCM substrate 7 having a plurality of LSI chips 6 mounted thereon is adhered to the side of the single-layer ceramic substrate 1 on which the pressure film wiring 4 is provided (see FIG. 4) by an insulating adhesive 8. When the insulating adhesive 8 is solidified, the insulating adhesive 8
It was carried out by holding at 70 ° C. for 2 hours. Here, when the MCM substrate 7 and the single-layer ceramic substrate 1 are bonded together, if all the through holes 2 are located under the MCM substrate 7, degassing at the time of airtight sealing cannot be performed. Therefore,
The single-layer ceramic substrate 1 is designed so that the through holes 2 also exist at positions not covered by the MCM substrate 7.

Next, after cleaning the MCM substrate 7 and the single-layer ceramic substrate 1 with oxygen plasma and argon plasma, M between the LSI chip 6 and the MCM substrate 7
The CM substrate 7 and the single-layer ceramic substrate 1 were connected by Au bonding wires 9 respectively. Next, the single-layer ceramic substrate 1 on which the connection was completed was covered with a ceramic box-shaped lid 10 so as to protect the MCM substrate 7 on which the LSI chip 6 was mounted, and fixed with an adhesive 11. The adhesive 11 was applied to the entire contact surface between the lid 10 and the single-layer ceramic substrate 1 to complete the seal. The adhesive 11 was solidified by holding it in an environment of 170 ° C. for 2 hours as in the case of the insulating adhesive 8.

Next, the single-layer ceramic substrate 1 to which the lid 10 is bonded is attached to the through-hole 2 of the single-layer ceramic substrate 1.
After reversing so that the open side faces upward, a solder ball 12 having a diameter of 0.8 mm was placed on the through hole 2.

Finally, the package was hermetically sealed in a heating furnace. First, solder balls 1 are placed on the through holes 2 described above.
The package in which No. 2 was placed was inserted into a heating furnace kept at room temperature. Next, the interior of the package was completely replaced with nitrogen gas by evacuating the heating furnace and introducing nitrogen gas into the furnace, and repeating the nitrogen purge several times. After substituting with nitrogen gas, the temperature inside the furnace was raised to 183 ° C. or higher at which the solder melted, and the solder balls 12 were melted. The melted solder reacts with the pad electrode 3 and closes the through hole 2 to complete the hermetic sealing. Further, the solder balls 12 remaining on the outer side of the single-layer ceramic substrate 1 could be used as the external ball electrodes 13. With the above procedure, the package for the multi-chip module using the single-layer ceramic substrate is completed.

[0018]

According to the present invention, since the MCM is mounted not on the laminated ceramic substrate but on the inexpensive single-layer ceramic substrate, the unit cost of the ceramic substrate can be reduced to one fourth.

Further, since the solder balls are melted and the through holes of the single-layer ceramic substrate are closed to hermetically seal, a large number of packages can be collectively processed by a heating furnace.

By using the present invention as described above,
Without losing the characteristics of MCM such as high-speed response and high-density wiring,
We have realized a package for MCM that can be assembled at low cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section of an embodiment of the present invention.

FIG. 2 is a diagram showing an assembly procedure of the present invention.

FIG. 3 is a diagram showing one surface of a single-layer ceramic substrate used in the present invention.

FIG. 4 is a diagram showing another surface of a single-layer ceramic substrate used in the present invention.

FIG. 5 is a view showing a cross section of a conventional pin grid array type package.

FIG. 6 is a cross-sectional view of a conventional plastic package.

[Explanation of symbols]

 1 Single Layer Ceramic Substrate 2 Through Hole 3 Pad Electrode 4 Thick Film Wiring 5 Bonding Pad 6 LSI Chip 7 MCM Substrate 8 Insulating Adhesive 9 Bonding Wire 10 Lid 11 Adhesive 12 Solder Ball 13 External Ball Electrode 21 Multilayer Ceramic Substrate 22 pin grid array 23 weld ring 24 electric welding part 25 die pad 26 lead frame 27 molding resin

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 25/04 25/18

Claims (2)

[Claims] 1. A package for shielding a multi-chip module from the outside air environment, wherein the package is formed of a material that reacts with a large number of through holes electrically connected at both ends and a solder located around the through holes. A single-layer ceramic substrate on which a pad electrode and a thick film wiring are formed,
For a multi-chip module, which is composed of an external ball electrode of solder that closes the through hole, and a ceramic or metal lid that covers the multi-chip module mounted on the single-layer ceramic substrate. Ball grid array package. 2. The ball grid array package for a multi-chip module according to claim 1, wherein the solder balls placed on the through-holes of the single-layer ceramic substrate after fixing the respective parts with resin or glass are used. The package is hermetically sealed by melting it in a vacuum or an inert gas atmosphere and reacting with the pad electrode, and at the same time closing the through hole with solder, and using the solder remaining outside the through hole as an external ball electrode. A method of manufacturing a featured ball grid array package for a multichip module.