JPH04233749A - Flexible chip carrier for electric assembly use - Google Patents

Abstract

PURPOSE: To reduce the influence of the environmental disturbance and effectively utilize the layout area of a circuit board, by extending conductive runners for electrically interconnecting pads and contacts, so as to interconnect integrated circuit chip pads and circuit board contacts within the periphery of the integrated circuit chip. CONSTITUTION: On a circuit board 101 an IC chip 103 is mounted. A flexible sheet 111 having an upper and a lower surfaces 113 and 115 is disposed between the circuit board 101 and the IC chip 103. Chip pads 107 and circuit board contacts 105 are electrically interconnected through conductive runners laid on the lower surface 115 of the flexible sheet 111. The conductive runners 109 are laid on the flexible sheet 111. If an electric assembly is subjected to vibration and/or other environmental disturbance, the influence of the external force on solder zones is substantially relaxed.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD This invention relates generally to the chip carrier field, and more particularly to flexible chip carriers that facilitate the interconnection of integrated circuit chips to main circuit boards.
Regarding career.

0002

[Prior Art] Due to the demand for miniaturization of electrical assemblies,
There is a need to devise ways to efficiently utilize the effective area on the main circuit board. One such method involves interconnecting the pads of an integrated circuit (IC) chip to corresponding contacts on the main circuit board, thereby encapsulating the IC chip within a conventional ceramic or plastic chip carrier. Eliminating the need. In this configuration, I
The pads of the C-chip are connected directly to conductive runners via contacts on the main circuit board. This method is currently used in the manufacture of small watches and other similar products in which the pads of the IC chip are soldered directly to contacts on the main circuit board. However, since IC silicon chips are fragile,
If the solder joint formed between the pad and the contact is subjected to even a small external force, the silicon chip will break or the solder joint will fail. Therefore, in applications such as two-way radio equipment where the electrical assembly is subject to vibration and/or other severe environmental disturbances, direct solder connections between IC chip pads and circuit board contacts are not appropriate and may pose serious unreliable conditions. May cause sexual problems.

0003

Furthermore, in conventional configurations, runners that interconnect pads to other devices are
Extending or fanning out of the area surrounding the IC chip. Generally, with this configuration, the layout area cannot be used effectively.

Accordingly, it is an object of the present invention to provide an electrical assembly that substantially reduces the effects of environmental disturbances and makes efficient use of circuit board layout area.

[0005]

SUMMARY OF THE INVENTION In accordance with the present invention, an electrical assembly includes an integrated circuit chip having a plurality of pads;
and a circuit board having contacts that couple to pads of the integrated circuit chip. The pads and contacts are electrically interconnected via conductive runners on a flexible sheet disposed between the circuit board and the integrated circuit chip. The conductive runners extend so that the chip pads and circuit board contacts are interconnected within the periphery of the integrated circuit chip.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a cross-sectional view of the electrical assembly of the present invention is shown at 100. Electrical assembly 100 may be an electrical circuit assembly that includes application-specific functional circuitry, such as a transceiver circuit board for a portable two-way radio device. Electrical assembly 100 includes an integrated circuit (IC).
) chip 103, which may be a well-known IC forming a functional block of electrical assembly 100, such as a microprocessor or other suitable functional IC. The IC chip 103 is manufactured using a known IC manufacturing method, and has chip pads 1 connected to an external circuit.
It has 07. IC chip 103 has chip pad 1
It is electrically contacted via 07. Chip pad 107 is formed as a semi-cylindrical solder ball in the preferred embodiment of the invention. An IC chip 103 is mounted on the circuit board 101, and the circuit board 101 interconnects the IC chip 103 with other functional elements and/or integrated circuits. The circuit board 101 has metallized contact portions 105, and the contact portions 105 are connected to I
This is an electrical contact that connects to C pad 107. Circuit board contacts 105 are placed on circuit board 101 using well known methods such as printed circuit boards.

A flexible sheet 111 having an upper surface 113 and a lower surface 115 is positioned between the circuit board 101 and the IC chip 103. Chip pads 107 and circuit board contacts 105 are electrically interconnected via conductive runners 109 located on the bottom surface 115 of flexible sheet 111 . Conductive runners 111 are placed on flexible sheet 111 using well known methods such as thin film methods. Flexible sheet 109 may be any well-known organic insulating material with sufficient resiliency to provide a cushioning mechanism between circuit board 101 and IC chip 103. Therefore, even if the electrical assembly is subjected to vibrations and/or other environmental disturbances,
The influence of external forces on the solder joints is substantially mitigated.

Chip pad 107 is connected to conductive runner 109 through cutout 117 . Cutout 117 is formed by etching the portion of flexible sheet 111 surrounding chip pad 107. The portion directly surrounding chip pad 107 is etched until the conductive portion of runner 109 is exposed. In a preferred embodiment of the present invention, the method for obtaining incision 117 includes a well-known excimer laser ( excimer laser)
This can be achieved using . Once the chip pad 107 is aligned with the top of the corresponding cutout 117, a suitable solder,
Electrical connections are made therebetween using thermocompression bonding or other interconnection methods. To this end, a flexible chip carrier consisting of a flexible sheet 111 is provided on the IC chip 103. It will be appreciated that the flexible sheet 111 and IC chip 103 arranged in this manner can form an integrated integrated circuit element.

Solder balls 119 are formed on the chip pads 107 that bond to corresponding conductive runners 109. The circuit board contacts 105 and conductive runners 109 are
They are coupled together using suitable solder, thermocompression bonding, or other interconnection methods that can be used to make electrical connections. Circuit board contacts 105 and runners 109
The interconnection between chip pad 107 and runner 109
It will be understood by those skilled in the art to choose the melting point of the solder such that it can be achieved without affecting the interconnection with the solder.

In FIG. 2, a bottom view of flexible sheet 111 configured to interconnect chip pads 107 and circuit board contacts 105 is shown. In this configuration,
The circuit contacts 105 are formed in a contact array type within the inner periphery of the IC chip 103. Conduction runner 1
09 is the chip pad 107 and the circuit board contact 10
5 to the flexible sheet 111 so that connections between the IC chip 103 and the IC chip 103 are made within the periphery of the IC chip 103. IC
A significant improvement in the layout efficiency of circuit board 101 is realized because the area beneath chip 103 is available for making the necessary interconnections between chip pads 107 and other circuit elements (not shown).

Referring to FIG. 3, a cross-sectional view of another embodiment of electrical assembly 100 is shown. In this configuration, the conductive runners 109 of the flexible sheet 111 are located on the top surface 113. As such, solder balls 119 formed on circuit board contacts 105 are coupled to conductive runners 109 through cutouts 317 . Cutout 317 can be formed in flexible sheet 111 using the same method described for cutout 117 in FIG.

From the above description, it is clear that by adding the dampening mechanism provided by flexible sheet 111, the electrical assembly of the present invention can withstand more severe environmental disturbances. Additionally, this flexible sheet efficiently utilizes the effective layout area of circuit board 101 to connect chip pads 107 and circuit board contacts 1.
Enables interconnection with 05.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment of an electrical assembly according to the invention.

FIG. 2 is a bottom view of the flexible sheet used in the electrical assembly of FIG. 1;

FIG. 3 is a cross-sectional view of another embodiment of an electrical assembly according to the invention.

[Explanation of symbols]

100 Electrical assembly 101 Circuit board 103 IC chip 105 Circuit board contact 107 Chip pad 109, 111 Conductive runner (flexible sheet) 117
,317 Incision

Claims (5)

[Claims] 1. An electrical assembly comprising: an integrated circuit chip having a surface consisting of an inner periphery and an outer periphery, the integrated circuit chip having a chip pad disposed on the outer periphery; a chip pad connected to the chip pad; a substrate having electrical contacts; and a membrane having a top surface and a bottom surface disposed between the substrate and the integrated circuit chip, the membrane having conductive runners disposed thereon; An electrical assembly characterized in that conductive runners extend to interconnect said chip pads and said electrical contacts within an inner periphery of said integrated circuit chip. 2. The conductive runner is disposed on a lower surface of the flexible membrane, and the flexible membrane has an incision that allows electrical connection between the chip pad and the conductive runner. Item 1. Electrical assembly. 3. The conductive runner is disposed on the upper surface of the flexible membrane, and the flexible membrane has an incision that allows electrical connection between the electrical contact and the conductive runner. 1 electrical assembly. 4. The electrical assembly of claim 1, wherein said membrane is a flexible membrane. 5. The electrical assembly of claim 1, wherein said substrate is a circuit board.