JPH04291995A - Method of connecting pattern of printed circuit board - Google Patents

Abstract

PURPOSE:To improve the workability and reliability upon wiring connection by increasing the amount of wirings for wire leading upon repairing and design alteration by previously forming an internal layer connection pattern used upon the design alteration or repairing on the lower surface of a board and on the lower surface of a surface layer formed on the board. CONSTITUTION:There are formed in succession on a board 1 a first thin film 2b of resin such as polyimide, an internal connection pattern 3, and a second thin film 2a of resin such as polyimide. Then, there are formed on the surface of the thin film 2a an LSI pin pad 5, doughnut-shaped vertical connection pad 4, and a wiring pattern 6. Upon alteration of wirings, after parts are once removed from the board 1 and an internal edge of the upper/lower connection pad 4 is irradiated with laser light 8 and hereby the thin film 2a of the internal edge is removed and a hole 9 is formed. Further, a conductive connection material 10 such as a solder is formed on the hole 9 to electrically connect the internal layer pattern 3 and the upper/lower connection pad 4.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a pattern connection method for printed circuit boards, and in particular to high-density printed circuits used to mount high-density LSIs such as PGA (pin grid array) LSIs and bump LSIs. The present invention relates to a pattern connection method for a printed circuit board when a design change or repair of the board occurs on the board.

0002

[Prior Art] Recently, printed circuit boards (hereinafter simply referred to as "boards") have become more densely packaged, and the shapes of components mounted on these boards have changed from the conventional outer lead type to bump types or pin-grid packages. This is changing to the inner lead type.

FIG. 7 shows a conventional technique, with FIG. 7(a) showing a side view thereof and FIG. 7(b) showing a perspective view thereof.

When mounting an inner lead type component as described above on a board, the board 70 is placed in advance in accordance with the position of the lead 72 protruding from the bottom surface of the component to be mounted (hereinafter referred to as LSI 71). The mounting was performed by forming a pad 73 on the surface of the semiconductor device and connecting the pad 73 and the lead 72 with solder.

[0005]Furthermore, on the surface of this board 70, in case the wiring at the time of design is changed or it is necessary to repair the board itself, a repair material is provided at the same time as the pad 73 is formed. Usually, the pad 75 is formed.

Then, in case the wiring is changed due to actual design change or repair of the board, the wiring 76 is passed through the gap between the leads 72 and the bottom surface of the LSI 71 in advance, and the wiring 76 is temporarily installed for repair. The wiring has been changed by connecting the wire 74 to the pad 75 with solder and then connecting one end of the wire 74 to the position where the new wiring is to be made.

[0007]

[Problem to be Solved by the Invention] However, with conventional pattern connection methods, the spacing between the leads protruding from components has become narrower year by year due to the recent increase in density, and there is a limit to the number of wires that can be passed between them. ing.

[0008] Furthermore, since the wiring is drawn out from the bottom of the component by hand, there are problems with workability and reliability.

Furthermore, if a pattern for changing the wiring is formed on the board in advance in case a design change occurs and one end of the pattern is exposed, the wiring may be damaged due to the reflection of noise from outside the board. The reliability of the connection will also be poor.

Therefore, an object of the present invention is to increase the amount of lead-out wiring when repairing or changing the design of a board, and to improve the workability and reliability of wiring connections at that time. It is something.

[0011]

[Means for Solving the Problems] The above object includes a step of forming an inner layer connection pattern 3 on the surface of a substrate 1, and a step of forming a surface layer 2 on the entire surface of the substrate 1 including the inner layer connection pattern 3. , on the surface of the surface layer 2, a first pad 5 for mounting components, a wiring pattern 6 connected to the first pad 5, and a wiring different from the wiring pattern 6 when a design change or repair occurs. The second opening to the pattern
In the step of forming the second pad 4, and only when the design change or repair occurs, a laser beam 8 is irradiated near the second pad 4 to form a hole 9 leading to the inner layer connection pattern 3. By forming the conductive connecting material 10 in the hole 9 using a ball bonding method, a wedge bonding method, or a combination thereof, the second pad
and the step of electrically connecting the inner layer connection pattern 3;
This is achieved by a printed circuit board pattern connection method characterized by comprising:

0012

[Operation] That is, in the present invention, an inner layer connection pattern is formed in advance on the surface of the substrate and on the lower surface of the surface layer formed on the substrate to be used when a design change or repair occurs. Since a multilayer wiring pattern can be secured on the surface of the substrate without increasing the area itself, the amount of wiring can be increased as a result.

Furthermore, by using the ball bonding method, the wedge bonding method, or a combination thereof, it is possible to automate the wiring under the component, improving workability and reliability.

Furthermore, since the inner layer connection pattern and the electrical wiring connected to the inner layer connection pattern are connected only when a design change etc. occurs, it is effective against reflections caused by external noise, and Reliability is also improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 6.

FIG. 1 is a diagram showing an embodiment of the present invention. FIG. 2 is a diagram showing a perspective view of an embodiment of the present invention.

FIG. 3 is a diagram illustrating the bonding technique. FIG. 4 is a diagram showing a bonding pattern.

FIG. 5 is a cross-sectional view of bonding using wedge bonding. FIG. 6 is a diagram showing another embodiment of the present invention.

In FIGS. 1 to 6, the same reference numerals indicate the same objects.

As shown in FIG. 1(a), a first thin film 2b of resin such as polyimide is formed on the surface of the substrate 1, and changes to the wiring of the substrate 1 are formed on the surface of the first thin film 2b. A dedicated inner layer connection pattern 3 and an inner layer pad 3a to be connected to the inner layer connection pattern 3 are formed in advance to be used only when repairing or repairing the board. It is desirable to prepare in advance the same number of internal connection patterns 3 as the number of leads of components mounted on the board 1. A second thin film 2a of resin such as polyimide is formed to cover the inner layer connection pattern 3 and inner layer pad 3a. Therefore, a layer called a surface layer 2 is formed on the surface of the substrate 1 by the first thin film 2b and the second thin film 2a.

On the surface of this second thin film 2a, there are LSI pin pads 5 that are in contact with the leads of inner lead type components, and doughnut-shaped upper and lower portions are formed on the upper surface of the inner layer pad forming position for connection with the inner layer connection pattern 3. A connection pad 4 and a wiring pattern 6 connecting the two pads 5 and 4 are formed.

As shown in FIG. 2, around the LSI pin pad 5, the wiring pattern 6, and the upper and lower connection pads 4, there are wires 6 for connecting to the inner layer pattern of the thick film substrate 1 and connections to the wires 6. A surface pad 11 is formed on the surface of the substrate 1 via a via 6a connected to the inner layer 3a, a via 12 connected to the other end of the inner layer connection pattern 3 whose one end is connected to the inner layer pad 3a, and the via 12.

Particularly when there is no need to change the pre-formed wiring on the substrate 1, each component operates according to the patterns formed on the first thin film 2b.

[0024] Now suppose that the wiring has to be changed or the board has been repaired and it becomes necessary to change the wiring.

Then, after once removing the components from the board 1 as necessary, as shown in FIG. The second thin film 2a of the part is removed and holes 9 are drilled.

Then, as shown in FIG. 8(c), a conductive connecting material 1 such as solder is inserted into the hole 9 drilled by the laser beam 8.
By forming 0, the inner layer connection pattern 3 and the upper and lower connection pads 4 are electrically connected.

That is, in the present invention, only when a design change or a repair of the board actually occurs, the pattern for the design change or repair is electrically connected to the board 1.
This prevents noise from entering from the design change pattern formed in the design change pattern and causing effects such as reflection.

In the present invention, a bonding technique shown in FIG. 3 is used as a method for connecting the doughnut-shaped upper and lower connection pads 4 and the inner layer connection pattern 3.

That is, a pad 31 formed on the surface of the substrate 30 and a pad 3 formed on the surface of a surface layer 33 covering a part of this pad 31 and formed on the surface of the substrate 30.
2, a hole 3 drilled by a laser beam is
A solder ball 36 having a ball portion 36a and a branch portion 36b at 4.
will be established. If possible, the diameter of this spherical portion 36a is the same as that of the surface layer 3.
A heating bonding chip having a head 35 which holds the branch part 36b at its tip from above is provided for the branch part 36b. By heating the head 35, the heat is transmitted to the bulb 36a via the branch 36b, melting the entire solder ball 36, and as the bulb 36a melts, the branch 36b also melts. The spherical portion 36a is connected to the pad 31 on the surface of the substrate 30, while the molten branch portion 36b is connected to the donut-shaped pad 32. This example uses a ball bonding method in which the ball part shown in Figure 4 (a) is crushed and the layer pattern is short-connected, but in addition, the branch part shown in Figure 4 (b) is completely melted. There is also a wedge bonding method that connects the pads on the surface layer in a bridge-like manner without bonding.
Although it is not a bridge shape combining a) and (b), one in which a branch part is connected to a part of a pad on the surface layer is used.

This technique is appropriately selected depending on the conditions during bonding, and furthermore, the bonding tip for heating to melt the solder ball is entirely automatically controlled.

FIG. 5 is a cross-sectional view of the inner layer connection pattern and the upper and lower connection pads bonded together using the wedge bonding method described above. The upper and lower connection pads 4 use solder balls 13 to connect the inner layer connection patterns 3, and the solder balls 1
The method is the same as the ball bonding method except that the branch portions 14 of No. 3 are bonded to a part of the upper and lower connection pads 4, so a description thereof will be omitted.

Another embodiment of the present invention will be described with reference to FIG. 6. As shown in FIG. 2, the other end of the inner layer connection pattern 3 will be described as being connected to the surface pad 11 of the substrate 1 using a via. However, if it is desired to increase the number of wires, it goes without saying that the other end may be directly connected to the EC pad 16 and drawn out using the wire 17. Note that 15 indicates a pattern cut portion.

[0033]

As explained above, in the present invention, by providing the inner layer of the surface layer with a pattern for changing the diameter or repairing the board as an inner layer connection pattern, the area required for design changes, etc. can be reduced. Even if the amount of wiring remains unchanged, the amount of wiring can be increased.

[0034] Since there is no need to wire the lower surface of the component with wires or the like, workability and reliability are also improved.

Furthermore, since the wiring patterns required for the design change are connected only when a design change occurs, it is possible to take measures against reflections caused by external noise, improve connection reliability, and improve component operation reliability. improves.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, in which (a) shows a wiring pattern formed on the surface of a substrate, (b)
(c) shows the state of laser beam irradiation, and (c) shows the solder connection state.

FIG. 2 is a perspective view of an embodiment of the invention.

FIG. 3 is a diagram illustrating a bonding joining technique.

FIG. 4 is a diagram showing a bonding pattern,
(a) is a ball bonding method, (b) is a wedge bonding method, and (c) is a combination of a ball bonding method and a wedge bonding method.

FIG. 5 is a cross-sectional view of bonding using wedge bonding.

FIG. 6 is a diagram showing another embodiment of the present invention.

FIG. 7 is a diagram showing a conventional example, in which (a) is a side view, (a) is a side view;
b) is a perspective view.

[Explanation of symbols]

Claims (2)

[Claims] 1. A step of forming an inner layer connection pattern (3) on the surface of the substrate (1), and forming a surface layer (2) on the entire surface of the substrate (1) including the inner layer connection pattern (3). process, a first pad (5) for mounting a component, a wiring pattern (6) connected to the first pad (5), and a design change or repair on the surface of the surface layer (2). a step of forming a second pad (4) which becomes an outlet to a wiring pattern different from the wiring pattern (6) in the case where the wiring pattern (6) is different from the wiring pattern;
Only when the design change or repair occurs, irradiating the vicinity of the second pad (4) with a laser beam (8) to form a hole (9) leading to the inner layer connection pattern (3); ,
By forming the conductive connecting material (10) in the hole (9),
A pattern connection method for a printed circuit board, comprising the step of electrically connecting the second pad (4) and the inner layer connection pattern (3). 2. The printed circuit board according to claim 1, wherein the method for forming the conductive connecting material in the hole (9) is a ball bonding method, a wedge bonding method, or a combination thereof. pattern connection method.