JPH0423836B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a wiring board, and particularly to a thin wiring board suitable for mounting a film carrier semiconductor device.

(Prior art) Until now, in film-shaped or thin printed wiring boards having terminals for mounting key switches, thin capacitors, and resistors, terminals for connecting film carrier semiconductor devices have been formed around the openings. has not been put into practical use, making it difficult to create ultra-thin electronic components. In addition, as a thin electronic component using other methods, film-on-frame (FOF)
However, the production process is complicated, with processes such as adhering the semiconductor chip onto the film, forming the frame, and forming the wiring using vapor deposition, photoresist processing, plating processing, etc. It was difficult to put it into practical use.

(Object of the present invention) An object of the present invention is to provide a new structure that enables mounting of a highly reliable film carrier semiconductor device, especially when double-sided wiring is performed on a thin printed wiring board or a film-like flexible board. The purpose of this invention is to provide a wiring board for.

(Structure of the Invention) The present invention has an opening for mounting a film carrier semiconductor device, and a connection terminal to which a lead of the film carrier semiconductor device is to be connected is provided around the opening. The wiring board has an isolation pattern frame layer or a wiring frame layer in a connection area around the opening on the board surface that does not have the connection terminal,
The area where the lead and the connection terminal are to be connected has a substantially constant thickness including the wiring layer and the wiring board material.

(Function) In order to connect the film carrier semiconductor device to the terminals around the openings of the flexible substrate, a connection method of thermocompression bonding all at once is suitable, but the terminals of the flexible substrate do not have a uniform height. In this case, it is thought that the load and heat applied to each film carrier semiconductor device having multiple leads will not be uniform, resulting in poor connections and resulting in a semiconductor device with poor reliability.

FIG. 13 is a top view of a conventional double-sided flexible wiring board, and FIG. 14 is a sectional view of section AA' in FIG. 13. As shown in the figure, terminal leads 3 are provided around the through opening 2 . A wiring lead 4 is provided on the other surface on which the terminal lead 3 is provided. This wiring lead 4 is included in the region 5 (double-dashed line) that connects the film carrier semiconductor, so in the cross section of the substrate A-A',
The state is as shown in FIG.

When the semiconductor device 6 having the film carrier lead 7 is placed on the substrate 1 in such a state, the 15th
It will look like the figure. In this state, the gear pumping state in the section A-A' is shown in Figure 16 and Figure 1.
It is shown in Figure 7.

As shown in FIG. 17, the substrate 1 is bent at the end of the wiring lead 4, and the heater pressure jig 9
The adhesion effect by the stage 8 causes a phenomenon in which it is only effective on some of the leads 7 and the leads 3. The quality of this connection was evaluated by a lead tension test, and the results are shown in FIG. As is clear from FIG. 18, it was found that those with normal strength of 40 gr or more and those with extremely poor strength of less than 10 gr appeared. Therefore, it has been found that it is necessary to develop a double-sided wiring board in which such a phenomenon does not occur in order to complete a thin electronic component mounted on a film carrier semiconductor device. In particular, it has been found that the non-uniformity of the height of the substrate opening is a significant factor, so in the present invention, the height around the substrate opening is made uniform, thereby making the conditions for connecting the film carrier lead to the flexible substrate uniform. , a highly reliable connection between the film carrier lead and the electrode terminal of the flexible substrate corresponding to each lead is obtained.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

1 and 2 show a top view and a bottom view, respectively, of a first embodiment of the invention. In this example, 0.1
This is a mm-thick glass epoxy substrate with Cu lead layers formed on both sides. In the figure, 11 is 10mm
A 0.1 mm thick glass epoxy substrate with corner openings 12, 13 is a 300 μm thick Cu lead with a thickness of about 30 μm.
Patterned in width. 20 is an epoxy solder resist film (the area outside the boundary of 20' is shown removed in the drawing), and is approximately
This coat part covers the Cu pattern with a thickness of 20 μm. The part without the coat part 20 is the bonding lead terminal 13 and the electrical contact terminal part.
These lead parts are plated with Ni and Au. In particular, the area within the dotted chain line 15 in FIG. 2 is the bonding area, and by designing the total thickness of the substrate thickness and the lead thickness to be almost constant, stable bonding performance can be obtained. Actually, including the substrate thickness, Cu thickness, and solder resist thickness,
Each lead 13 has a thickness of ±5 μm, which is approximately uniform. A cross-sectional structure taken along line B-B' is shown in FIG. Further, FIG. 4 shows the bonding state. As will be clear from this, Area 1
5, a uniform load is applied to each lead 13 and 17 in addition to the uniform load applied during bonding. 17 is a 35 μm thick Du lead with a film carrier Sn plating of 0.5 μm. 13 is pre-plated with Ni plating and Au plating of 4 .mu.m and 0.5 .mu.m, respectively, so that by applying pressure with heating heater 1 and stage 18, an Au-Sn eutectic alloy is easily formed and bonded.
Since each lead was uniformly heated and pressurized, the strength of the joint showed a distribution as shown in Figure 5.
As is clear from this, there was no bond with a bond strength below 20gr, and a highly reliable thin electronic device was obtained.

FIG. 6 is a bottom view of a second embodiment of the present invention, and FIG. 7 is a sectional view taken along line CC' in FIG. 6 and 7, 21 is a flexible board, 22 is an opening, 23 is a terminal lead, 3
Reference numerals 1, 31', 32, and 32' are all backside patterns, in which a Cu layer is formed to maintain uniform height, elasticity, and uniform heating within the bonding area around the through hole, that is, the opening. This is a matte wiring board pattern.

The Cu layer mats 31, 31', 32, 32' are provided in the shape of a frame on the opposite side where the joining leads are provided around the opening.
2' are provided separately on each side as shown in the figure.

Note that the Cu layer mat used in this example has a thickness of 15 μm.
Copper foil with a thickness of ~45 μm was used and provided uniformly. In addition, the flexible substrate No. 21 shown in Figure 7 is a triazine sheet containing glass fibers and has a thickness of 0.15 mm, but the Cu layers on both sides can be attached using adhesive or thermo-pressure welding without using adhesive. There are several methods that can be used, and any of them can be used in the present invention.

The wiring board of this example includes the wiring layer and wiring board material in the area where the leads and terminals are to be connected.
Since the thickness is approximately constant, a uniform and strong connection is possible as in the first embodiment. Moreover, since the Cu layer mats 31, 31', 32, and 32' that satisfy the above conditions are provided, stable bonding is achieved by uniformizing the substrate temperature during heating and pressurization, and the substrate is bonded by absorbing plastic deformation of the Cu layer. It can be effective in reducing warping.

FIG. 8 is a bottom view of the third embodiment of the present invention. In FIG. 8, the necessary test pads are covered with a solder resist 50, but the drawing shows the state without the solder resist. The present embodiment shown in FIG. 8 is a modification of the second embodiment, and includes a Cu layer mat in order to maintain a uniform height, maintain elasticity, and maintain uniform heatability within the portion belonging to the bonding area around the opening 42. It has 43. The only difference from the second embodiment is that the Cu layer mat 43 in this case is formed in a complete frame shape.
It is possible to achieve the same effect as in the embodiment.

FIG. 9 is a bottom view of the fourth embodiment of the present invention, and FIG. 10 is a sectional view taken along line D-D' in FIG.
FIG. 1 is a sectional view taken along line E-E' in FIG. 9. The present embodiment shown in these figures is another modification of the second embodiment. As shown in FIG. 9, in a portion 55 belonging to the bonding area around the opening 52, a uniform height, elasticity maintenance, and uniform heating property are maintained.
Cu layer mats 62, 62', 63, 63' are formed. Unlike the second and third embodiments, these Cu layer mats are partially formed with slits. Among the Cu layer mats 62 and 62' on the four sides, as shown in the cross-sectional view of FIG. The Cu layer mat 62' is formed symmetrically to the terminal lead and is wider than the terminal lead 53.
In addition, the Cu layer mats 63, 6 formed on the other sides
3' is the same as shown in FIG. 11 except that slits are formed in the Cu layer mat, but two terminal leads 53 are formed for each Cu layer mat. This embodiment can also exhibit the same effects as the second and third embodiments. The substrate used in FIGS. 10 and 11 is a polyimide sheet with a thickness of 0.125 mm.

The leads of the film carrier semiconductor device were bonded to the terminal leads of the wiring boards of the second, third, and fourth embodiments, and a tensile strength test was conducted. The results are shown in FIG. As is clear from the figure
Compared to the results of the first example in which the Cu layer mat is not provided, it is effective in achieving stable bonding by equalizing the substrate temperature during heating and pressurization, and reducing substrate warpage by absorbing the plastic deformation of the Cu layer. It was found that low bonding strength did not occur.

As shown in the examples above, it is necessary that the thickness of the entire board of the bonding lead portion of the flexible board on which the film carrier semiconductor device is mounted is as uniform as possible. An opening is provided in the area where the device is to be placed, and a terminal lead is provided on one side in the bonding area around the opening, or a frame-shaped metal mat layer is provided on the surface without the terminal lead. It turned out to be good.

Further, this frame-shaped metal mat layer is not limited to Cu, but may be made of A or Ni, or the surface may be plated with Au, Ag, Sn, solder, Ni, etc. It is clear that the resist may be uniformly covered.

Further, as shown in FIG. 6, it is clear that the Cu mat layer portion may be an electrical terminal, a ground terminal, or a floating terminal.

Furthermore, it is clear that the metal mat layer is effective even when provided on a single-sided wiring board.

(Effects of the Invention) As explained above, according to the present invention, there is an effect that it is possible to mount a highly reliable film carrier semiconductor device when double-sided wiring is performed on a thin printed wiring board or a film-like flexible board. is obtained.

[Brief explanation of drawings]

FIG. 1 is a top view of the first embodiment of the present invention, and FIG.
The figure is a bottom view of Fig. 1, Fig. 3 is a sectional view taken along line B-B of Fig. 2, Fig. 4 is a view showing the bonding state of the first embodiment, and Fig. 5 is a diagram of the bonding state of the first embodiment. Lead tensile strength characteristics after bonding, FIGS. 6 and 7 are a bottom view and a sectional view taken along line C-C' of the second embodiment of the present invention, and FIG. 8 is a diagram of the third embodiment of the present invention. bottom view,
9 to 11 are bottom views and cross-sectional views along D-D' and E-E' planes of the fourth embodiment of the present invention, and FIG. 12 is a bottom view of the fourth embodiment of the present invention. Figures 13 and 14 show the tensile strength characteristics after bonding. Figures 13 and 14 are top views and cross-sectional views taken along the A-A' plane of conventional wiring boards. Figure 15 shows a film carrier semiconductor device assembled on the wiring board shown in Figure 13. Figures 16 and 17
This figure shows a state of bonding to a conventional wiring board, and FIG. 18 is a diagram showing the tensile strength characteristics of a lead after bonding to a conventional wiring board. 1, 11, 21, 51...flexible board,
2, 12, 22, 42, 52...Opening part, 3, 1
3, 23, 53...terminal lead, 4, 14, 3
1, 31', 32, 32', 43, 62, 62',
63, 63'... Back pattern, 5, 15, 55
...Lead connection area, 6...Semiconductor device, 7,1
7...Lead of film carrier semiconductor equipment,
8, 18... Stage, 9, 19... Heater pressure jig, 10, 20, 50... Solder resist, 33... Cu layer mat slit, 20'...
Solder resist boundary.

Claims (1)

[Claims] 1. In a wiring board having an opening for mounting a film carrier semiconductor device, and a connection terminal to which a lead of the film carrier semiconductor device is to be connected, the connection terminal is provided around the opening. There is an isolation pattern frame layer or a wiring frame layer in the connection area around the opening on the board surface that does not have a A wiring board characterized by having a substantially constant thickness.