JPH03252158A - Lead frame - Google Patents

Abstract

PURPOSE:To obtain lead frames useful for easy low-cost manufacture component-mounting boards each having a recess of die pad deep as necessary by designing a component-mounting board so as to have an opening larger than a die pad in its corresponding part of the board. CONSTITUTION:A lead frame 1, which is integrated with a component-mounting board 7 having a recess of die pad 9 and electrically connects a component mounted on the die pad 9 to outside, is so designed as to have an opening 3 larger than the die pad 9 at its corresponding part of the board. Resin layers and copper foils, etc., are overlapped from both sides of the lead frame, pressed and integrated into a base material 14: this material is perforated, throughhole- plated etched, coated with solder resist, and plated. Then, the material is worked for a recess of die pad 9 to finish the manufacture of a component-mounting board 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is an electronic component mounting board that is integrated with an electronic component mounting board having a concave electronic component mounting section, and that is capable of mounting an electronic component mounted on the electronic component mounting section. It relates to a lead frame that is electrically connected to the outside.

(Prior Art) In recent years, as electronic devices have become increasingly dense, electronic components consisting of multiple active or passive elements are being mounted.
Various forms have been proposed not only for multi-chip packages containing one semiconductor device but also for monolithic packages mounting one active element and forming one semiconductor device. Among them, the present inventors have
99497, an example of this form has been proposed.

By the way, in electronic component mounting substrates having the above configuration, especially in the case of active elements, it is very common to provide a concave electronic component mounting portion. This is because if electronic components are mounted in the electronic component mounting area as is, the thickness of the semiconductor device after mounting the electronic components will become thicker, which is a trend toward higher density (= lighter, thinner, shorter, and smaller), which is the original goal. It is something that moves away from. Therefore, in this trend of higher density, it is very common to provide a concave electronic component mounting part on the electronic component mounting board, and the so-called spot boring process is used as the processing method. many.

On the other hand, in the lead frame that is integrated with this electronic component mounting board, there is no special processing applied to the part corresponding to the electronic component mounting part, and a so-called die pad is formed. It was common.

(Problems to be Solved by the Invention) However, forming a concave electronic component mounting portion on this electronic component mounting substrate has various problems. In other words, the concave electronic component mounting area is usually formed by counterbore machining, and the machining depth is 0.2 m due to the thickness of the electronic component.
In many cases, it is about 0.8 mm from m. And at this time,
The layer structure of the electronic component mounting board and the lead frame integrated with it is such that the lead frame has a thickness of 0.
15mm, the resin layer above and below it (however, here, the resin layer is referred to as the resin layer even if it contains glass cloth) 0
As a result of extensive research, the present inventors have recommended that the thickness of the base material as a whole be 0.586 mm to 0.986 mm, with a copper foil of 0.018 mm and a copper foil of 0.018 mm. For this recommended thickness, from the above 0.2 mm to 0,
When a concave electronic component mounting portion of about 8 mm is formed, the bottom surface of the processed electronic component mounting portion has various shapes as shown below, depending on the relationship between the processing depth and the thickness of the base material.

(a) Those that do not reach the lead frame.

(See Figure 14) (b) Ends in the center of the lead frame.

(See Figure 15) (C) One that completely removes the lead frame.

(See Figure 16) (d) Cases in which multiple forms or a mixture of the above (a) to (c) exist.

Among these, if only the form (a) is used, the processing conditions for removing the resin layer and forming the recess are the same as those for a normal electronic component mounting board consisting of a resin layer that is not integrated with the lead frame (i.e. This can be done under the same processing conditions as for electronic component mounting substrates that do not include lead frames.

Here, the processing conditions for forming recesses on a normal board for mounting electronic components are processing conditions that take into consideration the fact that the board often has copper foil, etc. for circuit patterns. Say something.

However, in the above embodiments (b), (C), or (d), in addition to the resin layer, the integrated thickness is 0.151 mm.
! Since it is also necessary to process a 25 mm lead frame, it is necessary to change the processing conditions to those for processing the lead frame, that is, the metal, rather than the processing conditions for processing the resin layer. These changes include slowing down the moving speed of the processing tool and shortening the replacement cycle of the processing tool, and these changes significantly increase the processing cost compared to when processing the resin layer. .

In addition, especially in the form (d), during subsequent surface treatment, steps may occur due to different processing speeds between the insulating layer portion and the lead frame portion, or because only one side is processed. , it becomes defective.

As mentioned above, electronic component mounting boards with concave electronic component mounting areas are expensive, and in order to make them cheaper, the depth of the electronic component mounting areas must be set to a depth that does not reach the lead frame. (For example, in the case of the plate thickness of 0.986 mm mentioned above, the depth of the electronic component mounting part is 0 when considering the tolerance of the plate thickness or the tolerance of the counterbore depth.
．． (Only those with a diameter of 2 mm or less were available). In other words,
It has not been possible to obtain an electronic component mounting board having a recessed electronic component mounting portion of the necessary depth at a low cost.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to easily and inexpensively manufacture an electronic component mounting board having a recessed electronic component mounting portion with a necessary depth. The goal is to provide useful lead frames for

(Means for Solving the Problems) The means taken by the present invention to solve the above problems are as follows: Also, a lead frame (1) for electrically connecting the electronic components mounted on the electronic component mounting section (9) to the outside, the lead frame (1) electrically connecting the electronic component mounted on the electronic component mounting section (9)
9), the lead frame (1) has an opening (3) larger than the electronic component mounting portion (9).

Next, the means taken by the above-mentioned present invention will be explained in detail below according to specific examples shown in the drawings.

FIG. 1 is a plan view of a lead frame (1) according to the present invention, and FIG. 2 is a sectional view thereof. Figure 3 shows a board (7) for mounting electronic components using this lead frame (1).
FIG. 4 is a sectional view thereof. In these figures, the Gui pad (2) of the lead frame (1)
is provided with an opening (3). This opening (3) is
It is designed to have larger dimensions than the electronic component mounting portion (9), which is processed into a concave shape for mounting electronic components. This dimension is preferably designed to be slightly larger than the electronic component mounting section (9). This is because by leaving as much of the Guipad (2) as possible, it is possible to dissipate heat generated from the electronic components, albeit slightly.

Next, a method of manufacturing an electronic component mounting board (7) using this lead frame (1) will be described.

First, after surface treatment is applied to the lead frame (1), a resin layer (lO), copper foil (11), etc. are applied to the lead frame (1).
) are laminated from both sides and pressed to form a lead frame (1).
The base material (14) was made integral with the base material (14) (see Fig. 5). Here, the surface treatment is for improving the adhesion with the resin layer (10), and there are no restrictions as long as the purpose is achieved. When using a copper-based lead frame (1), oxide film forming treatment, blasting treatment, etc. are often used. Furthermore, there are no particular restrictions on the resin layer (lO), and glass epoxy, glass triazine, glass polyimide, etc. are used. Lead frame(
In 1), various materials such as 42 alloy type can be used in addition to the above-mentioned copper type.

Thereafter, in the same way as a normal printed wiring board, drilling, through-hole plating (8), etching, and, if necessary, solder resist, gold plating, solder plating, etc. were performed (see FIG. 6). Here, the concave electronic component mounting part (9
) may be carried out after drilling or etching depending on the purpose, but there is no particular restriction as to which process is carried out. Furthermore, in the process of forming the concave electronic component mounting portion (9), the lead frame (1) corresponding to this portion is provided with an opening (3) larger in size than the concave electronic component mounting portion (9). Therefore, the lead frame (1), that is, the metal, is not exposed no matter how deep the lead frame (1) is processed, so the processing conditions with high work efficiency, such as those used when processing the resin layer (10), can be applied as they are. .

After that, the outer lead (4) of the lead frame (1)
is exposed, and the electronic component mounting board (7) shown in FIGS. 3 and 4 is completed.

As shown in FIG. 11, the structure of the electronic component mounting board (7) having the concave electronic component mounting portion (9) may be such that a heat dissipation plate (13) is inserted after punching. However, the electronic component mounting board (7) with this structure also has an opening (3) like this lead frame (1).
) can be similarly applied.

(Actions of the Invention) By adopting the above-described means, the present invention has the following effects.

That is, when forming the electronic component mounting board (7), when forming the concave electronic component mounting portion (9),
No matter what value the depth of the mounting part (9) is set, the lead frame (1) is not machined, so the machining speed can be set quickly and the machining is performed under machining conditions with less wear on the drill. This makes it possible. In addition, since the lead frame (1) is not exposed, the parts where the lead frame (1) is exposed and the parts where it is not are separated by surface treatment etc. after forming the concave electronic component mounting part (9). There is no unevenness caused by differences in processing speed,
This also makes it possible to improve the rate of non-defective products.

(Example) Next, each example of manufacturing an electronic component mounting board (7) using the lead frame (1) according to the present invention will be described in detail with reference to the drawings.

Example 1 FIG. 1 shows a lead frame (
1) is a plan view, and FIG. 2 is a sectional view thereof.

As shown in these figures, an opening (3) is provided in the goo pad (2) of the lead frame (1).

Next, on both sides of this lead frame (1), a resin layer (10) called prepreg and a copper foil (11) are combined,
Heat and pressurize the plate to a thickness of 0.986 mm.
(See figure 6), and then the circuit pattern (12) was formed through various processes such as hole drilling, through-hole plating (8), etching, solder resist printing, and gold plating in the same way as for ordinary printed wiring boards (see Figure 6). ). Then, the base material (1
4) A concave electronic component mounting portion (9) with a depth of 0.5 mm for mounting electronic components was formed by counterboring (
(See Figures 7 and 8). The depth of the counterbore in this case is normally the depth that would cut down to the center of the lead frame (1), but the lead frame (1) used here has an electronic component mounting area (9 ) is pre-drilled with an opening (3) larger than the electronic component mounting area (9), so even when counterboring to a depth of 0.5 mm, the lead frame (1) can be easily machined. The conditions for processing the resin layer (lO), that is, the base material (14), could be applied as they were.

Thereafter, the outer leads (4) were exposed, and the electronic component mounting board (7) shown in FIGS. 3 and 4 was completed.

Embodiment 2 FIG. 9 shows a lead frame (
1) is a cross-sectional view of the state after drilling and pattern formation.

Thereafter, in order to fit the heat sink (13) which will become the electronic component mounting part (9), holes were punched and counterbore was performed from the back side (see FIG. 10). At this time, the lead frame (
1) and the base material (14) consisting of the resin layer (1O) and the copper foil (11) had the same thicknesses as in Example 1, and the counterbore process was performed to a depth of 0.7 mm from the back surface. Therefore, since the lead frame (1) would normally be processed during hole punching and counterbore processing, it is necessary to perform counterbore processing under the lead frame processing conditions, but the lead frame (1) has an opening (3) larger than the electronic component mounting part (9) in the part corresponding to the electronic component mounting part (9), so the conditions for processing the resin layer (10), that is, the base material (14) I was able to process it by applying it as is.

Thereafter, a copper plate was attached as a heat sink (13) using an adhesive sheet, and the outer lead (4) was further exposed to complete the electronic component mounting board (7) shown in FIG. 11.

Embodiment 3 FIG. 12 shows a lead frame (1) according to a third embodiment of the present invention, and after laminating a resin layer (10) and a copper foil (11), it is heated and pressurized to form a base material (14). ), and is a sectional view after drilling and forming a recessed electronic component mounting portion (9).

After that, the first
The electronic component mounting board (7) shown in Figure 3 was completed.

Here, the lead frame (1) has an opening (3) larger than the electronic component mounting portion (9) in a portion corresponding to the electronic component mounting portion (9), as in Example 1 or 2. , concave machining could be easily performed. In addition, the counterbore process to form the concave electronic component mounting part (9) was performed before through-hole plating (8) because the mounting part (
This is to apply plating (6) to 9) as well.

(Effects of the Invention) As detailed above, the lead frame according to the present invention has
[A lead frame that is integrated with an electronic component mounting board having a concave electronic component mounting portion and electrically connects the electronic component mounted on the electronic component mounting portion to the outside, Its structural feature is that a portion corresponding to the electronic component mounting portion has an opening larger than the electronic component mounting portion.

Therefore, if you use this lead frame to form a board for mounting electronic components, when forming a concave electronic component mounting section, no matter what value you set the depth of the mounting section, the lead frame can be processed. Therefore, the machining speed can be set quickly and machining can be performed under machining conditions that cause less wear on the drill. In addition, since the lead frame is never exposed, unevenness may occur due to the difference in processing speed between areas where the lead frame is exposed and areas where the lead frame is not exposed during surface treatment after forming the concave electronic component mounting area. It is also possible to improve the yield rate without any problems.

Therefore, by using this lead frame, it is possible to obtain an inexpensive and high quality substrate for mounting electronic components.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a first embodiment of the lead frame according to the present invention, FIG. 2 is a sectional view thereof, and FIG. 3 is a plan view of a board for mounting electronic components using the lead frame shown in FIG. 1. FIG. 4 is a sectional view thereof. 5 to 8 are diagrams showing the steps of forming the electronic component mounting substrate shown in FIGS. 3 and 4, in which FIG. 5 is a sectional view of the step of forming the base material, and FIG. The figure is a sectional view after forming a hole pattern, FIG. 7 is a plan view after forming an electronic component mounting section, and FIG. 8 is a sectional view thereof. 9 to 11 are diagrams showing the process of forming an electronic component mounting board using the lead frame according to the second embodiment, in which FIG. 9 is a cross-sectional view after forming a hole pattern, and FIG. The figure is a cross-sectional view before attaching a heat sink to serve as an electronic component mounting section, and FIG. 11 is a cross-sectional view after attaching a heat sink to the electronic component mounting board. FIG. 12 and FIG. 13 are diagrams showing the process of forming an electronic component mounting board using the gate frame according to the third embodiment, and FIG. 12 shows the process after forming the electronic component mounting portion. FIG. 13 is a cross-sectional view after plating has been applied to form a substrate for mounting electronic components. FIGS. 14, 15, and 16 are cross-sectional views showing the relationship between the depths of the lead frame and the electronic component mounting portion. Explanation of symbols 1...Lead frame, 2...Die pad, 3...
・Opening, 4... Outer lead, 6... Plating, 7... Electronic component mounting board, 8... Through-hole plating, 9... Electronic component mounting part, 10... Resin layer, DESCRIPTION OF SYMBOLS 11... Copper foil, 12... Circuit pattern, 13... Heat sink, 14... Base material. that's all

Claims (1)

[Scope of Claims] A lead frame that is integrated with an electronic component mounting board having a concave electronic component mounting portion and electrically connects the electronic component mounted on the electronic component mounting portion to the outside. . A lead frame, wherein a portion corresponding to the electronic component mounting portion has an opening larger than the electronic component mounting portion.