JPH06260567A - Printed wiring board - Google Patents

Abstract

PURPOSE:To manufacture a semiconductor mounting board of high reliability, by perfectly preventing the contamination of bonding pads or the like which is to be caused by adhesive agent, without decreasing production efficiency and increasing cost. CONSTITUTION:Bonding pads 9 are arranged around a die pad 8 for mounting a bear chip 7. Through holes 15 penetrating the surface and the rear of a base member 1 are formed in the vicinity of the bonding pads 9. A land 16 of the through hole 15 is connected with the bonding pad 9 via a conductor pattern 17 for connection use. In order to prevent the flow of thermosetting adhesive agent 5 to the bonding pads 9, a conductor pattern 18 for escaping is branched from the conductor pattern 17 for connection use. After that, a printed wiring board 1 is temporarily bonded on a lead frame 2 by using adhesive agent 5, which are completely stuck by heat pressing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board,
In particular, the present invention relates to a printed wiring board that is temporarily adhered to a lead frame by a thermosetting adhesive and then permanently adhered by a heat press.

[0002]

2. Description of the Related Art Conventionally, as one of the methods for manufacturing a semiconductor package, for example, a bare I substrate is mounted on a semiconductor mounting substrate.
There is a method of performing wire bonding, resin sealing, and the like with a C chip (bare chip) mounted.

A semiconductor mounting substrate used in this type of semiconductor package is usually composed of a printed wiring board having a die pad for mounting a bare chip and a lead frame having a plurality of leads. When manufacturing such a semiconductor mounting substrate, the following methods have been conventionally used (see FIGS. 8 and 9).

First, by etching a metal plate (42 alloy, 52 alloy, etc.) into a predetermined shape, a lead frame 22 having leads 20 and islands 21 is manufactured. Further, electrolytic silver plating 24 or the like is applied to the tip end portion 23 of each lead 20.

On the other hand, the printed wiring board 25 is manufactured by using, for example, a copper clad laminate in which a copper foil is laminated on the surface of the insulating base material 26 as a starting material. Then, by performing a predetermined etching / plating or the like according to a conventionally known subtractive method, a plated through hole 27, a die pad 28, a bonding pad 29, a wiring pattern 30 and the like are formed in the insulating base material 26.

The lead frame 23 and the printed wiring board 26
Adhesion to and is performed using a thermosetting adhesive 31. The adhesive 31 is applied on the island 21 located substantially in the center of the lead frame 22, and the printed wiring board 25
Is first temporarily adhered to the coated surface. In this state, a hot press is applied to completely bond the printed wiring board 25 and the lead frame 22 to each other, whereby a desired semiconductor mounting substrate 33 on which the bare chip 32 can be mounted is manufactured.

[0007]

However, when the hot pressing is performed after the temporary bonding, the adhesive 31 exuding on the upper surface through the plated through holes 27 becomes the conductive pattern for connection 35.
It flows upward and contaminates the bonding pad 29 (see FIGS. 8 and 9).

That is, in the case of the conventional printed wiring board 25, normally, the bonding pad 29 and the land 34 of the plated through hole 27 are linearly connected by the short connecting conductor pattern 35 as shown in FIG. Is.

Therefore, even if the wire bonding is performed in this state, the bonding state between the bonding pad 29 and the bonding wire 36 becomes incomplete, and the reliability of the semiconductor mounting substrate 33 deteriorates.

As measures for preventing such exudation and flow of the adhesive agent 31 in advance, for example, the following can be considered. That is, the adhesive 31 is completely cured by first heating and pressing the adhesive 31 at a temperature of several tens of degrees lower than the conventional processing temperature (160 ° C to 180 ° C), and then heating and pressing at the conventional temperature. The method is to cure.

However, in the case of such a heating press consisting of two steps, the total time required for the heating press is about 1.5 times as long as the conventional one, so that the production efficiency is lowered and the cost is increased.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to reliably prevent the bonding pad and the like from being contaminated by an adhesive without lowering production efficiency and increasing cost. An object of the present invention is to provide a printed wiring board capable of manufacturing a highly reliable semiconductor mounting board.

[0013]

In order to solve the above-mentioned problems, in the invention described in claim 1, the lead frame is temporarily adhered to the lead frame by a thermosetting adhesive, and then permanently bonded by a hot press. In the printed wiring board, at least the bonding pad around the die pad for bare chip mounting and the land of the through hole penetrating the front and back of the base material are connected by a connecting conductor pattern, and the connecting conductor pattern is the adhesive. The gist of the present invention is to provide a relief conductor pattern for preventing the adhesive from flowing to the bonding pad on at least one of the lands shorter than the flow distance of the agent and the land.

According to the second aspect of the invention, after the lead frame is temporarily adhered by a thermosetting adhesive,
In a printed wiring board that is permanently adhered by a heating press, at least a bonding pad around a die pad for bare chip mounting and a land of a through hole that penetrates the front and back of the base material are connected by a connecting conductor pattern,
The gist is that the length of the connecting conductor pattern that is shorter than the flow distance of the adhesive is set to be longer than the flow distance of the adhesive during hot pressing. In this case, the connecting conductor pattern may be bent and provided.

[0015]

According to the structure of the present invention in which the escape conductor pattern is provided, the adhesive exuded by the heating press also flows to the escape conductor pattern side. For this reason, the adhesive that flows to the bonding pad side via the connection conductor pattern is dispersed, and the adhesive cannot reach the bonding pad.

According to the second aspect of the present invention, since the distance from the land to the bonding pad is longer than the flow distance of the adhesive, even if the adhesive flows on the connecting conductor pattern, the adhesive may flow. Cannot reach the bonding pad. The linear distance of the connecting conductor pattern should be at least about 0.5 mm to 1.0 mm.

Further, when the connecting conductor pattern is bent, the adhesive is less likely to flow than when the connecting conductor pattern is linear.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a semiconductor mounting substrate will be described below in detail with reference to the drawings.

FIG. 1 shows a semiconductor mounting substrate 3 composed of a printed wiring board 1 and a lead frame 2. In this embodiment, a printed wiring board (so-called double-sided board) 1 having conductor layers on both sides of an insulating base material 4 is used. The printed wiring board 1 is bonded onto the island 6 of the lead frame 2 via a thermosetting adhesive 5. In this embodiment, SAF V-40 (manufactured by Nikkan) and IEF (manufactured by Mitsubishi Yuka) are selected as the thermosetting adhesive 5 for bonding the both 1 and 2.

On the front surface side of the base material 1, die pads 8 for mounting bare chips 7, bonding pads 9 and 10, a wiring pattern 11 and the like are formed as conductor layers. A plurality of substantially rectangular bonding pads (hereinafter referred to as “second pads”) 9 are arranged around the die pad 8. These second pads 9 are parts to be later bonded to a first pad (not shown) on the bare chip 7 side via a bonding wire 12.

On the other hand, the bonding pads 10 are smaller than the second pads 9 and are regularly arranged at the outermost edge of the printed wiring board 1. These bonding pads 10 are portions to be bonded later to the tip portions 13 of the leads via the bonding wires 14.

A base material 4 is provided in the vicinity of each second pad 9.
The plated through holes 15 penetrating the front and back are formed, and lands 16 are formed on the peripheral edges of the plated through holes 15. The land 16 and the second pad 9 are
They are connected by the connecting conductor pattern 17.

Each of the connecting conductor patterns 17 is not linear and has a bent portion C at at least one location. Further, the lengths of all the conductor patterns 17 for connection are set to be longer than the flow distance of the adhesive 5 (about 1.0 mm in this embodiment) during hot pressing.

As shown in FIG. 1, a branch point P is provided in the middle of each connecting conductor pattern 17. From the branch point P, the wiring pattern 18 is branched in a direction substantially opposite to the connecting conductor patterns 17.
Each of these branched wiring patterns 18 is connected to the bonding pad 10 at the outermost edge. In addition,
In this embodiment, each branched wiring pattern 18 functions as a relief pattern for preventing the adhesive 5 from flowing.

Now, the printed wiring board 1 as in this embodiment is
When hot pressing is performed with the above configuration, the adhesive 5 oozing on the upper surface flows to both the connecting conductor pattern 17 side and the branched wiring pattern 18 side. Therefore, the amount of the adhesive 5 flowing along the connecting conductor pattern 17 and flowing to the second pad 9 side is significantly reduced as compared with the conventional case.

Further, according to this structure, the distance from the land 16 to the second pad 9 is set longer than the flow distance, and the bent portion C is also formed, so that the adhesive 5
Cannot reach the second pad 9.

As a result, the adhesive 5 which has hitherto been a problem
The second pad 9 is surely prevented from being contaminated by the above, and the bonding state between the second pad 9 and the bonding wire 12 is improved. Therefore, bondability is improved, and high reliability is ensured for the semiconductor mounting substrate 3.

Since it is not necessary to perform the conventional hot pressing consisting of two steps, the total time required for the hot pressing can be the same as before. Therefore, conventional problems such as reduced production efficiency and high cost are
It does not occur in this embodiment.

Further, when the present embodiment is viewed from a different viewpoint, the following can be said. In other words, for the branched wiring pattern 18 side, the connecting conductor pattern 17 functions as a relief pattern for preventing the adhesive 5 from flowing to the bonding pad 10 at the outermost edge.
Therefore, according to the structure of this embodiment, the contamination of the bonding pad 10 with the adhesive 5 can be prevented at the same time.

The present invention is not limited to the above embodiment, but can be modified as follows. For example, (a) as in another example 1 shown in FIG. 2, a wide portion 19a may be provided as an escape pattern for preventing the flow of the adhesive 5 at a substantially intermediate point of the connecting conductor pattern 17. .

(B) As another example 2 shown in FIG. 3, as a relief pattern for preventing the flow of the adhesive 5, a shoulder portion 19b is formed at a portion where the land 16 and the connecting conductor pattern 17 are connected. May be provided.

(C) As in another example 3 shown in FIG. 4, the land 16 itself may be provided with the escape pattern 19c. Further, as in another example 4 shown in FIG. 5, a land 19d having a large diameter may be formed so as to function as a relief pattern.

(D) As another example 5 shown in FIG. 6, a cross-shaped branch point 19e may be provided as an escape pattern at a substantially intermediate point of the connecting conductor pattern 17. (E) Further, it may be a substantially S-shaped connecting conductor pattern 17a as in another example 6 shown in FIG. By greatly bending the connecting conductor pattern 17a in this manner, it is possible to secure a distance from the land 16 to the second pad 9. Then, with such a bent shape, the flow of the adhesive 5 is blocked as compared with the case of the linear shape.

(F) Another functional pad portion different from the second pad 9 and the bonding pad 10 as described above,
For example, if there are pads for mounting chip resistors,
Of course, it is also possible to take measures as in the present invention against them.

[0035]

As described in detail above, according to the printed wiring board of the present invention, it is possible to surely prevent the bonding pad and the like from being contaminated by the adhesive without lowering the production efficiency and increasing the cost. Therefore, the excellent effect that a highly reliable semiconductor mounting substrate can be manufactured is achieved.

[Brief description of drawings]

FIG. 1 is a partially enlarged plan view showing a state in which a printed wiring board of the present invention is bonded onto a lead frame.

FIG. 2 is a plan view showing a relief pattern (wide portion) in a printed wiring board of another example 1.

FIG. 3 is a plan view showing a relief pattern (shoulder portion) in a printed wiring board according to a second example.

FIG. 4 is a plan view showing a relief pattern in a printed wiring board according to a third example.

FIG. 5 is a plan view showing a relief pattern (land having a large diameter) in a printed wiring board of Modified Example 4;

FIG. 6 is a plan view showing a relief pattern (cross-shaped branch points) in a printed wiring board of Modified Example 5;

FIG. 7 is a plan view showing a substantially S-shaped connecting conductor pattern in a printed wiring board of Modified Example 6;

FIG. 8 is a partially enlarged plan view showing a conventional printed wiring board.

FIG. 9 is a partially enlarged front sectional view showing a state in which a conventional printed wiring board is bonded onto a lead frame.

[Explanation of symbols]

1 ... Printed wiring board, 2 ... Lead frame, 4 ... Base material,
5 ... (thermosetting) adhesive, 7 ... Bare chip, 8 ... Die pad, 9 ... Bonding pad (= second pad),
Reference numeral 15 ... Through hole, 16 ... Land, 17 ... Connection conductor pattern, 17a ... Substantially S-shaped connection conductor pattern, 1
8 ... Branched wiring pattern as escape conductor pattern, 19a ... Wide part as escape conductor pattern, 1
9b ... Shoulder portions as escape conductor patterns, 19c ... Escape conductor patterns, 19d ... Large diameter lands as escape conductor patterns, 19e ... Cross-shaped branch points as escape conductor patterns.

Claims (3)

[Claims] 1. A printed wiring board, which is temporarily adhered to a lead frame by a thermosetting adhesive and is then finally adhered by a heating press, wherein at least a bonding pad around a die pad for mounting a bare chip and front and back surfaces of a base material. The bonding pad is connected to a land of a through hole penetrating through by a connecting conductor pattern, and is connected to at least one of the connecting conductor pattern shorter than the flow distance of the adhesive or the land. A printed wiring board provided with an escape conductor pattern for preventing the adhesive from flowing to the inside. 2. A printed wiring board, which is temporarily adhered to a lead frame by a thermosetting adhesive and is then finally adhered by a heat press, wherein at least a bonding pad around a die pad for mounting a bare chip and front and back surfaces of a base material. The land of the through hole penetrating through is connected by a connecting conductor pattern, and the length of the connecting conductor pattern which is shorter than the flowing distance of the adhesive is defined by the flowing distance of the adhesive during hot pressing. Printed wiring board characterized by being set longer than. 3. The printed wiring board according to claim 2, wherein the connecting conductor pattern is provided by bending.