JPH04142045A - Resin sealing method for semiconductor integrated element in surface mounting on electric wiring board - Google Patents

Abstract

PURPOSE:To prevent a threading phenomenon from being caused by a method wherein a changeover operation by using a doctor blade is executed and the amount of a resin filled into a through hole is made nearly uniform on the side of the movement start point and on the side of the end point of a squeegee. CONSTITUTION:At the filling operation of a resin 5 by actuating a squeegee 7, the resin 5 inevitably has a tendency to be swollen 51 on the side of the movement end point. In succession to the filling operation, a changeover operation by using a doctor blade 8 is executed from the side of the movement end point; the resin in a part which has been swollen 51 at the changeover operation is pushed back up to the intermediate part of a movement distance. Consequently, the filling state of the resin 5 which has been pushed back becomes nearly uniform on the side of the end point and on the side of the start point. Thereby, when the resin is transcribed in this state, the resin is cut well on the side of the end point and on the side of the start point and it is possible to substantially prevent a threading phenomenon from being caused.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a resin sealing method for a semiconductor integrated device in surface mounting of an electrical wiring board.

Prior art and its problems Recently, in surface mounting of electrical wiring boards, such as printed wiring boards, with the increase in density, semiconductor integrated elements are mounted directly on printed circuit boards in a bare state, and the elements and printed wiring boards are mounted directly on the printed circuit boards. There is a tendency for electrical connections to be made with In this case, the semiconductor integrated element mounted bare on the printed circuit board must be sealed with electrically insulating resin for the purpose of maintaining quality.

The present applicant previously discovered that in surface mounting of an electrical wiring board, a semiconductor integrated element mounted in a bare state on the board was sealed with a resin, and a through-hole pattern identical to the mounting pattern of the element was found. After aligning the through hole and the element using a stencil having a stencil and forming a gap necessary for sealing the element between the through hole and the element, the liquid sealing resin is poured into the gap through the through hole. A method of resin-sealing semiconductor elements for surface mounting of electrical wiring boards was proposed, in which semiconductor elements are injected and filled by the operation of a squeegee (for example, see Japanese Patent Laid-Open No. 82639/1983).

According to the above resin sealing method proposed by the applicant, ■ the thickness of the sealing resin layer becomes uniform and a stable and reliable resin sealing effect can be obtained; ■ resin sealing with the minimum resin sealing area is possible. [Phase] The thickness of the sealing resin layer is determined by the effective height of the through hole, making it easy to control the thickness.[Co., Ltd.] Even for large devices such as LSI Resin sealing can be done in one operation, and stable resin sealing is possible regardless of whether the device is large or small. ■ Regardless of the number of devices mounted, one operation is based on the printed circuit board. However, subsequent research has revealed that there are some problems in terms of uniformity of the thickness of the sealing resin layer and productivity. It has been found. That is, according to the previously proposed resin sealing method, as shown in FIG.
As a result, when transferring the resin at the opening in FIG. 5, the contact area between the resin (b) and the stencil (C) increases on the end point side of the squeegee movement, causing the stringing phenomenon (d) on the end point side. This excess thread (d) will either break and disappear if it is left in the condition shown in Figure 5 for a certain period of time, or it will take a considerable amount of time to break due to the amount of thread being drawn, resulting in a large time loss. Productivity decreases. Furthermore, since thread breakage occurs only at the end of the movement, the thread breakage becomes high as shown in Fig. 5C.
The thickness of the sealing resin layer becomes uneven.

One way to solve this problem is to increase the pressure when pressing the squeegee against the stencil, but since the liquid resin used for sealing has a high viscosity, even if the pressing pressure is increased, the stencil and The damage to the squeegee will be greater (just as it becomes,
It is not very effective in eliminating non-uniformity in the resin filling state.

Also, if the moving speed of the squeegee is slowed down, non-uniformity in the resin filling state tends to be resolved, but considering productivity,
Since the moving speed cannot be made very slow, it is substantially difficult to eliminate non-uniformity by controlling the moving speed.

The present invention has been made with the aim of eliminating such conventional problems.

Means for Solving the Problems As a result of extensive research in order to solve the above problems, the inventors of the present invention have determined that after finishing resin filling with a squeegee, the cutting back using a doctor knife starts from the end point of the squeegee movement. The inventors have discovered that all of the above problems can be solved when moving to an intermediate point in the travel distance, and have finally completed the present invention.

That is, in the present invention, when resin-sealing a semiconductor integrated element mounted bare on an electric wiring board, a stencil having a through hole pattern identical to the mounting pattern of the element is used, and the through holes and the element are sealed. Perform alignment and between the through hole and the element,
In the resin sealing method, in which a gap necessary for element sealing is formed and then the liquid sealing resin is forced into the gap through the through hole and filled by the operation of a squeegee, the liquid sealing resin is forced into the gap by the operation of the squeegee. Following filling, by moving the doctor knife from the movement end point side to the middle part of the stencil hole while maintaining contact with the stencil plate, the squeegee movement start point side and end point side of the hole are sealed. A method of resin-sealing a semiconductor integrated element in surface mounting of an electrical wiring board, characterized in that the filling state of the sealing resin is made almost uniform, and then a stencil is removed from the substrate to transfer the sealing resin. .

EXAMPLE Below, one implementation status of the resin sealing method of the present invention will be explained based on the attached drawings.

FIGS. 1(A) to 1(B) are schematic explanatory diagrams showing the basic principle of the resin encapsulation method of the present invention in the order of steps.
In order to resin-seal the semiconductor integrated element (2) mounted bare thereon, a stencil (3) having the same through-hole pattern as the mounting pattern of the element (2) is used.

In the first step shown in FIG. 1(a), the stencil (3) is fixedly set in a predetermined position of a screen printing machine (not shown), and the substrate (1) is placed on the slide table (not shown) of the printing machine.
4), and a predetermined amount of liquid sealing resin (5) is further supplied onto the stencil (3).

Next, operate the printing machine and press the through hole (3a) of the stencil (3).
) and the semiconductor element (2) mounted on the substrate (1), the stencil (3) is pressed against the surface of the substrate (1), and a stencil (3) is inserted into each through hole (3a). The corresponding element above (
2) are stored concentrically. This storage state is shown enlarged in FIG. 2, and there is a gap (6 ) is formed.

Next, the squeegee (7) is operated and the resin (5) is pushed through the through hole (3).
The void (6) in a) is extruded and filled.

This state is shown in FIG. After that, Figure 1 (
As shown in (b), the printing press is operated to move the stencil (3) back to its original position, thereby obtaining the element (2) sealed with the resin layer (5a).

As shown in FIG. 3, when the squeegee (7) is moved at the usual speed, the resin (5) filled in the gap (6) of the through hole (3a) stops moving as in the conventional method. On the point side,
There is a tendency to bulge (51) and the amount of filling increases. In this state, insert the resin (5) through the hole (3a).
) to the substrate (1), as mentioned above in the prior art, a stringing phenomenon occurs on the end point side, and this stringing phenomenon causes unevenness in the thickness of the sealing resin layer. It also causes a decrease in productivity.

In order to solve these problems, the present invention takes measures as shown in FIGS. 4(a) to 4(d). That is, as shown in FIG. 4(a), in the filling operation of the resin (5) by operating the squeegee (7), as long as the squeegee (7) is moved according to the usual method, the resin (5) will be filled at the end of its movement. ) tends to rise (51), so following this filling operation, as shown in FIG. (51) The resin in the portion is pushed back to the intermediate portion of the moving distance. By pushing back, the filling state of the resin (5) becomes almost uniform on the end point side and the starting point side, and when the resin is transferred in this state, as shown in Fig. 4 (C).
As shown in Figure 2, the resin is easily cut on the end point side and the starting point side, and virtually no stringing phenomenon occurs in these areas.

At the lower end of the doctor knife (8), stringing (52) occurs due to contact with the pushed-back resin, but due to the small contact area, the amount of stringing is small, and the string will break if left unattended for a short time.
Time loss due to string pulling is reduced and productivity can be improved. In addition, since the thread breakage occurs at the midpoint between the travel distances, the resin due to the thread breakage is collected at the midpoint of the upper surface of the resin layer (5a), and after collection, it flows to both sides and becomes substantially flat. This also solves the problem of uneven thickness due to thread breakage.

Incidentally, the preferred operating conditions according to the method of the present invention are listed below.

effect According to the method of the present invention, the following effects can be obtained.

■ By cutting back with a doctor knife, the amount of resin filled through the hole is approximately equalized on the start and end points of the squeegee movement. The occurrence of the pulling phenomenon is substantially eliminated.

■ During transfer, stringing occurs at the lower end of the doctor knife, halfway between the two points, but the amount of stringing is small, so thread breakage occurs in a short time, reducing time loss waiting for thread breakage. , productivity can be improved.

(2) Since the thread breakage occurs at the middle part of the sealing resin layer, the resin caused by the thread breakage flows equally from the middle part of the layer to both sides and is recovered. Therefore, the thickness of the sealing resin layer is kept substantially uniform throughout.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are detailed explanatory diagrams of the present invention;
The figure is a partially enlarged sectional view showing how the through hole of the stencil and the element to be sealed are aligned, FIG. 3 is a partially enlarged sectional view showing how the sealing resin is filled into the through hole, and FIG. (A) to (D) are detailed explanatory diagrams of the present invention, and FIGS. 5(A) to (C) are explanatory diagrams of the conventional method. In the figure, (1) is the substrate, (2) is the semiconductor integrated element, (
3) is a stencil, (4) is a slide table, (5) is a sealing resin, (6) is a gap, (7) is a squeegee, and (8) is a doctor knife. (Above) Figure Figure Figure a Figure Figure a Figure Figure

Claims (1)

[Claims] (1) When sealing with resin a semiconductor integrated device mounted bare on an electrical wiring board, use a stencil having a through-hole pattern identical to the mounting pattern of the above-mentioned element, and align the through-hole with the above-mentioned element. In the resin sealing method, after forming a gap necessary for sealing the element between the through hole and the element, liquid sealing resin is forced into the gap by operating a squeegee through the through hole. Following the forced filling of the liquid sealing resin by the squeegee operation, the squeegee moves the through hole by moving the doctor knife from the end point side of the movement to the middle part of the stencil hole while maintaining contact with the stencil. In surface mounting of electrical wiring boards, the filling state of the sealing resin on the starting point side and the ending point side is made almost uniform, and then the stencil is removed from the board to transfer the sealing resin. A resin sealing method for semiconductor integrated devices.