JP2001030647A - Mask structure for printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate extension and spreading of a paste for sealing a bare semiconductor element mounted on a recess of a substrate from the recess of the substrate. SOLUTION: A bare semiconductor element 8 is mounted in a recess 7 of a substrate 6, and connected to a circuit of the substrate 6 by wire bonding. A combination mask 1 obtained by adhering a resin layer 3 to a thin plate-like metal plate 2 is descended onto the substrate 6, a paste 9 on the mask 1 is moved by a squeegee 10, and filled (11) in the recess 7 of the substrate 6 from an opening 4. The paste extended from the recess 7 by a pressure of paste printing is spread through a gap between the substrate 6 and the mask 1, and enters to a groove 5 formed on the mask 1, stored in the groove 5 and not spread any more to its circumference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing mask structure, and more particularly to a printing mask structure for preventing a paste to be filled in a concave portion of a substrate from protruding around the concave portion by printing pressure.

[0002]

2. Description of the Related Art A printing mask is used for forming a concave portion (cavity) in a substrate, mounting a bare semiconductor element, and filling a paste (a sealing resin such as an epoxy resin) from above. Printing masks include, for example, an emulsion mask in which an emulsion resin is pasted on a stainless steel mesh and a metal mask using a thin stainless steel plate, and the metal mask has an advantage that the dimensional accuracy of the opening is high. It is difficult to follow the unevenness of the substrate,
At locations where the degree of adhesion to the substrate is insufficient, there is the disadvantage that the paste protrudes from the openings of the mask to the periphery. For this reason,
As shown in FIG. 3, a combination mask 1 in which a resin 3 is adhered to a thin metal plate (stainless steel) 2 has been devised, and the degree of adhesion is improved as compared with the above-described emulsion mask or metal mask. The problem that the paste 21 protrudes from the opening 4 of the mask 1 to the periphery due to the printing pressure has not been sufficiently solved.

[0003]

SUMMARY OF THE INVENTION According to the present invention, the paste which protrudes from the opening of the mask due to the pressure at the time of printing the paste,
The purpose is not to spread around.

[0004]

In order to achieve the above object, a printing mask structure according to the present invention is characterized in that a bare semiconductor element is mounted in a recess formed in a substrate, and an opening formed in the printing mask is placed in the recess. A groove is formed around the opening on the surface of the mask for printing that faces the substrate in the case of filling the paste and sealing the bare semiconductor element, and the paste that protrudes from the recess by pressing during printing is retained in the groove. And do not spread outside the groove.

As a printing mask, a thin metal plate having a thin plate resin adhered thereto is used, and the resin portion is removed or a part of the resin is removed to form a groove.

The groove is formed at a position surrounding the concave portion of the substrate, for example, at a position surrounding the concave portion of the substrate so as to be continuously formed all around.

The opening of the printing mask is formed to have a shape smaller than at least the outer shape of the opening of the concave portion of the substrate.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings. FIG. 1 is a sectional view of a main part of an embodiment of a printing mask structure according to the present invention. 1 is a combination mask (hereinafter, abbreviated as a mask) which is formed by attaching a thin resin layer 3 to a thin metal plate 2 made of stainless steel or the like. Reference numeral 4 denotes an opening of the mask 1, and reference numeral 5 denotes a groove formed by removing part or all of the resin layer 3 by cutting or the like. 6 is a multilayer substrate for electronic circuits,
Reference numeral 7 denotes a concave portion (cavity) for mounting the bare semiconductor element 8, 9 denotes a paste (liquid epoxy resin) for sealing the concave portion 7, and 10 denotes a silicon rubber for applying (printing) the paste 9. The squeegee 11 is a paste filled in the recess 7, and the paste 12 is a paste protruding from the recess 7 and accumulated in the groove 5. FIG. 2 is a view of the substrate 6 of FIG. 1 as viewed from above, and a portion 5 'sandwiched between two dotted lines corresponds to the groove 5 of FIG. Other symbols are the same as those in FIG.

The mask 1 is formed by attaching a resin layer 3 formed in a thin plate shape to a thin metal plate 2 made of stainless steel or the like, and has an opening 4 corresponding to the outer shape of a concave portion 7 of a substrate 6. The paste 9 is placed on the mask 1 and lowered on the substrate 6 fixed with a jig, and the squeegee 10
Is moved to fill the concave portion 7 of the substrate 6 from the opening 4 as shown by the arrow b (11), and the bare semiconductor element 8 is sealed. The substrate 6
For example, in a multilayer substrate for an electronic circuit, a bare semiconductor element 8 mounted in a recess 7 is connected to a conductive pattern of a substrate 6 by wire bonding. The opening 4 has a slightly smaller outer shape than the recess 7 so that the paste does not easily protrude outside the recess 7, but the paste protrudes from the recess 7 of the substrate 6 by the pressure of the paste 9 during printing. This paste flows into the gap between the substrate 6 and the mask 1 and tries to spread around the concave portion 7, but the groove 5 of the mask 1 (5 'in FIG. 2).
The paste 12 enters and accumulates here (12), from which the paste 12 does not spread outward. The groove 5 is formed continuously along the entire circumference so as to surround the periphery of the concave portion 7 of the substrate 6 as shown at 5 'in FIG. 2, for example.

[0010]

As described above, according to the printing mask structure of the present invention, when the paste runs out of the concave portion of the substrate due to the pressure of the paste at the time of printing, the protruding paste surrounds the concave portion of the substrate. Since the paste is stored in the groove of the mask formed at the position, the paste does not spread to the periphery any more.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an embodiment of a printing mask structure according to the present invention.

FIG. 2 is a top view of a main part of FIG.

FIG. 3 is a sectional view of a main part of an example of a conventional printing mask structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combination mask 2 Metal plate (stainless steel) 3 Resin layer 4 Opening 5 Groove 6 Substrate 7 Concave part (cavity) 8 Naked semiconductor element 9 Paste 10 Squeegee 11 Paste filled in concave part 12 Paste which overflowed

Claims (6)

[Claims] 1. A method for mounting a bare semiconductor element in a recess formed in a substrate, filling the recess with a paste through an opening formed in a printing mask, and sealing the bare semiconductor element. A groove is formed around the opening on the surface facing the substrate, so that the paste protruding from the concave portion by pressing at the time of printing is retained in the groove and does not spread outside the groove for printing. Mask structure. 2. The printing mask according to claim 1, wherein the printing mask is formed by attaching a thin plate resin to a thin metal plate, and the groove is formed by removing a part of the resin. Construction. 3. The printing mask structure according to claim 1, wherein the printing mask is formed by attaching a thin plate-shaped resin to a thin plate-shaped metal plate, and the groove is formed by removing the resin portion. 4. The printing mask structure according to claim 1, wherein the groove is formed at a position surrounding the concave portion of the substrate. 5. The groove according to claim 1, wherein the groove is formed at a position surrounding the concave portion of the substrate so as to be continuous over the entire circumference.
The printing mask structure of the above description. 6. The opening according to claim 1, wherein the opening is formed in a shape smaller than at least the outer shape of the opening of the recess.
6. The printing mask structure according to 3, 4 or 5.