JPH0441298A - Mask for printing - Google Patents

Abstract

PURPOSE:To enable the printing of an electroconductive matter on a substrate accurately by applying a soft sheet having a through hole for passage of the electroconductive matter on a sheet plate provided with a through hole for passage of an electroconductive matter for printing and a void at a position corresponding to a protrusion on the substrate in a such a manner as to let the through holes correspond each other. CONSTITUTION:A through hole 2 is cut in a soft sheet 1, for example, made of a resin to pass an electroconductive matter for printing such as solder paste. For example, a metal sheet 3 is applied on the under side of the sheet 1 and a void 4 for a protruded matter is provided at a position corresponding to a position corresponding to a protruded matter such as a chip mounted on a substrate while a through hole 5 is cut at a position corresponding to the through hole 2 for passage of the electroconductive matter for printing provided on the sheet 1. A substrate carrying a chip, for instance, is put tight on the under side of the sheet 3 and the solder paste is printed on the substrate via the through hole 2 of the sheet 1 and the through hole 5 of the sheet 3.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is generally applied to a chip on-board (chip-on-board) process in which wiring is preliminarily applied to a board on which a semiconductor chip is mounted, and resistors, capacitors, etc. are connected to the wiring. board)
The present invention relates to a mask for printing a conductive substance such as a solder paste used for wiring on a substrate in a semiconductor device known as a semiconductor device.

(Prior art) A resin is applied to a fabric made of fine metal wires, and a mask is used that has holes or grooves from which the resin is removed in the areas necessary for passing a conductive object for printing, and the conductive object is passed through the holes or grooves. Be careful not to print conductive objects on the board.

(Problems to be Solved by the Invention) When forming holes or grooves as described above, thin metal wires remain in the holes or grooves, obstructing the passage of conductive objects. Also,
The surface of the substrate is not flat due to the protrusions caused by the chips mounted on it, and the mask does not come into close contact with the substrate, making it difficult to accurately form the pattern of the conductive object for printing. Means) A flexible thin plate having a through hole for passing the conductive object for printing and a cavity at a position corresponding to the protrusion on the substrate and a through hole for passing the conductive object for printing. A certain sheet was pasted so that each of the above-mentioned through holes corresponded to each other.

(Function) The mask configured as described above does not leave any thin metal wires in the through holes through which the conductive object for printing passes, so that the conductive object for printing is completely printed on the substrate. Ru.

Further, since a through hole is provided in the thin plate at a position corresponding to the protrusion on the substrate, the protrusion enters this position and the mask and the substrate are brought into close contact.

Even if there is a protrusion that is thicker than the thin plate, the flexible sheet can be stretched appropriately to bring the mask and substrate into close contact. It is also possible to bulge out the planned position of this protrusion in advance.

(Example) FIG. 1 is a schematic cross-sectional view of one embodiment of the present invention.

In the drawing, a flexible sheet 1 made of, for example, plastic is provided with through holes 2 for passing a conductive material for printing, such as solder paste. This sheet 1
For example, a thin metal plate 3 is pasted on the lower surface of the board, and although it is not shown in the figure, a space for a protrusion is provided at a position corresponding to a protrusion such as a chip mounted on the substrate. 4, and a through hole 5 is provided at a position corresponding to the through hole 2 provided in the sheet 1 for passing a conductive object for printing. The through hole 5 is obtained by etching the thin plate 3.

For example, a substrate on which a chip is mounted is brought into close contact with the lower surface of the thin plate 30, and solder paste is printed on the substrate through the through hole 2 of the sheet 1 and the through hole 5 of the thin plate 3. At this time, since the chip enters the recess 4 of the thin plate 3, the close contact between the mask and the substrate is not disturbed. Even if the thickness of the chip is larger than the thickness of the thin plate 3, this can be avoided to some extent due to the flexibility of the sheet 1. It is also possible to leave the sheet l slightly bulging as shown in the figure.

(Effects of the Invention) Since the present invention has the above-described structure, the printing mask can be brought into close contact with the board and a conductive object such as solder paste can be applied onto the board, regardless of the protrusions on the surface of the board on which components are mounted. can be printed reliably.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of the present invention. 1... sheet, 2... through hole, 3... thin plate, 4... void, 5... through hole

Claims (1)

[Claims] 1. A flexible sheet having through holes for passing the conductive object for printing, and a thin plate having through holes for passing the conductive object for printing and voids at positions corresponding to the protrusions on the substrate. Printing mask pasted so that each hole corresponds to the other.