JPH0237697B2 - - Google Patents

Abstract

PURPOSE:To obtain the arbitrary and minute complicate form of a protective layer in response to a circuit by printing and forming a pattern of a weir by using prining ink into which expandable particulates are mixed, injecting a resin to a section surrounded by the weir and shaping the protective layer. CONSTITUTION:A pattern 10 afterwards functioning as a weir is printed and formed on a substrate 1, to which wirings 3 are wired, through a screen printing method by using expandable printing ink, and an IC chip 2 is die-bonded similarly on the substrate 1 with adhesives 7. When the substrate to which the weir pattern is printed and formed is heated and treated, printed expandable ink foams and expands, height increases, and 10a is shaped. Adhesives 7 bonding the IC chip 2 cure simultaneously. The IC chip 2 and the wirings 3 on the substrate are connected 4 through wire bonding. A resin for shaping a protective layer 5 is injected to the weir 10a formed by the foaming and expansion of expandable ink, and the weir section is sealed completely.

Description

DETAILED DESCRIPTION OF THE INVENTION When a partial protective layer for fine particles is formed using a resin or the like, the present invention can simultaneously create a weir to prevent the sealing resin from flowing out even if the fine particles are in one place or in multiple places. The present invention relates to a partial sealing method that allows formation with high accuracy and allows the shape of a weir pattern to be arbitrarily set.

Conventionally, when forming a hybrid integrated circuit on a wiring board made of ceramic or resin, for example, a method such as wire bonding is used to connect a mounted IC chip, etc. and a wiring part on the board. Alternatively, a protective layer made of resin or the like is provided partially on the connection portion, including the IC chip. The resin used to form this protective layer is heat treated (usually at 120°C to 150°C).
degree) and harden it. However, since the thermal expansion coefficients of the connecting wires, IC chips, and substrates are different, there is a risk that stress will be applied at each interface when the temperature returns to room temperature, causing problems such as disconnection of the connecting wires. In order to prevent this, the stress can be reduced, and one possible way to do this is to change the thermal expansion coefficient or elastic modulus of the protective resin layer, but usually the amount of resin used is as small as possible, and the protective A partial sealing method is used to minimize the amount of parts that are exposed.

For example, in the conventional example shown in FIG. 1, wiring 3 is provided on a substrate 1, an IC chip 2 is fixed with an adhesive 7, connections 4 are provided by wire bonding, and a protective layer 5 is formed by injecting resin. However, since no means were taken to prevent the resin from flowing out, the resin would leak into unnecessary areas, and as a result, the amount of resin used could not be reduced. In order to prevent the resin from flowing out, a frame 6 made of phenol resin or the like is glued around the area to be protected, as shown in FIG.
There is a method to use this as a dam to prevent resin from flowing out.

This method reduced the amount of resin used, but increased the steps of molding the frame and gluing and fixing it. On the other hand, since the frame 6 needs to be in close contact with the substrate 1, it is required to have flatness without warping or twisting, and although it requires a certain amount of adhesive area, it is also required to have a narrow width on the substrate. Although a fine and complicated shape is required depending on the wiring of the substrate 1, it is extremely difficult to set the shape arbitrarily.

In view of the disadvantages seen in the prior art as described above, the present invention provides a foam printing ink, for example, a foam printing ink, in order to simplify the manufacturing process of hybrid integrated circuits and provide a weir useful for forming a protective layer. A weir pattern is screen printed on one or more locations where a protective layer needs to be provided, using printing ink mixed with sexual fine particles (Each Expancel product: manufactured by Nippon Fluite, etc.). At the same time, the pattern is printed, and after the pattern is printed, it is heated to promote foaming and expansion of the foamable ink, and the expansion forms a weir having a height that prevents at least the resin from flowing out, and the resin is applied to the area surrounded by the weir. The present invention provides a partial sealing method characterized in that a protective layer is formed by injecting and curing a weir pattern, and the shape of a weir pattern can be arbitrarily set.

FIG. 3 is an embodiment of the present invention, and is a diagram showing the first formation order. On the substrate 1 on which the wiring 3 has been applied, a pattern 10 that will later become a dam is printed by screen printing using foam printing ink, and the IC chip 2 is also placed on the substrate 1 with an adhesive 7.
This shows the state after die bonding.

FIG. 4 is an embodiment of the present invention, and is a diagram showing the second formation order. In FIG. 3, when the substrate on which the weir pattern is printed is heat-treated, the printed foaming ink expands and increases in height to form the weir 10a. At the same time, IC chip 2
The adhesive 7 that adheres them is cured. moreover,
A state in which a connection 4 is made between an IC chip 2 and a wiring 3 on a substrate by wire bonding is shown.

FIG. 5 is a diagram showing the third and final stage of the formation sequence in an embodiment of the present invention. The figure shows a state in which a resin for forming a protective layer is injected into the weir 10a formed by the expansion of the foaming ink, and the sealing of the part is completed.

In this example, ink mixed with heat-expandable microparticles is used as a foamable printing ink. Even if it contains a decomposable blowing agent (or a volatile blowing agent that is a gas or volatile liquid at room temperature), or one that generates gas during drying or curing reactions. It is also possible to use ink that foams. In addition, in this example, foaming and expansion is promoted by applying heat treatment by heating, but foaming and expanding may be allowed to occur naturally, or by cooling, pressurization, electron beams, ultraviolet rays, etc. It is also possible to use a material that reacts and foams by irradiating it.

Regarding the printing method, although a screen printing method is used in this embodiment, other printing methods that can obtain the same effect may be used.

Although the ink is foamed and expanded before wire bonding, the ink may be foamed and expanded after wire bonding as long as it does not interfere with bonding and printing.

Furthermore, although this example describes the encapsulation of an IC chip with a resin protective layer in the manufacturing process of a hybrid integrated circuit, it may also be used to encapsulate other electronic components such as resistors, and may be used in the machining process. Of course, it can be applied to, for example, sealing screws or preventing adhesive from flowing out.

As described above, by using the present invention, the shape of the protective layer can be arbitrarily set according to the circuit without being limited by the processing accuracy of the molded product used as a weir, and a finer and more complex shape can be obtained compared to the weir formation using a molded product. Furthermore, even when weirs are provided at several locations, patterns at several locations can be formed at the same time.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional board without a weir to prevent leakage, and Figure 2 is a cross-sectional view of a conventional board with a weir provided by gluing a separately molded frame. In the figures, FIG. 3 is a sectional view of the first substrate in the embodiment of the present invention, FIG. 4 is a sectional view of the second substrate, and FIG. 5 is a sectional view of the third substrate. FIG. 6 is a schematic perspective view of a hybrid integrated circuit using the present invention. 1... Board, 2... IC chip, 3... Wiring,
4... Connection, 5... Protective layer, 6... Frame, 7... Adhesive, 10... Weir pattern (state before expansion), 1
0a...Weir pattern (state after expansion).

Claims (1)

[Scope of Claims] 1. In the mounting process of hybrid integrated circuits, etc., when a partial protective layer is formed using resin etc. to seal minute parts, on a circuit board, when heated, it expands. Using a foaming ink, a weir pattern for preventing resin outflow is printed on one or more necessary parts using a screen printing method, and the pattern is heated after printing to form the printed foam. The protective layer is formed by foaming and expanding the adhesive ink, forming a weir having a height that prevents at least resin from flowing out by the expansion, and injecting and hardening resin etc. into the area surrounded by the weir to form a protective layer. partial sealing method.