JPH04303989A - Thick film circuit board - Google Patents

Abstract

PURPOSE:To remarkably reduce the printing area of a solder resist layer so as to make a pattern finer and improve the yield by forming both an upper conductor layer and dam layer of conductor paste made of the same material containing the same conductive material having low solder wettability. CONSTITUTION:Lower conductor layers 12a-12e are formed on the surface of an insulating substrate 11 and an insulator layer 13 is formed on the layer 12d. In addition, an upper conductor layer 15 the part of which is connected to the layers 12c and 13e is formed on the substrate 11 so that the layer 15 can cross the layer 13. A frame-like solder resist layer (dam layer) 16 is formed on the substrate 11 including the layers 12b and 12c. The upper conductor and dam layers 15 and 16 are constituted as printed layers by respectively printing conductive paste 17 or insulating paste which contains conductive substances and low solder wettability and baking the paste after printing.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to thick film circuit boards, and more particularly to thick film circuit boards comprised of printed circuits, surface-mounted chip components, and the like.

0002

2. Description of the Related Art FIG. 2 shows a cross-sectional view of a conventional thick film circuit board.

Reference numeral 1 in the figure is an insulating substrate made of alumina or the like. A lower conductor layer 2 is formed on the surface of this insulating substrate 1. This lower conductor layer 2 is formed, for example, by printing and baking a silver-palladium based conductor paste. An insulator layer 3 is formed on a portion of the lower conductor layer 2 . A predetermined lower conductor layer 2 is provided on the insulating substrate 1.
A resistor layer 4 is formed so as to overlap with the resistor layer 4. An upper conductor layer 5 is formed on the insulating substrate 1 by printing so that a portion thereof overlaps with a portion of the lower conductor layer 2. A portion of the lower conductor layer 2 serves as a connection pad 2a, and a solder resist layer 6 is provided on the portion other than the connection pad 2a. On the connection pad 2a where the solder resist layer 6 does not exist, a solder paste layer 7 is provided by printing or the like. Here, as the solder resist layer 6, glass paste or resin paste is usually used. The solder paste layer 7
A chip component 8 is mounted on the top.

0004

[Problems to be Solved by the Invention] However, conventional thick film circuit boards have had the following problems. (1) Pattern refinement is required when forming the solder resist layer 6, but since the solder resist layer 6 is formed by printing, there are limitations and this is one of the causes of a decrease in yield. (2) Since the solder resist layer 6 has a relatively large printing area and its formation conditions are different from those of other layers, the cost increases. Furthermore, since the conditions for forming the solder resist layer 6 are different from those of other layers, special equipment is required, which also increases costs.

The present invention has been made in view of the above circumstances, and aims to significantly reduce the printing area of the solder resist layer compared to the conventional one, achieve pattern refinement, and improve yield. The purpose of the present invention is to provide a thick film circuit board that can reduce costs by eliminating the need for specialized equipment.

[0006]

[Means for Solving the Problems] The present invention provides an insulating substrate;
It includes a plurality of lower conductor layers formed on the insulating substrate, a chip component formed on a part of the lower conductor layer via a solder resist layer, and the lower conductor layer around the solder resist layer. It comprises a dam layer formed on the insulating substrate and an upper conductor layer formed on a part of the lower conductor layer with an insulator layer interposed therebetween, and the front upper conductor layer and the dam layer are each electrically conductive. This is a thick film circuit board characterized by a printed layer obtained by printing and baking a conductive paste or insulating paste containing a material with poor solder wettability.

In the present invention, examples of the material of the insulating substrate include ceramics such as alumina.

In the present invention, examples of the material for the lower conductor layer include silver-palladium conductive materials.

[0009] In the present invention, conductive materials such as silver-palladium may be used as the material for the upper conductor layer and the dam layer, and a conductive paste containing this conductive material may have poor solder wettability. is necessary.

0010

[Operation] In the present invention, the dam layer surrounding the solder resist layer and the upper conductor layer are made of the same material, and a conductive paste with poor wettability containing a conductive material with poor wettability is applied to a predetermined position. It is formed by printing, baking and drying. Use of such a conductive paste increases the height of the solder resist layer (dam layer) and prevents solder from flowing to areas other than the connection pads.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a thick film circuit board according to an embodiment of the present invention. 11 in the figure is an insulating substrate made of alumina or the like. A lower conductor layer 1 is formed on the surface of this insulating substrate 11.
2 (12a, 12b, 12c, 12d, 12e) are formed. This lower conductor layer 12 is formed, for example, by printing and baking a silver-palladium based conductor paste. An insulating layer 13 is formed on the lower conductor layer 12d by printing and baking an insulating paste. On the insulating substrate 11 are lower conductor layers 12a and 12b.
A resistor layer 14 is formed so as to straddle the area. On the insulating substrate 11, a part of the lower conductor layers 12c, 12
upper conductor layer 1 so as to connect to e and straddle the insulator layer 13.
5 is formed. A frame-shaped solder resist layer (dam layer) 16 is formed on the insulating substrate 11 including the lower conductor layers 12b and 12c, and a solder paste layer 17 is formed inside this dam layer 16. Note that the portion of the lower conductor layer to which this solder paste 17 is connected becomes a connection pad for chip components. A step portion is formed in this solder paste layer 17, and a chip component 18 is mounted so that both ends thereof straddle this step portion.

The thick film circuit board having the above structure is formed as follows. First, a silver-palladium-based conductive paste, for example, is printed on the surface of the insulating substrate 11 and fired to form the lower conductive layers 12a to 12e. Subsequently, the lower conductor layer 12
An insulating paste is printed on d and baked to form an insulating layer 13.
form. Next, a resistor paste is printed and dried so as to straddle the lower conductor layer 12d. Subsequently, conductor paste is printed and dried on the lower conductor layers 12a and 12b in the vicinity of the chip component connection pads, and resistor paste is applied.
The resistor layer 14, the upper conductor layer 15, and the frame-shaped dam layer 16 are formed by firing at the same time as the firing. Furthermore, a solder paste layer 17 is formed on the chip component connection pad within the frame of the dam layer 16 by printing or the like, and the chip component 18 is attached so that the solder paste formed portion becomes the electrode of the chip component 18 or the like. Mounted and soldered using reflow soldering etc., chip part 1
A thick film circuit board is manufactured by connecting connection pads such as 8 and fixing them. When printing the upper conductor layer, a conductor paste with particularly poor solder wettability is used to increase the height of the solder resist and prevent solder from flowing to areas other than the connection pads.

[0013] According to the above embodiment, however, there are the following advantages. (1) Solder resist layer (dam layer) 16 is attached to chip component 1
Since it is selectively provided only on the insulating substrate 11 including the lower conductor layers 12b and 12c on which the solder resist layer 8 is mounted, the printing area is greatly reduced compared to a conventional solder resist layer, and a finer pattern is realized. can. Therefore, yield is improved and work efficiency is improved.

(2) Since the printing area of the dam layer 16 is reduced, material costs can be reduced. (3) Since the upper conductor layer 15 and the dam layer 16 can be formed at the same time, the number of man-hours can be reduced and conventional equipment can be shared.

[0015] In the above embodiment, a case was explained in which a printed layer was formed using a conductive paste. Layers may also be used.

[0016]

As described in detail above, according to the present invention, the upper conductor layer and the dam layer are both made of the same material and are made of a conductive paste containing a conductive material with poor solder wettability. It is possible to provide a thick film circuit board in which the printed area of the layer is greatly reduced to achieve finer patterns and yields are improved, and the cost can be reduced by reducing the amount of material used in the solder resist layer and eliminating the need for dedicated equipment.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a thick film circuit board according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a conventional thick film circuit board.

[Explanation of symbols]

11... Insulating substrate, 12a to 12e... Lower conductor layer, 13...
Insulator layer, 14... Resistor layer, 15... Upper conductor layer, 16...
Solder resist layer (dam layer), 17...Solder paste layer, 1
8...Chip parts.

Claims (1)

[Claims] 1. An insulating substrate, a plurality of lower conductor layers formed on the insulating substrate, a chip component formed on a portion of the lower conductor layer with a solder resist layer interposed therebetween, and the solder resist layer. a dam layer formed on the insulating substrate including the lower conductor layer around the lower conductor layer, and an upper conductor layer formed on a part of the lower conductor layer via an insulator layer, and the front upper conductor layer and a thick film circuit board, wherein the dam layer is a printed layer obtained by printing and baking a conductive paste or an insulating paste containing a conductive material and having poor solder wettability, respectively.