JPH04170086A - Printed wiring board - Google Patents

Abstract

PURPOSE:To prevent the solder bride short by providing a second soldering resistance layer in such a way that it does not contact with a conductor pattern, and making a deep trench. CONSTITUTION:A first semiconductor resistance layer 6 with a width W is provided on the insulating board 2 between the conductor patterns 2a of a printed wiring board, and a second soldering resistance layer 7 is so provided as not to contact with the conductor pattern 2a, with the same width W as that of the first soldering resistance layer 6, on the first soldering resistance layer 6. As a result, a deep trench 4 with a depth d, consisting of the thickness of the first soldering resistance layer 6 plus the thickness of the second soldering resistance layer 7, is made between the conductor pattern 2a and the second soldering resistance layer 7. Hereby, even in the case of having performed the reflow method soldering for the narrow pitch surface mounting parts, the solder bridge short does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printed wiring board, and in particular to a printed wiring board that is provided with measures to prevent bridges during soldering.

[Conventional technology]

In the conventional printed wiring board, as shown in FIGS. 5(a), (b) and 6, when the distance S between two conductor patterns (pads) 2a becomes narrow to O,'7am7a, the conductor A method is disclosed in which a soldering resistance layer (solder resist) 3 is provided on an insulating substrate 1 between patterns 2a so as not to contact with the conductor pattern 2a, resulting in formation of a resistive layer 4, and Japanese Patent No. 12948
As shown in No. 18, a first soldering resistive layer 6 is provided on the conductive pattern (land) 2b of FIGS. 7 and 8 in contact with the conductive pattern 2b, and further, the first soldering resistive layer 6 A method has been implemented in which a second soldering resistive layer 7 is provided on top of the soldering resistor layer 7.

As is clear from the judgment of the Tokyo High Court in the patent suit, Case No. 11 of 1980, in which the trial decision was requested to be rescinded, this applies except for the part soldered onto the conductor pattern 2b. , printing a first soldering resistive layer 6;
The conductive pattern 2b and the first soldering resistance layer 6 are in contact with each other, and the groove 4 shown in FIGS. 5(a), 6(b) and 6 is not present.

[Problem to be solved by the invention]

This conventional method of setting the soldering resistance layer of a printed wiring board is difficult to perform when reflow one-way soldering is performed for narrow-pitch surface mount components with a spacing of 0.5 mm or less between conductor patterns, which has become popular in recent years. However, the effect of preventing solder bridge shorts was not satisfactory.

The reason for this is: (1) Cream solder (not shown) applied on the surface of the conductor pattern 2a in FIGS. 5(a), 6(b) and 6.
If the soldering resistor layer 3 is misaligned, both surfaces of the conductor pattern 2a and the soldering resistor layer 3 will be covered with solder cream, and when the solder cream is heated and melted, the solder cream will be dislocated between the conductor patterns 2a. Solder bridging occurs due to the solder 8. This is because the depth d of the edge 4 is the thickness of the soldering resistance layer 3, which is usually as thin as several μm to 20 μm.
This is caused by poor solder cutting.

(2) The printed wiring boards shown in Figures 7(a) and (b) have been mainly used for the purpose of preventing solder bridge shorts in flow-through one-way soldering, but when applied to reflow-flow one-way soldering, If the cream solder (not shown) applied on the surface of the conductor pattern 2b is misaligned toward the second soldering resistance layer 7, the solder will break because there is no groove 4 as shown in FIG. or what is not done.

It is in.

An object of the present invention is to provide a printed wiring board in which solder bridge shorts do not occur even when reflow one-way soldering is performed for narrow-pitch surface mount components with a spacing of 0.5 mm or less between conductor patterns, which has become popular in recent years. It's about doing.

[Means to solve the problem]

The present invention provides a printed wiring board in which a conductor pattern is formed on an insulating substrate, components are mounted on the surface of the conductor pattern, and leads of the components are soldered. The spacing between conductor patterns is 0.
A first soldering resistance layer is provided on the insulating substrate in a portion of 5W1II or less so as not to contact the conductor pattern, and a first soldering resistance layer is provided on the first soldering resistance layer so as not to contact the conductor pattern. A groove is formed between the conductive pattern and the second soldering resistive layer.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) and 1(b) are a plan view and a sectional view of a main part of a first embodiment of the present invention.

The first embodiment, as shown in FIGS. 1(a) and (b),
The spacing S between the conductor patterns 2a is 0.5 μl or less, and the distance between the conductor patterns 2a is as shown in FIG. 5(a).

The first width W corresponding to the soldering resistance layer 3 on the insulating substrate 1 between the conductive patterns 2a of the conventional printed wiring board shown in (b)
A second soldering resistance layer 6 is provided on the first soldering resistance layer 6, and a second soldering resistance layer 6 is provided on the first soldering resistance layer 6 with the same width as the width W of the first soldering resistance layer 6 so as not to contact the conductive pattern 2a. A layer 7 is provided.

This second soldering resistance layer 7 can usually be formed at the same time as the printing of the first soldering resistance layer 6 in a marking process of printing characters.

As a result, there is a depth d between the conductive pattern 2a and the second soldering resistance layer 7, which is the thickness of the first soldering resistance layer 6 plus the thickness of the second soldering resistance layer 7. (Usually, several tens of μ
m or more) can be formed.

FIG. 2 is a sectional view of component leads soldered to the printed wiring board of FIGS. 1(a) and 1(b).

As shown in FIG. 2, even if the cream solder (not shown) applied on the surface of the conductor pattern 2a is displaced toward the second soldering resistance layer 7, the deep groove 4 with a depth d When the solder cream gets into the groove, and when the solder cream is heated and melted, the solder breaks in the deep groove 4 with a depth of d.
As a result, the length of the second soldering resistance layer 7 that does not cause solder bridges due to the solder 8 between the conductor patterns 2a is sufficient if it is approximately equal to or longer than the length of the conductor patterns 2a.

FIGS. 3(a) and 3(b) are a plan view and a sectional view of a main part of a second embodiment of the present invention.

In the second embodiment, as shown in FIG. 3 (a>, (b)),
The basic structure is the same as that of the first embodiment shown in FIGS. Things are different.

In this case, the groove 4 has a step-like shape, and is characterized by good solder cutting when the cream solder is heated and melted, as in the first embodiment.

Further, when the second soldering resistive layer 7 is formed by character printing, a printing position shift of the soldering resistive layer 7 whose width Wl is equal to the width of the first soldering resistive layer 6 is allowed.

FIG. 4 is a sectional view of a main part of a third embodiment of the present invention.

In the third embodiment, as shown in FIG.
A second soldering resistance layer 7 is formed around the first soldering resistance layer 6 near point a. In this case, 7114
Since the shape of the second soldering resistance layer 7 side is formed by normal character printing, the ink drips and becomes slope-like. Moreover, the shape of the groove 4 may be a right angle. Regardless of the shape of the arm 4, the first. As in the second embodiment, the presence of the deep edges 4 allows for good solder breakage when the cream solder is heated and melted.

〔Effect of the invention〕

As explained above, the present invention provides the second soldering resistance layer so as not to contact the conductor pattern.
Since the deep grooves are formed, it is possible to prevent solder bridge short circuits due to slight printing misalignment or oversupply of solder cream during reflow soldering.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are a plan view and a sectional view of the main parts of the first embodiment of the present invention, and FIG. 2 is a component lead on the printed wiring board of FIGS. 1(a) and (b). FIGS. 3(a) and 3(b) are plan views and sectional views of essential parts of the second embodiment of the present invention, and FIG. 4 is a schematic diagram of the third embodiment of the present invention. 5(a) and 5(b) are a plan view of essential parts of an example of a conventional printed wiring board and its sectional view; FIG. 6 is a partial sectional view; FIG. 5(a),
(b) is a cross-sectional view of component leads soldered to the printed wiring board, Figure 7 is a plan view of another example of a conventional printed wiring board, and Figure 8 is a diagram showing components mounted on the printed wiring board of Figure 7. FIG. DESCRIPTION OF SYMBOLS 1... Insulating board, 2.2a, 2b... Conductor pattern, 3... Soldering resistance layer, 4... Groove, 5... Through hole, 6... First soldering resistor layer, 7... second soldering resistance layer, 8... solder, 9... component, 10...
・Parts lead.

Claims (1)

[Claims] In a printed wiring board in which a conductive pattern is formed on an insulating substrate, a component is mounted on the formed surface of the conductive pattern, and a lead of the component is soldered, between two conductive patterns facing each other on the same plane of the insulating substrate. A first soldering resistance layer is provided on the insulating substrate in a portion where the interval between
A second soldering resistive layer is coated on the soldering resistive layer so as not to contact the conductive pattern, and a groove is formed between the conductive pattern and the second soldering resistive layer. Printed wiring board.