JPH04328894A - Printed wiring board - Google Patents

Abstract

PURPOSE:To provide a printed wiring board where solder resist is prevented from scattering and separating even if solder resist must be formed covering a through-hole so as to meet requirements such as enhancement in wiring density and function. CONSTITUTION:Solder resist or a symbol mark 20 is formed on one side of a printed wiring board covering a through-hole 10, and solder resist or the symbol mark 20 is formed on the other side of the wiring board avoiding the through-hole 10.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided or multilayer printed wiring board having through holes, and more particularly to a printed wiring board having solder resists or symbol marks formed on both sides thereof.

0002

[Prior Art] Generally, in mounting technology using a printed wiring board, electronic components are mounted on the printed wiring board, and the connection terminals of the electronic components and the connection terminals of the printed wiring board are connected using solder, bonding wire, etc. It is being done. As devices become lighter, thinner, shorter, and more sophisticated, electronic components become more densely packaged and printed wiring boards become more densely wired.

[0003] Conventionally, solder resists have been formed on these printed wiring boards for the purpose of preventing adhesion of solder and contamination by flux and the like. As printed wiring boards become more dense and functional, various demands are placed on solder resists. For example, for thin printed wiring boards with a thickness of about 0.5 mm, a solder resist containing a large amount of filler to suppress thermal expansion is used to suppress warping. In addition, a solder resist containing a large amount of this filler is printed on the through-holes, and is used to fill in the through-holes and hide the holes in appearance.

[0004] Also, of course, with the trend toward higher density wiring, the wiring density of conductor circuits will increase, so everything other than connection terminals for soldering etc. should be covered with solder resist as much as possible, that is, conductor circuits for wiring, including through holes, Printing is performed as solidly as possible to prevent adjacent conductor circuits from being exposed through the openings in the solder resist. However, when solder resist was printed solidly on both sides of the through hole, the following problem occurred. To form solder resist by printing on both sides of a printed wiring board, first print solder resist on one side of the board,
Generally, it is dried and hardened using a hot air dryer, then a solder resist is similarly printed on the remaining one side, and then dried and hardened in the same manner. At this time, if the previously printed solder resist covers the through hole and prints solidly, and then you want to cover the through hole and print solidly on the other side, the through hole will be printed on both sides. This causes the through hole to become blocked by solder resist, and when it dries and hardens, the air inside the through hole expands and blows away the solder resist that was printed later. If this blown-off solder resist adheres to the connection terminals mentioned above, it will naturally become impossible to connect, and if the area near the through-hole that was originally intended to be printed peels off and flies off, the conductor circuit will be damaged. They were exposed and became inconvenient.

[0005]

SUMMARY OF THE INVENTION The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to avoid defects such as solder resist being blown off and contaminating connection terminals.

[0006]An object of the present invention is to prevent scattering and peeling of the solder resist even when it is necessary to form a solder resist to cover through holes due to the demand for higher density wiring and higher functionality. Our goal is to provide printed wiring boards that do not have any problems.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the means taken by the present invention are described with reference numerals used in the embodiments.
In the printed wiring board 100 with solder resists or symbol marks 20 formed on both sides thereof, the solder resist or symbol mark 20 formed on one side of the through hole 10 is formed so as to cover the through hole 10,
A printed wiring board 100 characterized in that the solder resist or symbol mark 20 formed on the remaining one side is formed avoiding the top of the through hole 10. ”.

[0008]

[Function] The function of the printed wiring board 100 according to the present invention constructed as described above will be explained as follows.

First, in the printed wiring board 100 of the present invention, a solder resist 20a is already formed on one side of the substrate 100 so as to cover the through holes 10, as shown in FIGS. This solder resist 20a
is generally formed by a printing method on the so-called solder side of the board, which is opposite to the component side on which components are mounted. Then, apply solder resist 2 over the through hole 10 on the solder side.
By covering with 0a, the wiring conductor including the through hole 10 on the solder side is prevented from being exposed from the solder resist 20a and causing a solder bridge or the like. Moreover, this solder resist 20a may be formed into a dry film. Here, Mazu solder resist 20
a is formed to cover at least the top of the through hole 10. Then, a solder resist or symbol mark 20b is formed on the surface of the substrate opposite to the solder resist 20a (in the above example, the component side), avoiding the through hole 10 this time.

At this time, the solder resist or symbol mark 20b is formed with a so-called clearance so as not to cover the top of the through hole 10, and the size of this clearance is set to be larger than the land of the through hole 10. It may also be set simply according to the size of the through hole 10. It is important to set the through hole 10 so as not to block it. Since the solder resist 20a and the solder resist or symbol mark 20b are formed in this way, only one side of the through hole 10 is covered, and the air inside the through hole 10 is not trapped, so that the heat generated during drying and curing after printing is avoided. This prevents the solder resist or symbol mark 20 on the through hole 10 from being blown away due to expansion.

[0011]

[Example] Next, printed wiring board 100 according to the present invention
Embodiments shown in the drawings will be described in detail. Figure 1
1 is a sectional view showing an embodiment of a printed wiring board 100 according to the present invention. In FIG. 1, a solder resist 20a is formed on one solder side of a board 100 by a printing method so as to cover the through holes 10, and a solder resist 20b is formed on the other side of the board, which is a component surface, by a printing method. It is formed avoiding the top of the through hole 10. Therefore, on the solder side, the through holes 10 and the wiring conductors are all covered with the solder resist 20a, except for the mounting holes, etc.
When soldering is performed using a flow solder, solder bridges are less likely to occur between the through holes 10 on the solder surface or between wiring conductors. Furthermore, since only the solder surface of the through hole 10 is covered with the solder resist 20a, and the solder resist 20b on the component surface is provided avoiding the top of the through hole 10, the solder resist 20a is covered with the solder resist 20a.
The solder resist 20 on the through-hole 10 is no longer blown off by heating during drying and curing.

FIG. 2 is a sectional view showing another embodiment,
The difference from the embodiment shown in FIG. 1 is that the solder resist 20a covering the through hole 10 is partially divided on both sides of the substrate 100. What is important here is that if you look at each through hole 10, which through hole 10
Also, only one side is covered with the solder resist 20, and the solder resist 20 is formed on the other side avoiding the through holes 10. Further, in the embodiment shown in FIG. 2, electronic components are mounted on both sides, and a design that prevents solder bridging near the electronic components can be achieved. FIG. 3 is a sectional view showing still another embodiment, in which one side of the through hole 10 is covered with a dry film solder resist 21a, and the other side of the through hole 10 is covered with a dry film solder resist 21b avoiding the top of the through hole 10. Through holes 1 are formed on the dry film solder resist 21b.
The symbol mark 22 is formed avoiding the area above 0. The symbol mark 22 is formed by printing in the same way as the solder resist 20.
It can also be used to prevent solder adhesion.

[0013]

Effects of the Invention As detailed above, in the present invention, a solder resist or a symbol mark is formed on a through hole by a dry film or by a printing method,
Even when high-density wiring or high functionality of a printed wiring board is desired, it is possible to provide a printed wiring board without problems caused by scattering or peeling of the solder resist.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a printed wiring board according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the printed wiring board according to the present invention.

FIG. 3 is a sectional view showing still another embodiment of the printed wiring board according to the present invention.

FIG. 4 is a sectional view showing a conventional printed wiring board.

[Explanation of symbols]

10 Through hole 20 Solder resist or symbol mark 100
printed wiring board

Claims (1)

[Claims] 1. A printed wiring board having a through hole and a solder resist or symbol mark formed on both sides thereof, wherein the solder resist or symbol mark formed on one side of the through hole covers the through hole. A printed wiring board characterized in that the solder resist or symbol mark formed on the remaining one side is formed avoiding the through hole.