JPH036880A - Printed wiring board and manufacture thereof - Google Patents

Abstract

PURPOSE:To sharply improve connection reliability in the printed wiring board to mount surface-mounting components and insertion components mixedly by forming a circuit using an electrodeposition type of UV resist after covering a through hole alone with solder plating. CONSTITUTION:Solder plating 5 is precipitated 5mum or more in thickness at an exposed land part 12 and inside a through hole 3. Electrodeposition type photosensitive resist (hereinafter called electrodeposited UV resist) 6 is applied on exposed copper and solder platings of the land part and through hole part. A negative mask, where specified circuits are patterned, is aligned, and after sticking if fast, ultraviolet rays are applied so as to harden the electrodeposited UV resist 6 at the surface circuit section land part and the through hole part by light. Thereafter, unhardened part is removed. Next, the exposed part of a copper foil 2 not covered with an etching resist 7 is dissolved and removed. By separating the etching resist 7, a copper foil pattern 13, wherein solder 5 is adhering to only the through-hole part 3, is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printed wiring board, and more particularly to a printed wiring board in which surface-mounted parts and inserted parts are mixed, and a method for manufacturing the same.

[Conventional technology]

(Prior Art 1) Conventionally, a printed wiring board in which surface-mounted components and inserted components coexist is provided with through-hole portions 3 and surface-mounted land portions 17, as shown in FIG. here.

Since the surface-mounted part (18) and the inserted part (19) (see FIG. 8I) cannot be soldered together at the same time, the steps shown in FIGS. 5A to 5C are performed. Figure 5A is a front view of Figure 4. First, in the process shown in Figure 5B, the surface-mounted component 18 is soldered on the surface-mounted land s17 with the solder paste 20. However, due to overheating in the process shown in Figure 5B, the surface of the copper foil in through hole N5 is oxidized.
In soldering the push-in part 19 in the process shown in Figure CK,
Soldering defects such as insufficient flow-up 21 of solder 5 and gummy holes 22 were likely to occur.

Furthermore, as shown in FIGS. 6 and 7A, there is also a structure in which the entire pattern is plated with solder or coated with solder 5 in advance, and the through-hole portions 5 are coated with solder.

However, in a state where the solder 5 is preliminarily attached to the surface land portion 17, a phenomenon (wicking 25) in which the solder is repelled and a connection failure occurs is likely to occur, as shown in FIG. 7B.

A structure in which a part of the solder plated layer provided on the copper foil pattern on the surface of the board is removed is disclosed in JP-A-61-123196.
Although it is described in the above publication, it does not solve the above problem.

(Prior art 2) In order to maintain the reliability of the through-holes, the soldering method shown in Figure 8 is commonly used to form circuits on high-density boards with small-diameter through-holes (φ0.5 myt or less). The process is shown below.

The alphabet ANI below is the figure number A-IK in Figure 8.
It corresponds to this.

A: Drill holes in the copper-clad laminate 1 and perform copper inserts.

A through hole 3 is formed.

B: Laminate a film-filled photosensitive resist 11 over the entire surface of the substrate, and expose using a positive mask 10.

A plated resist 4 is formed by C development.

D Perform solder plating.

E Peel off the plated resist 4. (Formation of etching resist using solder plate 5) F Etching is performed.

G. The etching resist 5 is peeled off to form a pattern 13.

I Print the ruler resist 26.

1. Mount and solder parts 18 and 19.

However, as patterns become more AM-oriented (resolution of 50-μ or less), the conventional film-type photosensitive resist 11
As shown in FIG. 9A, resist resolution failure 23, resist v
! Since the jyII defect 24 occurred, it was difficult to form a circuit.

On the other hand, there is a method that uses a single-layer photosensitive resist to form a high-image resolution #1 line pattern.

When using an electro-SM sensitive resist, as shown in Figure 9 BK, the film thickness is thinner than that of a film type resist, and its retention with the copper foil surface 2 is excellent, making it possible to form high-resolution [fine line patterns]. be.

However, in the case of the electron ;) l type, the inside of the through hole must also be exposed, so for /h diameter through holes,
jtLlolV, as shown in 44C, light 9 is irradiated (
<, there is a concern that some parts may not be exposed. Therefore, after development and etching, through-hole defects 16 occur as shown in the tenth defect B, and the reliability of one through-hole decreases.

As a method for forming an L# rock pattern in high places without sacrificing the reliability of through holes, Japanese Patent Application Laid-open No. 6L-24709O
There is an invention described in the publication @, but the layer resist is used as a plating resist, and since the solder plating becomes the etching resist, the etching accuracy is
It is considered to be equivalent to the conventional solder plating method.

[Invention tries to solve @Zhao]

As described above, in Prior Art 1, the heating process of the surface mounting center oxidizes the steel surface, and the soldering properties of through-holes deteriorate during the next soldering process during the flow-up process. In the above, there was a problem in which solder paste was repelled during surface mounting, resulting in poor connection.

SUMMARY OF THE INVENTION An object of the present invention is to provide a printed mounting board and a method for manufacturing the same that solves these problems at the same time.

[Failure to solve the problem]

In general, -S is formed by covering only the through holes with solder and then forming a circuit using a conductive layer mUr resist.

[Effect]

The reliability of the small-diameter through-holes during etching is maintained by soldering, and the surface circuitry has high resolution I! Since it is possible to form an L11all/IM pattern, it is effective for forming a high-density circuit board having small-diameter through holes.

In the case of the 11I printed circuit board formed by the above method, solder remains only in the through-hole portions, so soldering of the surface-mounted parts insertion parts is sometimes quick.

7a- Problems such as insufficient uploading can be solved.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. !
I will clarify. FIG. 1 is a schematic diagram of the manufacturing process of a printed wiring board according to the present invention, and the details thereof will be explained below.

The following Alphabella) A-J is the figure number A-,= of the song 1 diagram.
This corresponds to 1.

A PJ'r foot position f of the copper-clad laminate 1 [K Drill through hole Thereafter, copper plating with a thickness of 10 to 5 Ωμm is deposited on the entire surface including the inner surface of the through hole by a commonly used through hole plating process (for example, Sibley's pTH process). As the steel plating to be deposited at this time, it is effective to use a thick chemical steel plating composed of the following components from the viewpoint of suppressing variation in plating thickness and stabilizing quality.

Example of chemical copper plating solution components Copper sulfate pentahydrate 10-121/J caustic soda formalin EDTA・2N.

Additive chemical steel plating condition example pH 12-12.5. Liquid temperature: 7o±1℃ B Photosensitive film, such as Hitachi Chemical's 7Otek 850
After pasting A F T-513 on the entire surface, it was exposed to light using a positive mask 10 as shown in Figure 2 so that the copper was exposed only in the land area for the predetermined through-hole, and then developed. A resist 4 is formed. The land diameter 14 of the positive mask 1Ω used at this time (as shown in the assembled diagram) is 0*05 compared to the land diameter in the finished state of the printed board <US diagram 15)K.
By using a product made smaller by ~0.1 mm,
It is possible to prevent copper 11kB due to mask displacement in the land portion.

c4 Solder plating 5 is deposited to a thickness of 5 μm or more inside the exposed land portions 12 and through holes 5 under the following component 1 conditions.

Solder plating liquid component example 10-121i 5-4mj, /7 56-46ji/1 Appropriate amount Boron fluoride Tin fluoride Boron fluoride Lead borohydrofluoride Additive Solder plating condition example Electron fi density 1 ~! , 4/dm” liquid temperature
20 to 30° C. Peel and remove the solder plating resist 4.

In the case of the above 7 otek 865 AFT-50, it is 5~
It can be easily peeled off and removed by subsequently applying a 5% caustic soda solution at 50°C.

E Solder plating on exposed copper, land areas, and through holes K tfffi photosensitive resist [hereinafter @
@UV Resist 5] 6 is survived.

Sibley Exhibition Eagle 20 is an electric layer UV resist 6.
00 and one condition is liquid temperature 20~30℃ electric g'i
i was about 40 to 60 mA/cLm2, and the time was set to the time when the current value reached the minimum. Electricity at this time
The film thickness of the jtUV resist was approximately 10 to 20 μm.

100~2007/j 5Ω~100y/J 200~4001/j Appropriate Weight F After aligning the negative masks depicting the predetermined circuit and layering them closely, we used a Fukōshin equipped with an ultra-high-pressure mercury lamp to produce a 56-wavelength mask.
Ultraviolet light of about 5 nm at 200 m//C-! irradiate the surface circuit portion land 1iit1. UV of through-hole part
The resist 6 is photocured. Thereafter, a developer manufactured by Sibley Co., Ltd. was used as a developer, and the uncured portion was removed by bath decomposition. This electric layer UV resist 6 becomes an etching resist 7 for the first step etching.

The portion of the copper foil 2 that is not removed by the etching resist 7 is dissolved and removed using m2 iron chloride, copper chloride, an alkali etchant, or the like.

By peeling off the H-etching resist 7, a fi14 pongee pattern 13 with solder 5 attached only to the through-hole portion 3 is formed. A stripping solution manufactured by Sibley is used as the stripping solution.

Through the process described above, a printed wiring board having the variations shown in FIG. 1H can be obtained.

In this structure, a solder pad 5 is provided in the through-hole portion 5, and the copper foil 2 is exposed in the surface-mounted land portion 17.

In the subsequent component mounting process, as shown in FIG. 1, parts other than the surface-mounted land 17 and the through-hole cap 5 are covered with solder resist 26, and then, as shown in FIG. The one-sided part 18 is attached to the one-sided land part 1711
C solder and also insert the insert part 19 into the through-hole part 3.
solder after inserting it into the

Therefore, when soldering a component with one side of the inserted part, sometimes the copper foil 2 is on the surface land [17] and the solder plating 5 is exposed on the through-hole part 5, so it is difficult to solder the parts with one side attached.
The lack of a-up 21° wicking 25 as shown in FIG.

Note that the following method can also be used to form solder inside the through hole. In other words, since holes are made in a copper-plated, 11-layer board or a multilayer board on which inner layer circuits have already been laminated and pressed, chemical steel plating alone is applied to the entire surface including the inside of the through-hole, or electrical steel plating is deposited on top of chemical copper plating for 1P or more. Then, cover the through hole with a film-like photosensitive resist.

After developing, etching, and peeling the circuit to form a layer, the solder resist is a must! After coating the area and printing masking tape or chemical-resistant ink on areas that do not require soldering, the exposed land area.

A layer of 0.1 μm or more of molten solder is applied to the through-hole portion, and then the masking tape or chemical-resistant ink is removed. In this case, the surface circuit is covered with copper, and the land portion and through-hole portion are covered with solder.

〔Effect of the invention〕

As explained in detail above, according to the present invention, the lack of flow-up (FIG. 5C), which was a problem in the prior art,
and wicking (Fig. N7B) can be eliminated at once, and the connection reliability between the two components can be significantly improved in a printed wiring board on which surface-mounted components and inserted components are mounted together.

In addition, during the back-path process, as shown in Figure 5, circuit formation can be performed using etching resist 7 while protecting through-hole 5 with solder 5, without impairing the reliability of the through-hole. , high resolution +1 [pattern formation becomes possible.

[Brief explanation of drawings]

Figures A to I are circuit forming process diagrams and component mounting diagrams of an embodiment of the printed wiring board of the present invention. Figure 2 is an external view showing the alignment of the substrate and positive mask.
The aKS diagram is an external view of the printed wiring board showing the state after formation of etching resist by electrodeposition. Figure 4 is an external view of a conventional exposed steel foil printed wiring board;
Figure ANC shows a schematic diagram of the process for soldering a printed wiring board in Figure 4, and Figure 5A is a cross-sectional view of the printed wiring board.
Figure 5B is a sectional view showing soldering of surface-mounted parts, and Figure 5C is a sectional view showing soldering of inserted parts. Figure 6 is an external view of a conventional soldered printed wiring board; Figures 7A and B are schematic diagrams of the soldering process of the printed wiring board in Figure 6; Figure 7A is a cross-sectional view of the printed wiring board. , FIG. 7B is a sectional view showing soldering of surface-mounted parts. Figure 8 shows the conventional printed wiring board circuit forming process and ideal parts (Figure C), Figure 9 A and B show the valley film type
11A is an external view showing the state of formation of a nokturn by the L layer type photosensitive resist, ag10 Figures A and B are Kaede#@ cross-sectional views showing the Anamojima Hikari when using the electric layer type resist, and Figure 10A is
Figure 10 B is developed by Fukumitsu. It is a l#r side view showing the state of etching. (Explanation of symbols) 1...Copper-clad laminate 2...Copper foil 3...Through hole 4...Solder plating resist 5...Solder plating 6...Electric; LV type photosensitive resin Resist 7...Etching resist 9...Irradiation light 10...
Positive mask 11...Film type photosensitive resist 12...Land portion 16...Steel foil pattern 14...Solder plating land diameter (positive mask diameter) 15
...Finished land diameter 16...Through hole defective part 17...Surfaced land s18...Surfaced part 19...
・Insert parts 20...Solder paste 21・
-Insufficient flow up 22...Gummy hole 2S...
・Resist resolution failure 24...Resist dense layer failure 25
...Kuitsuking 26...Solder resist Sumitomo Ei 1 Diagram B Kozu Izumi 11 Diagram Q Hirozu F 3 Inventory diagram H Diagram 1 β Day J (2) Kaka 528m-, -ichino2 Nijiruiwa et al. z 9 items z 9 bow B zuwanto ko B fig. E ka 8 times F concave A 8 fig. 8 ζ- fig. ζ 8 fig. 4 0H

Claims (6)

[Claims] 1. A printed wiring board having a through hole and a surface circuit, the printed wiring board comprising a through hole portion in which copper on the inner surface of the through hole is covered with solder, and a surface circuit portion partially not covered with solder. 2. 2. The printed wiring board according to claim 1, wherein the surface circuit portion not covered with solder includes a surface-mounted land for mounting surface-mounted components. 3. After solder plating is applied only to the through-holes with a copper plating layer and the through-holes of a printed wiring board with a surface copper layer, a photosensitive resist is applied to the entire surface, and the necessary circuits are exposed, developed, etched, and peeled off. A method for manufacturing a printed wiring board, characterized in that a solder plating layer is formed in the through holes and a copper layer is formed in the surface circuit by performing the above steps. 4. 6. The method for manufacturing a printed wiring board according to claim 5, wherein the photosensitive resist is an electrodeposition type UV resist. 5. 4. The method of manufacturing a printed wiring board according to claim 3, wherein the photosensitive resist is a film resist. 6. After drilling holes in a copper-clad laminate or a multilayer board that has already been laminated and pressed with inner layer circuits, chemical copper plating alone is applied to the entire surface including the inside of the through hole, or electrolytic copper plating is deposited to a thickness of 1 μm or more on top of the chemical copper plating, and a film-like film is formed. After forming a circuit by covering the through holes with photosensitive resist, exposing, developing, etching, and peeling, coat the necessary parts with solder resist, and print masking tape or chemical-resistant ink on the parts that do not require soldering. Apply no molten solder to the exposed lands and through holes.
．． A method for producing a printed wiring board, characterized in that the land portions of the surface circuitry and the through-hole portions are covered with solder by attaching the masking tape or chemical-resistant ink to a thickness of 1 μm or more, and then removing the masking tape or chemical-resistant ink.