JP2501174B2 - Method for manufacturing surface mount terminal - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component for surface mounting and, more particularly, to a method of manufacturing a surface mounting terminal which can achieve good reflow soldering.

Along with the miniaturization of electronic equipment, electronic components mounted on a wiring board are also miniaturized and lead wires (terminals) are also miniaturized. The mounting method is such that a through hole for inserting a lead wire is not provided in a printed board. Surface mounting (SMT, Surface Mount Technolo
gy) has become popular.

As the terminals are miniaturized in this way, the remelted solder flowing out from the soldering portion often adversely affects the components, and a countermeasure for this is desired.

[0004]

2. Description of the Related Art The surface mounting of electronic components is an electronic device having a connection terminal in which a solder coating is applied by electroplating or hot dip plating on a connection pad made of a conductive material patterned on the surface of a wiring board or the like. So-called reflow soldering (reflow s) in which parts are placed and the solder coating is remelted by infrared heating or vapor phase heating to solder the terminals to the connection pads.
oldering).

For example, FIG. 4 shows a hybrid for surface mounting.
An IC is shown. A plurality of substantially L-shaped surface mounting terminals 2 are provided in two rows on a ceramic substrate 1 on which circuit elements are formed, and the lower side of the L shape is brought into contact with a connection pad on a wiring board. In this state, the preliminary solder of the terminal connection portion 21 is melted and connected.

[0006] It is usual that this terminal is formed by forming a comb-like connecting member by pressing a good conductive material such as a copper alloy and performing a predetermined surface treatment by continuous plating.
As shown in the enlarged cross-sectional view of FIG. 5, this structure has, for example, a base material 22 made of a phosphor bronze material, which is first plated with a base metal 23 made of a base metal material such as nickel, and then excellent in corrosion resistance such as gold and palladium. In addition, a noble metal plating 24 of a noble metal having good wettability to solder is applied, and then the surface of the connection portion 21 to the wiring board is melted or electroplated to obtain a solder coating 25.
Was thickly applied to form the connection portion.

[0007]

In the reflow soldering process, the terminal portion is heated to re-melt the solder material deposited on the terminal connecting portion in advance, and the connecting pad of the wiring board 3 as shown in FIG. Solder with 31.

In the conventional surface treatment of the surface mounting terminal, since the solder plating is deposited on the noble metal plating film having good wettability with respect to the solder, the solder before heating is deposited only on the connection portion of the terminal. Even when the reflow soldering is performed, it is re-melted by the heating during the reflow soldering and moves from the connection portion to above the terminal.

Recent electronic parts are remarkably miniaturized and highly densified, their terminals are also extremely miniaturized, and the connection part and other functional parts are close to each other. It often happens up to.

However, the functional portion is originally a portion that needs to be covered with a noble metal plating film, and various problems occur when it gets wet with solder. For example, the upper end of the terminal 2 of the hybrid IC shown in FIG. 6 is bonded and connected to the pattern 11 on the ceramic substrate 1 by gold-gold diffusion.
As shown in, there is a problem that remelted solder 25 'impairs the long-term reliability of the bonding connection if it wets this part, and in the contact of the connector etc., if the precious metal plated contact part close to the terminal part gets wet with the connector There is a problem that the reliability of contact decreases. Therefore, a surface mount terminal with a solder barrier has been proposed in which a base metal film layer of nickel or the like having poor solder wettability is exposed between the noble metal functional part and the connection part to stop solder rising at the barrier part. . However, as a method of forming the barrier portion, since the method of forming the functional portion and the connecting portion separately by partial plating on the base metal undercoating was adopted, the boundary of the barrier portion could not be formed accurately. ,
In order to effectively prevent soldering, there is a problem that the length of the barrier portion becomes long and the size of the terminal cannot be reduced.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a surface mounting terminal capable of forming a solder barrier portion with high accuracy.

[0012]

FIG. 1 is a diagram showing a manufacturing process of a surface mounting terminal of the present invention. The above conventional problems are
As shown in Fig. 1, these are surface mounting terminals used for soldering electronic components to the connection pads of the wiring board by reflow soldering, and the surface of the connection part (B) with the wiring board is solder plated (44 The surface of the functional portion (C) at the opposite end of the connecting portion (B) is plated with a noble metal (43), and the boundary between the connecting portion (B) and the functional portion (C) is In the method of manufacturing a surface mounting terminal that has a barrier portion (A) that is exposed to the base metal plating (42) with poor solder wettability, the entire surface of the base material (41) made of a conductive material is used. The base metal is ground-plated, then the surface including the functional portion (C) is partially plated with a noble metal, and then the functional portion is masked with a resist film to remove the precious metal plating film other than the functional portion. Mask the functional part (C) including the long underlying plating film with the plating resist film (52), and then cover the surface including the connection part (B). The surface-mounting terminal of the present invention is characterized in that the barrier plating (44) is formed, and then the plating resist film is removed to expose the base plating of the predetermined length portion to form the barrier portion (A). It is solved by the manufacturing method.

[0013]

[Function] Since the nickel plating exposed portion at the boundary between the connection portion and the function portion has poor wettability with respect to solder, it does not get wet by the remelted connection portion solder, and the solder of the precious metal film on the surface of the function portion Even if the wettability is good, it works as a barrier against the migration of solder, so that it is possible to prevent the solder from rising onto the functional portion. Since the boundary between the functional portion and the barrier portion is formed by the mask and the boundary between the connecting portion and the barrier portion is formed by the plating mask, the boundary of the barrier portion can be clearly formed, and the variation in the length of the barrier portion can be achieved. Since the number of terminals is reduced, the terminal can be downsized.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a manufacturing process of the surface mounting terminal of the present invention, and FIG. 2 is an enlarged sectional view of the surface mounting terminal of the present invention.

In FIG. 2, reference numeral 41 is a base material of a surface mounting terminal formed by machining a thin plate made of a conductive material such as copper alloy into a predetermined shape, and a base metal such as nickel is used as a base plating 42 on the entire surface. It has been subjected.

A solder plating 44 having a thickness of several 10 μm is deposited on the connection portion B to be soldered to the connection pad of the wiring board by electroplating, hot dip plating, etc.
Is a functional part C that exposes the base metal undercoat 2 and the end opposite to the connection part is bonded to the ceramic substrate 1.
As a result, a precious metal plating 43 such as gold or palladium is applied on the surface. A barrier portion A is formed at the boundary between the connecting portion B and the functional portion C by exposing the nickel material of the undercoat over the surface for a predetermined length.

FIG. 1 shows a sequence of steps for manufacturing the surface connection terminal having the above film structure. First, nickel base plating 42 is applied to the entire surface of the base material 41 as shown in FIG. Then, the noble metal plating 43 is applied to the upper functional portion by partial plating or the like, but the lower boundary of the noble metal plating 43 is usually not clear due to the wraparound of the plating solution during the partial plating. Therefore, by masking the desired functional portion C with the resist film 51 as shown in FIG. 9B and removing the remaining noble metal plating film, the boundary with the exposed portion of the base plating 42 shown in FIG. A clear noble metal plating film 43 is formed. Next, the exposed portion A of the base plating 42 having a predetermined length and the noble metal plating film 43 are masked with the plating resist 52, and the solder plating 44 is applied to the surface of the connection portion. Then, the resist 52 is peeled off to obtain the intermediate member shown in FIG. 2D, and the L-shaped bending is performed at the D portion, for example, to form the surface mounting terminal shown in FIG.

FIG. 3 shows a state of a solder connection portion when the electronic component 1 having such a surface mounting terminal is mounted on the connection pad 31 of the wiring board 3 by reflow soldering.
The exposed portion of the underlying plating at the boundary between the connection portion and the function portion is made of a nickel material having poor solder wettability, and thus functions as a barrier portion against molten solder, preventing remelted solder from flowing out from the connection portion, and the function portion The surface treatment with and is maintained.

Table 1 shows the experimental results showing the effect when the present invention is applied to the terminals of the hybrid IC shown in FIG.
This is to observe whether or not the barrier part is formed, the length of the barrier part is changed, and the solder wets over the barrier part and reaches the upper functional part. The connection was placed on a hot plate heated to C for 1 minute to re-melt the solder and observed.

[0020]

[Table 1]

The results show that the solder rise can be completely prevented by forming the barrier portion exposing the underlying nickel plating over a length of 0.1 mm or more.

As described above, according to the present invention, since the barrier portion having a clear boundary line can be formed between the connection portion of the surface mounting terminal and the functional portion, the length of the barrier portion for preventing solder rising Can be made smaller, and therefore the overall size can be made smaller.

[0023]

As described above, according to the present invention, at the time of reflow soldering, it is possible to miniaturize the surface mounting terminal capable of preventing solder rising to other than the desired soldering connection portion, It is remarkable that it contributes to miniaturization and high density of electronic parts.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of a surface mounting terminal of the present invention.

FIG. 2 is an enlarged cross-sectional view of a surface mounting terminal according to the present invention.

FIG. 3 is a schematic view showing the effect of the surface mounting terminal of the present invention.

FIG. 4 is an external view of a surface mount hybrid IC.

FIG. 5 is an enlarged sectional view of a conventional surface mounting terminal.

FIG. 6 is a diagram showing a solder rise of a conventional surface mounting terminal,

[Explanation of symbols] 1-ceramic substrate, 11-pattern, 3-wiring substrate, 31
--Connecting pad, 41--Base material, 42--Nickel plating, 43--Precious metal plating, 44--Solder plating, A--Barrier part, B--Connecting part, C--Functional part

Claims (1)

(57) [Claims] 1. A surface mounting terminal used for soldering an electronic component to a connection pad of a wiring board by reflow soldering, wherein a surface of a connection portion (B) with the wiring board is solder plated (44). , Functional part at the opposite end of the connecting part (B)
The surface of (C) is plated with precious metal (43),
In the method for manufacturing a surface-mounting terminal, in which a barrier portion (A) formed by exposing a base metal plating (42) having poor solder wettability to the surface is provided at the boundary between (B) and the functional portion (C). The base metal (41) made of a conductive material is ground-plated on the entire surface, then the surface including the functional portion (C) is partially plated with a noble metal, and then the functional portion is masked with a resist film. Remove the noble metal plating film other than the functional part, then mask the functional part (C) including the underlying plating film of the specified length with the plating resist film (52), and then solder-plat the surface including the connection part (B). (44) is performed, and then the plating resist film is removed to expose the base plating of the predetermined length portion to form the barrier portion (A), which is a method for producing a surface mounting terminal.