JP2522111B2 - Lead solder plating equipment - Google Patents

Description

Description: “Industrial application field” The present invention relates to a lead solder plating apparatus for performing solder plating on a lead of a semiconductor device such as an IC (semiconductor integrated circuit).

"Conventional technology" High reliability when mounting semiconductor devices such as ICs.
There is a need for an inexpensive mounting method. But,
As the scale of semiconductor integrated circuits has increased in recent years, the number of pins and the pitch of IC packages on which they are mounted have been increasing, and the situation in which precision soldering technology has not progressed in response to this has arisen. Is coming.

In other words, when soldering multi-pin and narrow-pitch IC terminals, it is extremely difficult to stably supply a fixed amount of solder to a fine soldering portion.
At present, these ICs are largely relied on by hand work.

However, there is a problem in the soldering operation that when supplying solder to a minute part, the amount of supplied solder is not constant. For this reason, if the amount of supplied solder is small, the strength of the joint is insufficient.If the amount of solder is excessive, there is a problem that adjacent terminals are joined by a solder bridge and short-circuited. I was

Therefore, as a method of mounting this type of semiconductor device on a substrate, a terminal of the semiconductor device, for example, a lead of an IC is plated with solder in advance, and when the substrate is joined to a circuit, the solder is externally applied to the joint. And joining them.

Here, the solder plating applied to the terminals of the semiconductor device is provided for the purpose of improving the wettability with the solder supplied from the outside, and is formed with a thickness of about several μm. However, only with solder plating having such a thickness, the bonding strength is insufficient, so that the insufficient solder is supplied from the outside by a method described below to perform the bonding operation.

As a solder supply method, a method of using a thread solder, a method of previously applying a solder paste to a pad of a substrate to which terminals are joined by screen printing, a method of applying a solder paste to a pad of a substrate by a dispenser, a melting There is a method of immersing the board in a solder bath.

However, with multiple pins such as QFP (Quad Flat Package),
In an IC having a main body with a narrow lead interval, for example, an IC with a lead interval of 0.65 mm or less, if the amount of supplied solder is slightly excessive, a solder bridge between the leads occurs after reflow (melting), In addition, if there is any shortage, it is extremely difficult to supply an appropriate amount of solder because the bonding strength is insufficient.

Therefore, as described below, the applicant of the present application has proposed a method of applying an appropriate amount of solder to a lead of an IC by applying a thick-film solder plating to the lead.

FIG. 6 shows a jig 1 and an electric solder plating method for applying electric solder plating to a large number of leads 6 of a multi-pin package IC such as QFP. This jig 1 includes a rectangular upper frame 3 made of metal such as brass, a non-conductive lower frame 2, and a plurality of screws (not shown).

Then, as shown in the figure, the leads 6, 6,... Of the main body 5 of the multi-pin package IC such as QFP are sandwiched between the lower frame 2 and the upper frame 3 and fixed with screws. Solder plating bath A
Are arranged so that most of the leads 6, 6,... Are immersed in the solder plating bath A, and electroplating is performed using the jig 1 as a cathode and the solder ingot 7 as an anode. In such electroplating, the plating thickness of the QFP leads after plating is substantially uniform.

"Problems to be Solved by the Invention" By the way, QF plated with solder as described above
The plating thickness of the leads (1 to 32) on each side of P is 7th
As shown in the figure. Leads 1 and 32 are leads provided near the corners. That is, in the conventional electroplating, the plating thickness of the lead near the corner of the QFP tends to be thicker than that of other leads. Here, in general, there is a strong positive correlation between the solder plating thickness and the mounting strength when mounting on a substrate. Therefore, the variation in the solder plating thickness leads to the variation in the bonding strength between the lead and the substrate after reflow at the time of mounting, which causes a problem that stable mounting cannot be performed.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solder plating apparatus capable of reducing the variation in plating thickness and uniforming the bonding strength after mounting.

"Means for Solving the Problem" The present invention relates to a mounting means for mounting a semiconductor, and a cathode provided for a lead arranged around the main body of the semiconductor mounted on the mounting means. An anode arranged at a predetermined distance from the lead, and a plating solution which is arranged around the placing means and which is to be supplied to the semiconductor, is divided into a plurality of supply points, and the supply point in the lead is provided. And a plating solution separating and supplying means for supplying the plating solution at each supply location to the leads corresponding to each supply location by supplying an electric current between the anode and the cathode. It is characterized by electrodepositing solder.

[Operation] According to the above configuration, the semiconductor is inserted in the vicinity of the corner of the main body of the semiconductor, in the gap between the leads extending in different directions with respect to the semiconductor, and between the cathode and the anode. The partition member made of the insulating material isolates the ions of the solder plating solution so that the plating thickness of the lead at each corner is approximately the same as the plating thickness of the other leads.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a front sectional view showing the structure of a solder plating apparatus according to an embodiment of the present invention. In this figure, reference numeral 11 is a cathode made of a titanium material, which has a substantially rectangular parallelepiped shape, an upper portion thereof is covered with a cover 10 made of an insulating material, and a lower portion thereof is provided with a concave portion having a shape corresponding to the main body portion 5 of the semiconductor device. ing. The titanium material around the recess comes into contact with all the leads 6, 6, ... arranged on the four sides of the main body 5. 12 is PEEK
The base is made of an insulating material such as a material, and the upper part thereof has central portions removed to form fence-shaped portions 12a, 12a, ... Abutting on the respective base portions of the leads 6,6 ,. In addition, the base 12
Has a taper on its side so that its cross-sectional area decreases toward the bottom. 14 is a holding member, which is a base
A mortar-shaped recess that abuts the 12 tapered portions is formed. An anode 13 is provided around the holding member 14 at a position facing the cathode 11.

Further, in each corner of the QFP, insulating fences 15, 15, ... Made of an insulating material are provided between the leads 6, 6 ,. FIG. 2 shows the positional relationship between the above-mentioned anode 13, QFP, and insulating fence 15. In this figure, the insulating fences provided at the respective corners are provided at the respective corners so as to separate the leads 6, 6 ,. Further, FIG. 3 shows a sectional view of the above-mentioned corner portion. In this figure, the lower end of the insulating fence 15 is in contact with the anode, and the upper end is in contact with the coating material 16 formed of an insulating resin coated on the exterior of the cathode 11. In addition, the fourth
The figure shows a QFP and insulating fence 15 installed on the anode 13.
FIG. This insulating fence 15 isolates ions in the solder plating liquid in a solder plating step described later. This will lead 6,6,
…… Prevents the plating thickness from becoming thicker than other leads.

Solder plating by this solder plating apparatus is performed as follows. The semiconductor device for which lead forming has been completed is placed on the lower pedestal 12, and the bases of the leads 6, 6, ... On the four sides of the main body 5 are supported from below by the fence-shaped portions 12a, 12a ,. Next, the cathode 11 is mounted on the semiconductor device, and the titanium material around the concave portion on the lower surface of the cathode 11 and the wall 12
The leads 6, 6, ... Are sandwiched by a, 12a, .... The lower support 12 on which the semiconductor device and the cathode 11 are mounted is a holding member.
It is housed in a mortar-shaped part 14 and the distance d between the leads 6, 6, ... And the anode 13 is an appropriate distance of several mm to several tens of mm, for example, about 5 m.
The cover 10 and the holding member 14 are appropriately sandwiched so as to be m. In this way, the mounting of the semiconductor device is completed, the solder plating apparatus is immersed in the solder plating solution, and the current is passed through the cathode 11 and the anode 13.

According to the solder plating apparatus of the present embodiment, the ions in the solder plating liquid are isolated at the corners of the electrodes. Fifth
The drawing is a film thickness distribution diagram showing the plating thickness of each lead obtained in this example. As is clear from this figure, the plating thickness of the leads at each corner is almost the same as the plating thickness of the other leads, and it can be seen that variations in the plating thickness are reduced. As a result, uniform bonding strength can be obtained between the mounted leads and the substrate.

[Advantages of the Invention] As described above, according to the present invention, it is possible to obtain an advantage that variation in plating thickness can be reduced and bonding strength after mounting can be made uniform.

[Brief description of drawings]

FIG. 1 is a front sectional view showing the structure of a lead solder plating apparatus according to an embodiment of the present invention, FIG. 2 is a plan view showing a state in which a semiconductor device is mounted on the apparatus, and FIG. FIG. 4 is a cross-sectional view showing an insulating fence at a corner, FIG. 4 is a perspective view showing the positional relationship between the anode and the insulating fence of the apparatus, and FIG. 5 is a film thickness distribution showing the plating thickness of each lead obtained in the same example. 6 and 6 are views for explaining solder plating using a conventional solder plating jig, and FIG. 7 is a film thickness distribution chart showing the plating thickness of each lead by the conventional solder plating jig. 5 ... Main body, 6 ... Lead, 11 ... Cathode, 13 ... Anode, 15 ... Insulation fence.

Claims (1)

(57) [Claims] 1. A mounting means for mounting a semiconductor, a cathode mounted on a lead arranged around a semiconductor body mounted on the mounting means, and a predetermined distance from the lead. And an anode arranged with a space between them, and the plating solution to be supplied to the semiconductor, which is arranged around the placing means, is divided into a plurality of supply points and is supplied to the lead corresponding to the supply point in the lead. And a plating solution separating / supplying means for supplying a current between the anode and the cathode so that the plating solution at each supply location causes solder to be deposited on the leads corresponding to each supply location. And lead solder plating equipment.