JP2678247B2 - IC package manufacturing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electric package, particularly an IC package in which lead pins such as a pin grid array type are brazed. (Prior Art) Conventionally, in a pin grid array type IC package, a metal lead pin is brought into contact with an opening of a via hole (through hole) provided in a substrate, and a conductive layer is formed through a conductor filling the pin with the via hole. It is connected. As shown in FIG. 5, when the pin (B) is brought into contact with the metallized layer (A) which is connected to the conductor to be filled in the via hole, first, a columnar shape is formed on the head (C) of the pin (B). The silver brazing filler metal (D) is placed so that one of the upper and lower end surfaces of the brazing filler metal (D) is in contact with the brazing filler metal (D), and the brazing lead pin is formed to form a brazing lead pin. Is brought into contact with the metallized layer (A) of the IC package, the brazing material (D) is melted, and the two are joined together. (Problems to be Solved by the Invention) However, in the above-mentioned conventional one, although the pin head and the end face of the columnar brazing material are in surface contact with each other, these surfaces microscopically form a rough surface and There is a slight gap (G) in the gap. Therefore, since the solder flows around this gap of the joint surface and flows around it first, when the silver solder is welded to the pin head, gas is entrained in the molten silver solder, which causes Void in the silver solder
(E) is formed [FIG. 5, (B)]. When the pin head is joined to the metallized layer in this state, the above-mentioned void (E)
However, due to its specific gravity, it floats up and is exposed at the joint, and it is a recess (pit).
(F). If there is such a recess (F), the Ni-Au plating in the subsequent step is not performed, and the plating is not applied to the inside of the recess (F). Therefore, the silver brazing material (D) is not formed in the recess (F). Oxidation, sulfurization and elution occur. Furthermore, there is a drawback that elution and corrosion proceed or the brazing strength is reduced due to residual plating solution (CSNa) which is not removed in the recess (F). Therefore, the present invention is intended to improve the drawbacks of the conventional ones described above, and to prevent the formation of voids in the brazing filler metal upon melting the brazing filler metal and to effectively bond the metallized layer and the pin. To do. (Means for Solving the Problem) A means for solving the problem is to form a lead pin to be joined to a metallized layer of an IC package by brazing, to a flat joining surface of the head of the lead pin, or to form a curved portion of a spherical or cylindrical brazing material. Set by line contact, heat and melt this brazing filler metal above the liquidus temperature and spread outward from this point or line contact position, while preventing the generation of bubbles in the brazing filler metal and brazing In the manufacturing method, a lead pin is prepared, the pin head is brought into contact with a metallized layer of an IC package, the brazing material is melted, and the lead pin is melt-bonded to the metallized layer. (Operation) According to the above configuration, when the metallized layer and the pin head are joined, a spherical or cylindrical brazing material intervening between the two is used in advance, and the curved surface portion of the brazing material is applied to the pin head. Place them in close contact with each other and weld them. In particular, when the brazing filler metal is welded to the lead pins, the brazing filler metal melts at the liquidus temperature or higher, so the brazing filler metal does not become a semi-molten state and melts sufficiently, and when the brazing solidifies, there is almost no unevenness on the surface. . Therefore, when contacting the metallized layer of the substrate and melting the brazing material again, air bubbles are not enclosed in the brazing material due to the unevenness. Moreover, the spherical or cylindrical brazing filler metal melts while being in point or line contact during welding on the pin head,
In this state, the gas is pushed outward and is welded to the pin head, so that air bubbles are not entrained inside the molten brazing material and voids are not formed in the brazing material. Therefore, when the pin head and the metallized layer are joined through the brazing material, there is no void (void) in the brazing material, and therefore no recess (pit) is formed in the welding brazing material portion. For this reason, deterioration and elution of the brazing material or deterioration of the welding strength will not occur in the plating step which is a subsequent step. (Example) This will be further described with reference to an example shown in the drawings. FIG. 1 shows a pin grid array (PGA) type IC package, in which (1) is a metallization layer. Reference numeral (2) is a pin, which is brought into contact with the lower surface openings of via holes (through holes) (7) (7) provided in the substrate (5) made of ceramic. The pin (2) is made of an electrically conductive material such as an iron-nickel cobalt alloy. The via hole (7) is filled with a conductive paste (8) which is a conductor, and the upper end of the conductive paste (8) is connected to the wiring layer (6) made of tungsten or the like on the substrate (5). FIG. 2 is a perspective view from the bottom of FIG. After nickel plating, the head (3) of the pin (2) is attached to the metallized layer (1).
Are welded through the silver brazing material (4). Before melting, this silver brazing material (4) is formed into a spherical shape with a diameter of 0.61 mm after cutting the silver brazing wire into the required dimensions as shown in Fig. 3 (a), and has a diameter of 0.5 mm and a length of 5.0 mm. Lead pin (2) diameter 0.75m
It is placed on a flat joint surface of a head (3) having a thickness of m and a thickness of 0.25 mm, and heated to 900 ° C in the heating part (liquidus temperature 840 ° C) and welded [Fig. 3 (b)]. Similarly, in the case of a cylindrical silver brazing material, a silver brazing material (4 ') made of an Ag-Cu15% alloy having a diameter of 0.55 mm and a length of 0.5 mm is used by contacting the curved surface portion with the head (3). It is placed and heated and melted at 900 ° C in a heating furnace to form a brazing lead pin (Fig. 4). After that, the brazing lead pin contacts the metallized layer (1) with the head (3) of the pin (2) [Fig. 3 (c)], and the brazing material (4).
The pin (2) and the metallized layer (1) are joined by heating and melting of (4 ') [Fig. 3 (d)]. The metallization layer (1) is provided by printing on the lower surface opening of the via hole (7) and is covered with nickel plating (9). Upon welding the brazing filler metal on the pin (2), the spherical or cylindrical brazing filler metal (4) (4 ') is joined to the flat joint surface of the pre-melting pin head (3) on the pin head (3). Since the point contact or line contact is made, the gas around the brazing filler metal (4) (4 ') is extruded outwardly to be melted, and there is a space in the melting brazing filler metal (4) (4'). Is not formed. Furthermore,
The brazing filler metal melted at the liquidus temperature or higher does not become a semi-molten state, so that no unevenness occurs on the surface. The pin head (3) provided with the void-free brazing filler metal (4) (4 ') is brought into contact with the metallized layer (1) of the nickel-plated IC package, and then the brazing filler metal (4) (4'). ) Is remelted to join the two. Lead pin obtained by this invention
1000 pieces and 20000 pieces of lead pins according to the conventional example were respectively immersed in a stripping solution containing potassium cyanide to melt the silver brazing material, and even one lead pin according to the present invention was found to have voids. I couldn't, but
Some of the lead pins in the conventional example had voids in 97 of the 2000 lead pins. This allows
It was confirmed that this invention has a remarkable effect on the occurrence of voids. Also, regarding the corrosion occurrence rate, the conventional one has 10 packages, but the present invention has none. It has been clarified that atmosphere melting or vacuum melting is irrelevant to the cause of the above-mentioned void formation, and that it is not related to the surface treatment of the pins. (Effect of the invention) As described above, a brazing lead pin with no voids in the brazing material and no irregularities on the surface elutes, corrodes, or loses strength at the brazing joint between the metallized layer of the IC package and the pin as in the past. Therefore, the IC package including the lead pin obtained by the present invention has an effect of being excellent in environmental resistance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an IC package manufactured according to the present invention, FIG. 2 is a perspective view of FIG. 1 seen from the back side, and FIGS. The joining process using the spherical brazing filler metal of the present invention, FIG. 4 shows the welding of the columnar brazing filler metal on the lead pin, and FIGS. 5 (a) to (d) show the conventional joining process. 1 ... metallized layer, 2 ... pin, 3 ... pin head, 4.
4 '... Silver brazing material, 5 ... Substrate

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Naoki Kato               14-18 Takatsuji-cho, Mizuho-ku, Nagoya               Shutogyo Co., Ltd. (72) Inventor Kazuo Kimura               14-18 Takatsuji-cho, Mizuho-ku, Nagoya               Shutogyo Co., Ltd.                (56) References JP-A-60-113449 (JP, A)

Claims (1)

(57) [Claims] Set the curved surface of the spherical or cylindrical brazing material on the flat joint surface of the lead pin head by point or line contact, and then heat and melt the spherical or cylindrical brazing material above the liquidus temperature to obtain this point. Alternatively, prepare a brazing lead pin that is brazed to the above flat joint surface by preventing the generation of bubbles in the molten brazing material while expanding outward from the line contact position, and place the above pin of this lead pin on the metallization layer of the IC package. A method for manufacturing an IC package, in which the head portion is brought into contact, the brazing material is melted, and the lead pin is joined to the metallized layer.