JPH0472398B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and device for connecting a chip carrier, and in particular, the present invention relates to a method for mounting a chip carrier on a printed wiring board made of an organic resin material substrate. This chip carrier mounting connection is characterized in that it prevents warping and distortion of the board by heating it with an infrared heater from the top side and a block heater from the bottom side to reflow the solder paste, making the connection simple and quick. Concerning methods and apparatus.

In the past, leadless chip carriers made of ceramic substrates were developed to meet requirements such as high-density packaging.

However, due to the coefficient of thermal expansion, the ceramic chip carrier described above can only be mounted on a printed wiring board made of a homogeneous ceramic substrate, and ceramic substrates generally have a large specific gravity, resulting in a heavy overall weight. At the same time, due to its low thermal shock resistance, a fixed plate thickness, for example, 2 to 5 mm, is used, and in order to keep up with the high-density packaging associated with the recent miniaturization of electronic components. It is disadvantageous. Moreover, in order to protect the parts on which electronic components are mounted, air-tight sealing using frit bonding or brazing is required, so although air-tight sealing is possible, the work is complicated and the materials used are expensive. This resulted in the drawback of high costs.
On the other hand, a metal substrate has been developed that has a coefficient of thermal expansion equal to that of a ceramic substrate by laminating dissimilar metal plates, but it is expensive and has not yet been widely used.

In view of such conventional circumstances, the present invention has been developed by replacing the chip carrier made of ceramic with a chip carrier made of an organic resin material, thereby creating a chip carrier tower of the same quality on a substrate made of an organic resin material with an equivalent coefficient of thermal expansion. A chip carrier mounting connection that enables mounting to be carried out within a short period of time, and is intended to prevent warping and scorching of organic resin material substrates due to heating caused by solder connections between the substrate and the terminals of the chip carrier. This paper proposes a method and its apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, the method and apparatus of the present invention will be explained in detail based on drawings and embodiments.

FIG. 1 is a schematic side view of a printed wiring board using a substrate made of an organic resin material, in which solder paste is reflowed by heating by direct thermal conduction from the back side with a block heater or the like. In this drawing, reference numeral 1 denotes a heater, the most typical of which is a heating device based on thermal conduction called a ceramic heater. 2 is a printed wiring board using a substrate made of an organic resin material, the most typical one being a glass fiber reinforced epoxy resin copper-clad board (hereinafter also abbreviated as "glass epoxy board" for convenience);
Examples include paper, phenol resin substrates, paper, epoxy resin substrates, polyimide resin substrates, and modified triazine resin substrates. Note that t indicates the height of the warp of the substrate, and concave warpage usually occurs due to heating from the back side of the substrate. That is, a printed wiring board made of a glass epoxy board, for example, tends to be distorted or warped by heating due to differences in the density of the conductor circuits formed on its front and back surfaces, as well as differences in thermal expansion and contraction between the plastic and the conductor circuits.

In particular, as shown in FIG. 1, it is well known that heating only one side of the back surface of a glass epoxy substrate tends to cause concave warping or twisting distortion.
This also applies to the case where a chip carrier made of a glass epoxy board is mounted on a printed wiring board made of a glass epoxy board and soldered to it as in the present invention.

That is, as shown in the schematic side view of FIG. 2, for example, the connection terminals 6 of the chip carrier 5 made of glass epoxy substrate are brought into contact with the connection terminals 4 of the printed wiring board 3 made of glass epoxy substrate. When the printed wiring board 3 and the chip carrier 5 are heated for soldering only from the back side of the board, as shown in the schematic side view of FIG. Even if the height of the arrow is high, concave warping or twisting distortion will occur. In this case, the printed wiring board 3 has a larger board thickness and size than the chip carrier 5, so even if the glass epoxy board is made of the same material, the warp height will be slightly different, and the conductor formed on both boards Due to differences in circuit density, etc., the warpage heights of the two boards may further differ. Therefore, the distance between the connection terminals 4 of the printed wiring board and the connection terminals 6 of the chip carrier becomes increasingly large, and the thickness of the solder paste coating 7 coated or printed on the surface of the connection terminals of the printed wiring board increases. On the other hand, the solder melted by heating is used to fill the gap between both terminals, and the solder does not reach the side of the connection terminal 6 of the chip carrier insufficiently, or in some cases, it does not spread at all. This results in disadvantages such as not being able to solder.

Therefore, in order to eliminate and improve the above-mentioned drawbacks, the present invention gradually heats glass epoxy from the upper surface side (side A) of the substrate by radiation using an infrared heater 8, as shown in the schematic side view of FIG. A process of promoting thermal expansion on the A surface side of the substrate to make it slightly convexly warped on the A surface side;
The back side of the board, which has become slightly warped, is rapidly heated by the block heater 9 (on the side), and the back side of the board, which has become slightly warped, expands thermally, and as shown in Figure 6, the warp is corrected so that the front and back sides are balanced and the board becomes smooth. In order to realize a method characterized in that a printed wiring board made of a base material of an organic resin material and a chip carrier of the same quality mounted thereon are reliably soldered together in combination with a process step of The aim is to provide the most suitable equipment for this purpose.

That is, the connecting terminal portions of a printed wiring board made of an organic resin material are coated with solder paste by a printing method, etc., and the parts coated with the solder paste are coated with a board made of an organic resin material having an equivalent coefficient of thermal expansion. After positioning and mounting the chip carrier, the top surface of the chip carrier is heated by radiation using an infrared heater, while the bottom surface is rapidly heated by heat conduction using a block heater to reflow the solder paste and slightly heat the chip carrier. This is a method for quickly and reliably joining the connection terminals of a chip carrier to the connection terminals of a printed wiring board by correcting a convexly warped board to a smooth state. Note that it is preferable to perform the heating using the infrared heater gradually, so first perform preheating to raise the temperature of the entire board, and then mainly reflow the solder paste coated on the surface of the connection terminals of the board. Providing heating is the most preferred embodiment of the invention. To this end, as shown in FIG. 6, an infrared heater 10 for preheating and an infrared heater 11 for main heating are provided on the upper surface side of the substrate carrier 12, while a block heater 9 It is advantageous to use a device for connecting a chip carrier, which at least has a heating device mainly based on thermal conduction, which is provided on the underside of the substrate carrier 12.

Examples of the present invention will be described below.

(Example) A paste of eutectic solder (63% tin, 37% lead) was applied to the surface of the connection terminal of a printed wiring board that was processed using a conventional method using a commercially available glass epoxy board with one side copper-plated and 0.5 mm thick. Applied by silk screen printing,
After positioning and mounting the chip carrier made of glass epoxy board on the part where the solder paste was applied in this way,
While transporting the substrate so that it passes through a preliminary heating zone in which six 500W infrared heaters are arranged for 5 seconds, and then through a main heating zone in which 10 1000W infrared heaters for 200V are arranged in 10 seconds, the bottom side The solder paste was rapidly heated with a block heater and reflowed to obtain a composite board in which the connection terminals of the printed wiring board and the connection terminals of the chip carrier were reliably connected by solder. In this case,
The connection terminal portion is heated by the infrared heater on the top side and rapidly heated by the block heater on the bottom side, and the high melting point solder paste melts within a short time of 15 seconds, forming a printed wiring board as shown in Figure 7. The molten solder on the terminal surface forms a spherical film 13 due to surface tension, and then the surface tension of the molten solder automatically aligns the terminal surface of the chip carrier to the correct position with the terminal surface of the printed wiring board. Due to the so-called self-alignment effect (self-alignment), both terminals were accurately and reliably joined together, making it possible to connect the chip carrier to a fixed position on the printed wiring board.

As described above, according to the present invention, a leadless chip carrier of the same quality can be precisely mounted on a printed wiring board made of an organic resin material, and it is possible to prevent distortion caused by warping or twisting of the board during heat mounting, and also by heating. Mounting connections can be made within a relatively short time without causing deterioration due to scorching of the substrate.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view of a state in which a substrate is heated on a ceramic heater, Fig. 2 is a schematic side view of a state in which a chip carrier of the same quality is mounted on a printed wiring board made of an organic resin material of the present invention, and Fig. 3 The figure is a schematic side view of a chip carrier on a printed wiring board with concave warpage, Figures 4 and 5 are schematic side views of the heated state by the method of the present invention, and Figure 6 is a schematic side view of the device of the present invention. , FIG. 7 is an enlarged side view of a connecting terminal portion between a printed wiring board and a chip carrier according to the method of the present invention. In the above drawings, 1...ceramic heater,
2... a glass epoxy board, 3... a printed wiring board made of a glass epoxy board, 4... a connection terminal on the printed wiring board, 5... a chip carrier made of a glass epoxy board, 6... a connection terminal on the chip carrier, 7...Solder paste coating, 8...Infrared heater, 9...Block heater, 10...Preliminary heating zone, 11...Main heating zone, 12...Substrate carrier, 1
3...Spherical molten solder film, A side...upper surface side of the substrate, B side...lower surface side of the substrate.

Claims (1)

[Scope of Claims] 1. After mounting a leadless chip carrier made of an organic resin material on a printed wiring board made of an organic resin material via solder paste, preheating and main heating subsequent to the preheating are performed. A chip carrier tower-mounted connection method for reflowing solder paste, wherein the preheating is gradual heating by radiant heat transfer using an infrared heater from the leadless chip carrier side, and the main heating is the A method for connecting a chip carrier on a tower, characterized in that rapid heating is performed by heat conduction using a block heater from the printed wiring board side in addition to radiant heat transfer. 2. A chip carrier in which a leadless chip carrier made of an organic resin material is mounted on a printed wiring board made of an organic resin material via a solder paste, and then preheating and main heating subsequent to the preheating are performed to reflow the solder paste. A mounting connection device comprising: a board transport means for transporting the printed wiring board on which the leadless chip carrier is mounted; and a first half of the board transport means for carrying out the preheating, the board transport means for transporting the printed wiring board on which the leadless chip carrier is mounted; a means for gradually increasing preheating by radiant heat transfer using an infrared heater provided on the upper surface side of the substrate conveying means; A chip carrier comprising a heating means using radiation heat transfer using an infrared heater provided therein, and a heating means using heat conduction using a block heater provided on the lower surface of the substrate transport means, and a main heating means using rapid heating. Tower connection device.