JPH0318756B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an IC package or a multilayer wiring board. [Prior Art] A conventional technology will be explained with reference to FIG. (1) Print wiring on a green sheet using a paste prepared from tungsten, molybdenum powder, etc. (2) These are laminated and bonded and fired in a reducing atmosphere. 3 Nickel plating is applied and the pin 4 is attached to the electrode part 3.
are joined using silver solder. In addition, 1 is a ceramic wiring board, 2 is a mounting part for mounting an IC element, and P is the pitch dimension of the pad part 3. [Problems to be Solved by the Invention] The conventional technology has the following drawbacks. In the step (2) above, the laminate undergoes firing shrinkage of 10% to 20%. The shrinkage rate is affected by the ceramic raw material used, green sheet molding conditions, wiring printing and lamination processing conditions, and firing conditions, and it is extremely difficult to always control the shrinkage rate to a constant level. Therefore, the pitch dimension P is non-uniform. On the other hand, the arrangement pitch of pins 4 to be connected to this wiring board 1 is 2.54 mm (100 mil) or 1.27 mm.
(50mil) is a constant eyelet size. Therefore, there is a difference between the arrangement pitch of the pins 4 and the arrangement of the pad part 3, and when trying to join the pins 4 to the pad part 3 with silver solder, the pins 4 may be deviated from the center of the electrode pad part 3 or It protrudes from part 3 (the larger the wiring board is, the more noticeable it is). For this reason, the pin 4 and the adjacent pad portion 3 often shoot, or the pin 4 and the pad portion 3
This may cause a decrease in the bonding strength. An object of the present invention is to enable external electrodes having the same pitch to be bonded to the center of the pad portion, thereby preventing shortening between the external electrode and the adjacent pad portion, and ensuring uniform bonding between the external electrode and the pad portion. An object of the present invention is to provide a method for manufacturing a wiring board that provides a high bonding strength. [Means for Solving the Problems] In order to achieve the above object, the present invention prints a paste prepared from tungsten or molybdenum powder on the outer surface of a ceramic green sheet at regular intervals, and then bakes the green sheet to form a ceramic green sheet of the same size. A pad portion for taking out the electrode is formed which has a larger area than the tip surface of the external electrode having a mounting pitch and is electrically conductive with the internal wiring, and has a larger area than the tip surface of the external electrode at the parallel pitch. A structure is adopted in which a glass paste having a softening point lower than the firing temperature is applied so that the glass paste is exposed, and the glass paste is baked at a temperature lower than the firing temperature in a reducing atmosphere to form an electrically insulating glass coating. did. [Actions and Effects of the Invention] The present invention has the following actions and effects. The glass paste is applied so that the pad portion has the same dimensions as the pitch between the external electrodes and is larger than the tip surface of the external electrodes, but is exposed. Since the softening point of this glass is lower than the firing temperature of the green sheet, it is possible to bake at a temperature lower than the firing temperature. Therefore, the green sheet that has already shrunk during firing will not shrink further during glass firing, and once fired, the pitch of the pad portion will be the same as the pitch of the external electrode, allowing the external electrode to be bonded to the center of the pad portion. . Therefore, the insulation between the external electrode and the adjacent pad portion is ensured, and the bonding strength between the external electrode and the corresponding pad portion can be made uniform. [Example] An example of the present invention will be described based on FIG. 2. In FIG. 2, 11 is a ceramic wiring board;
12 is an IC element mounting part, 13 is a fired layer of tungsten or molybdenum, 14 is a pad part, 15
is glass, and 16 is a pin. The glass 15 is required to be able to be baked in a reducing atmosphere at 1000° C. to 1400° C., and to have a composition that will not be affected by nickel plating or gold plating. In this example, Al ₂ O ₃ −
It is SiO ₂ −CaO−K ₂ O system and baked at 1400°C. Next, the manufacturing method will be described. (1) Ethyl cellulose, _{dibutyl phthalate ,} trichlene,
The slurry prepared by adding an appropriate amount of nonion is formed into a green sheet using the known doctor blade method. (2) Spread this green sheet 15.24cm x 10.16cm (6
x 4 inch), and punched them at specified positions to create pores with a diameter of 0.254 mm (10 mil), then prepared tungsten powder and filled the pores with paste. do. (3) Using the same tungsten paste, print the wiring pattern at the specified positions on these sheets, and make the pad part 14 for taking out the external electrode with the conventional pad size of 2.1336mmφ±1% (84milφ±1%).
The size is increased to 2.54mmφ±1% (100milφ±1%) and printed. The pitch between the centers of each pad is 120mil±1%. (4) These three sheets are laminated and bonded, the resin is removed at 250°C, and then fired at 1550°C in a mixed atmosphere of hydrogen and nitrogen. The pad size of fired product is 2.1082mmφ±1
% (83milφ±1%), pitch dimension between pad centers is 2.54mmφ±1% (100milφ±1%)
It is. (5) Separately, the glass composition includes 13% by weight of Al ₂ O ₃ ;
SiO ₂ 75% by weight, K ₂ O 8% by weight, CaO2.8% by weight,
A mixed powder containing 1.2% by weight of Na ₂ O is melted to form a frit, which has a glass softening point of 1100°C, and a paste is produced by turning this into powder and adding a solvent. Apply this glass paste on the surface of the fired product on which the tungsten pad was formed, and
Leaving 1.778mmφ (70milφ), the pitch between each pad center is 2.54mm (100milφ), 0.0254mm
(1mil) thickness and baked in a reducing atmosphere at 1400℃. As a result of this baking, the wiring board 11 does not change in size, and a pad surface made of tungsten with the desired pitch (2.54 mm) and shape (1.778 mmφ) printed on glass is formed, and unnecessary parts are covered with glass. The shape is covered with 15. (6) Next, the external take-out pins 16 are plated with nickel to a thickness of 0.00254 mm (0.1 mil) and set at a constant pitch; silver brazing material is used for 0.508 mm (20 mil), and the pins are heated at 850°C. Join. This is completed by applying gold plating to a thickness of 0.00254 mm (0.1 mil). The effects of this example will be described. (1) The pin 16 can be bonded to the center position of the pad portion 14, and the bonding strength can be made uniform. (2) The pads are reliably insulated and there is no need to shoot, resulting in stable quality. (3) The glass is _Al2O3 - _SiO2 - _CaO - _K2O and has a coefficient of thermal expansion of 6.0× ^10-6 /°C. Note that the temperature of ceramic is 5.9×10 ^-6 /°C. For this reason,
Provides sufficient rapid heating and cooling resistance, durability, and chemical resistance. (4) The larger the ceramic wiring board 1 becomes, as well as general-shaped products, the more effective it becomes, and the more reliable and stable quality products can be manufactured. Next, the results of measuring the bonding strength between a comparison product in which the step (5) above was omitted and the invention product will be described along with Table 1. Note that five samples were manufactured for each, and the bonding strength of the pins was measured using an Autograph (manufactured by Shimadzu Corporation). The bonding strength of the invented pin 16 was approximately constant at 8.5 kg or more. Also, the temperature starts from 150℃.
In a rapid heating and cooling test of 10 repetitions of air blowing at 15°C, there was almost no peeling between the ceramic and glass and no cracks in the glass. 【table】

[Brief explanation of the drawing]

FIG. 1 shows a conventional wiring board with pins connected thereto, with A being a sectional view of the main part thereof, and B being a partial bottom view thereof. FIG. 2 shows a wiring board according to an embodiment of the present invention, in which pins are bonded, A is a sectional view of the main part thereof, and B is a partial bottom view thereof. In the figure, 11... wiring board, 14... pad part (electrode extraction pad part), 15... glass (glass coating), 16... pin (external electrode).

Claims (1)

[Claims] 1. A paste prepared from dungsten or molybdenum powder is printed on the outer surface of a ceramic green sheet at regular intervals, and this green sheet is fired to form a ceramic green sheet with a larger area than the tip surface of an external electrode having the same pitch. and
forming a pad portion for taking out an electrode that is electrically conductive with internal wiring, and having a softening point lower than the firing temperature so that the pad portion is exposed at the juxtaposed pitch and in an area larger than the tip surface; A method for manufacturing a wiring board, comprising: applying a glass paste; and baking the glass paste at a temperature lower than the baking temperature in a reducing atmosphere to form an electrically insulating glass coating.