JPH0553267U - High density multilayer circuit board - Google Patents

Abstract

(57) [Summary] [Structure] In a multilayer circuit board in which a plurality of printed circuit resin boards having circuit patterns formed on both surfaces of the board are laminated via solder bumps 6, the surface opposite to the bump bonding surface of the interior material 1 is previously prepared. Correspondingly, the solder bump abutting pressure equalizing pad 10 made of a metal foil thicker than the circuit pattern 2 is formed in advance, and the pressure is balanced at the time of pressurizing / heating. [Effect] A solder bump bonded body having less distortion over the entire bonding surface of the boards can be obtained, and a highly reliable multilayer circuit board that does not suffer damage even when repeated thermal shock is obtained.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a high-density multilayer circuit board in which a plurality of circuit boards are joined by solder bumps.

[0002]

[Prior Art]

 FIG. 2 is a cross-sectional explanatory view of a conventional example, in which a circuit pattern 2 on the back side of the interior material 1, a circuit pattern 3 on the front side, and a circuit pattern 5 on the back side of the cover material 4 are pressed via solder bumps 7a, 7b. The interior material 1 and the exterior material 4 were joined by raising the temperature while adding.

[0003]

[Problems to be solved by the device]

 However, this type of structure has a drawback in that when a thermal shock is applied, a part of the solder bump joint is peeled off, or a crack is likely to occur at a crystal grain boundary in the solder layer.

As a result of investigating the sample in which the defect has occurred, it has been found that it is related to the amount of displacement of the resin layer of the printed circuit board when the solder bumps are pressure bonded. That is, a part of the large number of solder bump joints has a pressure lowering area 8 in which the circuit pattern 2 is not formed on the back surface side of the interior material 1. In such an area having no circuit pattern on the back surface side, the following distortion occurs when joining is performed by pressurization / heating.

When the copper foil forming the circuit pattern on the back surface side and the void portion corresponding to the thickness of 18 μm are pressed at the same time, the interior material 1 is deformed by compression and tension due to softening of the resin layer. However, a strain region 9 is generated in the solidified joining region of the solder. Therefore, when a thermal shock was applied in a temperature range from a low temperature range to a high temperature range (such as a thermal shock test), stress was accumulated at the solder interface, causing microcracks to cause damage.

[0006]

[Means for Solving the Problems]

 The present invention is intended to solve these problems, and in order to achieve the purpose, a multilayer circuit board is formed by laminating a plurality of printed circuit resin boards having circuit patterns formed on both sides of a substrate through solder bumps. The printed circuit resin board is provided with a metal foil corresponding to the solder bump on a surface different from the bump bonding surface, and the thickness of the metal foil is formed to be equal to or larger than the circuit pattern thickness on the same surface. However, the embodiments will be described in detail below with reference to the drawings.

[0007]

【Example】

 FIG. 1 is a cross-sectional explanatory view of an embodiment of the present invention, in which a circuit pattern 2 and a solder bump abutting pressure equalizing pad 10 made of metal foil are provided on the back surface side of an interior material 1. The circuit pattern 3 on the front surface side of the interior material 1 and the circuit pattern 5 on the back surface side of the exterior material 4 are heated while applying pressure 7a and 7b via the solder bumps 6 to bond the interior material 1 and the exterior material 4 to each other. ..

In the case of such a configuration, the solder bump abutting pressure equalizing pad 10 and the circuit patterns 3 and 3 ′ on the front side which are behind the circuit pattern 2 are solder bump bonding in which uniform pressing conditions are satisfied. It can be performed.

As a result, no tension action is generated even after the completion of compression and pressing, the joint portion has low strain, and it is sufficiently durable against repeated thermal shock. Next, a more detailed description will be given.

Bump lands having a diameter of 1 mm to be joined to the covering material 4 are provided on one surface of the interior material 1 having a circuit pattern of a copper foil having a thickness of 18 μm on both surfaces. A 1.5 mm diameter solder bump abutting pressure equalizing pad 10 is provided on the back side of the bump land at a position corresponding thereto. A tin / lead eutectic solder cream is printed on the surface to be joined to the surface material 4, and a reflow process in a nitrogen atmosphere is performed to form solder bumps 6.

Next, the interior material 1 is abutted against the surface material 4 provided with a circuit pattern in advance, the dispersion plate is placed on the surface on which the pressures 7a and 7b act, and the temperature is 230 ° C. and the pressure is 5.5 Kg. / Cm @ 2 is added and the mounting material 4 and the interior material 1 are solder bump bonded.

[0012]

[Effect of the device]

 As described above, a solder bump bonded body having less distortion over the entire bonding surface of the boards can be obtained, and a highly reliable multilayer circuit board that is not damaged by repeated thermal shock can be formed.

[Brief description of drawings]

FIG. 1 is an explanatory sectional view of an embodiment of the present invention.

FIG. 2 is a sectional explanatory view of a conventional example.

[Explanation of symbols]

 1 Interior Material 2, 5 Circuit Pattern 3, 3'Circuit Pattern 4 Surface Material 6 Solder Bump 8 Depressed Area 9 Strained Area 10 Solder Bump Abutting Pressure Equalizing Pad

Claims (1)

[Scope of utility model registration request] 1. A multi-layer circuit board comprising a plurality of printed circuit resin boards having circuit patterns formed on both sides of the board, wherein the printed circuit resin boards are laminated via solder bumps, wherein the solder is provided on a surface different from a bump bonding surface of the printed circuit resin board. A high-density multilayer circuit board, characterized in that a metal foil is provided corresponding to the bumps, and the thickness of the metal foil is formed to be equal to or greater than the thickness of a circuit pattern on the same surface.