JPH0671144B2 - Multi-layer high-density mounting module - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a multilayer high-density mounting module in which a plurality of substrates each having a circuit pattern are stacked and a chip component is built in an intermediate layer of the substrates.

(Prior Art) Stacking a plurality of glass fiber and epoxy resin boards with circuit patterns, providing holes for embedding parts in the board of the intermediate layer, and incorporating chip parts such as ceramic chip capacitors for the purpose of circuit miniaturization There is a high-density mounting module. The circuit patterns of the plurality of substrates are, for example, tin,
Solder bump bonding with lead or eutectic solder is performed, and liquid epoxy resin is filled into the voids formed therebetween to complete the multilayer substrate.

However, the conventional structure in which the circuit pattern of each substrate is formed through the solder bumps of this type is, for example, when the solder bumps are repeatedly heat-treated several thousands times under the condition of -40 ° C to + 80 ° C. There was a problem that a crack was generated at the joint and the circuit was destroyed. That is, a glass fiber or an epoxy resin substrate is adhered with copper foil or the like and etched to form a circuit pattern. As mentioned above, when multilayering the substrate, tin,
Lead and eutectic solder are used to bond via solder bumps.
In a module board having a large heat capacity as the board becomes multilayered, copper in a copper foil diffuses into a tin component at the time of solder bump bonding for multilayering, and a brittle intermetallic compound is formed at a bonded portion. On the other hand, the glass fiber epoxy resin substrate has an extremely large coefficient of thermal expansion in the thickness direction of the substrate as compared with the solder metal due to its structure. The amount of expansion and displacement in the thickness direction of the resin substrate due to temperature drop and temperature rise, such as in a thermal cycle, concentrates at the solder bump joints, causing cracks at the aforementioned embrittlement joints of the circuit pattern solder bumps, causing a circuit destruction phenomenon. Occurred. In particular, this tendency was one of the major problems in the high-density mounting module in which multiple resin boards with a thickness of 1.0 mm or more were used because of the built-in components, and the amount of displacement in the thickness direction was large.

(Problems to be Solved by the Invention) The present invention is characterized in that a plating layer of platinum or palladium is formed on the surface of a circuit pattern copper foil used for a resin substrate, and the purpose thereof is to provide a plurality of substrates in which components are embedded. Another object is to provide a high-density mounting module in which the circuit pattern is not broken even if the layers are laminated and bonded via solder bumps or a long-term thermal cycle test is performed.

(Embodiment) FIG. 3 is an explanatory view of an embodiment of the present invention, and is an enlarged cross-sectional view of a main part of a high-density mounting module. Reference numeral 1 is a first layer substrate made of a glass fiber epoxy resin material, 2 is a second layer substrate having a space for embedding a component, and 3 is a functional layer such as an IC or a transistor on a surface layer, or is embedded inside a substrate such as a capacitor The third layer substrate on which impossible components are mounted, 4 is a copper foil circuit pattern which is attached to the surface of the resin substrate with an adhesive or the like, 5
Is a solder bump joint portion made of tin, lead, or eutectic solder, 6 is an epoxy resin filling a void portion between the substrates, and 7 is an electric component embedded in the substrate such as a ceramic chip capacitor.

In practicing the present invention, the circuit pattern on each substrate is electroplated with at least 0.5 microns thick platinum or palladium. Tin, lead and eutectic solder cream are printed and heated to form solder bumps. The electric component 7 is fixed on the same plane as the circuit pattern through a resin or the like in the hole of the substrate, and solder bumps for bonding are formed in the same manner as other solder bumps for bonding. In order to obtain the positional relationship between the substrates, the temperature is increased by pressing through a jig or the like to melt the solder and laminate the substrates. A liquid epoxy resin is impregnated into the voids between the substrates and a curing process is applied to complete the substrate. With such a configuration, tin does not form an intermetallic compound with platinum palladium, does not have brittleness, and a solder bump bonded state with stable bonding strength can be obtained.

Platinum and palladium have a low affinity with oxygen, and the surface layer thereof does not deteriorate the wettability of solder. In the structure where multiple substrates are laminated, the surface of the circuit pattern needs to have a thickness of 2.0 μm or more for nickel used for the same purpose, but when processing high frequency signals, the conductor surface loss of the circuit pattern However, there is no loss in the configuration using platinum. Furthermore, in the case of nickel, the process of coating the nickel layer with gold plating to improve the wettability to solder is complicated, and the formation of intermetallic compounds due to the diffusion of tin and gold in the solder components is slight, but solder bump bonding The brittleness tendency of the part is shown.

In addition, the thickness of platinum plating on the surface of copper foil may be very small because it does not cause erosion due to diffusion into solder components, but the amount of platinum plating is small and the circuit pattern configuration is complicated. Since the plating is performed via various conductive paths, a value of at least 0.5 micron or more is required for this type of purpose.

(Effects of the Invention) As described above, when a plurality of resin substrates are joined together via solder bumps, a platinum or palladium plating layer is laminated on the surface of the circuit pattern so as to cover at least 0.5 μm. There is an advantage that it is possible to provide a high-density mounting module in which the circuit is not destroyed even if displacement occurs due to thermal expansion of the substrate in the thickness direction.

[Brief description of drawings]

The drawing is an embodiment of the present invention and is an enlarged cross-sectional view of a main part of a high-density mounting module. 1 ... 1st layer substrate, 2 ... 2nd layer substrate, 3 ... 3rd layer substrate, 4 ... Copper foil circuit pattern, 5 ... Solder bump joint part, 6 ... Epoxy resin, 7 ... Electricity parts.

Claims (2)

[Claims] 1. A multi-layer high-density mounting module comprising a plurality of resin substrates having a circuit pattern made of copper foil, which is made of a material containing tin formed on the circuit pattern.
A multilayer high-density mounting module, characterized in that a solder bump and a surface of the circuit pattern in contact with the solder bump are coated with platinum or palladium plating. 2. A multilayer high-density mounting module, wherein the platinum or palladium plating according to claim 1 has a thickness of 0.5 μm or more.