JP2009032926A - Compound substrate and its printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compound board and its printed circuit board with less solder cracks in a connecting lands and fewer cracks in electronic components, and the like, and superior in connecting reliability in the printed circuit board, under a high-temperature atmosphere, when the electronic components are mounted on the printed circuit board. <P>SOLUTION: The compound board has a core substrate with its coefficient of thermal expansion in the thickness direction and lower than its glass transition temperature and lower than 45 ppm/°C, and an insulating layer having a glass cloth arranged at one side or both sides of the core substrate. A coefficient of elasticity in the insulating layer is smaller than that in the insulating substrate, and the rate of a resinous component in the insulating layer lies in a range of 65% and 93%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a composite substrate having high connection reliability and a printed wiring board thereof.

  Conventionally, a high-heat-resistant ceramic wiring board has been mainly used in a high-temperature environment such as an engine room of an automobile. However, an alternative to a printed wiring board is being studied due to the recent demand for lower prices. However, the thermal expansion coefficient difference between the copper wiring and the mounted components and the wiring board on the printed wiring board is large, and cracks in the through-holes, solder cracks, and surface layer circuits are likely to occur in a high temperature environment. Will fall.

  Therefore, there is an increasing demand for a printed wiring board having high connection reliability, which is unlikely to cause defects such as cracks in a high temperature environment.

As a method of preventing the occurrence of through-hole cracks in a printed wiring board, a method of blending a large amount of an inorganic filler in the resin composition of the wiring board and reducing the thermal expansion coefficient of the resin composition so as to approach the thermal expansion coefficient of copper However, since the resin composition containing a large amount of inorganic filler has a high elastic modulus, it will apply more stress to the solder part due to the difference in thermal expansion coefficient between the component and the wiring board. , Solder cracks are likely to occur.
Therefore, a method of providing a resin composition having a low elastic modulus on the surface of the printed wiring board (Patent Document 1) has been proposed as a means for reducing the stress caused by the difference in thermal expansion coefficient between the electronic component and the printed wiring board. ing. This method makes it difficult for solder cracks to occur.
JP 2006-315391 A

However, a resin composition having a low elastic modulus has a large thermal expansion, and a disconnection of the surface layer circuit is likely to occur. In other words, only the method of blending a large amount of inorganic filler in the resin composition of the printed wiring board or the method of providing a resin composition having a low elastic modulus on the surface of the printed wiring board is a requirement for the connection reliability of the printed wiring board. I can't respond enough.
An object of the present invention is to provide a composite substrate excellent in connection reliability and a printed wiring board thereof with less occurrence of through-hole cracks, solder cracks, surface layer circuit breakage, and the like in a high-temperature environment.

In order to solve the above problems, a core substrate having a thermal expansion coefficient in the plate thickness direction of less than 45 ppm / ° C. below the glass transition temperature, and an insulating layer having a glass cloth disposed on one or both surfaces of the core substrate A composite substrate wherein the elastic modulus of the insulating layer is smaller than the elastic modulus of the core substrate, and the resin content in the insulating layer is 65% to 93% I will provide a.
Further, the present invention provides the composite substrate, wherein the elastic modulus of the insulating layer is 10 GPa or less.
Moreover, the printed wiring board which has a circuit using the said composite substrate is provided.

  According to the present invention, in a high-temperature environment, not only through-hole cracks and solder cracks but also the occurrence of surface layer circuit disconnection and the like can be produced, and a printed wiring board excellent in connection reliability and its printed wiring board can be manufactured. Become.

  The core substrate described in the present invention is a substrate having a thermal expansion coefficient in the plate thickness direction of less than 45 ppm / ° C. below the glass transition temperature, and an insulating layer having a glass cloth on one or both sides. If it is 45 ppm / ° C. or more in the thickness direction, it is not preferable because it causes a through-hole crack.

  Further, if it exceeds 20 ppm / ° C. in the XY direction (plate surface direction) at 130 ° C. or lower, the difference from the thermal expansion coefficient of the mounted component becomes large, which is not preferable because it tends to cause cracks. Moreover, the thickness of a core board | substrate may be common thickness, and although it does not specifically limit, It is preferable that it is the range of 0.2-3.2 mm.

  Specific examples of the core substrate include, for example, MCL-E-679F and MCL-BE-67G (H) which are glass epoxy copper clad laminates (both manufactured by Hitachi Chemical Co., Ltd., trade names) and the like. Can be used. Moreover, you may have an inner layer circuit.

  The insulating layer described in the present invention is a resin-impregnated base material (prepreg) having a glass cloth, and is provided on one side or both sides of the core substrate. The elastic modulus at room temperature is preferably 10 GPa or less. When this elastic modulus exceeds 10 GPa, the stress generated under a high temperature environment cannot be sufficiently relaxed, and it becomes difficult to sufficiently prevent the occurrence of solder cracks and the like.

  The resin composition of the insulating layer is not particularly limited. For example, an insulating resin such as an epoxy resin, a rubber such as acrylonitrile butadiene rubber, a curing agent such as a phenol resin, and a curing acceleration such as 2-ethyl-4-methylimidazole. An agent, a flame retardant, a plasticizer, a filler, a solvent, etc. can be used, and the elasticity modulus of an insulating layer can be adjusted by adjusting the compounding quantity of each composition, and the quantity of a solvent suitably.

The resin content of the insulating layer needs to be 65% to 93%. If the resin content is less than 65%, the stress generated in a high temperature environment cannot be sufficiently relaxed, and solder cracks are likely to occur. If the resin content exceeds 93%, the thermal expansion coefficient in the Z direction is increased. It tends to be too big.
The resin content of the insulating layer refers to the volume ratio of the resin to the total volume of the insulating layer when the resin composition is impregnated with a glass cloth and dried at 150 ° C. for 10 minutes to form a resin-impregnated base material (prepreg). .
Moreover, in the copper foil with resin which does not have a glass cloth, since the thermal expansion coefficient of an XY direction depends on that of resin, it becomes easy to generate | occur | produce the disconnection of a surface layer circuit.

The composite substrate described in the present invention is a substrate in which the insulating layer is disposed on one side or both sides of the core substrate, and the insulating layer is stacked on the core substrate and formed by heating and pressing. The heating and pressing conditions at this time are preferably performed under conditions of a temperature of 150 to 180 ° C. and a pressure of about 9 to 20 MPa. However, the characteristics of the laminate, the reactivity of the insulating resin composition, the capability of the press, and the desired lamination The thickness can be appropriately determined in consideration of the thickness of the plate, and is not particularly limited.

  In the composite substrate of the present invention, a metal layer is formed on one side or both sides as necessary. For example, a metal foil such as a copper foil is placed on one side or both sides of the laminated plate and heated and pressed. Can be formed. The heating and pressurization is preferably performed under conditions of a temperature of 150 to 180 ° C. and a pressure of about 9 to 20 MPa. However, the characteristics of the laminated board, the reactivity of the insulating resin composition, the ability of the press, and the desired laminated board The thickness can be appropriately determined in consideration of the thickness of the material, and is not particularly limited.

  The composite substrate of the present invention includes (1) a step of forming a circuit by etching the metal layer of the core substrate, (2) a step of heating and pressing after sequentially laminating an insulating layer and a metal foil on the circuit, and (3) It can be manufactured by a process of forming a circuit by etching a metal layer as the outermost layer, and a multilayer printed wiring board having a desired number of layers can be obtained by repeating steps (2) and (3). it can. In addition to the above steps, processing steps for producing a multilayer printed wiring board, such as a through-hole forming step and a plating step, can be performed as necessary.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<Preparation of copper-clad laminate>
A circuit board was formed by etching a glass epoxy copper clad laminate MCL-E-679F (trade name, manufactured by Hitachi Chemical Co., Ltd.) having a thickness of 1.0 mm, and a core substrate was produced.

  Next, a resin component obtained by impregnating a glass cloth 1078 type (IPC standard) with a varnish of an epoxy resin-based insulating resin composition A having an elastic modulus of 7 to 10 GPa and drying for 10 to 15 minutes in a dryer at 150 ° C. A 65% B-stage prepreg TCP-300 (trade name, manufactured by Hitachi Chemical Co., Ltd.) was sandwiched between the core substrate and the copper foil and heated and pressurized at 185 ° C. for 70 minutes under a vacuum of 3.0 MPa. A copper clad laminate for evaluation was produced.

(Example 2)
By using the same method as in Example 1 except that 1037 type glass cloth was used and the resin content of prepreg TCP-300 (trade name, manufactured by Hitachi Chemical Co., Ltd.) impregnated with insulating resin composition A was 78%. A copper clad laminate for evaluation was produced.

(Example 3)
By using the same method as in Example 1 except that 1027 type glass cloth was used and the resin content of prepreg TCP-300 impregnated with insulating resin composition A (trade name, manufactured by Hitachi Chemical Co., Ltd.) was 85%. A copper clad laminate for evaluation was produced.

Example 4
By using the same method as in Example 1 except that 1015 type glass cloth was used and the resin content of prepreg TCP-300 (trade name, manufactured by Hitachi Chemical Co., Ltd.) impregnated with insulating resin composition A was 93%. A copper clad laminate for evaluation was produced.

(Example 5)
A circuit is formed by etching a copper foil of a glass epoxy copper clad laminate MCL-BE-67G (J) (trade name, manufactured by Hitachi Chemical Co., Ltd.) having a thickness of 1.0 mm, and between this core substrate and the copper foil A prepreg TCP-300 (trade name, manufactured by Hitachi Chemical Co., Ltd.) impregnated with a 1078 type glass cloth and impregnated with an insulating resin composition A having a resin content of 65% is sandwiched between 185 ° C. and a pressure of 3.0 MPa under vacuum. The laminate was heated and pressed for 70 minutes to produce a copper clad laminate for evaluation.

(Example 6)
By using the same method as in Example 4, except that 1037 type glass cloth was used and the resin content of prepreg TCP-300 (trade name, manufactured by Hitachi Chemical Co., Ltd.) impregnated with insulating resin composition A was 78%. A copper clad laminate for evaluation was produced.

(Example 7)
By using the same method as in Example 4 except that 1027 type glass cloth was used and the resin content of prepreg TCP-300 (trade name, manufactured by Hitachi Chemical Co., Ltd.) impregnated with insulating resin composition A was 85%. A copper clad laminate for evaluation was produced.

(Example 8)
Using a 1078 type glass cloth, the resin content of prepreg GEA-67 (trade name, manufactured by Hitachi Chemical Co., Ltd.) impregnated with an epoxy resin-based insulating resin composition B having an elastic modulus of 21 to 25 GPa is 65%. A copper clad laminate for evaluation was produced in the same manner as in Example 1 except that.

(Comparative Example 1)
Example 1 using MCL-E-679F (trade name, manufactured by Hitachi Chemical Co., Ltd.) as the glass epoxy copper clad laminate as the core material and GEA-679F (trade name, manufactured by Hitachi Chemical Co., Ltd.) as the prepreg A copper clad laminate for evaluation was produced by heating and pressing at 185 ° C. for 150 minutes at a pressure of 3.0 MPa under vacuum in the same manner.

(Comparative Example 2)
By the same method as in Example 1 except that 1080 type glass cloth was used and the resin content of prepreg TCP-300 (trade name, manufactured by Hitachi Chemical Co., Ltd.) impregnated with insulating resin composition A was 62%. A copper clad laminate for evaluation was produced.

(Comparative Example 3)
Insulating resin composition film TCP-300 (Hitachi with copper foil) obtained by applying and drying the varnish of insulating resin composition A onto a copper foil so that the resin film thickness becomes 60 μm and drying (150 ° C., 10 minutes). A copper clad laminate for evaluation was produced in the same manner as in Example 1 except that Kasei Kogyo Co., Ltd. trade name) was used for the insulating layer.

(Comparative Example 4)
A prepreg TCP-300 impregnated with an insulating resin composition A at a resin content of 65% using a glass epoxy copper-clad laminate of MCL-E-67 (trade name, manufactured by Hitachi Chemical Co., Ltd.) having a thickness of 1.0 mm as a core plate. A copper clad laminate for evaluation was prepared in the same manner as in Example 1 using (trade name, manufactured by Hitachi Chemical Co., Ltd.).

(Comparative Example 5)
A copper clad laminate for evaluation was produced in the same manner as in Comparative Example 4 except that the resin content of prepreg TCP-300 impregnated with insulating resin composition A (trade name, manufactured by Hitachi Chemical Co., Ltd.) was 78%. .

(Comparative Example 6)
A copper clad laminate for evaluation was prepared in the same manner as in Comparative Example 4 except that the resin content of the prepreg TCP-300 (trade name, manufactured by Hitachi Chemical Co., Ltd.) impregnated with the insulating resin composition A was 85%. .

(Comparative Example 7)
Example 1 using MCL-E-67 (trade name, manufactured by Hitachi Chemical Co., Ltd.) as the glass epoxy copper clad laminate as the core material, and GEA-67 (trade name, manufactured by Hitachi Chemical Co., Ltd.) as the prepreg A copper clad laminate for evaluation was prepared by heating and pressing at a pressure of 2.5 MPa at 180 ° C. for 60 minutes in a similar manner under vacuum.

<Evaluation of copper clad laminate>
(Connection reliability of through hole (TH) and non-through hole (IVH))
After drilling 0.3mm through holes in each evaluation copper-clad laminate, drilling non-through holes with CO ₂ laser, and applying copper plating with a thickness of about 20μm on the inside and on the surface of the copper-clad laminate, unnecessary parts The surface copper was etched to form a circuit. Thereafter, flux was applied as a solder resist formation and finishing treatment to complete the sample.
Next, each sample obtained above is put into a temperature cycle tester, and the connection resistance value is measured every 500 cycles with -45 ° C, 30 minutes and 125 ° C, 30 minutes repeated as one cycle, and up to 4000 cycles. When the connection resistance value exceeded ± 10% with respect to the initial resistance value before the introduction of the testing machine, the presence or absence of cracks was confirmed by cross-sectional observation. Tables 1 and 2 show the number of acceptable cycles until the connection resistance value exceeds ± 10% with respect to the initial resistance value. Judgment criteria were good at 3000 cycles or more, and bad at less than 3000 cycles.

(Surface layer circuit (pattern) disconnection)
Each evaluation copper-clad laminate was subjected to copper plating having a thickness of about 20 μm, and a circuit having widths of 100 μm, 75 μm, and 50 μm was produced by etching. Thereafter, flux was applied as a solder resist formation and finishing treatment to complete the sample. Next, each sample obtained above was put into a temperature cycle testing machine, and the connection resistance value of the pattern was measured every 500 cycles, with -45 ° C, 30 minutes and 125 ° C, 30 minutes repeated as one cycle, When the connection resistance value exceeded ± 10% with respect to the initial resistance value before the introduction of the testing machine by 4000 cycles, the presence or absence of circuit disconnection was confirmed by surface observation. Tables 1 and 2 show the number of acceptable cycles until the connection resistance value exceeds ± 10% with respect to the initial resistance value. Judgment criteria were good at 3000 cycles or more, and bad at less than 3000 cycles.

(Solder crack)
Each evaluation copper-clad laminate was subjected to circuit formation by etching to form a chip mounting electrode. Thereafter, flux was applied as solder resist formation and finishing treatment. After that, a solder paste is applied onto the electrode, and chips of sizes 1005, 1608, 2125, and 3216 are mounted on the electrode, put into a reflow furnace, and the chip is soldered to a copper-clad laminate to prepare a sample. Completed. After that, the sample on which the chip is mounted is put into a temperature cycle testing machine, and the sample is taken out every 500 cycles with -45 ° C, 30 minutes and 125 ° C, 30 minutes repeated as one cycle, and solder cracks are observed by cross-sectional observation. Was confirmed (maximum 4000 cycles). The criterion for determining the occurrence of solder cracks is that the crack size is 50% or more of the connection length between the component and the solder. Tables 1 and 2 show the number of acceptable cycles until a solder crack occurs. Judgment criteria were good at 2500 cycles or more, and bad at less than 2500 cycles.

  As shown in Table 1 and Table 2, in Examples 1 to 8 according to the present invention, not only through-hole cracks and solder cracks, but also printed circuit boards with excellent connection reliability that are less likely to cause surface layer circuit breakage and the like. And the manufacture of the printed wiring board is attained. In particular, in Examples 1 to 7 in which the elastic modulus of the insulating layer is 10 GPa or less, the solder crack resistance is further improved.

Claims (3)

  A core substrate having a coefficient of thermal expansion in the plate thickness direction of less than 45 ppm / ° C. below the glass transition temperature, and an insulating layer having a glass cloth disposed on one or both surfaces of the core substrate, and the elastic modulus of the insulating layer However, the composite substrate is smaller than the elastic modulus of the core substrate, and the ratio of the resin component in the insulating layer is 65% to 93%.   The composite substrate according to claim 1, wherein the elastic modulus of the insulating layer is 10 GPa or less.   A printed wiring board having a circuit using the composite substrate according to claim 1.