Patent Application
20080132131
1. Field of the Invention
The present invention relates to a printed circuit board (PCB) material, which is a polybutadiene-based thermosetting resin, with the corporation of a peroxide curing agent or crosslinking agent to form an insulation layer on a copper clad laminate. In accordance with the requirement of the process, inorganic particulate filler with high surface area, such as silica, and a metallic coagent are selectively added into resin matrix. The resulted prepreg shows almost no stickiness, easy to be handled, thus favorable for an automatic process and suitable for a general hot press operation. The obtained prepreg possesses low stickiness, and no slip is found during laminating at the room temperature. The resin composition of the invention is characteristic in the incorporation of a unique metallic coagent; the peeling strength thereof is excellent, thus most suitably applied in high-frequency circuit board.
2. Description of the Related Art
In the previous arts, circuit boards are made from polybutadiene as a main material with addition of non-woven reinforcing cloth, particulate filler, initiator, brominated flame retardant, etc. For example, in U.S. Pat. No. 4,241,132, the composition of circuit boards comprises polybutadiene polymer (70 wt % of 1,2-addition polybutadiene rubber, Ricon 150 Sartomer) and reinforcing fiber, such as polypropylene fiber. In the insulation composition, the dielectric constant or dissipation factor of resin should comply with reinforcing fiber. The disadvantages are as follows:
The PCB composition is disclosed in U.S. Pat. No. 4,997,702 which also includes inorganic fillers or reinforcing fibers with 20-70 wt % of total compositions, in addition to epoxy resin, wherein fibers comprise glass fiber or polymer fiber, and fillers comprise particulates clay or minerals, e.g. silica. Its obvious drawbacks are:
The thermosetting composition for circuit board revealed in U.S. Pat. No. 5,223,568 includes:
Although the performance of the said circuit boards is not bad, there are still some drawbacks as following:
The circuit board disclosed in the U.S. Pat. No. 6,048,807 comprises:
The circuit board disclosed in U.S. Pat. No. 6,071,836 is characterized in that:
As the description mentioned above, the performance of the said circuit boards is quite good, but there are some drawbacks to be improved as follows:
In addition to US Patents, there are other literatures relating the application of polybutadiene on circuit board material, For example, a novel 1,2-polybutadiene flame retardant substrate material described in N. Sawatari et al., IEEE Transactions on Electrical Insulation, Vol. EI-18, No. 2, April 1983 shows the handling of 1,2-polybutadiene at semi-hardening stage (B stage) is difficult, it is very hard to be sticky free, also easy to be burned and the adhesion with copper foil is poor. In order to solve these problems, some ways are proposed in the said literature: to use a lot of high molecular weight polybutadiene to eliminate the stickiness in B stage, and to add a small amount of modified low molecular weight polybutadiene resin to facilitate the flow during copper foil laminating. But no usage of any type of filler is mentioned.
In EU 0202488 A2, a polybutadiene-based circuit board is revealed; wherein a high molecular weight brominated prepolymer is blended to reduce the stickiness of polybutadiene substrate and flammability. On the other hand, JP-04 258,658 reveals the incorporation of a high molecular compound to control the stickiness, while the main function of the compound is to provide flame retardant, better adhesion to copper and heat resistance. No other filler is described, and the circuit board still has the disadvantage of a high dissipation factor.
In the “High performance of 1,2-polybutadine resin of Electrical Industry” by R. E. Drake, ANTEC 84 pp. 730-733, 1984, it is clearly reported that the traditional polybutadiene resin is used as PCB substrate, and that a reactive monomer reacts with the polybutadiene and cures together. In U.K. Patent Application No. 2172892, it is described that a circuit board is made from the thermoplastic copolymer of unsaturated double bond containing styrene and polybutadiene.
The present invention relates to a polybutadiene-based PCB substrate with improved electric, chemical and heat resistance properties as compared to the related arts. The object of the present invention is to provide a novel polybutadiene-based PCB substrate with better heat resistance, thermo expansion coefficient, dielectric constant, dissipation factor, no stickiness, adhesion strength, and the present invention also provides a novel circuit board composition of polybutadiene thermosetting resin and the manufacturing process thereof.
The first object of the present invention is to provide a lot of unsaturated vinyl groups for a crosslinking reaction to form a superior heat resistance of circuit board composition.
The second object is to provide a suitable amount and kind of fillers to form a circuit board composite with low stickiness, easy lamination, and good electric properties, such as low dielectric constant and dissipation factor.
The third object of the present invention is to provide a circuit board composite which can reach a peeling strength with a ordinary copper foil over 4 lbf/inch.
The fourth object of the present invention is to provide a circuit board composite with a lower hygroscopic property than a common CCL (copper clad laminate).
The fifth object of the present invention is to provide a low temperature (170-220° C.) substrate hot pressing process which can avoid a brominated flame retardant agent to be decomposed to deteriorate the heat resistance of circuit substrate.
This invention provides a novel polybutadiene circuit board composition including:
20-35 wt % of resins which comprises a polybutadiene polymer resin with a high vinyl group content (more than 70 wt %.) and MW equal or more than 100,000 g/mol, and a low molecular weight polybutadiene (MW=5,000˜10,000 g/mol), and a kind of cycloolefin compound with at least two vinyl group, and/or a terpolymer made from acrylic acid, acrylonitrile and butadiene;
10-30 wt % of woven glass fiber reinforced cloth;
25-50 wt % of particulate filler, which is preferably, fused silica;
10-30 wt % of a brominated flame retardant (for better flame retardant);
1-10 wt % of metallic coagents (for elevating the peeling strength between resin and metal); and
A peroxide initiator.
The composition of the present invention contains a high vinyl polybutadiene thermosetting resin. The content of 1,2-addition vinyl group is more than 85% in the resin composition, which provide a lot of unsaturated vinyl groups for crosslinking reaction and forming the highest crosslinking density after curing. Thus it can give circuit boards having a superior heat resistance.
Another technology characteristic of the present invention is in that the formulation is obtained from suitably selecting the dose and the type of fillers to let the varnish viscosity not too high to be impregnated, and after semi-curing, there is almost no stickiness between prepreg, thus it is easy to laminate and to improve Z-axis thermal expansion coefficient and dielectric properties (such as dissipation factor), to cut the production cost. The most important one is that it can be applied in the current board hot pressing process, and use the pressing process at a lower temperature.
In addition to above technology features, the most important features of the present invention lie on:
Base resins, fillers, metallic coagents, crosslinking agents, glass fiber cloth, flame retardant agents and peroxide curing initiators will be used in the present invention, and the sources thereof are described sequentially as follows:
The base resin used in the present invention is a thermosetting resin composition which comprises (1) polybutadiene resin; and (2) a kind of cycloolefin compound with at least two vinyl group, and/or (3) a terpolymer obtained from the polymerization of acrylic acid, acrylonitrile, butadiene, which can take part in crosslinking reaction during curing, wherein (1) polybutadiene resin may be a solid or liquid at the room temperature, but it should be a blend of a high molecular weight (MW≧100,000 g/mol) solid resin and a low molecular weight (MW=5,000˜10,000 g/mol) liquid resin, and its 1,2-addition vinyl group content is above 70 wt %, preferably above 90 wt %. The high vinyl containing polybutadiene resin can give a lot of unsaturated vinyl groups for crosslinking, thus can increase crosslinking density, and thereby can result in superior high temperature resistance.
The preferable high molecular weight resins are RB series resins, such as RB810, RB820 and RB830, and more than 90 wt % 1,2-addition polybutadiene solid resin. RB series resins are available from Japan Synthetic Rubber Corp. Low molecular liquid resins, such as Ricon153 and Ricon154 resins (Sartomer Corp.) or B3000 and B1000 resins (Nippon Soda Corp.) are preferable.
Another kind of thermosetting resins (2) includes cycloolefin compound with at least two vinyl group and/or a terpolymer made from acrylic acid, acrylonitrile and butadiene, wherein cycloolefin compound with at least two vinyl double bonds can undergo cross linking reaction via vinyl double bonds, and cycloolefin in the molecular chain can suppress hygroscopic, dielectric constant and dissipation factor, such cycloolefin copolymer are produced from the reaction of ethylene, norbornene, ethylidene norbornene monomers etc. with a metallocene catalyst.
1. Synthesis of Cycloolefin Copolymer (COC-A):
4.01 kg of high purity NB (norbornene), 2.27 kg of ENB (5-Ethylidene-2-norbornene) and 2.59 kg of toluene are introduced into a high pressure reactor, heated up to 100° C., then 0.2 kg of 10 wt % of cocatalyst (MAO/toluene) and 6×10−5 kg of metallocene catalyst are injected, the mixed gases of ethylene (800 ml/min) and hydrogen (50 ml/min) are introduced to conduct polymerization under a pressure of 18 kg/cm2. After reaction is completed, toluene is added to dilute the solid content to below 10 wt %, hydrochloric acid is used for neutralization, then filtrate is added into large amount of acetone, cycloolefin copolymer (COC-A) is precipitated as solid and dried in oven,
2. Synthesis of Cycloolefin Copolymer (COC-B):
Butyl-NB is obtained from the reaction of adding DCPD to 1-hexene. 2 kg of high purity Butyl-NB, 1 kg of NB (norbornene), 2 kg of ENB (5-ethylidene-2-norbornene) and 1 kg of toluene are incorporated into a high pressure reactor, heated to 100° C., 0.08 kg of cocatalyst (MAO/toluene, 10 wt %) and 2×10−5 kg of metallocene catalyst are added, then the mixed gases of ethylene (800 ml/min) and hydrogen (50 ml/min) are introduced to conduct polymerization under a pressure of 10 kg/cm2. After reaction is completed, toluene is added to dilute the solid content to below 10 wt %, hydrochloric acid is used for neutralization, then filtrate is added into large amount of acetone, cycloolefin copolymer (COC-B) is precipitated as solid and dried in oven,
3. Synthesis of Cycloolefin Copolymer (COC-C):
Hexyl-NB with long chain is obtained from the reaction of adding DCPD to 1-octene. 2 kg of a high purity Hexyl-NB, 2.8 kg of ENB (5-ethylidene-2-norbornene), and 1 kg of toluene are incorporated into a high pressure reactor, heated to 100° C., 0.08 kg of cocatalyst (MAO/toluene, 10 wt %) and 2×10−5 kg of metallocene catalyst are added, then the mixed gases of ethylene (800 ml/min) and hydrogen (50 ml/min) are introduced to conduct polymerization under a pressure of 10 kg/cm2. After reaction is completed, toluene is added to dilute the solid content to below 10 wt %, hydrochloric acid is used for neutralization, then filtrate is added into large amount of acetone, cycloolefin copolymer (COC-C) is precipitated as solid and dried in oven,
In addition, another resin (3) resulted from the polymerization of acrylic acid; acrylonitrile and butadiene can be used to improve the adhesion strength between resin and copper foil. Examples of these resins are Carboxyl terminated butadiene acrylonitrile rubber series (such as CTBN1300×8, CTBN1300×13, CTBN1300×31) available from Noveon Corp.
The particulate fillers used in the present invention are titanium dioxide, barium titanate, strontium titanate, silica (including amorphous silica and fused silica); the dose thereof is 25-50%, preferably 30-45% of the weight of total composition.
They can be used alone or in a mixture thereof. The best filler is amorphous silica, preferably chosen from those with a high surface area, e.g. fused silica. As compared with normal amorphous silica (generally, 10 μm), those with a high surface area can reduce stickiness more efficiently. Among them, fused silica, e.g. AEROSIL200 of Degussa Corp. is preferable, which is characterized in 200 m2/g of specific surface area and 12 nm of particle size.
The examples of these fillers include E44I (10 micron amorphous Silica, CE Minerals), FB-35 (Fused Silica, Denka), Minsil 5 (Fused Silica, Minco), Min-sil 20 (Fused Silica, Minco), Nnvacite 325 (Natural crystalline silica, Minerals), GP7I (Fused Silica, Harbison Walker).
The metallic coagents used in the present invention are the complex compounds made from the reaction of alkaline metals, alkaline earth metals or zinc element and acrylic acid; generally these reagents are metallic diacrylate (e.g. SR633, SR636, SR638, SR705, SR706), metallic dimethacrylate (e.g. SR634, SR708), and metallic monomethacrylate (SR709) etc. which are available from Sartomer Corp.
During the hot curing process, firstly a metallic coagent with higher reactivity can react with a peroxide curing initiator to form a free radical containing compound, then conduct a crosslinking reaction with polybutadiene resin or other double bond containing resins, thereby every molecular chain possesses acrylate, thus enhance the peeling strength between resin and metal, i.e. improve the adhesion strength of resin and copper foil.
The crosslinking agents for increasing the degree of crosslinking include triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, divinylbenzene or the mixture thereof.
The glass fiber cloth content is 10-30 wt % of the total composition, the glass fiber cloth made by NAN YA Plastic Corp. is used as a reinforcing material, and the specifications of glass fiber cloth depend on the application of boards as follows:
The flame retardant agents used in the present invention are mainly bromine-based flame retardant agents. The dose thereof is 10-30 wt %. The preferable bromine-based flame retardant agents are for example Saytex BT-93W (ethylene bistetrabromophthalimide), Saytex 120 (tetradecabromo-diphenoxy benzene) or Saytex 102 (decabromo-diphenoxy oxide).
A free radical initiator is added to accelerate a crosslinking reaction. The said initiator will be decomposed to form free radical, thereby initiates a crosslinking polymerization. The preferable free radical initiators are e.g. organic peroxides, such as dicumyl peroxide (DCP), t-butylperbenzoate (TBPB) and t-butylperoxy hexyne-3. These are commonly used hardening agents, and the dose thereof is 0.2-3 wt %.
In addition to above-mentioned three cycloolefin copolymers, the other are listed in the following table:
104.3 parts by weight of a high molecular weight polybutadiene rubber (RB810), 63.6 parts by weight of low molecular weight polybutadiene rubber (Ricon154), 85.9 parts by weight of cycloolefin copolymer (COC-A) and 12.5 parts by weight of CTBN1300×8 are homogeneously mixed; then 13.3 parts by weight of SARET 633, 429.5 parts by weight of silica filler (FB-35), 163.2 parts by weight of brominated flame retardant (SAYTEX8010), 8 parts by weight of cross linking agent (TAIC), 8 parts by weight of hardening initiator (DCP) are added and homogeneously agitated, hereafter 111.7 parts by weight of woven glass (#1080) is impregnated in the resultant liquid, and at 130° C., they are semi-hardened to form a prepreg, 8 sheets of prepreg are laminated and sandwiched in 2 copper foils (NAN YA's 1 oz), the resulted composite is hot pressed under the condition of 30 kg/cm2 (426 psi), 195° C. for 3 hours to become a circuit board composite, the tested physical properties are listed in Table 1.
The dose of COC-A is increased to replace part of RB810, in other words, 61.3 parts by weight of PB810, 636 parts by weight of Ricon154 are mixed, then 128.9 parts by weight of COC-A and 12.5 parts by weight of CTBN1300×8 are added and homogeneously mixed; 13.3 parts by weight of SARET 633 and 429.5 parts by weight of FB-35 filler, then 163.2 parts by weight of SAYTEX8010 and 8 parts by weight of TAIC, 8 parts by weight of DCP are incorporated and mixed homogeneously, 111.7 parts by weight of 1080 woven glass is impregnated therein, and at 130° C., they are semi-hardened to form a prepreg, 8 sheets of prepreg are laminated and sandwiched in 2 NAN YA's 1 oz copper foils, the resulted composite is hot-pressed under the condition of 30 kg/cm2 (426 psi), 195° C. for 3 hours to obtain a circuit board composite, the tested physical properties are listed in Table 1.
The dose of COC-A is decreased, while the dose of RB810 is increased, in other words, 147.2 parts by weight of RB810, 63.6 parts by weight of Ricon154, 43.0 parts by weight of COC-A and 12.5 parts by weight of CTBN1300×8 are homogeneously mixed; then 13.3 parts by weight of SARET 633, 429.5 parts by weight of FB-35 filler, 163.2 parts by weight of SAYTEX8010, 8 parts by weight of TAIC, 8 parts by weight of DCP are added sequentially, and mixed homogeneously, 111.7 parts by weight of 1080 woven glass is impregnated therein and at 130° C., they are semi-hardened to form a prepreg. 8 sheets of prepreg are laminated, and sandwiched in 2 NAN YA's 1 oz copper foils, then hot-pressed under the condition of 30 kg/cm2 (426 psi), 195° C. for 3 hours to obtain a circuit board composite, the tested physical properties are listed in Table 1.
Ricon154 resin is substituted by Ricon153, in the other words, 104.3 parts by weight of RB810, 63.6 parts by weight of Ricon153, 85.9 parts by weight of COC-A and 12.5 parts by weight of CTBN1300×8 are mixed homogeneously; then 13.3 parts by weight of SARET 633, 429.5 parts by weight of FB-35 filler, 163.2 parts by weight of SAYTEX8010, 8 parts by weight of TAIC, 8 parts by weight of DCP are added sequentially, and mixed homogeneously, 111.7 parts by weight of 1080 woven glass is impregnated therein and at 130° C., they are semi-hardened to form a prepreg. 8 sheets of prepreg are laminated, and sandwiched in 2 NAN YA's 1 oz copper foils, then hot-pressed under the condition of 30 kg/cm2 (426 psi), 195° C. for 3 hours to obtain a circuit board composite, the tested physical properties are listed in Table 1.
No SARET 633 is added. 105.7 parts by weight of RB810, 64.6 parts by weight of Ricon154, 87.1 parts by weight of COC-A and 12.6 parts by weight of CTBN1300×8 are mixed homogeneously; 435.3 parts by weight of FB-35 filler, 165.4 parts by weight of SAYTEX8010, 8.1 parts by weight of TAIC and 8.1 parts by weight of DCP are added sequentially, and mixed homogeneously, 113.2 parts by weight of 1080 woven glass is impregnated therein and at 130° C., they are semi-hardened to form a prepreg. 8 sheets of prepreg are laminated, and sandwiched in 2 NAN YA's 1 oz copper foils, then hot-pressed under the condition of 30 kg/cm2 (426 psi), 195° C. for 3 hours to obtain a circuit board composite, the tested physical properties are listed in Table 1.
Ricon153 is used to replace RB810 resin, i.e. 104.3 parts by weight of Ricon153, 85.9 parts by weight of COC-A and 12.5 parts by weight of CTBN1300×8 are mixed homogeneously; then 13.3 parts by weight of SARET633, 429.5 parts by weight of FB-35 filler, 163.2 parts by weight of SAYTEX8010, 8 parts by weight of TAIC and 8 parts by weight of DCP are added sequentially, and mixed homogeneously, 111.7 parts by weight of 1080 woven glass is impregnated therein and at 130° C., they are semi-hardened to form a prepreg. 8 sheets of prepreg are laminated, and sandwiched in 2 NAN YA's 1 oz copper foils, then hot-pressed under the condition of 30 kg/cm2 (426 psi), 195° C. for 3 hours to obtain a circuit board composite, the tested physical properties are listed in Table 1.
Increasing of COC-A dose can raise peeling strength slightly and decrease hygroscopic (moisture absorbance); if the low molecular weight polybutadiene rubber Ricon153 (molecular weight MW<5,000) is used to replace Ricon154 resin, there is no significant effect shown, but if RB810 (MW>5,000) is substituted, the peeling strength is deteriorated, and the heat resistance at tin welding is obviously not enough. As shown in Table 1, the incorporation of SARET633 (the dose thereof is 5 phr of the thermosetting resin) can improve the peeling strength, in other words, if SARET633 is not added, the peeling strength becomes worse.
The dose of fillers is reduced. 141.5 parts by weight of RB810, 75.9 parts by weight of Ricon154, 85.4 parts by weight of COC-A and 14.9 parts by weight of CTBN1300×8 are mixed homogeneously; then 15.9 parts by weight of SARET 633, 341.6 parts by weight of FB-35 filler, 194.7 parts by weight of SAYTEX8010, 9.5 parts by weight of TAIC and 9.5 parts by weight of DCP are added sequentially, and mixed homogeneously, 111.0 parts by weight of 1080 woven glass is impregnated therein and at 130° C., they are semi-hardened to form a prepreg. 8 sheets of prepreg are laminated, and sandwiched in 2 NAN YA's 1 oz copper foils, then hot-pressed under the condition of 30 kg/cm2 (426 psi), 195° C. for 3 hours to obtain a circuit board composite, the tested physical properties are listed in Table 2.
The dose of COC-A is elevated to replace part of RB810, i.e. 98.8 parts by weight of RB810, 75.9 parts by weight of Ricon154, 128.1 parts by weight of COC-A and 14.9 parts by weight of CTBN1300×8 are mixed homogeneously; then 15.9 parts by weight of SARET633, 341.6 parts by weight of FB-35 filler, 194.7 parts by weight of SAYTEX8010, 9.5 parts by weight of TAIC and 9.5 parts by weight of DCP are added sequentially, and mixed homogeneously, 111.0 parts by weight of 1080 woven glass is impregnated therein and at 130° C., they are semi-hardened to form a prepreg. 8 sheets of prepreg are laminated, and sandwiched in 2 NAN YA's 1 oz copper foils, then hot-pressed under the condition of 30 kg/cm2 (426 psi), 195° C. for 3 hours to obtain a circuit board composite, the tested physical properties are listed in Table 2.
The dose of COC-A is reduced and replaced by increasing RB810 content, i.e. 184.2 parts by weight of RB810, 75.9 parts by weight of Ricon154, 42.7 parts by weight of COC-A and 14.9 parts by weight of CTBN1300×8 are agitated homogeneously; then 15.9 parts by weight of SARET633, 341.6 parts by weight of FB-35 filler and 194.7 parts by weight of SAYTEX8010, 9.5 parts by weight of TAIC and 9.5 parts by weight of DCP are added sequentially, and mixed homogeneously, 111.0 parts by weight of 1080 woven glass is impregnated therein and at 130° C., they are semi-hardened to form a prepreg. 8 sheets of prepreg are laminated, and sandwiched in 2 NAN YA's 1 oz copper foils, then hot-pressed under the condition of 30 kg/cm2 (426 psi), 195° C. for 3 hours to obtain a circuit board composite, the tested physical properties are listed in Table 2.
Ricon153 resin is used to replace Ricon154 resin, i.e. 141.5 parts by weight of RB810, 75.9 parts by weight of Ricon153, 85.4 parts by weight of COC-A, 14.9 parts by weight of CTBN1300×8 are agitated homogeneously; then 15.9 parts by weight of SARET 633, 341.6 parts by weight of FB-35 filler, 194.7 parts by weight of SAYTEX8010, 9.5 parts by weight of TAIC and 9.5 parts by weight of DCP are added sequentially, and mixed homogeneously, 111.0 parts by weight of 1080 woven glass is impregnated therein and at 130° C., they are semi-hardened to form a prepreg. 8 sheets of prepreg are laminated, and sandwiched in 2 NAN YA's 1 oz copper foils, then hot-pressed under the condition of 30 kg/cm2 (426 psi), 195° C. for 3 hours to obtain a circuit substrate composite, the tested physical properties thereof are listed in Table 2.
No SARET 633 is added. 143.8 parts by weight of RB810, 77.1 parts by weight of Ricon154, 86.8 parts by weight of COC-A and 15.1 CTBN1300×8 are agitated homogeneously; then 347.1 parts by weight of FB-35 filler, 197.9 parts by weight of SAYTEX8010, 9.7 parts by weight of TAIC and 9.7 parts by weight of DCP are added sequentially, and mixed homogeneously, 112.8 parts by weight of 1080 woven glass is impregnated therein and at 130° C., they are semi-hardened to form a prepreg. 8 sheets of prepreg are laminated, and sandwiched in 2 NAN YA's 1 oz copper foils, then hot-pressed under the condition of 30 kg/cm2 (426 psi), 195° C. for 3 hours to obtain a circuit board composite, the tested physical properties are listed in Table 2.
Following the same steps as Example 5, but Ricon153 is used to replace RB810.
The dose of fillers is reduced 25 wt %, and the brominated flame retardant agent content is raised to meet the requirement of flame retardant of circuit board substrate. 164.1 parts by weight of RB810, 88.1 parts by weight of Ricon154, 99.0 parts by weight of COC-A and 16.6 parts by weight of CTBN1300×8 are agitated homogeneously; then 18.4 parts by weight of SARET633, 254.7 parts by weight of FB-35 filler, 225.5 parts by weight of SAYTEX8010, 11.1 parts by weight of TAIC and 11.1 parts by weight of DCP are added sequentially, and mixed homogeneously, 111.0 parts by weight of 1080 woven glass is impregnated therein and at 130° C., they are semi-hardened to form a prepreg. 8 sheets of prepreg are laminated, and sandwiched in 2 NAN YA's 1 oz copper foils, then hot-pressed under the condition of 30 kg/cm2 (426 psi), 195° C. for 3 hours to obtain a circuit board composite, the tested physical properties are listed in Table 2.
To raise the contents of thermosetting resin and SARET633 (the amount used is 5 phr of thermosetting resin) can improve the peeling strength and lower the dielectric constant; but if the filler content is under 30 wt % of total composition, both heat resistance and flame retardant become worse.
Following the steps of Example 1-8, the only difference is that COC-A is replaced by COC-B; the tested physical properties of circuit board composite are listed in Tables 3 & 4.
Following the steps of Comparative example 1-5, the only difference is that COC-A is replaced by COC-B; the tested physical properties of circuit board composite are listed in Tables 3 & 4.
Following the steps of Example 1-8, the only difference is that COC-A is replaced by COC-C; the tested physical properties of circuit board composite are listed in Tables 5 & 6.
Following the steps of Comparative example 1-5, the only difference is that COC-A is replaced by COC-C; the tested physical properties of circuit board composite are listed in Tables 5 & 6.
The change of the kind of cycloolefin copolymer in the thermosetting composition has little effect on dielectric constant and dissipation factor, but COC-C with longer chain branching shows better toughness, more rubber-like property and superior heat resistance at tin soldering than those of COC-B, while COC-A with no chain branching is the worst. Nevertheless, the longer the chain branching of cycloolefin copolymer, results in the more the hygroscopic and the worse the peeling strength.
According to the examples and the tested physical properties mentioned above, the following summaries are concluded:
According to above statements, and as compared with a traditional copper foil laminate, the printed circuit board (PCB) in the present invention shows better electrical properties, i.e. lower dielectric constant and dissipation factor, also a lower moisture absorbance (hygroscopic).
Regarding the peeling strength, even if an ordinary copper foil is used in the present invention, the peeling strength can be up to 4 lbf/inch, which is much better than 0.25 lbf/inch shown in a traditional copper foil PCB substrate. In addition, the product in the present invention shows a better heat resistance, and the hot pressing temperature is only 195° C., i.e. a high temperature (over 250° C.) is not necessary during curing processing, thereby results in the physical properties of PCB substrate to be extremely superior.
Although the preferable embodiments of the present invention are disclosed as above, the scopes of them are not restricted therein; any skilled one can modify and revise the practice of the present invention. All of these modifications and revisions still belong to the attached claims of the invention.
