[background technology]
Because flexible printed circuit board is to highdensity trend development, control to the excessive glue amount of the impression of PCB surface and coverlay also more is tending towards strict, and along with the variation in market, the demand of flexible circuit board also progressively improves, so the also lifting thereupon of requirement to production capacity in its processing factory.Process for pressing is an important process during flexible circuit board is produced, and it is a kind of process (as bonding copper-clad plate and coverlay) that each layer loose mail is bonded into integral body by adhesive (as B-Stage semi-solid preparation resin) under the condition of HTHP with molecular link.Temperature, pressure curve such as Fig. 1 of this whole pressing process, wherein the A curve is the time dependent curve of temperature, and the B curve is the time dependent curve of pressure, and the T0 moment and T1 are the increasing temperature and pressure process constantly, the resin of semi-solid preparation is got back to fluid state after absorbing heat reduction viscosity; Along with the rising of temperature, pressure, the resin that changes fluid into flows toward the pressure lower under suppressing, to filling fully in inner plating face Wu Tong district; The T1 moment and T2 are the HTHP process constantly, liquid adhesive is after absorbing a large amount of heats, polymerization reaction and its viscosity occur also strengthens thereupon gradually, slowly be solidified into hard macromolecule state, curing cross-linking reaction to adhesive is complete, thereby with the form realization adhesive of chemical bond and combining of loose mail; T2 constantly and T3 be the cooling high-pressure process constantly, finish the product after bonding, also need under the situation of high pressure, lower the temperature, to avoid causing the product distortion because of instantaneous temperature reduction.The main evaluating of process for pressing process is: the presentation quality of overflow glue amount, the interlayer temperature difference, peel strength and product.
The test and the computational methods of the glue amount of overflowing are as follows: be placed on each one of the superiors, middle level and undermost flexible print circuit board respectively after pressure is closed, the maximum distance that overflows and locate to glue in the edge of opening place that measurement amount flexible circuit board surface coverage film is washed open under 100 times metallomicroscope, every all measure up and down in five fixing positions, five groups of data are all got in each position, and the mean value of getting 75 groups of data that obtained is the excessive glue amount after the pressing.
The method of testing of the interlayer temperature difference is as follows: adopting diameter is the material temperature line six roots of sensation of 3mm, and one is connected on the superiors respectively, in the central authorities and edge of middle level and orlop flexible circuit board, and two every layer; The other end is connected on the warm tester of material, and in the process of pressing, temperature writes down the data that each layer reaches maximum temperature by expecting that warm line is converted to the signal of telecommunication and demonstrates data, calculates the maximum temperature difference and promptly is defined as the interlayer temperature difference.
Existing compression method, and is equipped with the supporting bracket of the good diffusion barrier of separating property and fillibility, high rigidity and has the resilient coating of heat insulation withstand voltage properties as the auxilliary material of main filling with silicane rubber plate, carries out hot pressing in the vacuum hotpressing machine.Silicane rubber plate is a coating silicon rubber and be prepared from by hot pressing is crosslinked on glass fabric, be suitable for use on the resilient coating of pressing, it has following advantage: buffering effect is strong, the serviceability temperature scope is wide, thermal endurance is good, be fit to that high temperature uses, release is good and adhere after come off easily.
Yet, with the silicane rubber plate is that main compression method of filling auxilliary material has following shortcoming: 1) the silicane rubber plate access times are generally at about 300-500 time, the cost height, and silicane rubber plate is in its poor flatness after pressing repeatedly, wayward in the production process, easily cause the excessive glue amount of pressing product inhomogeneous; 2) silicane rubber plate poorly conductive, because material fricative static in the pressing process is difficult to eliminate, the flying dust in the absorbed air causes silicane rubber plate contaminated easily easily, causes the surface indentation of product to increase in the process of pressing; 3) silicane rubber plate thickness is thicker, and heat insulation and slow pressure effect is too strong, causes the interlayer temperature difference serious, and influences pressing lamination level, makes the pressing inefficiency.
[summary of the invention]
The object of the present invention is to provide a kind of packed layer that can reduce the compression method of the little flexible circuit board of PCB surface impression and excessive glue amount and be exclusively used in this method.
The object of the present invention is achieved like this: a kind of compression method of flexible print circuit board, it is characterized in that: all order is placed diffusion barrier and supporting bracket in the upper and lower both sides of copper-clad plate, side at the copper-clad plate copper face is placed packed layer and resilient coating in proper order between diffusion barrier and supporting bracket and to the supporting bracket direction, to form a lamination unit, and to this lamination unit hot pressing, coverlay is adhesive in the copper-clad plate, wherein, packed layer adopt have good coating property, fluidity is low and cooling procedure in the little material of contraction change.
Described packed layer adopts thermoplastic material.
Described thermoplastic material is selected from: high density polyethylene (HDPE), low density polyethylene (LDPE), LLDPE, haloflex, polyvinyl chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene propylene copolymer and ethylene acrylate copolymer
The scope of the thickness of described packed layer is 0.05mm-0.4mm.
The scope of the fusing point of material that described packed layer adopts is 80~150 degree.
Described diffusion barrier is selected from: single face is coated with silicon PET film, polypropylene screen and poly-methylpent film.
A kind of packed layer that is exclusively used in flexible circuit board pressing, its adopt have good coating property, fluidity is low and cooling procedure in the little material of contraction change.
Compared with prior art, the present invention has following advantage: the material of this packed layer has high fillibility, the glue amount of overflowing is reduced, and can make the excessive glue amount of each time pressing even, simultaneously because this packed layer is a medical disposable material, be not easy contaminated, thereby can effectively avoid the surface of copper-clad plate to produce impression.
[embodiment]
See also Fig. 2, the compression method of a kind of flexible circuit board of the present invention is to be used for coverlay is pressed together on copper-clad plate, be provided with adhesive between this coverlay and the copper-clad plate, the hot pressing by the vacuum hotpressing machine makes bonding with the form realization of chemical bond and coverlay and copper-clad plate of this adhesive.This compression method is as follows: all order is placed diffusion barrier and supporting bracket in the upper and lower both sides of copper-clad plate, side at the copper-clad plate copper face is placed packed layer and resilient coating in proper order between diffusion barrier and supporting bracket and to the supporting bracket direction, to form a lamination unit, and to this lamination unit hot pressing, coverlay is pressed together in the copper-clad plate, wherein, packed layer by have good coating property, fluidity is low and cooling procedure in the little thermoplastic material of contraction change make.
When this copper-clad plate is single face, only need packed layer 4 and resilient coating 3 be set order between the diffusion barrier 8 of this copper-clad plate 7 copper faces one side (side that coverlay is promptly arranged) and supporting bracket 1, promptly described lamination unit order from the bottom to top is: supporting bracket 1, resilient coating 3, packed layer 4, diffusion barrier 8, coverlay 2, copper-clad plate 7, diffusion barrier 6 and supporting bracket 5.
When this copper-clad plate is double sided board, need packed layer and resilient coating all be set in the both sides of copper-clad plate between diffusion barrier and supporting bracket, promptly described lamination unit order from the bottom to top is: supporting bracket, resilient coating, packed layer, diffusion barrier, coverlay, copper-clad plate, coverlay, diffusion barrier, packed layer, resilient coating and supporting bracket.
This supporting bracket is made by hardness height, thermal conductivity synthetic steel good, that evenness is high, and this supporting bracket does not have specific (special) requirements to thickness, and pressure suffered when it is mainly used to guarantee evenness and guarantees copper-clad plate hot pressing is even.
This resilient coating material high by gas permeability and that have certain heat-proof quality and a withstand voltage properties is made, as brown paper etc.This resilient coating does not directly touch flexible circuit board, and it is located at the side that copper-clad plate has copper face.When copper-clad plate was single face, this resilient coating was located at this copper face one side, and when copper-clad plate when being two-sided, this resilient coating is located at this copper-clad plate both sides.
This diffusion barrier by the temperature tolerance height, separating property is good and material that fillibility is good is made, it is coated with silicon PET film, polypropylene screen or polymethylpentene etc. as single face.
Good coating property, fluidity are low by having for this packed layer, the little thermoplastic material of contraction change is made in the cooling procedure, this material is selected from: high density polyethylene (HDPE), low density polyethylene (LDPE), LLDPE, haloflex, polyvinyl chloride, polyvinyl alcohol (EVA), ethylene-vinyl alcohol copolymer, ethylene propylene copolymer and ethylene acrylate copolymer.The scope of the thickness of this packed layer is 0.05mm-0.4mm, the scope of its fusing point is 80~150 ℃, when temperature in the hot pressing reaches the fusing point of this packed layer material and does not reach the high pour point of adhesive (as epoxy resin) as yet, packed layer i.e. fusing fully, thereby have high fillibility, can realize effective control the excessive glue amount of flexible circuit board surface coverage film; Above-mentioned on the other hand packed layer material cost is lower, for disposable use consumptive material, is not prone to contaminated phenomenon, thereby can effectively avoid the impression on copper-clad plate surface; In addition, because the thickness of above-mentioned filling layered material only is 1/5~1/40 of silicane rubber plate thickness, therefore can reduce the height of each lamination unit, on short transverse, make in the vacuum hotpressing machine, disposablely to stack the more lamination unit of more number, thereby improved production efficiency greatly.
Now be that example illustrates compression method of the present invention with the single-side coated copper plate:
Embodiment 1:
Lamination unit composed as follows: supporting bracket adopts the mirror steel plate of hardness between RC44-45; Diffusion barrier uses polypropylene screen, and its thickness is 50um; Resilient coating is a brown paper, and its density is 0.19kg/cm
3Packed layer is a polyethylene film, and its thickness is 0.12mm; Copper-clad plate is platform rainbow XSIR050513HJY, and its thickness is 44um; Coverlay is platform rainbow FD0525HL, and its thickness is 38um.With this lamination unit at 170 ℃ of high temperature, high pressure 25kg/cm
2, pressing time is to carry out pressing under 90 minutes the condition.
Embodiment 2:
This lamination unit composed as follows: supporting bracket adopts the mirror steel plate of hardness between RC44-45; Diffusion barrier uses single face to be coated with silicon PET film, and its thickness is 50um; Resilient coating is a brown paper, and its density is 0.19kg/cm
3Packed layer is the EVA film, and model is Hyundai Pertochemical EF440, and thickness is 0.06mm; Copper-clad plate is platform rainbow XSIR050513HJY, and thickness is 44um; Epiphragma is platform rainbow FD0525HL, and thickness is 38um.With this lamination unit at 170 ℃ of high temperature, high pressure 25kg/cm
2, pressing time is to carry out pressing under 90 minutes the condition.
Embodiment 3
This lamination unit composed as follows: supporting bracket adopts the mirror steel plate of hardness between RC44-45; Diffusion barrier uses single face to be coated with silicon PET film, and its thickness is 50um; Resilient coating is a brown paper, and its density is 0.19kg/cm
3Packed layer is the EVA co-polymer membrane, and model is Huntsman PE11207, and thickness is 0.1mm; Copper-clad plate is platform rainbow XSIR050513HJY, and thickness is 44um; Coverlay is platform rainbow FD0525HL, and thickness is 38um.With this lamination unit at 170 ℃ of high temperature, high pressure 25kg/cm
2, pressing time is to carry out pressing under 90 minutes the condition.
Embodiment 4
This lamination unit composed as follows: supporting bracket adopts the mirror steel plate of hardness between RC44-45; Diffusion barrier uses single face to be coated with silicon PET film, and thickness is 50um; Resilient coating is a brown paper, and its density is 0.19kg/cm
3Packed layer is the ethylene butyl acrylate co-polymer membrane, and its model is Atofina 7BA01, and its thickness is 0.2mm; Copper-clad plate is platform rainbow XSIR050513HJY, and thickness is 44um; Coverlay is platform rainbow FD0525HL, and thickness is 38um.With this lamination unit at 170 ℃ of high temperature, high pressure 25kg/cm
2, pressing time is to carry out pressing under 90 minutes the condition.
For comparative descriptions effect of the present invention, existing flexible circuit board with existing method pressing is that example describes, and its method is as follows:
Comparative example 1:
This lamination unit composed as follows: supporting bracket adopts the mirror steel plate of hardness between RC44-45; Diffusion barrier uses polypropylene screen, and its thickness is 50um; Resilient coating is a brown paper, and its density is 0.19kg/cm
3Packed layer is the thick silicane rubber plate of 2mm; Copper-clad plate is platform rainbow XSIR050513HJY, thick 44um; Epiphragma is platform rainbow FD0525HL, and thickness is 38um.With this lamination unit at 170 ℃ of high temperature, high pressure 25kg/cm
2, pressing time is to carry out pressing under 90 minutes the condition.
Comparative example 2
This lamination unit composed as follows: supporting bracket adopts the mirror steel plate of hardness between RC44-45; Diffusion barrier uses single face to be coated with silicon PET film, and its thickness is 50um; Resilient coating is a brown paper, and its density is 0.19kg/cm
3Packed layer is the thick silicane rubber plate of 2mm; Copper-clad plate is platform rainbow XSIR050513HJY, and thickness is 44um; Epiphragma is platform rainbow FD0525HL, and thickness is 38um.With this lamination unit at 170 ℃ of high temperature, high pressure 25kg/cm
2, pressing time is to carry out pressing under 90 minutes the condition.
The comparative result of embodiments of the present invention and comparative example is as follows:
The test result of table 1, the glue amount of overflowing
|
Embodiment 1 |
Embodiment 2 |
Embodiment 3 |
Embodiment 4 |
Comparative example 1 |
Comparative example 2 |
Excessive glue amount |
0.10mm |
0.11mm |
0.09mm |
0.10mm |
0.14mm |
0.15mm |
Table 2, interlayer differential temperature survey result
Temperature |
The upper strata temperature |
The intermediate layer temperature |
Near-bottom temperature |
Maximum temperature difference |
Embodiment 1 |
162℃ |
160℃ |
164℃ |
4℃ |
Comparative example 1 |
160℃ |
138℃ |
163℃ |
25℃ |
As from the foregoing, since the material of packed layer of the present invention adopt have good coating property, fluidity is low, the little thermoplastic material of contraction change is made in the cooling procedure, so have the advantage that excessive glue amount is little and interlayer has a narrow range of temperature.