Background technology
Flexible printed wiring board (Flexible Printed Circuit, FPC) be to be that basic material combines by having flexual insulating body and Copper Foil, in order to carry various actives and passive device, after assembling, can be applicable to IT periphery, information, consumption electronic products etc., especially in the related application of mobile phone and LCD, quite high growth is arranged.Because a large amount of flexible printed wiring boards that use in the new-type electronic products such as mobile phone, display, mobile phone has become one of considerable downstream application product of flexible printed wiring board.
For mobile phone, the demand of characteristic such as (for example folding, rotation, slip lid etc.), volume be little, in light weight because colored, distinctive appearance its employed circuit board is not only significantly increased in quantity, and the functional requirement of each circuit board is also inequality.With regard to the configuration design demand of mobile phone, be gradually varied to clamshell phone, cover-slide-type handset or rotary mobile phone by in the past stand hand-set, its common point is to increase the anti-flexible printed wiring board of destroying or force to yield and can transmit a large amount of signals in the turning point.
Generally speaking, flexible printed wiring board can be divided into the double-decker that three ply board that glue system is arranged and no glue are according to its architectural difference.Usually, double-deck flexible printed wiring board can be applicable to high-density line and performance requirement high product.Moreover, owing to advantages such as the thickness of double-deck flexible printed wiring board are less relatively, and it is little to have bounce, and pliability is good, become another major product of flexible printed wiring board gradually.
Flexible printed wiring board mainly is that flexible copper foil substrate (FCCL) forms in conjunction with cover layer (Coverlay), and its copper clad laminate then comprises Copper Foil metal level and insulating body two parts.The Copper Foil that is used as metal level can be divided into rolled copper foil (Rolled Annealed Copper, RA) or electrolytic copper foil (Electrodeposited, ED) two kinds, lower but the lattice variations of the manufacturing cost of electrolytic copper foil has different othernesses with property very, is easy to generate shortcoming cracked or fracture behind the circuit etching.On the other hand, rolled copper foil flexible preferable is suitable for flexible printed wiring board, and manufacturing cost is higher, but flexible preferable, is more suitable for flexible printed wiring board.Yet the thickness of rolled copper foil also has its restriction, is unfavorable for reducing the integrated circuit plate thickness.On the other hand, reduce the Copper Foil metal layer thickness, also may cause the difficulty of circuit design and processing except increasing cost.
Therefore, still need a kind ofly can reduce integrated circuit plate thickness, promote the soft board pliability, satisfy the demand of circuit spacing miniaturization, have the flexible printed wiring board of good intensity, electrical characteristic and dimensional stability.
Embodiment
Below will further specify the present invention, scope perhaps in it should not be construed as limiting the invention in any form by specific embodiment.
Fig. 1 is the instantiation of expression flexible printed circuit board structure of the present invention.This flexible printed wiring board 100 comprises insulating body 120, and these insulating body 120 surfaces are formed with patterned metal layer 140, and 160 of cover layers fixedly are covered in this pattern metal laminar surface by patterned metal layer surface glue adhesion coating 150.The example of this insulating body comprises, but non-polyester matrix, polyethylene terephthalate matrix, polyimide matrix or liquid crystal polymer (LCP) matrix, polyethylene cycloalkanes (PEN) matrix, epoxy resin/glass fabric (FR4) matrix or its mixture of being limited to is preferably polyimide matrix.
With regard to no glue is double-deck copper clad laminate structure, can utilize the squash type rubbing method polyimides predecessor polyamic acid or polyimides coating to be coated the extra thin copper foil metal surface of metal level raw material earlier, 50 to 350 ℃ closed nitrogen oven bakings 15 to 240 minutes, dehydrate with cyclisation or directly carry out drying, form thickness between 5 to 30 microns, be preferably between 6 to 10 microns polyimide film as insulating body.
Flexible printed wiring board of the present invention, it uses the copper metal as metal level, and the example comprises, but non-cathode copper, calendering copper or sputter/plating (the Sputtering and Plating) copper of being limited to.The thickness of this copper metal layer is preferably between 1 to 5 micron between 1 to 8 micron, is more preferred between 1 to 3 micron, for example the extra thin copper foil of 1,2,3,5,8 microns of used thicknesses.Shown in Fig. 2 a to Fig. 2 c, in this instantiation, use the metal level raw material 200 that comprises carrier 210, peel ply 220, reaches extra thin copper foil metal 230.After these extra thin copper foil metal 230 surfaces form polyimide film 240, carrier 210 and peel ply 220 are peeled off, shown in Fig. 2 b, promptly forming the no glue shown in Fig. 2 c is double-deck copper clad laminate 250.
Shown in Figure 1, in the flexible printed circuit board structure of the present invention, 160 of cover layers are fixedly to be covered in this pattern metal laminar surface by patterned metal layer surface glue adhesion coating 150.This tectal thickness is preferably between 4 to 6.5 microns between 3 to 10 microns, is more preferred between 4 to 4.5 microns.In this instantiation, use the aromatic polyamide film as ultra-thin cover layer, for example use the PPTA film as the coverlay in the flexible printed circuit board structure of the present invention, or use other to have height and peel off characteristics such as transition temperature and low-expansion coefficient, electric insulating quality is good, and thickness is no more than 10 microns, preferablely is no more than 6.5 microns, the better ultra-thin cover layer that is no more than 4.5 microns.
Flexible printed wiring board of the present invention is a used thickness between 3 to 10 microns ultra-thin cover layer, the collocation extra thin copper foil is as metal level, can make this flexible printed wiring board metal level, adhesive layer, and the cover layer gross thickness be no more than 16 microns, thereby have preferable flexibility and pliability, be particularly suitable for the slimming electronic product.
Embodiment
The flexibility test
Use device shown in Figure 3 to carry out
Test condition
Voltage: AC220V
Measuring range: 410 grams
Readable: 0.001 gram
Test R angle: 2.35mm
Testing procedure
1, adjusts two feets of tester, make air level be positioned at the leveling instrument center;
2, connect instrument power source, with the instrument zero clearing;
3, open glass door, (size 10mm * 30mm) end is fixed on the holder of pallet top, and the other end is stuck on the deck at pallet center, makes test piece become one " U " font, shuts glass door after finishing with test piece;
4, rotary apparatus right-hand member knob slowly counterclockwise slowly descends deck, contacts with following square washer until it, and the R of test piece at this moment angle is 2.35mm;
5, treat that indicator light is bright after, both can read contravariant power reading;
6, after test finishes, the knob dextrorotation to original position, is opened glass door, take off test piece;
7, repeat steps 3-6 suddenly, test other test pieces.
The flexibility test
Use device shown in Figure 4 to carry out
Test condition
Working voltage: AC220V
Test R angle: 1.0mm
Testing procedure
1, adjusts two feets of tester, test piece is fixed on the tester table;
2, connect instrument power source, with the instrument zero clearing;
Set: test condition:
Spacing H:2.0mm, place, R angle: 1.0mm
Frequency: 30 times/minute
Shift motion: 32mm
3, treat that indicator light is bright after, can write down the experimental test data;
4, after test finishes, the knob dextrorotation to original position, is taken off test piece;
5, repeat above-mentioned steps, test other test pieces.
Embodiment 1
The PPTA film (poly-paraphenyleneterephthalic amide film) that uses 4.2 microns is as cover layer, utilize the epoxy resin sticker that this PPTA thin-film covering layer is pasted the layer on surface of metal of the double-deck copper clad laminate of forming to sputter Copper Foil and polyimide insulative layer, form structure shown in Figure 1.Be cut into the flexible printed wiring board specimen 1 of 10mm * 30mm, carry out the test of flexibility and flexibility, repeat three times, calculating mean value, and in flexibility test back calculating resistance varying-ratio, test result is embedded in table 1.
Embodiment 2-5
Repeat embodiment 1, according to the thickness of listed adjustment thin-film covering layer of table 1 and copper metal layer.Be cut into the flexible printed wiring board specimen of 10mm * 30mm, carry out the test of flexibility and flexibility, repeat three times, calculating mean value, and in flexibility test back calculating resistance varying-ratio, test result is embedded in table 1.
Comparative example 1-3
Repeat embodiment 1, listed according to table 1, replace 4.2 microns PPTA film as cover layer with the polyimide film of 12 microns of thickness, utilize the epoxy resin sticker that this thin-film covering layer is pasted the layer on surface of metal of the double-deck copper clad laminate of forming to sputter Copper Foil and polyimide insulative layer, form structure shown in Figure 1.Be cut into the flexible printed wiring board comparative sample 1 of 10mm * 30mm, carry out the test of flexibility and flexibility, repeat three times, calculating mean value, and in flexibility test back calculating resistance varying-ratio, test result is embedded in table 1.
Table 1
|
Specimen 1 |
Specimen 2 |
Specimen 3 |
Specimen 4 |
Specimen 5 |
Comparative sample 1 |
Comparative sample 2 |
Comparative sample 3 |
A. overburden cover (micron) |
4.2 |
6.2 |
9 |
4.2 |
4.2 |
12.5 |
12.5 |
12.5 |
B. adhesive layer thickness (micron) |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
C. metal layer thickness (micron) |
1 |
1 |
1 |
3 |
5 |
1 |
3 |
5 |
A+b+c gross thickness (micron) |
10.2 |
12.2 |
15 |
12.2 |
14.2 |
18.5 |
20.5 |
22.5 |
Thickness of insulating layer (micron) |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
Flexibility (gf) |
3 |
5 |
8 |
5 |
10 |
12 |
12 |
13 |
Flexibility (ten thousand times) |
50 |
50 |
50 |
40 |
40 |
30 |
30 |
25 |
Show that according to table 1 result flexible printed wiring board of the present invention has preferable flexibility and flexibility, after the specimen test piece was carried out 400,000 times or simulated the flexibility test of slide phone slip up to 500,000 times, its circuit still can keep normal electrical property efficiency.
Above-mentioned specification and embodiment only are illustrative principle of the present invention and effect thereof, but not are used to limit the present invention.