Background technology
No matter the flexible circuit board of prior art is single sided board, double sided board or multi-panel, generally all adopts copper material or Cu alloy material as wiring material layer.For example, in traditional double-faced flexible wiring board, as shown in Figure 1, the structure of its flexible circuit board is, the centre is a layer insulating 6 (for example being made by typical PI material), is respectively equipped with the line layer 3,7 that Copper Foil is made on the two sides of insulating barrier, the outside at this two-layer line layer is respectively equipped with the covering rete 5,5 that (for example mode of bonding, coating, coating or printing) play protective action (be typically CVL or relevant can resistant to elevated temperatures PVC class insulating material).
The defective of the flexible circuit board of this prior art is many-sided.
For example, Copper Foil is very high as its material cost of wiring material layer, and the cost of raw material of copper material will be more and more higher, so the cost of traditional circuit plate is very high.Even some manufacturer is in order to save material cost, copper thickness is reduced, but material cost is still high, does like this service behaviour that copper thickness is excessively reduced and cause affecting wiring board, for example reliability, intensity, conductivity, thermal diffusivity etc.
The more important thing is that the solder joint on the line layer of this flexible circuit board (or title " pad ") obviously also is the brazing point.If this brazing point is exposed to meeting oxidation within very short time in the air ambient, so that in the technique of follow-up welding electronic component, affect its solderability, for example can cause after solder joint sealing-off, the welding poorly conductive, solder bond intensity is low even do not weld, etc.For this reason; in the prior art; the manufacturer usually understands butt welding point and carries out Passivation Treatment with chemical method; but; the effect of this Passivation Treatment is still bad; brazing point after the passivation still can severe oxidation after the long period in being exposed to air, solderability and the soldering reliability of impact welding procedure subsequently.In the practice of prior art, because the brazing point solderability of flexible circuit board is poor, causing the problems of welded quality of application product such as LED lamp band, LED module etc., and then affect the situation in rate of finished products, reliability and the useful life of application product, is very general.
Therefore, have flexible circuit board and a manufacture craft thereof that is coated with tin welding spot in the urgent need to a kind of in this area, with alleviate or even avoid defects, and reduce product cost.
Summary of the invention
In view of the above, the utility model has been proposed.The utility model is intended to solve above technical problem with other.
According to the utility model, a kind of flexible circuit board that is coated with tin welding spot that has is provided, comprising: the metallic circuit layer, described metallic circuit layer is provided with solder joint; Cover on the described metallic circuit layer but do not cover coverlay or the welding resistance printing ink of described solder joint, wherein, described solder joint is applied with the tin layer on the surface.
According to a preferred embodiment of the present utility model, described metallic circuit layer is the aluminum or aluminum alloy line layer.
According to another preferred embodiment of the present utility model, described metallic circuit layer is aluminium foil layer, alloy foil layer, aluminium alloy conductor layer or aluminum conductor layer.
According to another preferred embodiment of the present utility model, described metallic circuit layer is copper foil layer, copper alloy foil layer, copper alloy wire layer, copper conductor layer, aluminium nickel coat, copper-clad nickel dam, iron layer or steel layer.
According to another preferred embodiment of the present utility model, described tin layer is the tin cream of printing or the tin layer of immersion plating.
According to another preferred embodiment of the present utility model, the thickness of described metallic circuit layer is the 10-1000 micron.
According to another preferred embodiment of the present utility model, the thickness of described metallic circuit layer is the 50-500 micron.
According to another preferred embodiment of the present utility model, the thickness of described metallic circuit layer is the 100-200 micron.
According to another preferred embodiment of the present utility model, described flexible circuit board is single-sided flexible circuit board or double-faced flexible wiring board.
The utility model also provides a kind of LED lamp band, and it comprises according to flexible circuit board of the present utility model and is welded on LED on the described solder joint.
Flexible circuit board of the present utility model has been because its solder joint has passed through and has been coated with tin and processes, so its non-oxidizability and solderability improve greatly, and its material cost and cost of manufacture can reduce greatly, thereby improved reliability and the yields of wiring board product.
In following description to the drawings and specific embodiments, will set forth one or more embodiments of the detail of the present utility model.From these descriptions, accompanying drawing and claim, can know other features, objects and advantages of the present utility model.
Embodiment
The below will be described in more detail the utility model.
The single face (being the side of mounting related components) that term " one-sided circuit board " only refers at this wiring board is provided with circuit.
Term " double-sided wiring board " refers on the two sides of this wiring board and all is provided with circuit.
Before describing the utility model in detail, those skilled in the art are to be understood that, " components and parts " should do the understanding on the most wide in range connotation in this application, the components and parts that namely comprise all types of electronic devices and components for circuit, electric components or other type, various resistance for example, the components and parts of various surface mount (SMT) type, the components and parts of support rack type, various high power devices etc., comprise great power LED, etc.
In addition, term " wiring board " and " circuit board " can use interchangeably in the application.
Be described in further detail below in conjunction with manufacturing process and the structure of drawings and Examples to flexible circuit board of the present utility model.
The related materials of flexible circuit board
The raw material volume of traditional double-faced flexible wiring board is also referred to as the coiled material of copper-clad plate.As shown in Figure 1, Fig. 1 is the partial section of the flexible circuit board of prior art, has shown the structure of the flexible circuit board of prior art.In the structure of this flexible circuit board, typical structure is five layers, namely, two-layer line layer 3,7 (modal is to adopt Copper Foil, can be described as again in the present embodiment and covers copper layer or Copper Foil, and these terms use sometimes interchangeably), and be bonded in insulating barrier 6 between this two-layer line layer 3,7.Insulating barrier 6 has formed the basal layer of flexible circuit.The outside at this two-layer line layer 3,7 is respectively equipped with the covering rete 5,5 that (for example mode of bonding, coating, coating or printing) plays protective action, and this covering rete for example can be made by CVL.
Certainly, although not shown in Fig. 1, in fact, usually can be respectively equipped with adhesive layer at two-layer line layer 3,7 with insulating barrier 6, be used for line layer and insulating barrier are glued together.Therefore, under a lot of situations, this flexible circuit board structure of prior art is actually seven layers complicated structure.
The material of insulating barrier 6 has many kinds, and wherein the most commonly used is polytetrafluoroethylene, polyimides, polyester and PI (PI) material.Polyimide material has non-flammable, physical dimension is stable, has higher tensile strength, and the ability with the welding temperature of bearing, polyester is also referred to as PETG (being called for short PET), its physical property is similar to polyimides, have lower dielectric constant, the humidity of absorption is very little, but non-refractory.Polyester presents rigidity in cryogenic applications.These materials all can be used for forming insulating barrier.
In traditional prior art, generally all adopt Copper Foil as the line layer in the flexible circuit.It can adopt the mode of electro-deposition (ED), forging (RA).Copper Foil is the material with compliance, can be made into many kinds of thickness and width.The Copper Foil of forging also has the level and smooth characteristics of hard except having pliability, it is suitable for being applied among the occasion that requires dynamic deflection.
In the prior art, adoptable material is fine copper or copper alloy aborning at present, zinc yellow copper for example, and the thickness of Copper Foil is more than the 10Z.If the employing fine copper, then the General Requirements of fine copper is T2 copper.The requirement of copper alloy is generally Tp2 or copper content more than 20%, and remaining composition can be zinc (Zn) or other trace additives.
Fig. 2 also is the partial section of the single-sided flexible circuit board of prior art, has shown the structure of the single-sided flexible circuit board of prior art, comprises copper foil circuit layer 8 and covers copper foil circuit layer 8 double- edged coverlay 5,5.
Although Fig. 1 of prior art and Fig. 2 do not show, those skilled in the art know, are exposed to solder joint (pad) in the air ambient what the copper foil circuit layer was provided with that some not coating epiphragmas cover, are used for welding electronic component and/or circuit.
Fig. 3 has shown the front schematic view of single or double flexible circuit board, has shown the coverlay 5 that has covered the copper foil circuit layer and solder joint 2 that the not coating epiphragma 5 that exposes covers.
The main design of flexible circuitry panel products of the present utility model and technique
According to the utility model, the solder joint (pad) that is exposed in the air ambient on the copper foil circuit layer of prior art is carried out the coating processing, apply in the above the coat of metal that one deck is difficult for oxidation and has good solderability.Like this, both can omit passivation process step of the prior art, and can provide superior solderability for wiring board again.
Exemplary technological process
The general fabrication processing that those skilled in the art will appreciate that the flexible circuit board of prior art is known, does not therefore give unnecessary details one by one, and the main inventive concept of flexible circuit board of the present utility model concentrates in the processing of butt welding point.
Below in conjunction with single-sided flexible circuit board the utility model is described.
According to one preferably but do not have restrictive execution mode, the manufacture craft of single-sided flexible circuit board of the present utility model is as follows:
Wall scroll aluminum or aluminum alloy wire (for example flat conductor) is provided, and it will be as the line layer 8 of wiring board; Line layer is carried out cross cutting or die-cut, form a plurality of otch (for example otch shown in Figure 3), thereby form corresponding a plurality of part of path 8, so just between adjacent part of path 8, formed the disconnection of circuit.Like this, by between adjacent part of path 8 at pad locations burn-on LED and/or other components and parts, just can form the coupled in series of circuit; Stick reverse side coverlay 5 and carry out pressing at this finished reverse side with line layer of a plurality of part of paths 8; Be provided at the front coverlay 5 of windowing in pad 2 places, then at the positive contraposition applying front of line layer 8 coverlay 5 and carry out pressing, so just can obtain the single-sided flexible circuit board of exposed pad 2.
As mentioned above, substitute Copper Foil as wiring material layer with aluminium or aluminium alloy (or aluminium foil) as line material, not only can guarantee the satisfactory electrical conductivity of circuit, more crucial a bit is greatly to reduce the material cost of wiring board.For example, the material cost of aluminum wiring board will be the copper foil circuit plate 1/4th or even lower.
Certainly, those skilled in the art obviously are appreciated that and also can adopt other material to be used as the material of line layer, for example iron, steel etc., and these all belong to scope of the present utility model.
Certainly, those skilled in the art it is also understood that, also can not change the copper foil material of the line layer of traditional flexible circuit board, just improveing the zinc-plated processing of being coated with of solderability with butt welding point replaces traditional Passivation Treatment, so also can realize the purpose of improving the solder joint solderability of the present utility model.These also all belong to scope of the present utility model.
The below introduces pad 2 is coated with zinc-plated processing.
According to a preferred embodiment, after coverlay 5 is all sticked on line layer 8 two sides, be coated with zinc-plated treatment process on pad 2 surfaces that expose, for example adopt the mode of silk screen printing to print the last layer tin cream, perhaps adopt the mode immersion plating last layer tin layer of hot-dip.Because tin has superior solderability, conductivity and good non-oxidizability, therefore just can obtain non-oxidizability and solderability and all obtain the pad 2 improved, thereby obtain the improved flexible circuit board of solderability.
According to another preferred embodiment, also can be after coverlay 5 be sticked at the back side of line layer 8, the wiring board that face exposure is gone out whole line layer 8 carries out zinc-plated processing or print solder paste, then take out, the coverlay of windowing is in advance sticked in the positive contraposition of wiring board after processing, like this, pad 2 surfaces that expose also have the tin layer.
According to another preferred embodiment, also can directly replace coverlay 5 with the mode of printing welding resistance printing ink.That is, after line layer 8 two-face printing welding resistance printing ink, print solder paste or immersion tin on the pad 2 that exposes.Perhaps, behind the back up welding resistance printing ink of line layer 8, the wiring board that face exposure is gone out whole line layer 8 carries out print solder paste or immersion tin, and then at the positive printing of wiring board welding resistance printing ink so that on the positive pad 2 that exposes also the surface also have the tin layer.
Afterwards, as required, carry out conventional baking-silk-screen-electrical measurement-anti-oxidation-profile-FQC-packing-shipment etc. operation, just can obtain single-sided flexible circuit board of the present utility model.
According to another preferred embodiment, the thickness of the utility model line layer is preferably the 50-500 micron in the scope of 10-1000 micron, more preferably at the 100-200 micron.
This structure of the present utility model and manufacture craft are improved solderability and non-oxidizability so that can greatly reduce material cost and production cost, improve reliability and conductivity.
According to a preferred embodiment of the present utility model, the components and parts that mount or carry at flexible circuitry panel products of the present utility model can comprise all kinds of LED and resistance.For example, the model of preferred LED can comprise: 335,3528,5050,5060, etc.The model of preferred resistance can comprise as follows: 0603,0805,0812, etc.
Obviously, this area designer is appreciated that fully that according to different application scenarios and customer requirement flexible circuitry panel products of the present utility model can comprise various types of LED, resistance and other components and parts etc.
Above by the agency of specific embodiment of the utility model.Yet should be appreciated that under the prerequisite that does not break away from spirit and scope of the present utility model, can carry out various modifications.Therefore, other embodiment also belongs to the protection range of claim of the present utility model.Therefore the utility model is not limited to disclosed the drawings and specific embodiments, and scope of the present utility model is limited by claim.