created by mr. chris ahn rev.02 : 2004.oct. 12. * fpcb application
TRANSCRIPT
Created by Mr. Chris AHN
Rev.02 : 2004 .Oct . 12
* FPCB Application* FPCB Application
Product which has space problem, a kind of connector role when need electrical coupling in work segment.
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- Transfer way of electric currency - Space reduction by its Flexibility (As thickness of Cu is thin Flexibility improves)
- Excellent insulation ability - High dimensional stability and heat resistance, Excellent Flexibility
- Sensitive with thermal shock - According to acryl & epoxy Mixing rate, it’s divided into Acryl type & Epoxy type
- Essential element on assembly and connective area - Strengthen solder joints and increase abrasion resistance - it makes better handling during Assembly process
* FPCB Concept & Structure* FPCB Concept & Structure
1. Advantages and Disadvantages of Using FPCB1. Advantages and Disadvantages of Using FPCB
Advantages Disadvantages
* Possible to make more compact and light products* Possible flexibility and strong resistance against it* Light, thin, slim, only occupies small area - 25um of Base Film( Total thickness of 100~140um)* Possible for 3 dimensional wiring* Possible to omit for connector, wire and soldering (cost reduction) * Assembly of high density wires is possible* Less default for wiring* Easier Assembly* Higher reliability* Repeating manufacturing method is possible (Roll to Roll)
* Possible Stress on conductor* Easier scratch on PCB and inconvenient handling* If partial stress is concentrated, life-time would be shorten * Less mechanical strength * Difficult to do assembly with heavy weight parts* Low Bonding strength of copper * Higher price with Complex structure and long process * Difficult Design rule* Difficult to repair If there is a mistake on design* Can not use general soldering device* Total problem even though partial defect* Only possible for stiffener by manual process * Not stable sizes, it’s changeable with wiring design* Difficult for Inspection * Higher price than normal Rigid PCB
2. The standard for Using FPCB2. The standard for Using FPCB
* The improvement of Reliability
for Miss-wiring and connection
Price comparison
Functional comparison
Reliability comparison
* Size & weight of product are decided, work is available only by FPC
* High reliability and long-term
life cycle needs on such as Printer
Head/ magnetic head
* FPCB > RPC + CONNECTOR + WIRE
3. Various wiring methods3. Various wiring methods
1) Direct soldering on Tape wire : the cheapest method
2) After putting connector into Rigid PCB, connection with Tape wire or FPCB
:Using L type connector according to the flexible shape
3) Construction by FPCB type ( with stiffener )
: Less wiring space and high flexibility / Impossible repairing
4) Direct soldering FPCB on RPCB : Same function with 3), but low reliability on soldering Area
4. Application of FPCB4. Application of FPCB
Purposes Usages
3 dimensional wiring camera, cassette, recorder, transceiver, missile, mobile phone
Flexibility printer, hard disk drive, floppy disk drive, CD player
High density of wiring FAX, medical equipment
Thin and compact assembly
Electrical calculator, small measuring instrument, DASH BOARD of vehicle
5. Structure & Materials of FPCB5. Structure & Materials of FPCB
Structure
Single sided
structure
Double sided
Through hole
structure
Double sided
exposure
structure
Cover-lay film StiffenerUnique structure
1) Structure & Key note of Single side FPCB
1) Structure & Key note of Single side FPCB
Cover-lay film
Cover-lay adhesive
Base film
Stiffener
Stiffener adhesive
CCL adhesive
Copper foil
Edge Plating
* Base material : heat resistance plastic FILM with 12.5 ~ 125um ( flexible )
* Base FILM : Using with flexible area
(No using for flexible => using Solder Mask type )
- Soldering heat resistance but no mechanical strength
* Stiffener : Soldering for parts area or connecting area need mechanical strength and hardness
(working by Manual)
- With the complex shape of Stiffener would be most cost for the product.
2) Structure & Key note of Double sides FPCB with Through hole
2) Structure & Key note of Double sides FPCB with Through hole
Edge plating THROUGH HOLE
Stiffener
Cover lay film
Adhesive
Copper plate
Copper foil
Adhesive Base film
Adhesive
Copper foil
Copper plate
Adhesive
Cover lay film
* Making conductors and through-hole treatment on each sides of BASE
- High affect on FPCB characteristic
- Low flexibility with dual circuit on each sides
- Easier to crack on Copper Plating on through hole refer to the base Copper( Low resistance )
* No plating on through hole if it’s not necessary
Adhesive
3) Structure & Key note of Double sides FPCB with Exposure type
3) Structure & Key note of Double sides FPCB with Exposure type
Stiffener
Insulation film
Conductor
Plating
* Indistinct classification between Base film and cover lay film
* Same structure with Single side FPCB, but Drilling on the insulation film
* Single Conductor layer, but Possible wiring same with Double sides FPCB
* Possible solder mask printing on one side for insulation purpose
Materials
1) Copper Clad Laminate ( CCL )1) Copper Clad Laminate ( CCL )
material
ClassificationPOLYIMIDE ( PI ) POLYESTER(PET) GLASS EPOXY(GE)
Standard thickness
12.5 , 25 , 50 , 75 , 125um 25 , 50 , 75 , 125um 100 , 200um
Heat resistance Possible Soldering Soldering depends on condition
Possible Solderoing
flammability UV94V-0 UL94HB UL94V-0
Mechanical strength
Easier cracking OK with hothouse Good
Hygroscopicity High Low Low
Flexibility Good Good Bad
Price Expensive Cheap Medium
2) Coverlay2) Coverlay
* Using same conditioned film with base material
* Possible using of Polyester coverlay with Polyimide Base for cost reduction
* Possible using of exclusive Solder mask ink for FPCB
3) Stiffener3) Stiffener
* Using Stiffener to improve mechanical hardness ( Low mechanical hardness FPCB itself)
* Different stiffener using with different purposes ( Refer to the chart 1, next page )
* Adhesive : Oppressive adhesive and Thermosetting adhesive
Oppressive Adhesive Thermosetting Adhesive
1. Cheap and easier for handling2. Low adhesive strength, possible strip by Creep3. Bad solvent resistance4. Easier treatment
1. High reliability but expensive with complex structure. It affect higher price for FPCB 2. Using with Rigid-Flexible PCB with Through hole3. Glass Epoxy and Polyimide types only
materialsclassification
GLASS EPOXY(GE) PAPER PHENOL(PP) POLYIMIDE POLY ESTER(PET)
Thickness(mm)0.1 , 0.2 , 0.3 , 0.40.6 , 0.8 , 1.0 , 1.2 1.6 , 2.0 , 2.4
0.8 , 1.0 , 1.2 , 1.41.6 , 2.4
0.025 , 0.05 , 0.0750.125
0.025 , 0.05 , 0.0750.1 , 0.125 , 0.1880.25
Heat resistance Possible soldering Possible soldering Possible soldering Impossible soldering
Flammability UV94V-0 UV94V-0 UV94V-0 No Heat Resistance
Mechanical strength
Same with Rigid PCB Same with Rigid PCB Low Low
FlexibilityNo flexibility with the thickness over 0.3mm
No Good Good
Oppressive Adhesive
Possible Possible Possible Possible
Thermosetting Adhesive
Possible Impossible Possible Impossible
Price Expensive cheap Very expensive Very cheap
* Standard for Thickness* Only normal stiffener shown, there are many kinds of materials for stiffener
Chart 1. Comparison of stiffeners
4) Base Copper plate4) Base Copper plate
* Using Rolled Copper foil for FPCB
* Using Rolled copper foil though it is not for used on flexible area but only with partially flexible pattern used
* Higher price of Rolled copper foil compare with Electrolytic copper foil and using with pre-treatment to improve low adhesive strength
6. Manufacturing Process for FPCB6. Manufacturing Process for FPCB
* Much Longer and complex process compare with Rigid PCB manufacturing process.
If there is not enough knowledge for FPCB process, it might be impossible to produce it
* Higher and detail understanding required to designer for comprehensive understanding of correct process capability and manufacturing process
* The lamination process for Coverlay film and stiffener adhesive process is the Key different factors with Rigid PCB
1) ROLL TO ROLL type Process1) ROLL TO ROLL type Process* Easier Automation of product line and continuation of process
* Possible applying Roll to Roll type process until circuit formation by Etching
( Impossible applying on coverlay and later process )
( Applying Roll to Roll type depends on the width of roll, thickness of raw material , circuit details )
* Good for faster product speed, cost reduction but difficult for applying to Small and medium products
2) Materials2) Materials* Careful factor for Design : Size of Raw material
* Width of Roll : Normally 480 mm & 380 mm ( 240mm , 160mm width of CCL for Automatic Line)
* Using Double sided CCL 480mm x 1000mm
3) Circuit Formation3) Circuit Formation
* Making etching resist with Photo resistor method or Solder Mask Printing method, then removing (etching) unnecessary copper with using Copper chloride or Iron chloride
* Possible occurring of shrinkage or wave with CCL its own character of warpage while laminating on Base Film (possible cause of the problem while lamination for film and stiffener on later process)
4) Through – hole 4) Through – hole
* Processing by Routing for Hole and Slot, but difficult to be done with below 1.0 mm hole or slot ( refer to the below chart 2 )
* Clear working by small pitch of routing for Slot ( Much time need )
* Seldom to use Punching Tooling with very high prices and difficult to change the Outline though it’s possible to make the complex outline
Chart 2. Difficult cases for working
Below 1mm
Below 0.5mm on Inner corner angle ( R )
Below 1mm
5) Making Hole on Coverlay film5) Making Hole on Coverlay film
* Routing process for NC drill, large hole and slot
* Larger Hole size compare with Plated Through Hole(PTH) and slot hole, so need much working time
* For Double sides, Using different NC Drill program with PTH program
* Using Punching process, If there are many slot holes and if the working volume is Mass production
6) Surface Treatment6) Surface Treatment
Solder plating
Electrolytic Plating Melting Plating
Thickness 1~30 ㎛ ( OK to control) ~ 5 ㎛ ( Difficult to control )
Composition
OK to control Difficult to control
Stability Unstable in accordance with circuits Remainder by each pattern
shine Possible but difficult Possible
Heat Treatmen
t
~100 ℃ , ~ 10 분 ~ 260 ℃ , 10 초 ( pet 재료는 불가능 )
Price Cheap Expensive
Gold Plating
* For better corrosion resistance ( usually done very thin cause of High price, but it affects bad corrosion)
Although stable plating thickness approx below 0.5um, there might be some Pin-Hole on the surface
* Careful factor for Nickel plating : No Nickel plating on flexible parts because Nickel is more harder than Gold or Copper.
there might be Crack and Void on 1oz conductor with only 1~2um of Nickel plating
* Although Gold plating, there is difference with the degree of Purity for gold, so notify the Spec. on working sheet
PRE-FLUX(OSP)
* No plating on copper, but spread treatment on it
* Careful treatment with drying process with the possible burnt-out of Flux. It caused for bad soldering condition.
7) Outer Cutting7) Outer Cutting
* Punching (refer to the Chart 3 ) and Hand working
* Possible tearing and crack on Thin film of FPCB
Can be improved with the Pattern reinforcement of Copper Conductor
Simple Frame Punching Formal Frame Punching
Precision ~ ± 0.2 mm ~ ± 0.05 mm
Durability ~ couple of thousand slot Approx.100,000 slot ( Possible reusing with grinding )
Delivery Short ( ~ 2weeks ) long ( approx. 1month)
Price Cheap Expensive
Difficult Working Shape No angle
Small circle
Slit with No width
Slot with the width below 1MM
Small R( angle ) + straight line
Chart3. Comparison of Punching
8) Inspection and Packing8) Inspection and Packing* Inspection : Open and Short, Function , Size , Outer Cleaning (Same with Rigid PCB inspection )
Flexibility and Coverlay film inspection
* Packing : Cushion Packing with drier to avoid humidity on Polyimide material
Thank YouThank You
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