The Cost Contrast of Rigid Flex PCB and conventional PCB

Relocating to a rigid flex PCB design from the standard strategy of using cord settings up to join two or more PCB’s has noticeable advantages consisting of:
the capability the suit a smaller kind variable, less weight, boosted transmission capacity and raised existing bring abilities.

A common question that we are asked is ways to contrast the cost of a rigid flex PCB with the standard method.

Generally, if you look just at the PCB cost, a rigid flex PCBconstruction is going to be more pricey. But after evaluating the overall cost of the assembly, extremely commonly there is a price financial savings.

The adhering to listing is not indicated to be all-inclusive. Every application will certainly be distinct. Our hope is that this checklist aids promote the mind when doing a contrast of the two modern technologies.

Points to think about when comparing the total expense of an assembly:

You are merging several boards right into 1 design
Rigid PCB’s.
Wire.
Cost of wires and adapters.
Diminish Tubing.
Connectors.
Wire Ties.
Wire Pens.
Products.

Price of the assembly operation. You can now run one assembly rather than 2 or 3.
Human Labor.
Cord Assembly Test.
Kitting for assembly.
In Process Evaluation.
PCB Tooling/Test.
On Board/ Last Test.
Misc. expenses– design time, etc

.
Evaluating:. Possibility of one test procedure AND the ability to examine the complete assembly prior to installation.

Dependability.
No solder connections between boards.
Integrity comes from a great design.
The flex port is currently an essential part of the board.
Order Processing Costs.
Receiving.
Inbound Evaluation.

Order generation.
Material Storage space.

As I pointed out, this checklist is far from full and meant to cause conversation on the prices of a complete assembly. We are always right here to help answer any concerns or offer added info on both price contrasts and rigid flex PCB design. much more info, please visit our website at www.ifastpcb.com.

Rigid flex PCB manufacturers prepare for wearables market boom

Shipments of wearable tools worldwide will certainly rise by 43 percent between 2014 and 2019. This translates to a broader application base for rigid flex PCB boards.

From clinical and armed forces equipment to the hot mobile devices, rigid flex PCB manufacturers in China are targeting prospects in the potentially big wearables market. Global shipments of such products are projected to skyrocket at 43 percent CAGR in 2014-19, according to IDC.

By unit, the total amount will strike 173.4 million at the end of the period from 28.9 million in 2014, offering another application chance for the hybrid PCB classification.

Today, smart devices, laptops and tablet PCs are the vital markets for this PCB board, however mainland China PCB manufacturers have actually now alloted a section of their PCB result for worn electronic devices. The application’s share at iFastPCB, which started providing rigid flex PCB boards in 2015, is about HALF.

Flaunting the consolidated advantages of rigid and flex PCB boards, this PCB type has actually the included benefit of area and weight reduction. This is due to the fact that its building and construction removes the requirement for ports, cables and bow cable televisions in layouts calling for multiple PCBs. Improved efficiency and reliability are also the variant’s strength as a rigid flex PCB can be twisted, folded up and rolled, making them proper for wearables produce.

Some PCB manufacturers are functioning to upgrade their options for this market too. They highlight HDI kinds, which go beyond traditional multilayer designs in circuit density. Landmass China PCB manufacturers such as iFastPCB could end up such sophisticated PCBs.

The rigid flex PCB group is still a minority in the local PCB sector. It accounts for less than 5% of iFastPCB return. PCB manufacturers are positive the widening application base and resulting rise in demand will sustain greater than 10 percent growth in sales each year.

Production of rigid flex PCB is concentrated in Europe, North America and Asia, with the very first 2 areas churning out variants primarily made use of in the military/aerospace, clinical and automotive electronic devices areas. Asia, on the other hand, concentrates on the consumer electronic devices market.

For the mainstream multilayer section, domestic distributors remain to emphasize higher circuit thickness to keep up with the trends for miniaturizations and several functions in incurable applications. Higher layer matter, tighter line size and spacing and reduced hole sizes continue to be as purposes. Presently, the array includes 3 to 12-layer choices with 1.4 mil being the minimum in line size and spacing, and 0.1 and 0.05 mm openings respectively with mechanical and laser boring.

In the mainland, there are more than 100 PCB manufacturers of the PCB type, which one-third are homemade business. The remainder includes foreign-invested business such as Compeq, Unitech and Career. Virtually half of this swimming pool runs in Guangdong province, specifically in the cities of Shenzhen and Dongguan.

Common products
Multilayer systems constitute the mass of rigid flex PCB manufacturing in the mainland, although PCB makers continue to provide solitary- and double-sided kinds. No matter classification, these boards embrace FR-4 base materials for the rigid part and polyimide or PET DOG for the flexible PCB portion. ENIG, OSP, and immersion tin, silver and gold are used for the surface area finish.

China PCB manufacturers get CCL and FCCL in your area and from Taiwan. The vital sources of the previous material consist of Nanya, Iteq, GDM, Shengyi and EMC. The second in 3L and the much more commonly utilized 2L types originate from Taiflex, Shengyi, Poise, ThinFlex and Microcosm. For solder mask, Goo, Taiyo, Tamura and GreenCure are the significant foreign service providers.

Mainstream 3-layer systems have 2R +1 F setup, 4-layer 2R +2 F, 5-layer 2R +1 F +2 R, 6-layer 2R +2 F +2 R and 10-layer 4R +2 F +4 R. In regards to minimum line width and spacing, those with 2, 3 and 4mil are a lot more typical compared to variations with 1.4 and 1.6 mil. By hole dimensions, as big as 0.3 mm to as little as 0.05 mm are the options.

iFastPCB supplies 2 to 6-layer models with 3mil as least line size and spacing and 0.2 mm holes. Leading Electronic’s as much as 10-layer option has 3mil and 0.1 mm as minimum criteria.

Material cost is steady and will certainly help rigid flex PCB manufacturers maintain prices amid climbing up labor expense

Rigid Flex PCB Design for an Cutting-edge Helmet Display(1)

The EA Game firm involved Virtual Reality Solutions to produce a prototype of screen connected to the headgear. This safety helmet screen presented a heads-up screen of instrumentation and digital depictions of important information. The helmet was the heart of the Virtual Reality equipments, making it possible for the individuals to make the most of the whole system for incredible video gaming experience.

PCB demands. The headgear display screen supported the PCB in its mechanical housing, and an HDMI cable fed into the video resource. An optical wire attached to the display screen, which brought light to the headset’s LCOS microdisplay. The light illuminated the screen and was predicted into waveguides that offered details to the user’s eyes.

The headset display was just one of the very first reported binocular HMDs in growth making use of a liquid crystal and silicon microdisplay.This innovative technology substantially lowered the expense, volume and weight of standard helmet-mounted screens, changing bulky optics systems with slim, light-weight, see-through diffractive optics. The screen’s physical requirements posed interesting challenges for the PCB.
( 1) The system had to be tiny sufficient to install to the pilot’s safety helmet and enable motion without creating pain.
( 2) To avoid pilot injury, it needed to right away launch all connections to the plane in the event the pilot needed to eject from the aircraft.
( 3) The boards had to be flexible sufficient to twist around the system’s optical components and accommodate adapters at various angles.
( 4) As a result of size restrictions, the design can only burst out traces on the eastern and western sides of the major FPGA element, rather than a north-south-east-west pattern.

Xilinx offered valuable details concerning time of flight inside the plan, as did the IBIS designs of the Micro memory modules. The plan for the memory component was significantly smaller than the Xilinx FPGA, and the Xilinx time of flight info was important. We had the ability to fine-tune out the differences in the memory components after layout was completed.

The design used a Xilinx FPGA and a 64-bit large DDR3 memory bus, where each of four elements had a 16-bit broad data bus. Timing was matching to a few picoseconds on the flight times via the board. Among the a lot more tough parts of the design was that the link between the FPGA and memory required simulation at a very broadband, so the timing restrictions were tight. With such limited margins, it was very important to think about the travel time of trip inside the packages in addition to on the board. For these factors, die-to-die time of trip was picked, instead of simply pin-to-pin time of trip.

Rigid Flex PCB Design Rules Guaranteeing Reliable Products (2)

In-design inter-layer checks can reduce mistakes that may be presented throughout the design process, consisting of the following locations:.

– Mask-to-pad, metal-to-coverlay, coverlay-to-pad.
– Gap/overlap between mask layers.
– Edge-to-edge void in locations such as the bend line to the element, via-to-bend line, and stiffener-to-bend area.
– Bend line/area to stiffener, pin and via, element.- Gold mask-to-coverlay, stiffener adhesive-to-stiffener, and pin-to-coverlay.
– Minimum overlap, such as when 2 geometries overlay by a minimum or more (e.g., solder mask overlay into the transition zone).

Normal Rules for Compound Designs

Mechanical restrictions.

Rigid flex PCB drive additional policies when the flex circuit is folded up or curved inside an unit. Normally, the mechanical engineer provides the bend line, bend radius and bend location to the PCB designer. With modern-day EDMD (IDX) interface, this data can be automatically imported into the PCB design tools. These bend locations call for developers to:.

– Avoid putting pads also near to the bend location to stop peeling.
– Do not put vias or pins as well near stiffeners, to stay clear of shorting.
– Do not overlap bend areas with stiffeners, to prevent peeling.
– Stay clear of placing vias in bend areas to prevent fracturing the substrate gradually.

Mechanical designers specify the borders for areas– rigid, flex, rigid– where the number of layers and consequently densities are different in each zone. Nonetheless, they need additional information concerning layer frameworks and thickness for the areas, layers over top and below base to properly design the thickness of the last PCB assembly, and to execute accident checks before handing the design to PCB manufacturing. Instances of such layers consist of paste mask, coverlay, stiffeners, exterior copper, and various other materials that affect total elevation, density, and bend efficiency.

Inter-layer checks.

For sophisticated flex and rigid flex PCB designs, PCB designers need to stick to new design guidelines from the producers. These new layers and surface area finishes require detailed in-design inter-layer checks of nonconductive layers in rigid flex PCBs.With an accurate image, developers could perform more exact DRCs, obtain much better comments, and offer better data to the MCAD tool for fabrication. Not having these checks expands the design cycle. In-design inter-layer checks give a correct-by-construction technique that prevents unnecessary design iterations and, sometimes, costly prototype constructs. Devices giving a pictorial view of the stack-ups based on different substrates allow developers to visualize the layout stack-up intent as it is being specified.

Routing.

Routing on flex circuitry usually calls for arcs within the routes. A lot of the geometry on the flex portion, consisting of board overview, teardrops and routing, calls for arcs and tapered shifts. Group routing features should lug a team of internet (bus) throughout the flex, while quickly locking to the contour of the flex/board outline. PCB developers obtain modifications each day; including an extra trace to a directed collection of nets need to not force rerouting of the whole bus. Transitions in line sizes require tapering and all pad/via entry/exits be tear-dropped to minimize tension at the solder joints. A lot of PCB design devices sustain push-and-shove routing, yet these capabilities now need to support push-and-shove with arcs in the traces.

As the intricacy of a flex or rigid flex PCB increases, the quantity of time a designer invests rises as a result of manual checks. Today’s CAD tools should provide a means for designers to leverage new PCB fabrication techniques without extending design time. The breadth and depth of in-design checks needs to cover 30 or more new flex and surface area finish layers. Customers must also have the ability to integrate their own layers for the device to examine, so they don’t need to wait for tool updates.

Rigid Flex PCB Design Rules Guaranteeing Reliable Products (1)

Breakthroughs in fabrication have actually translated right into new design constraints and standards.

For several years flex and rigid flex PCB commonly turned up in products as a flexible cable television between 2 rigid boards. The past five to seven years have actually brought tighter space constraints and miniaturization challenges. Developers should currently put parts on the flexible circuit, using it like a rigid substrate. Utilizing both the rigid and the flexible areas for components, while feasible, presents new design restrictions that call for more advanced PCB design methods.

To prevent fracturing or unnecessary stress on parts, prevent putting elements and vias at the bend locations. A typical, well-known rule is that routing must be orthogonal to the bend line to minimize material stress at the bend. Routing on the following layer with the bend location should be offset to stay clear of the I-beam result. Traces that do not follow this policy could accidentally add rigidity to an area that is planned to be flexible. In addition, the area where rigid and flex zones come together may need overlap of material and require unique spacing for holes and conductive materials. It is handy to consider the transition area a stress-relief area. it shows a four-layer rigid board attached to a two-layer flex PCB, which on its opposite connects to another four-layer rigid board.

Rigid and flex PCB frequently use different materials, and the rigid section generally has even more layers than the flex section. Many advanced makers could sustain these designs with more than two flex layers. To ensure flex circuits with added layers work well in all problems, stiffeners that bring rigidity to these PCBs are placed near components or port locations or on the contrary side. Stiffeners are made from materials such as stainless-steel or aluminum, with the enhancement of dielectric material like a polyimide build-up. Smaller units often call for the flexible section to be curved or folded up.

The PCB cross-section editor for a solitary stack-up must now support numerous cross-sections standing for the different PCB laminates. In addition to supporting conductor, plane and dielectric layers, cross-section editors have to include new mask and finishing layers above and below the surface areas of the flex PCB, such as:.

Electroless nickel electroless palladium immersion gold (ENEPIG) for unique plating areas.
Stiffeners– aluminum or stainless steel– that limit bending where parts are placed, to stay clear of splitting or peeling off.
Material masks that consist of (valuable) steels, adhesives and solder paste masks.
A coverlay (cover layer), which is an adhesive-coated film pushed into the stack-up to shield the circuit.
Developments in fabrication have reached materials and the variety of added mask/conductive layers for flex and rigid flex PCB. New materials– conductive/nonconductive layers, and surface area coatings– need developers to by hand examine if the design components on the flex circuit are meeting the maker’s design standards. This includes a substantial quantity of time to the design phase.

To stay clear of manual checks and guarantee the design is developed appropriately, designers need in-design inter-layer checks to flag issues as they are developed. Checking at the PCB manufacturing sign-off stage is too late in the design cycle to discover errors, and makes the design process unpredictable. Real-time capability can stay clear of taxing actions later on at the same time.

Rigid Flex PCB Design for an Cutting-edge Helmet Display (2)

There were two components to the simulation. The initial was an intriguing job: to make sure that the design met the timing demands of the DDR3 by considering time and size suit. The second part was to ensure signal integrity; factors to consider for impedance matching would certainly make sure no impedance interruptions would certainly create signal stability problems. While the signal rates were high, they were low enough for loss to be a significant worry, given the trace sizes involved.

One of the DDR3 needs was that the address and control data would exist in a fly-by setting, linking between the controller and all 4 memory ICs. To stick to the timing restriction that required the clock path to be longer compared to the data and DQS lines, one had to include size to the clock. This, certainly, contravened office demands. Along with this, for the very first and second memory IC, earlier along the path, the information occasionally came from a part of the FPGA, that made the information course quite long.

The trace size in between the memories and FPGA ranged 1.5″ to a number of inches in length. The address and control signals took a trip to all four memory parts, while the data were coming from a part of the FPGA that was potentially farther away. It was a challenge to preserve hold-ups to make sure that the write timing in the DDR3 would work.

To make certain timings matched, standard routing was carried out first and afterwards matched the lengths. It was determined which layers would certainly be made use of for every of the signals and teams travelled with each other; for instance, each data lane was placed on the same layer. An initiative was made to minimize the variety of vias and various other functions needed to get to completion path.

The FPGA had some versatility with respect to which pins could be made use of for which objectives. Nonetheless, as speed boosted, it presented restrictions due to the fact that details groups of pins for certain lanes of data were required. The most significant problem came with the address and control lanes, all taking a trip in big groups on the very same layers of the PCB board.

The obstacle came when it was time to match segments. This was tough because of the absence of room. An easy point-to-point suit for the address and control lanes wouldn’t be adequate. Instead, we matched every segment: in between the controller and the initial IC, very first IC to the second IC, and so forth. Luckily, because the ICs were a specific distance apart, it was essentially a point-to-point match, and the trace sizes were similar. The most significant challenge was matching the segment from the FPGA to the first memory IC. The lengthiest path specified how much time the trace should be, and in some cases we should boost the trace by a huge fraction of an inch to suit this. To include so much size, trombones or accordions were needed, which took up space on the board.

The BGA bundles for the HDMI and FPGA controller presented trace breakout problems. In a similar way, the HDMI controller was a very fine-pitch BGA; it didn’t have very many pins, but it was a 0.5 mm pitch BGA, so bursting out in a conventional pattern would be hard. Although the FPGA wasn’t a particularly large or dense part, as a result of the board’s little dimension, traces might only break out on the east and west sides as opposed to the typical north-south-east-west pattern.

Rigid Flex PCB Design for an Cutting-edge Helmet Display (3)

Controlled impedance requirements. The HDMI video clip input had numerous different requirements for controlled impedance. The length of the trace made use of was extremely little, and the signals were relatively sluggish compared with DDR, so trace size had not been an issue. Nevertheless, the HDMI required 100Ω differential pairs, while the memory ran at 80Ω. For that reason, it was an intriguing challenge to guarantee controlled impedance, and it was hard ahead up with a rigid flex PCB stackup that would leave ample office for 80Ω, along with 100Ω, without coming to be too thin and challenging for PCB manufacturers making.

HDI PCB and blind and buried vias PCB were put on break out traces from the HDMI and FPGA controller. The HDMI controller pattern likewise used via-in-pads. It worked to do some “what-if” circumstances and see how the HDI stackup could potentially appear. We experienced a few iterations on that particular with a couple of various kinds of materials, looking at the impedance control preparation.

At first, FR-4 material was under consideration, yet after some screening, we decided to opt for a material that had a reduced dielectric constant, achieving reduced loss, signal honesty and preferable line-space ratio for impedance controlled traces.

Utilizing HDI PCB lowered the number of layers required in the board in general, and after stabilizing the cost with the advantages of HDI PCB modern technology, it was chosen this was the appropriate instructions.

There were 3 rigid sections in the final design:.
1) A main section with the FPGA, DDR3 ICs, and power supply systems;.
2) an area with slower, analog-type components and even more power products;.
3) an area that included a very little HDMI receiver with several possible alignments to accommodate the incoming input wire.

The rigid flex PCB remedy. As the design moved on and it became clear that area was a worry, it was determined to attach the rigid boards with a flexible bow to prevent using basic physical ports that needed more area.

The last rigid flex PCB stackup was 10 layers. The rigid boards used 8 layers and carried all the impedance-controlled and high-speed traces. The other two layers were the flex PCB signal layer, which was also made use of as the VCC layer in the main rigid part of the board. There was some collaboration between layers of the rigid and flex sections, but for the most component these were treated independently.

Rigid Flex PCB permitted the board to fit into the little housing on the helmet-mounted display system. The flex ribbon could bend a variety of ways, accommodate different angles, and be rolled up and totally taken in within the volume of the container, offering alternatives on how the boards would certainly become part of the system and twist around the optical parts.

Anything that called for impedance control was taken care of entirely within one of the rigid structures. Breaking it down right into those areas permitted us to stay clear of any type of need for impedance control on the flex, which was a big win insofar as expense goes.

Rigid flex PCB designs can save costs during system assembly

A straight line is not always the shortest route in between 2 points in digital products: Thanks to rigid flex PCB architecture, circuits can be folded up onto themselves with 180º bends– laid over at minimal height– thus reducing product dimensions. In addition, if a product has moving areas with electronic devices embedded, rigid flex PCB building is the ticket.

Credit rating rigid flex PCB architecture for the presence of smartphones and various other pocket-sized electronic wonders. However, to understand the advantages of rigid flex PCB building (consisting of light-weight settings up) specific design constraints use specifically to the flex PCB layers in a stackup. Do not attempt your first (or second, or 3rd) rigid flex PCB design before you consult your prototype PCB manufacturer.

Utilizing Flex in Rigid Flex PCB Assembly

Unlike a traditional PCB stackup, foil building could not be used for flex layers. The flex layers in a rigid flex PCB assembly are built from unreinforced base substrates usually containing polyimide dielectric film, clad with rolled stiff copper.

Therefore, the clothed base material is first drilled, holes are uniquely layered, then the traces and pads are engraved. Bondply, a layer of polyimide film with sticky layer on both sides, isolates that conductor layer from the following, etc.

Flex PCB materials are flexible under all conditions, consisting of processing. Throughout the final lamination of the rigid flex stack, they are much less dimensionally secure compared to the rigid core and prepreg materials that sandwich them. Vias should be farther from the side of the rigid area adjoining the flex bow than the minimum distance in rigid-only stacks, preferably a minimum of 50 mils from the side, yet absolutely no less than 30 mils. This rule is the one most broken in rigid flex PCB designs.

Look for assistance to develop your stackup and design rules. Differing coefficients of thermal expansion amongst the flex base material, adhesives, prepreg, and rigid cores calls for a really careful balance of densities, especially for impedance-controlled designs. There can be many layers of flex in a rigid flex design, relying on the bend distance of the bow portion and whether it will continue to be stationary after assembly. Flex layer count must be limited in vibrant applications. Consult your PCB manufacturer. If greater than four flex layers are needed, bonding adhesive should be absent in the areas that are made to bend. The bend radius need to be no less than 12 times greater than the circuit density.

Properly Making use of Trace Routing

Trace routing in the ribbon location will be bent, not angled, to boost peel toughness. This suggestion is opposite the transmitting technique for rigid PCB boards.

To enhance ribbon flexibility, aircrafts ought to be cross-hatched; nevertheless, the cross-hatch complicates impedance control. Again, a cautious equilibrium is needed. In some applications, a large, solid strip under vital traces suffices. Traces on different layers must be surprised vertically, not put atop each other, to increase ribbon adaptability.

Annular rings need to be as huge as possible in flex-only areas to reduce the danger of peeling, and the change from the annular ring to the trace need to be teardrop-shaped for the very same factor. Adding tabs or anchors also aids to avoid peeling.

The stiffeners can be laminated flooring when the cover-coat is bound and are the preferred technique to stop splits. The very best technique is to avoid making use of sharp edges in a flex PCB design.

An extremely standard list for rigid flex PCB designs includes these transmitting factors to consider:
– Stagger flex traces up and down layer to layer
– Turns must be gradual
– Vias needs to be no closer to the side of the rigid board than 30 mils at the flex change
– Minimize flex PCB layers

Keep in mind, rigid flex PCB designs might be expensive to produce, however they could save prices throughout system assembly. Such design usually is the only way to squeeze the required product functions within the target package volume. It’s far better to get in touch with a PCB manufacturer during the drawing board.

Rigid Flex PCB Design Layout Demands

Rigid flex PCB are distinct with their integrated building of both rigid PCB and flex PCB circuits technologies. Being distinct features a variety of distinct needs that must be reviewed and executed during the rigid flex PCB layout phase of the design process.

The first 2 needs relate to minimal room requirements, as gauged to the Flex Transition Area within the design, of plated through holes (PTH) and exterior layer copper functions. The 2nd 2 deal with the mechanical flexibility and integrity of the flex PCB areas when the parts are bent into the called for form.

The Flex To Rigid Transition Areas

The “Flex Transition Zone” is specified as the length of the rigid area lay out at which the layer framework modifications from a rigid location to a flex PCB location only.

The Flex Shift Zone are created by the demand to extend the flex PCB location coverlays by a little range into the rigid areas. This allows the flex coverlays to be captured by the lamination of the rigid area layers and ensure a gapless shift between the flex PCB locations and the rigid locations. The flex coverlays do not extend throughout the rigid areas as needed by IPC 2223C design criterion for flexible PCB.

Layered Via Hole to Flex Transition Area min. spacing = 0.050″

– Makes certain plated through hole integrity by avoiding any type of PTH from being drilled through the flex coverlays as they engage and are captured by the Rigid location layer lamination.
– Coverlays are laminated to the flex PCB layers utilizing a flexible adhesive, either acrylic or epoxy based. These adhesives have a really high co-efficient of thermal growth.
– A plated through opening pierced with a coverlay will go through substantial Z-Axis growth and contraction tension during both the assembly re-flow process and possibly throughout the operation of the finished product. This has actually been determined as a primary root cause of cracked opening layering leading to either prompt product failing or long term latent failure reliability problems.
– This demand is called out in IPC2223C Sec. 5.2.2.3.

External Layer Copper function to Flex Transition Zone minutes. spacing = 0.025″

– Makes certain enough spacing to permit reliable external layer imaging processing.
– Rigid layers, while in production panel configuration and before last lamination process, are required to have the flex PCB locations got rid of. This creates in internal edges, created by the height distinction in between the rigid location and the flex location, which the exterior layer photo transfer movies must transition.
– Min. spacing 025″ offers adequate space for film attachment and a trusted imaging process.

Flex PCB Area Via Holes

– Not advised and will be stayed clear of if design permits.
– Includes significant expense as a result of the extra drilling and layering processes.– Needs blind via manufacturing processes.
Potentially creates mechanical tension concentrators in flex PCB layers which might bring about damage if part is curved in the vicinity of these vias.
– If design does require flex area vias:
-Guarantee vias are located far from the certain bend place(s) in flex areas.
-Have PCB manufacturers testimonial design to assess and establish if any kind of risk variables exist.

Flex PCB Location Trace Layout

-Traces need to be maintained directly and parallel, if design permits.
-If trace direction adjustments are required utilized rounded edges and minimize as long as feasible.
-Aids remove prospective mechanical anxiety concentrators which may bring about breakage when flex PCB location is curved right into setting.
-Stagger traces on surrounding layers, if design enables.
-Improves versatility and reliability by reducing the “I-Beam|” effect of traces positioned directly over one another from layer to layer.

Rigid Flex PCB Design Guide for IoT/Wearable Product (1

Today, technology patterns are increasingly toward flex circuits or a combination of rigid flex PCB for IoT/wearable PCB designs. You could say those patterns place us on a various footing, so to speak. Therefore, it is essential to get a manage on new design terminology and things that should be factored in as you transfer to this following degree of embedded design.

This includes the following:

– Reduced and high modulus boards
– Bend radius, proportion, and stress
– Dielectric density
– Via placement
– Board layers and linked copper amounts
– Regular copper versus hardened copper
– Copper density

Board modulus refers to its structure– a reduced modulus means a softer construct, while high modulus refers to a harder board with stiffener. A stiffener that offers strength to the flex circuit for secure soldering is revealed; components mounted on the opposite side of the stiffener. Stiffeners are an economical way to rigidize specific areas on the rigid flex PCB boards, such as SMT locations, pin locations, or hole pattern places for part mounting.

SMT areas do not always require stiffeners depending on the elements being mounted at that place. Nonetheless, including a stiffener is mosting likely to include hardly any cost to the assembly. Stiffeners are utilized to strengthen solder joints and are occasionally used to compel bend lines in the selected areas. Stiffeners can be made from FR4, polyimide, copper, or aluminum-based materials.

Coming around the bend

Despite the application, a rigid flex PCB must be flexible and flexible, however the concern is: How flexible and bendable can it be? The jury is still out on the preciseness of bendability (or “bendableness”). As of this writing, the IPC is being rather conservative with its call. So, essentially, the exact interpretation or gauge of bendability hasn’t already been selected and possibly will not be because of its ambiguous nature. The best suggestions offered is to rely on a knowledgeable EMS Supplier that has a number of wearable/IoT PCB designs under its belt and has a warehouse of crucial nuances associated with flex PCB bendability.

Having stated this, it excels to know terms like bend span, bend ratio, and stress, all which are totally linked. Bend span, as the name indicates, is just how much you could flex that flex circuit before something breaks or incurs a concealed crack. It’s also needed to recognize that the dimension of the bend distance is carried out from the bend’s bottom surface. Again, it’s advisable to companion with a savvy EMS Carrier to analyze and fix bend span concerns and concerns.

The second term, bend proportion, takes into consideration the proportion of the bend span to the density of the flex circuit. For example, the bend ratio for a multi-layer flex circuit for a medical electronic devices wearable tool goes to the very least 20:1. By comparison, for the solitary and double-sided flex circuits the bend proportion should be at the very least 10:1. Tighter bends may develop the threat of circuit damage. It’s always preferable to use more progressive angles instead of an appropriate angle bend with a sharp span. Bend span is determined by measuring the distance from the inside surface area of the bend to the facility of the span.

It’s also essential to understand there are two facets connected with flex PCB circuits flexing. One is static or single bending; the other is vibrant flex entailing multiple flexing operations. The bend radius for fixed flexing need to be at least 10 times the thickness of the wiring and the strain on the crucial layers should be 2.2% or less. On the other hand, the bend distance for vibrant rigid flex PCB must be 25 times or less.

The bend radius for vibrant rigid flex PCB, such as the example populated with µBGA bundles, must be less than 0.8% for 50,000 cycles, less than 0.6% for 100,000 cycles, less than 0.4% for approximately one million cycles, and less than 0.2% for a million cycles or more.

As was noted above, the bend span, bend ratio, and strains developed by the bending action of the boards are inextricably linked. When it comes to pressures, these are already integrated in when the rigid flex PCB manufacturer produces the flex circuit. In other words, stress is inherent in the different circuit layers and can be mitigated with stress relief tools such as stiffeners.

Dielectric thickness

Dielectric materials within the flex circuit can trigger even more stress depending upon their thickness. Dielectrics vary in their proportion of stiffeners to density. Picking a dielectric material according to the underlying application offers the completed flex circuit the quality it requires. In terms of impedance designs, the conductor widths and dielectric thicknesses can be gotten used to satisfy the required resistance outcomes.

As previously kept in mind, high modulus PCBs are difficult boards with stiffeners. Right here, bend span is exceptionally vital and needs to be factored in since the computation of bend proportion need to additionally incorporate the density of the stiffener, consequently boosting the overall density for the flex PCB. Maintaining the bend ratio little rises the flex circuits’ integrity.

This indicates that it is necessary to comprehend the strain at various levels within rigid flex PCB layers. Then, this implies knowing which layers use just what quantities of copper. Changing the quantities of copper has the most negative effect on pressure distinction.

For example, take a rigid flex PCB with a Hoz of copper weight. This will bend with a certain stress quantity with a particular bend ratio. However, if the amount of copper were to be increased to one ounce, the flexibility would certainly be substantially minimized, and the bend proportion would certainly be limited since the copper thickness has increased, therefore creating a total more thick flex design. All this suggests that you have to calculate the bend ratio very thoroughly.

In addition, you need to inspect copper thickness at different layers within the flex material. This is since the thickness affects the bend proportion and the strain variable. You can make use of specific types of flex material for certain applications, so it’s not an instance of “one-size-fits all.”