How to introduce gold finger PCB just few steps to your customers?

How to introduce gold finger PCB just few steps to your customers?
Jim will discuss gold finger PCB manufacturing in three parts below:

–You shoul know Gold Finger definition
–The use area of Gold Finger
–Introduce of Gold finger PCB

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You shoul know Gold Finger definition

Gold Finger is gold-plated terminal of a card-edge connector, usually, fingers are done by flash gold (hard gold) and the gold thickness is requested to be from 3u“ to 50u“ because fingers are mainly used for pluging for many times.
When PCBs will be repeatedly installed and removed electroplated gold is used for edge-connector contacts or as they are more commonly known: Gold fingers.

The use area of Gold Finger

Gold contact surfaces are often used on circuit boards with membrane switches which are a technology of choice for industrial, commercial and consumer products.

Introduce of Gold finger PCB

However, the gold fingers (gold-plated contact pins) found on PCBs are quite unlike Auric’s stubby, fat digits.
To begin with, the plating thickness of a PCB gold finger is typically a mere 300 micro-inch. At this thickness the hard gold is expected to survive 1,000 cycles before wear through.

Product type: 4 layers PCB
Board thickness: 1.60±0.15mm
Copper thickness: 2OZ out layer 1OZ innner Layer
Minimum hole size: 0.50mm
Surface finish: ENIG+gold finger
Minimum line width/space: 0.125/0.125mm
Gold thickness on gold finger: 20u“

Product type: 6 layers gold finger PCB
Board thickness: 1.60±0.15mm
Copper thickness: 2OZ out layer 1OZ innner Layer
Minimum hole size: 0.50mm
Surface finish: ENIG+gold finger
Minimum line width/space: 0.15/0.13mm
Gold thickness on gold finger: 30u“

If you want place our gold finger PCB,please mail to info@htdcircuits.com

The right way of impedance controlled method

HTD PCB manufacturer expert told you the right way of impedance controlled method.


In our TV/satellite cable example the antenna is the source, the TV the load and the coaxial cable the conductor.  The cable has conductors and insulators and the dimensions of these along with their electrical characteristics are measured to carefully control the electrical impedance of the cable. If we want the signals in our PCB to

transfer along the path from a signal source to a load via a conductor or track efficiently, we need to control impedance. So what can I do to control impedance?

For the signal to get from the source to the load the impedance’s along the line must match. Therefore, the output impedance of the source, the impedance of the track and the input impedance of the load must match.

Before you PCB manufacturing, you should know The definition of Impedance

Before you PCB manufacturing, you should know The definition of Impedance
Impedance, with its complex mathematical formulae and terminology can be mystifying, I get it.
Here we strip back the terms and pare down the formulas to let that dangling penny drop.
So, lets dive in and get to grips with something you’ve probably have heard of but sometimes struggle to get your head around.

So - What Exactly is Impedance?

OK, so in DC circuits, where the current flow is steady, there is one type of opposition to this flow which is called “Resistance”.
AC circuits can experience resistance too, but they also can experience another form of opposition to the current flow, “Reactance”.


In AC circuits, then it is the combination of these two forms of opposition to current flow that is called impedance (impedance is signified by the symbol Z).
So essentially, in AC circuits, opposition to current flow is Resistance + Reactance = Impedance (Z).
Just like DC circuit resistance, AC circuit impedance is measured in ohms (Ω). Source: PCB Forum

Why Should PCB manufacturer consider a used machine?

A new machine with all the options you want, the PCB manufacturer support you expect, and a warranty that protects you is always the first choice, but there are some good reasons to consider a factory reconditioned unit vs. new:
•A factory reconditioned machine can save you up to 50%, depending on age and condition of the unit
•If you have a short-term project that you want to minimize your cost and/or loss, buying a reconditioned machine could be a good choice
•If you have a complex application that you’re not sure will even work, and you can’t afford the cost of custom equipment, you may be able to create a work-around with a reconditioned unit, along with the technical support of the OEM

Original PCB manufacturers will often take in older equipment in trade, or buy back machines that their customers have outgrown.
They will also seek to purchase back their own brands from companies going out of business.
This means you have a pretty good chance of finding a pick and place machine, reflow oven, wave soldering or other system that meets your needs direct from the manufacturer’s reconditioned inventory. They won’t always offer these machines on their websites, so you just need to remember to ask.

Sometimes a manufacturer is forced to downsize and sell off some equipment that may no longer fit what they need.
So they decide to sell it on eBay or another discount online site. It may be in perfect working order, and it may be something you want test out before investing in a full line.
I suggest contacting the manufacturer directly to see what support, warranty and training they offer even before making an offer on an online store.
You should also consider the type of equipment and its average life cycle. If you can, check to see how many miles (or years of operation) are on stencil printers, pick and place machines, reflow ovens, or soldering systems. Source: PCB007

Two biggest applications market share of Flexible PCB

Aerospace Applications
The heads-up display (HUD) as used in aerospace is a familiar technology with a clear purpose: displaying operational data directly in the pilot’s field of vision alleviates the need to look away from a potential target to read critical operational data during flight.
A recent extension of the HUD, applied to wearable technology, provides remote 3D holographic images in a flip-down visor mounted to a helmet.
The holographic waveguide helmet-mounted display (HWVD) from HoloEye Systems provides high-resolution true 3D imaging, using flexible PCB cables to drive the waveguide optical system, which uses HoloEye’s liquid crystal on silicon (LCOS) display technology.
The flexibility, reliability, and performance of the flex PCB cables makes the HWVD effective in realtime use for avionics, and the light overall weight makes it feasible to mount the display directly on the pilot’s helmet, instead of in the aircraft.



Medical Application
A medical device company utilizes flex PCB manufacturer designs as important components of a new class of hearing-assist devices, providing higher range and resolution (125 Hz to 10,000 Hz) than currently available hearing devices.
The underlying premise is revolutionary: a small photoreceptor and micro-actuator are placed inside the ear canal, with the micro-actuator in contact with the eardrum.
Outside the ear, as in conventional hearing devices, a microphone captures sound and a digital signal processor (DSP) converts it to digital signals to be sent into the ear. But here’s where things get exciting: the digital signals actuate an infrared laser located inside the ear canal, which in turn excite the photoreceptor, turning the digitized audio into a small current which drives the micro-actuator, causing the eardrum to vibrate.

Flex PCB design permitted the engineers to mount the microphone, DSP, and battery in a tiny, compact package that fits behind the ear, and which allows the laser to provide both power and signal to the passive photoreceptor and micro-actuator.
While this is currently still an investigational device, the technology is promising and exciting.

The product relies on the miniaturization made possible by flex PCB design to convert sound waves into laser signals that drive a micro-actuator inside the user’s ear, turning the user’s eardrum into a speaker.
The product relies on the miniaturization made possible using flex PCB designs to convert sound waves into laser signals that drive a micro-actuator inside the user’s ear, turning the user’s eardrum into a speaker.
The amount of applications and uses for flex PCBs within the consumer industry are too exhaustive to list. But simply put: if you wear it, carry it, or drive it, there’s a good chance it has flexible PCBs in it.
The first flex PCB most people think of is typically the connector between the keyboard and screen of a laptop. Similarly, flip phones use flex PCBs to connect the two halves of the phone.
The moving print head of modern printers use flex PCBs in place of the older-style ribbon connectors; likewise, the read/write head of disk drives—which require billions of flexing operations during the product’s lifecycle—have benefited from the increased reliability and cost-effectiveness of flex PCBs.
Automotive applications in particular carry a number of advantages, not only in the usual arena of reliability, but even more so for the weight savings that a flex PCB offers compared with a standard PCB and wiring harness.
Weight is the enemy of fuel efficiency (or range, for electric/hybrid vehicles), and flex PCBs greatly reduce the labor involved in manufacturing a traditional automotive wiring harness. And the inherent resistance of flex PCBs to vibration makes them ideal for the harsh environment inside a motor vehicle.

Whether for cost reduction, longevity, improved product quality or performance, flexible PCBs offer an effective way to connect the various modules of an electronic system.

Useful tips from Prototype flexible PCB manufacturer

Most electronic projects begin with at least one build of prototype parts before moving into volume PCB manufacturing.
But the definition of a flex circuit prototype can vary considerably from one project to another.
In many cases, a prototype build is only a few parts used to verify form, fit and function, with engineering trying to determine if something actually works. In other instances, a prototype must not only satisfy the requirement of form, fit and function but the materials and processes used in the prototype stage are expected to be representative of what is used during serial volume production.
These prototype parts may also be used for customer qualification testing with the intention of ‘baselining’ a design, process sequence, or equipment.
It is more descriptive to refer to these parts as ‘pre-production prototypes’ or even ‘qualification parts.’

While there tends to be differences in what an individual company may view as the scope of a prototype, there are several elements common to most prototype requirements. These generally include compressed lead times, low volume and in most instances soft tooling.

Some companies expect multiple runs of prototypes with the intention of going into production with a ‘copy exact’ design.
This approach is intended to reduce startup costs but may delay a design decision as a part iteratively evolves through multiple build cycles.
Early involvement between the designer and the circuit fabrication manufacturer often helps eliminate some of the iterations.

There are a few different prototype manufacturing and support strategies evident in the flexible circuit industry.
Some “prototype shops” specialize in low volume, quick-turn flexible circuits and don’t intend to support volume production. T
hese quick-turn shops may have less formal manufacturing systems and often are more restrictive with material limitations due to stocked inventory.
They depend on skilled operator/technicians to accompany parts throughout the manufacturing sequence within facilities structured to quickly produce low volume parts.
In many cases, once the quick turn prototype phase is complete the customer will seek sources for the serial production parts in an alternative facility.

Another option occurs when a circuit fabrication facility operates a prototype area separate from the production area.
This might include separate staffing in addition to equipment and physical location.
With this option the prototype area deploys similar but alternative processing equipment and technology.
When the prototype stage has been completed, the product is moved to the production group and is tooled to run at high volume.

These two strategies have the advantage of allowing each group or facility to focus more on its competency.
A production facility can focus on high-volume production. The prototype facility can focus on fast turnaround.

This strategy can also have some disadvantages.
First, some projects require prototypes to be representative of production parts.
A prototype built in a different facility with different equipment and perhaps using different chemistries and process materials is not likely to satisfy a customer with a strict requirement for a product that’s tested and qualified as a final step before volume production.
Differences between prototype and production could include plating and etching chemistries, imaging resists, press materials and processing methods.
Even if the two parts built in different facilities both meet IPC 6013 tests and inspections, high reliability customers are likely to have issues with these differences. Second, there is a ‘lessons learned’ consideration.
A prototype build offers an opportunity to optimize processing to improve yields or efficiency—which ultimately converts to price.
If the prototype is built somewhere else, the production facility will go through their own learning curve.

Another printed circuit prototype model is to fabricate with the same equipment, chemicals and process materials as volume production parts.
This requires more sophisticated scheduling and nimbleness with equipment set-up and tooling.
But in this way, the transition from prototype stage to production manufacturing becomes a matter of scale.
It has the advantage of using the same equipment between the initial run and subsequent builds.
A key requirement is to produce parts without any long lead time tooling. Numerically controlled drilling and routing, laser direct imaging, laser ablation and NC-controlled punches are examples.
There is no time waiting for a tool and very little setup time, and changes can be made quickly.

Physical tools may be introduced to improve efficiency or throughput when parts move to steady state and higher volume.
Examples of physical tooling might include a hard tool blank die to define the cutline instead of an NC-controlled router, more sophisticated assembly fixturing, or use of a dedicated electrical test fixture instead of a universal flying probe tester.

Prototypes present a vital opportunity to not only reduce start-up costs, but to provide the customer a better part with higher quality levels and better delivery performance.
Early design involvement by the supplier can often result in a more robust product with lower manufacturing costs—and fewer prototype builds. Source:iconnect007

The comparison of two basic PCB material: FR4 and CEM3

The comparison of two basic PCB material: FR4 and CEM3
HTD PCB manufacturing experts will from 8 points to discuss.


1,Material
FR4:  glass fiber material

CEM-3:  composite epoxy material

2,Price
FR4: cheap

CEM-3: Lower cost than FR4

3,Flame-retarded rating
FR4:  UV94V-0, UV94V-1

CEM-3:  UV94V-0, UV94V-1

4,Strength
FR4:  rigid

CEM-3:  rigid

5,Thickness
FR4:  Min .05mm,  Max 3.2mm

CEM-3:  Min .6mm,  Max 1.6mm



6,Application
FR4:  Mobile Communication, Digital TV, Satellite, radar etc.

CEM-3:  Different Fillers Create Different Functions, like White or Black Board for LED Industry, High CTI Board for Household Electrical Appliance Industry.

7,Main composition
FR4:  Glass Fiber Paper + Resin+Copper + hardener

CEM-3:  Glass Paper +Glass Cloth +Fillers

8,Property
FR4: High Strength, Good Thermal Stability, Good Dielectric Properties, Through Hole Metallization, most widely used in the world

CEM-3:  Mechanical Property, Easy to Punch

The multilayer PCB is different from double layer PCB

Printed circuit boards, abbreviated as PCBs have become an integral part of the electronics world. They provide the users as a relief from the abstruse process of point-to-point wiring and circuit complexities. They have surely relieved us from buying plenty of wires and electronic equipment and have made our job much simpler by putting them on a short board. From day-to-day general electronic products to medical equipment, dedicated service equipment, and high-reliability products, everywhere we can see the undefeated usages of PCBs. So we can call it as a wonder of the modern electronics.
In accordance with the rapid growth of PCB usages, there has been also a transforming change in PCB production. Many electronic equipment manufacturers in china produce PCB as well, where there are some of them dedicating themselves solely to PCB production. There are various techniques of producing a frisky circuit from a lump of electronic components and a board. This wide variety of PCB manufacturing arts has been able to produce a number of different types of PCBs. The PCBs can be comprised of several layers. So on the basis of a number of layers included the PCBs have been categorized into two major parts such as one layered PCB and Multilayer PCB.
The multilayer PCB is different from double layer PCB, where both of the Sides of the PCB are printed with electronic component and wires. The multilayer PCBs are consisted of at least 3 layers of conductive materials.
The preparation of multilayer PCBs is somehow different than others. The alternating layers of core materials are pressed together to make the multilayer PCBs. The process is performed carefully to make sure that no air is stuck between the layers. The conductors are purely coated by resins for safety purpose. An adhesive element is used to stick the different layers together. The adhesive is properly melted before using and once it is used between the layers, it is cooled down. Multilayer PCBs are highly beneficial and popular among engineers. They can serve multiple tasks at one hand.
• The increased flexibility: If proper connections are made according to the need of a particular project the multilayer PCBs can be used to produce a wide variety of circuit combinations, thus increasing the flexibility of usage.
• Density: The increased number of layers can be a great step towards assembling a variety of different electronic components thus increasing the assembly density.
• Reducing the complexity: The multilayer PCBs have greatly reduced the job of wiring the components individually.
• Less space: As the components are tied together in a single PCB with multiple layers, the space of the circuit is reduced.

The PCB manufacturing process is very important

The PCB manufacturing process is very important for anyone involved in the electronics industry.
Printed circuit boards, PCBs, are very widely used as the basis for electronic circuits.
Printed circuit boards are used to provide the mechanical basis on which the circuit can be built.
Accordingly virtually all circuits use printed circuit boards and they are designed and used in quantities of millions.



The PCB manufacturing process can be achieved in a variety of ways and there are a number of variants.
Despite the many small variations, the main stages in the PCB manufacturing process are the same.

PCB constituents
Printed circuit boards, PCBs, can be made from a variety of substances.
The most widely used in a form of glass fibre based board known as FR4.
This provides a reasonable degree of stability under temperature variation and is does not breakdown badly, while not being excessively expensive.
Other cheaper materials are available for the PCBs in low cost commercial products.
For high performance radio frequency designs where the dielectric constant of the substrate is important, and low levels of loss are needed, then PTFE based printed circuit boards can be used, although they are far more difficult to work with.

In order to make a PCB with tracks for the components, copper clad board is first obtained.
This consists of the substrate material, typically FR4, with copper cladding normally on both sides.
This copper cladding consists of a thin layer of copper sheet bonded to the board.
This bonding is normally very good for FR4, but the very nature of PTFE makes this more difficult, and this adds difficulty to the processing of PTFE PCBs.

Basic PCB manufacturing process
With the bare PCB boards chosen and available the next step is to create the required tracks on the board and remove the unwanted copper.
The manufacture of the PCBs is normally achieved using a chemical etching process.
The most common form of etch used with PCBs is ferric chloride.

In order to gain the correct pattern of tracks, a photographic process is used.
Typically the copper on the bare printed circuit boards is covered with a thin layer of photo-resist.
It is then exposed to light through a photographic film or photo-mask detailing the tracks required.
In this way the image of the tracks is passed onto the photo-resist.
With this complete, the photo-resist is placed in a developer so that only those areas of the board where tracks are needed are covered in the resist.

The next stage in the process is to place the printed circuit boards into the ferric chloride to etch the areas where no track or copper is required.
Knowing the concentration of the ferric chloride and the thickness of the copper on the board, it is placed into the etch froth e required amount of time.
If the printed circuit boards are placed in the etch for too long, then some definition is lost as the ferric chloride will tend to undercut the photo-resist.

Although most PCB boards are manufacturing using photographic processing, other methods are also available. One is to use a specialised highly accurate milling machine.
The machine is then controlled to mill away the copper in those areas where the copper is not required.
The control is obviously automated and driven from files generated by the PCB design software.
This form of PCB manufacture is not suitable for large quantity but it is an ideal option in many instances where very small quantities of a PCB prototype quantities are needed.

Another method that is sometimes used for a PCB prototype is to print etch resistant inks onto the PCB using a silk screening process.

Multi-layer printed circuit boards
With the complexity of electronic circuits increasing, it is not always possible to provide all the connectivity that is required using just the two sides of the PCB.
This occurs quite commonly when dense microprocessor and other similar boards are being designed.
When this is the case multilayer boards are required.

The manufacture of multi-layer printed circuit boards, although it uses the same processes as for single layer boards, requires a considerably greater degree of accuracy and manufacturing process control.

The boards are made by using much thinner individual boards, one for each layer, and these are then bonded together to produce the overall PCB.
As the number of layers increases, so the individual boards must become thinner to prevent the finished PCB from becoming too thick.
Additionally the registration between the layers must be very accurate to ensure that any holes line up.

To bond the different layers together the board is heated to cure the bonding material.
This can lead to some problems of warp.
Large multi-layer boards can have a distinct warp on them if they are not designed correctly.
This can occur particularly if, for example one of the inner layers is a power plane or a ground plane.
While this in itself is fine, if some reasonably significant areas have to be left free of copper.
his can set up strains within the PCB that can lead to warping.

PCB holes and vias
Holes, often called via holes or vias are needed within a PCB to connect the different layers together at different points. Holes may also be needed to enable leaded components to be mounted on the PCB.
Additionally some fixing holes may be needed.

Normally the inner surfaces of the holes have copper layer so that they electrically connect the layers of the board. These "plated through holes" are produced using a plating process.
In this way the layers of the board can be connected.

Drilling is then accomplished using numerically controlled drilling machines, the data being supplied from the PCB CAD design software.
It is worth noting that reducing the number of different sizes of holes can help reduce the cost of the PCB manufacture.

It may be necessary for some holes to only exist within the centre of the board, for example when inner layers of the board need to be connected.
These "blind vias" are drilled in the relevant layers prior to the PCB layers being bonded together.

PCB solder plating and solder resist
When a PCB is soldered it is necessary to keep the areas that are not to be soldered protected by a layer of what is termed solder resist.
The addition of this layer helps prevent unwanted short circuits on the PCB boards caused by the solder. The solder resist normally consists of a polymer layer and protects the board from solder and other contaminants.
The colour of the solder resist is normally deep green or red.

In order to enable the components added to the board, either leaded or SMT to solder to the board easily, exposed areas of the board are normally "tinned" or plated with solder. Occasionally boards, or areas of boards may be gold plated.
This may be applicable if some copper fingers are to be used for edge connections.
As the gold will not tarnish, and it offers good conductivity it provides a good connection at a low cost.

PCB silk screen
It is often necessary to print text and place other small printed idents onto a PCB.
This can help in identifying the board, and also in marking component locations to aid in fault finding, etc.
A silk screen generated by the PCB design software is sued to add the markings to the board, after the other manufacturing processes for the bare board have been completed.

PCB prototype
As part of any development process it is normally advisable to make a prototype before committing to full production.
The same is true of printed circuit boards where a PCB prototype is normally manufactured and tested before full production.
Typically a PCB prototype will need to be manufactured quickly as there is always pressure to complete the hardware design phase of the product development.
As the main purpose of the PCB prototype is to test the actual layout, it is often acceptable to use a slightly different PCB manufacturing process as only a small quantity of the PCB prototype boards will be needed.
However it is always wise to keep as close as possible to the final PCB manufacturing process to ensure that few changes are made and few new elements are introduced into the final printed circuit board.

Summary
The PCB manufacturing process is an essential element of the electronics production lifecycle.
PCB manufacturing employs many new areas of technology and this has enabled significant improvements to be made both in the reduction of sizes of components and tracks used, and in the reliability of the boards.
Source: https://chinastencils.wordpress.com/2016/10/10/the-pcb-manufacturing-process-is-very-important/

4MCPCB is an Experienced Aluminum PCB Manufacturer

4MCPCB has been producing Aluminum Printed Circuit Boards (also called Metal base PCBs) for many years. Although originally envisioned for use in the power-supply industry these substrates are now most widely used in High Brightness LED products.

Aluminum Printed Circuit Boards Contain a Thin Layer of Thermally Conductive Dielectric Material that Transfers Heat

There are many names for these products; Aluminum clad, aluminum base, Metal clad printed Circuit Board (MCPCB), Insulated Metal Substrate(IMS or IMPCB), Thermally conductive PCBs, etc… but they all mean the same thing and perform the same way.

How Are Aluminum PCBs Made?

A thin layer of thermally conductive but electrically insulating dielectric is laminated between a metal base and a copper foil. The copper foil is etched into the desired circuit pattern and the metal base draws heat away from this circuit through the thin dielectric.





Benefits of Aluminum PCBs

Heat dissipation is dramatically superior to standard FR-4 constructions.
The dielectrics used are typically 5 to 10 times as thermally conductive as conventional epoxy-glass and a tenth of the thickness
Thermal transfer exponentially more efficient than a conventional rigid PCB.
Lower copper weights than suggested by the IPC heat-rise charts can be used.


Applications of Aluminum PCBs

Although Power Converters and LEDs are the largest users of these products, Automotive and RF companies are also looking to take advantage of the benefits of these constructions. While a single layer construction is the simplest, other configuration options are available at Amitron, including:

Flexible Aluminum PCBs

One of the newest developments in IMS materials is flexible dielectrics. These materials feature a polyimide resin system with ceramic fillers which provides excellent electrical insulation, flexibility and of course thermal conductivity. When applied to a flexible aluminum material like 5754 or similar, the product can be formed to achieve a variety of shapes and angles which can eliminate costly fixtures, cables and connectors. Although these materials are flexible, they are intended to be bent into place and remain in place. They are not suited for applications that are intended to be flexed regularly.



Hybrid Aluminum PCBs

In a ‘Hybrid’ IMS construction a “Sub-assembly” of a non-thermal material is processed independently and then bonded to the aluminum base with thermal materials. The most common construction is a 2-Layer or 4-Layer Sub-assembly made from conventional FR-4. Bonding this layer to an aluminum base with thermal dielectrics can help dissipate heat, improve rigidity and act as a shield. Other benefits include:

Less costly than a construction of all thermally conductive materials
Provides superior thermal performance over a standard FR-4 product
Can eliminate costly heat sinks and associated assembly steps
Can be used in RF applications where a surface layer of PTFE is desired for its’ loss characteristics.
Use of component windows in the aluminum to accommodate through-hole components. This allows connectors and cables to pass connections through the substrate while the solder fillet creates a seal without the need for special gaskets or other costly adapters.


Multilayer Aluminum PCBs

 Common in the high performance power supply market, multilayer IMS PCBs are made from multiple layers of thermally conductive dielectrics. These constructions have one or more layers of circuitry buried in the dielectric with blind vias acting as either thermal vias or signal vias. While more expensive and less efficient at transferring heat as a single layer designs, they provide a simple and effective solution for heat dissipation in more complex designs.



 Through-Hole Aluminum PCBs

In the most complex constructions a layer of aluminum can form a ‘Core’ of a multilayer thermal construction. The aluminum is pre-drilled and back-filled with dielectric prior to lamination. Thermal materials or sub-assemblies can be laminated to both sides of the aluminum using thermal bonding materials. Once laminated, the completed assembly is thru-drilled similar to a conventional multilayer PCB. The plated through holes pass through the clearances in the aluminum to maintain electrical insulation. Alternatively a Copper core can allow both direct electrical connections as well as with insulated through holes.

How flex stackups and materials effective manufacturing process?

Today, in what will be the first of many flex tips, we will be discussing optimal flex stackups and materials. One of our customers recently sent us a four-layer stackup that needed a little tweaking. We talked it over with our design engineers and came up with solutions and alternatives to all the issues at hand. It’s amazing how a few changes to your stackup design can ensure durability and manufacturability on your flex board.
The Board:
This was a four-layer flex board with zif connectors requiring controlled impedance.
The high-speed zif connectors connected finger areas from the edge to the top of the board.
The Issues:
The board’s flex layers were located on the outside of the stackup, which increased the possibility of manufacturing problems and issues.
Making sure the board met the impedance requirements.

The Solution:
We embedded the flex layers in the center of the stackup. This protected the layers during the manufacturing process and ensured that the less-durable flex layers were not exposed to outer-layer plating. This is how most rigid-flex stackups are designed. When the flex layers are on the outside, panels are harder to handle and harder to process. This made the board more durable and easier to manufacture. It also allowed for better impedance and better control around the flex finger area.
Because the flex layer is a separate process, putting the flex layers inside allows flex manufacturers the ability to etch away from the design while protecting the flex layers. Putting the rigid material on the outside also allows us to manufacture what is essentially a rigid panel. The flex layers are also protected by our surface plating because it should brittle the material. The material used also played a large part in making this board rigid-flex instead of flex. Rigid AP material was used, allowing for better impedance and reliability. It was a much better option than the original FR-4 material.