What’s the difference between PI base material, PI coverlay, and PI stiffener?

As a special engineering material, PI has been widely used in aviation, aerospace, microelectronics, nano, liquid crystal, separation membrane, laser and other fields.It has flame retardant, high temperature resistance and low temperature resistance at the same time, long-term use temperature in -200℃~426℃.

Polyimide(PI) is very common in Flexible Board, it exist in base material, coverlay, even stiffener. Maybe some people feel confused about it, so today let discuss what’s the difference between them?

The difference in function:

  1. PI base material: For FPC base material, it have two types, adhesive base material or adhesivelesss base material. No matter for adhesive base material, or adhesivelesss base material, Polyimide(PI) is essential.
  2. PI coverlay: Its main function is used for circuit insulation.
  3. PI stiffener: Often applied to the area on the back of the FPC goldfinger. The PI stiffener is used to increase the thickness and hardness of the finger, which is easy to insert and remove.

The difference in thickness:

  1. PI base material: For the PI in base material, 1/2mil, 1mil are very common, its thickness even can arrive 4mil, 5mil(Dupont adhesivelesss PI material).
  2. PI coverlay: On coverlay, the PI thickness have two choice, 1/2mil or 1mil.
  3. PI stiffener: For PI stiffener, the thickness have many option according to customer’s need, such as 0.075mm, 0.1mm, 0.125mm, 0.15mm, 0.175mm, 0.2mm, 0.225mm, 0.25mm.

The difference in color choice:

  1. PI base material: No choice for option.
  2. PI coverlay: PI coverlay have three color, yellow, white and black.
  3. PI stiffener: It will change with the thickness change. The thicker it is, the darker it is. For example, 0.075mm PI stiffener looks like brown, 0.25mm PI stiffener more close to dark.

Wish above information is helpful for you. If you have any question, pls feel free to contact us.

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How to decrease the burr when drilling?

As we all know, the burr will influence the product quality and looks not so beautiful, so today I’ll share you how we to decrease the burr when drilling.

  1. First, the drilling bit must be new.

Usually, the drilling bit can be used for drilling 3000-5000 holes.

To avoid burr, we will change new drilling bit after drilling 2000 holes.

drilling holes
  • The drilling speed must be suitable.

Normally, the drilling speed is around 20W/drilling. The speed shouldn’t be too fast or too slow. If too fast, it might cause holes burning.

The best drilling speed is 16W/drilling.

(Rigid PCB have no requirement).

  • Pile up the boards shouldn’t be too much.

Flex boards pile up shouldn’t exceed 8PCS.

And it will be better to put some clear paper between each two boards.

(Rigid PCB have no requirement.)

If you want to know more about other process, please let us know, we will share with you by email.

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How to calculate impedance of FPC?

Due to Flexible boards are suitable for more and more fields with their unique advantages of lightness, thinness and compactness. There are also many boards that need to be assembled components or various signal transmission, so the requirements for impedance are increasing.

Normally there are four factors will affect impedance. 1), DK Value. 2), copper thickness. 3), copper trace and space. 4), dielectric layer thickness (PI&coverlay). You can know more details from below picture.

Er1: DK value for base material, the DK value of different brands’ materials and thickness are not the same, the normal range is 3.15 to 4.2

T1: copper thickness, this is the finished copper thickness, it’s marked 30um in below table, that’s means the base copper thickness will be around 18um.

W1: copper trace width, and S1 is copper trace space. Trace width and space are important for impedance.

H1: dielectric layer thickness, that is the PI thickness of the base material, PI thickness with adhesive thickness for adhesive materials.

W1&S1: copper width and space.

C1/C2/C3: coverlay thickness. 1/2mil coverlay is 28um, 1mil coverlay is 50um.

CEr: DK value for coverlay, 1/2mil coverlay is 2.45, 1mil coverlay is 3.4

Impedance diagram

Normally customers has required impedance value and total board thickness (stack up). So what can we do to meet the customer’s required impedance?

The first step, adjust copper trace and space to meet impedance, the smaller the trace width, the greater the impedance. Our minimum copper trace and space is 2mil, if we still can not meet impedance when copper trace adjusted to 2mil, then we have to move to second step.

The second step, normally the reference layer of impedance is copper foil, we can change the copper foil to grid copper, because the greater the grid spacing, the greater the impedance value.

The third step, if the above two steps still cannot meet the impedance requirement after adjustment, we need to communicate with the customer to adjust the stack up which included copper thickness, dielectric layer thickness and coverlay thickness.

Finally, we can calculate impedance and adjust copper traces for you if you need our service. If you would like to know more details, please contact us sales@bestfpc.com

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How to improve the bending effect of multilayer rigid-flex PCB?

Normally the rigid-flex PCB need to use in a small space area, and the flex area needs to be bent repeatedly or better bend radius. So many customers are concerned about the bending effect of the flex area, do you know how to improve the bend effect when you design? Here are a few suggestions for your reference.

The first one, the thickness of flex PCB board. The thinner the board, the better the flexibility. Such as below 6 layers stack up with 2 layers flex, we can used 1/3 oz copper instead of 1/2oz or 1oz, and 1/2mil PI instead of 1mil PI, then total thickness will be around 0.1mm.

The second one, adhesiveless material instead of adhesive material. The adhesive in base material will also affect the flexibility. Such as below stack up of flex part, there is no adhesive between Copper and Polyimide, but the coverlay must be glued and then laminated.

The third one, design a loose leaf (air gap) for flex area. Loose leaf can reduce the total thickness of flex part, especially for multilayer flex circuits in rigid-flex PCB design. Such as below sample pictures, no matter 2 layers or 4 layers in flex part, many customers will add one air gap. If you think the flexibility is not very good when we add one air gap, it’s okay to add two or more air gaps for multilayer flex PCB.

If you would like to know more details, please send your questions to our email sales@bestfpc.com

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Best Technology Wishes You Merry Christmas and Happy New Year 2020

Christmas and New Year is just around the corner. Merry Christmas to everyone. As the year 2019 is coming to an end, the team at Best Technology would like to wish you a happy, healthy, and prosperous New Year 2020. We believe that it is time to focus on the year that has gone and say thanks to all valuable people who helped us to become trusted and well-known PCB manufacturers in China.

We acknowledge that the year 2019 has been a surprise for us, wherein we got several opportunities to serve for our customers. The challenges that came along with these opportunities has helped us refine ourselves for better and stand tall among all our competitors. Being an industry-leader in flex, rigid, and rigid-flex PCB manufacturing, we could easily fulfill your orders in the specified time and in compliance with required specifications. Although technology plays a major role, we could never have achieved this success without our employees, who always made the most of their abilities to help meet our commitment of on-time deliveries.

rigid flex pcb

rigid flex pcb

On this holiday season, we would love to send our warmest wishes to the team who stood by us through challenges and our valuable customers for investing their time, money, and faith in our capabilities. This helps to serve you better. We are expecting to achieve more milestones in the upcoming year. This is not possible without your supports and faith. We hope this relationship will grow stronger in the New Year.

The entire team of Best Technology Wishes you a Merry Christmas and Happy New Year 2020 again!!!

For your easy reference, below is our holiday schedule:

Christmas Day: We will be closed on Dec 25, 2019 and resume working on Dec 26, 2019

The New Year: We will be closed from Jan 18, 2020 to Feb 1, 2020 and we will resume working on Feb 2, 2020

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Queries to Ask When Choosing a Flex PCB Prototype Manufacturer

Most of today’s flex PCB manufacturing process begins with a prototype production. There are several advantages of building a working model of the flex circuit before attempting the mass production of these boards. Building a prototype not only helps to test the board’s function but also aids in improving it as per the requirement. Additionally, prototype creation helps in detecting errors at the earliest, and decide upon the final design and other specifications of the board. Since prototype creation plays such a decisive role, it must be executed by an experienced service provider. But, how to find an experienced service provider? Do not worry, you can evaluate the competencies of flex PCB prototype making by asking a few questions such as:

1.How long have you been providing Flex PCB prototypes to the customers: Although the question seems basic, it helps to evaluate the total experience of the manufacturer. A PCB manufacturer with several years of experience will be certainly equipped and professional enough to understand your prototype requirements than a startup.

2.How long will you take to complete the prototype making from the order accepted date? Although the turnaround time varies as per the capabilities of the manufacturer, the manufacturer must be able to create Flex PCB Prototypes in 24 to 48 hours or within a week’s team. More than the said time frame is not usually acceptable when it comes to prototype creation.

3.What are the quality standards you implement to get the prototype right and functional? Again, standard and certification compliance varies across the industry. Since there are several international standards formulated to ensure the boards quality, you must know the quality standards followed by the chosen manufacturer.

flexible circuits

flexible circuits

4.Do you own a well-equipped manufacturing facility to proceed with the approved prototypes for mass production? There are some PCB production manufacturers that are specifically functioning to meet the prototype demands of the customers, and not in mass production. Lack of cutting-edge production facilities, advanced equipment, and man power are amongst a few reasons why such production houses limit their service to only prototyping. Hence, you must ensure the extent of their service.

5.What methods do you use to assure quality? It is inevitable to have the same level of quality checks throughout every stage of the flex PCB prototypes production. Hence, while choosing a PCB production manufacturer, it is extremely significant to ensure that they are performing the inspection stringently utilizing the best of techniques such as visual inspection, X-ray inspection, and Automated Optical Inspection.

Flex PCB prototypes can be extremely helpful as they help both the manufacturers and customers to check the board against various parameters before the mass production. Best Technology, your best supplier of flex PCB prototyping services with consistent good quality. Contact us to get a free quote today.

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Introduction to A Flexible Circuit Coverlay

During the flexible printed circuit board manufacturing process, a flex circuit coverlay (aka coverfilm) is used to encapsulate and protect the external circuitry of a flexible circuit board.
A flexible circuit coverlay serves the exact same function as solder mask that is used on a rigid printed circuit board. The difference with a flex coverlay is the needed element of flexibility and durability it provides to the flex PCB design.
The coverlay consists of a solid sheet of polyimide with a layer of flexible adhesive that is then laminated under heat and pressurized to the circuit surfaces. The required component feature openings are mechanically created using drilling, routing, or laser cutting.
Typical coverlay thickness is 0.001″ polyimide with 0.001″ of adhesive. Thicknesses of 0.0005″ & 0.002″ are available, but only used as needed to meet specific design requirements.
For more information visit our website to learn more about our flex & rigid-flex PCB manufacturing process!

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The Future of Flexible Circuits

As predicted by Best Technology Co.,Ltd., the market for flexible circuits is going to continue to expand steadily in the future, just as it has been doing for the past three decades. The reasons for this are not hard to find, as, on one hand, flexible circuits continue to support the existing technology so important to different industries, while on the other hand, advanced flexible circuits are able to comfortably meet the futuristic demands being made by up-coming industries, including the military, avionics, aerospace, telecommunication, consumer electronics, medical, and automotive.

One of the latest applications that flexible circuits have independently triggered as an explosion is the wearable electronics market. Wearing electronics on the body essentially calls for comfort, and flexible circuits guarantee this. Some examples of wearable electronic applications prevalent on the market are wrist-worn activity and body function monitors, foot-worn sensors, wearable baby monitors, medical sensors, pet monitors, and electronics on worn clothing. By bending and forming flexible circuits to suit the curve of the human body, the applications provide comfort for long wear and use.

Since establishment on June 28, 2006, Best Technology has been dedicated to being your best partner of flexible circuits solutions for our customers. We prefer to lose quantity rather than lose quality and with adhering to the company culture for so many years, more and more customers have been attracted by us. We are so grateful for what we have obtained so far and we will insist on providing the most satisfactory products and services for our customers. Welcome to Best Technology.

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When You Want Your Flex Circuit Boards on Time

If you have a new product launch on the books, and it’s going to be a big project. Your PR department is already spinning the press release, and your marketing department has been laying the groundwork for months. Suddenly, your flex circuit board vendor says that they’re running two weeks behind. That’s not a problem, is it?

As a business owner, you can’t afford to miss a product launch deadline or to run out of inventory when your customers are eager for your products. That means every single step in your supply chain must be reliable. If one vendor falls behind, the entire system grounds to a halt, meaning costly delays or mad scrambling, which is unacceptable.

Then,when you are seeking for vendors, consistency is the key. At Best Technology, we understand how important it is to meet your deadline. We are experts in manufacturing flexible circuit boards and rigid flex circuits based on the highest quality standards and we have accumulated much experiences since our establishment on June 28, 2006. We also own an excellent shipping department capable of getting your order to you on time wherever you are. You can rest assured we will not fall behind and cause delays!

If you are looking for a new flex circuit vendor or are unsatisfied with your current vendor, contact us today. We will give you a surprise.

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Imaging Process for Flexible Circuits

One of the first steps in manufacturing a flexible circuit is to build a circuitry pattern. In order to define the circuit pattern correctly, one needs to understand the basic process for building a circuit. Processes tend to fall in one of the following two categories:

1. Subtractive

The substrate begins with copper bonded to the dielectric, the unnecessary metal is removed; the remaining metal defines the circuit traces. The basic process steps for a subtractive process are:

Create resist pattern

Etch away exposed metal

Remove resist

Continue to process

Many possible methods are adopted for the creating the resist pattern, the following are two of the more common ones.

I. Screen Print

Screen print resist pattern

Cure resist

Etch

Remove resist

II. Photo Image

Apply resist coating

Photo expose image onto resist

Develop away unexposed resist

Etch

Remove resist

Screen printing stands for a tool made by forming a negative of the desired pattern on a woven screen mesh. The resist material is pushed through the open mesh and forms the circuit pattern on the substrate. The initial state of the resist material is normally a paste or semi-liquid. After the material is applied to the substrate, the resist needs to be cured. The cured resist protects the covered copper areas during the etching process.

In regards to photo imaging, a photo tool is created that is the negative of the desired pattern. The photo tool is placed over the resist coated substrate and flooded with a UV light. The photo tool allows the light to cure the resist where the pattern is to be created and blocks the light everywhere else. The UV light causes a chemical reaction in the resist and transforms it to have the chemical and physical properties to withstand the etching process. The developing solution strips away all the “un-cured resist” exposing the bare copper to be etched away.

2.Additive

The substrate begins with just the bare dielectric (possibly with a seed coating), the metal is added to the surface to directly form the circuit pattern. The basic process steps are:

Apply conductive material

Cure conductive material

Continue to process

The additive material is usually a paste and is often applied by screen printing. The applied paste is then cured to reach its optimal properties. Materials that have outstanding conductive properties tend to require very high temperatures to cure. The dielectric substrate for flexible materials is a limiting element for the temperature level and tends to restrict the types of additive materials that are used to create a circuit pattern. Generally speaking, the electrical, physical and chemical properties of this type of circuit are significantly lower than the properties achieved via the subtractive process.

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