Custom PCB board has to go through the flying probe test?

When Custom PCB board from China PCB manufacturer, does each board has to go through the flying probe test?

For small batch PCB system board, system board, will be on the model fly needle detection, if the test through will deliver the goods to you; for high-volume PCB system board, system board, will do a test needle plate tester for PCB test, than flying probe test more quickly fly. Because this can rest assured the sincerity of the PCB board manufacturer.

Flying probe test for PCB is the electrical test of some main problems the solution, mainly check PCB is open, short circuit; it used a probe to replace needle, using multiple driven by a motor, can fast moving electrical probe with the device pins make contact and electrical measurements were performed.

PCB Stack-Up Principle

PCB stack-up has a great influence on the EMC (electromagnetic compatibility) performance of a product. A good stack can reduce radiation from the loops on the PCB and the cables attached to the board. On the other hand, a poor stack-up can increase the radiation from both of these mechanisms considerably.

To design multi-layer PCB circuit boards, designers need to confirm the circuit boards structure firstly according to the scale of circuit, the size of circuit boards, and the requirements of electromagnetic compatibility (EMC). That is to say, designers have to use 2, 4, 6, or more layers of circuit boards. If the design requires the high density ball grid array (BGA) devices, the minimal number of wiring layers must be considered. For years, people always think that the less PCB layers would spend the lower cost. However, many other factors affect PCB manufacturing costs. In recent years, the differences between costs of multi-layer boards have been reduced significantly. As soon as the number of layers been determined, the placement of the inner layer and different signals in these layers are decided --- this is the stack-up design of multi-layer PCB. Careful planning and rational stack-up designs beforehand will save a lot of efforts in the following wiring and future production.

After the number of circuit board layers determined, It needs to reasonably arrange the placement order of the circuit of each layer. In this part, there are two main factors to be considered. One is the distribution of special signal layers. The other is the distribution of power layer and ground layer.
The more layers circuit boards have, the more varieties arrangement on special signal layers, ground layers and power layers have. Thus, it is more difficult to choose the best combination method, but the general principles are as follows

(1) The signal layer should be next to an internal power layer (internal power/ground layer), shielded by the copper film of internal power layer.

(2) The internal power layer should be integrated with ground layer tightly. That means, the thickness of medium between internal power layer and ground layer should take the smaller value, improving the power supply capacitor between the internal power layer and ground layer, and increasing the resonant frequency. If the electric potential difference between internal power layer and ground layer is not important, a smaller insulation thickness can be used, like 5mil (0.127mm).

(3) To avoid the two signal layers directly adjacent. It is easy to introduce crosstalk between adjacent signal layers, leading to the fail of the circuit. To place a ground layer between two signal layers can avoid cross talk efficiently.

(4) Multiple grounded internal power layers can reduce the ground impedance effectively. For example, A signal layer and B signal layer use ground plane respectively can reduce common-mode interference effectively.

(5) The symmetry of layer structure.

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PCB Design Considerations

In recent years, electronic products have been around military equipment , computers, communications equipment , mobile storage equipment, mobile communications equipment, and other related fields , and in size, integration, function and other aspects of the increasingly high demand , and consumer electronics in several generations per year the pace of development update , as an important part of the printed circuit boards and electronic products are constantly improve and update .  

 China now is the world's printed circuit board (PCB) production superpower , PCB species from single-sided to double-sided, 4-28 layer to multilayer ; from the through -hole conduction technology to blind hole conduction technology , Then HDI (High Density Interconnection) high density interconnect technology and technology progress. System board means is endless , different processes are different system boards also have advantages and disadvantages depending on the application object. Currently , the production of printed circuit boards are mainly used in two aspects, One enterprise production , the second is the school teaching and research .

In PCB design should pay attention to :

1 . Making physical borders:  closed physical borders of a future component placement , alignment is a basic platform , and also the layout automatically plays the role of constraint , otherwise , coming from the schematic elements will be overwhelmed . Here we must note accurately , otherwise after installation problems will be big trouble . There is a corner where the best arc , on the one hand to avoid sharp corners scratched workers , but also can reduce stress. 

2 . The introduction of component and networks: the network element and the introduction of good painting border should be very simple , but there are often problems must be solved one by one carefully follow the prompts errors , or later have to spend more effort.

3 , The layout element: lifetime layout and trace elements of the product , stability, EMC has great influence , should pay special attention to the place.

4 . Placed the order : the first place and the structure of the fixed location of the components, such as electrical outlets , lights , switches, connectors category , the placement of these parts LOCK function after a good software lock , will not make it in the future mistaken move . Then place a special element on the line and large components , such as the heating element , transformers , IC and so on . Finally, place a small device .

5 .Pay attention to heat : component placement pay special attention to heat issues . For high-power circuit , the heating element should be those such as power transistors , transformers, etc. try to place aside dispersed layout , easy heat dissipation , not concentrated in one place , nor too high capacitance in order to avoid premature aging of the electrolyte .

6. The wiring principle : when two panel wiring , two wires should be perpendicular , oblique , or curved alignment, avoiding parallel to each other , in order to reduce the parasitic coupling ; as the input and output circuits printed wire should try to avoid rabbit adjacent parallel , in order to avoid feedback between these wires plus ground wire is best . Traces corner as greater than 90 degrees , 90 degrees or less to prevent the corner , but also minimize the use of 90 -degree corners.

7 .Adjustment and improvement: after the completion of wiring to do is to text, individual components , traces some adjustments and copper , in order to facilitate production, commissioning and maintenance .

8 , checked for network ; sometimes because of misuse or negligence painted board network of relationships with different schematics , checking is necessary. So after drawing the plate must not rush to the manufacturer .

9 . Using the simulation function : so you can find some of the problems in advance , greatly reducing the workload for subsequent commissioning

So for China printed circuit board production enterprises should use traditional chemical system board technology for teaching and research universities and research institutions can use mechanical system board technology.

Printed circuit board (PCB) fixture test introduction

Rapidly increasing complexity of PCB assemblies makes visual defect detection nearly impossible. Receiving a PCBA without electrical verification can significantly delay design verification of prototypes and system integration of low volume PCBAs. The cost and time to develop fixture based in-circuit testing (ICT) is prohibitive in the prototype stage and the investment in ICT or functional test is tough to justify for low volume manufacturing. 

 

Vergent Products offers a solution – flying probe fixtureless testing based on parametric test of each component. Fixtureless test development is low cost and very fast. There is no costly fixture to design and build. Tests are generated from CAD information which enables a high degree of test coverage and flexibility. 

 

Testing your low volume products and prototypes allows for detection and repair of electrical defects such as wrong parts, reversed parts, missing parts, solder opens, and major solder defects. Fixtureless testing can help you improve your products time-to-market by achieving the highest possible quality levels early in the product life cycle. Fixtureless test allows your engineers to focus their efforts on prototype design verification instead of debugging process issues. 

 

Fixtureless testers use a flexible moving probe system. Multiple probes are automatically moved very rapidly to various test points on the assembly – hence the name: “flying probe”. These probes are capable of static DC voltage, current, resistance, capacitance, and inductance measurements. Test points are derived from CAD data to ensure accuracy and to maximize test coverage. 

    

Here is a brief description of some of the features of the Seica S40 has to offer: 

    1>Four independently moving topside contact probes; Test speeds up to 12 – 20 tests per second 

    2>Test area up to 16” x 20” 

    3>Positioning repeatability accuracy of +/- 0.12mils; Minimum positioning resolution of +- 0.20 mils in each axes 

    4>Minimum probe contact pitch of 0.12 mils between probe pins; Minimum pad size of 4.0 mils 

    5>Maximum component height of 0.9 inches including board thickness 

    6>Automated optical inspection, in-circuit programming, and boundary scan functional test capable (optional) 

 

For best turn around time on board test program generation and debug please provide: 

    1>Schematics 

    2>ASCII CAD data 

    3>Raw card 

    4>Populated board 

 

The test development NRE charges are very reasonable. 

introduction of circuit board drilling and PCB drilling File

A circuit board drilling is just like a common drill, except that it is optimized for drilling holes in the printed circuit board as opposed to drilling holes in other materials such as wood. To make a drill on PCB, the first factory should have the PCB drilling file. The drill file is also commonly referred to as an NC (numerically controlled) drill file in the industry. Excellon is the preferred term used with our Wonderful PCB Limited services. The Excellon drill file defines the hole locations and tool numbers (X & Y coordinates).

PCB drilling File General Requirements:

•All PCB holes are plated through meaning, there will be solder or silver in the PCB hole barrel.

•Must be Excellon format

•Must be ASCII text viewable. Please open with "Word" or "notepad" to verify a numeric list of X & Y coordinates. There should be no strange graphical characters.

•PCB drill file should not contain "G01", "G54", or any reference to "D" codes when opened in a text editor. This indicates a Gerber format and is most likely a drill drawing rather than an NC file.

•Properly formatted PCB drill files have sizes separated with "T" codes that indicate tool numbers. (T01, T02, etc)

•A tool report with sizes is necessary if the sizes are not included in the drill file header.

•For Slots or Cutouts (PCB Express only): Fabrication Drawing, NC Drill File, or Gerber file is necessary to define slot/cutout size and/or location. ◦To achieve a plated slot or cutout place the feature on the drill layer and include an outer layer pad at least the size of the slot or cutout.  Maximum diameter for a plated feature is 0.250"

To have PCB drilling file, and now we need to know there are two main drilling holes in the circuit board. One is NPTH hole, another is PTH hole.All the holes in the single sided printed circuit board are NPTH hole. That’s because no need for electronic conduction between layers in single sided PCB. It has just one copper foil layer. PTH hole will appear in double sided or multilayer PCB.

These holes exist for the electronic conduction among layers. So it may have Copper in these holes.

Back drilled holes can be back drilled before filling (no exposed copper), or after filling (exposed copper looking down on a cross-section of the barrel of the hole), or on non-filled holes. That means that they could be drilled before filling which means before the second drill for the unfilled holes (drill the identified back drill holes, plate, back drill, fill, drill non-filled holes, plate again) or after second plate (drill the filled holes, plate, fill, drill the identified back drill holes and the non-filled holes, plate, back drill the back drilled holes), or they could be back drilled at the end of all the processes if no holes have filling (drill all, plate, drill the back drilled holes).

There will be over size clearances for plane layers and there will be pad suppression for signal layers, so the only exposed copper is the "top" of the barrel. That should not be a problem in most applications and so back drilling (stub drilling) is not itself sufficient reason to incur the cost of via filling. But if VIAs are going to be filled, it makes sense to fill the holes but only before back drilling. Filling after back drilling has its own special issues.

Identifying the back drilled holes in a separate drill file or set of files, and indicating back drill on a drill chart, automatically, from an input say in the design of the pad stack, seems to be missing and would be nice to have. Right now we have to add all these notes about what layer not to breach and how deep is the hole (or conversely, what is the maximum remaining stub) by some special designation in the hole chart that points back to a sheet 1 note - having logic in the design tools to do this would be a plus. (author: Albee)    

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PCB Layer Introduction From Wonderful PCB Limited

PCB board layer analysis:

1.       Top Layer, also known as component Layer, is mainly used to place components, for than the laminates and sandwich plate can be used to wiring.

2.       Mid layer, can have up to 30, in a multilayer signal lines used for cloth.

3.       Bottom layer, also known as the welding layer, mainly used for wiring and welding, sometimes also can be placed components.

4.       Top overlayer, Projection of the contour is used to indicate components, components of symbols, nominal value or model and various kinds of comment character.

5.       Bottom overlayer, Same as the top silk layer effect, if various annotation on top silkscreen layer contain, so don't need to be at the bottom screen printing layer

6.       Internal planes, it is mainly used as the signal wiring layer, Protel DXP contains 16 internal layer

7.       Mechanical layers

8.       Solder mask layer, there are top solder mask and bottom solder mask. It is Protel PCB corresponds to the welding plate and the hole in the PCB file data automatically generated plate layer, laying resistance welding is mainly used in the paint. The board layer adopts negative film output, plate layer displayed on the bonding pad and a hole part represents not solder resist paint shop area on a circuit board, which is for welding parts.

9.       Past mask layer, there are top past mask and bottom past mask. When it is welding furnace used to correspond to the SMD components of solder joints, is also a negative form of output. Board layer to display on some representative circuit boards welding plate and the hole are not spread the area of solder paste, is can't to welding parts.

10.   Keep-out layer, it is mainly used for electrical drawing PCB border

11.   Multilayer, it is mainly used for layout multilayer circuits

12.   NC drill

13.   Drill drawing, it is used for setting drill profile.

Wonderful PCB circuit board factory production circuit board used in all kinds of electronic products, PCB type can be divided into: gold-plated board, heavy gold plate, tin plate. OSP antioxidant plate, tin plate, gold finger plate, plate, carbon oil LanJiao plate, high-frequency boards, aluminum circuit boards, etc. Products are widely used in computers, communication products, household electrical appliances. Product sales throughout the country China, receive the praise of users, welcome to inquire, to choose.  

PCB Design – How To Create Circuit Boards

To create a PCB Design you need to draw holes, pads and wires for your circuit. Then you send this drawing to a manufacturer or you etch it yourself.

 

Sounds hard? Don’t worry, there are many free tools out there that will help you do this.

 

Starting with schematics

 

Before you start drawing wires and stuff, you need to know what circuit you want to build. So you need to find or design schematics for your circuit. And you need a PCB design software. Then you are ready to begin the process.

 

Start by drawing your schematic diagram into the software you have chosen.

 

PCB design process

 

Preparing the board layout

 

Now it’s time to draw the board. You need to transfer your schematic diagram into a drawing of your printed circuit board.

 

Drawing PCB’s is artwork. Take your time, and make sure it looks good. Follow the design guidelines for drawing circuit boards.

 

Most PCB software will have tools that will help you draw your board from the schematic. I can’t cover them all, but I’ve written a PCB design tutorial for Eagle to help you learn.

 

Things To Think About

 

Will you put the circuit board in a box? Remember that tall components might need to be laid down flat to fit. With a drawing of your components placed on your board, print it out on a sheet of paper. Use this paper version of your board to test that it will fit the box and that your connectors will fit.

 

Getting your PCB manufactured

 

When you are done drawing your board, it is time to get your PCB design ready for manufacturing.

 

This basically means you need to check your board for errors and convert your board layout to Gerber files. Then, choose a cheap PCB manufacturer and get your board made.

Wonderful PCB Manufacturing Services

As one of the leading printed circuit board manufacturers based in Shenzhen China, Wonderful PCB has been offering world market with quickturn high-quality PCB prototype to production services at a reasonable price for 18 years. To provide customers with more professional and advanced circuits board, we're committed to adhering to the strictest standards during our PCB manufacturing process, we're fully compliant with the ISO 9001 ISO 14001 quality management system. We're capable to provide an instant quotation for your custom PCB. Additionally, we offer PCB making inspirations, PCB layout tips from top PCB design companies and PCB news on our website from time to time. Our customers are satisfied with our fine product quality, on-time delivery, fair pricing and superior service.

Most PCB manufacturers only allow one customer design to be processed per production sheet because of the complex and technical challenges found with different customer's orders. This is expensive because the set-up costs for each sheet manufactured are charged entirely to each client.  Furthermore, daily production schedules change constantly according to demand. Our printed circuit board manufacturing process is completely different from raditional PCB manufacturer’s production processes. We run PCB designs from different customers (but requiring identical technical specifications) on the same sheet and process them together.  The greater the number of different PCBs on a sheet, the lower the set-up cost will be for each client. Manufacturing of different PCB material configurations and specifications are scheduled to run to a weekly timetable, much like a train network. This allows us to plan our capacity and lower our costs through enhanced capacity utilisation and precise scheduling. We have achieved our success by perfecting our fabrication workflow. Our PCB service has been designed for efficiency and low cost.

One of our customers speak highly of us like this: “We choose Wonderful PCB because they offer the entire service from producing the PCB through to ordering parts, assembling and testing. Compared with other manufactures, we appreciate that Wonderful PCB is really communicative during the whole production process. Possible issues are discussed and solved immediately. Hence, we received high quality PCBs with negligible reject rate. In the end Wonderful PCB offers attractive prices, considering the offered services.

“I've using Wonderful PCB for years, and they provided me with good-quality, low-cost PCBs. I used Wonderful PCB to manufacture mobile phone parts, as well as some research developments for some projects. In all this cases, they offered very competitive prices, as well as good quality. They always have met my requirements and deadlines. Also they have been very helpful, supportive and responsive, when some problems appeared in our designs. Finally, last year I used their PCB assembly service for first time, and they operated smoothly in a short time, at a very cheap price” another customer said.

The relevant knowledge of PCB

1. The raw materials

 

At the beginning of the 20th century to the late 1940 s, is the infancy of the PCB substrate material industry development. It mainly displays in: the development characteristic of this period with the resin substrate material, reinforced material and insulating substrate, get a preliminary exploration on technology. These are the most typical substrate material for printed circuit board, copper clad with the advent of development, create the necessary conditions. On the other hand, in order to foil etching method (subtraction method) manufacturing circuit PCB manufacturing technology for the mainstream, the initial establishment and development. It is copper clad on the determination of the structure, characteristic, has played a decisive role.

 

2. polychlorinated biphenyl

 

PCB polychlorinated biphenyls (PCBS) in 1929 until the late 70 s north American business using a synthetic organic compounds, while Canada not the chemical processing production, but also has been widely used in electrical equipment insulation, heat exchangers, water systems and other special applications.

 

After decades after people realize the polychlorinated biphenyls (PCBS) on the global environment pollution, which is a mixture of various chlorinated biphenyl, has a great harm to human body. The Canadian government has taken measures to try to eliminate the PCB, but happened in Canada in 1977 illegal import, processing and sales of the phenomenon of PCB, and the PCB in 1985 illegal released into the natural environment, and the Canadian constitution allows owners continue to use the PCB equipment until the life period of equipment. Canada since 1988, the provincial government began for PCB storage, transportation and destruction of the rules.

 

PCB is not easy to break down in a natural environment, but also spread very far, PCB in production and processing, use, transport and waste disposal process into the air, soil and river and sea, small Marine organisms and fish breathe to PCB, and they have become great Marine food, as a result, PCB went into the body of the all sea life, including mammals of Marine biology. The accumulation of PCB in the Marine organism far beyond it in the water content, almost is the number of thousands of times.

the article from: The relevant knowledge of PCB

Rules on PCB construction

Today, let’s introduce primary knowledge on PCB. Here suggest some rules on PCB construction. Mostly are about the information on SMD and DIP assembly.

1. About SMD assembly

In SMD assembly, we must pay attention to the mininum gap between components (capacitors, resistors and IC chips). Usually, we suggest the best gap between independant component and IC chip is 0.5-0.7mm. But, the gap may change according to the configuration of fixture.

2. About DIP assembly

If in DIP assembly, the gap between resistors is 1-3mm, which is wider than SMD assembly. What needs to notice is to make sure enough gap in DIP assembly. Thinking of difficulties of assembly process, nowadays seldom use DIP technology.

3. About the place of decoupling capacitor

Around power port of IC will need to place an decoupling capacitor. The decoupling capacitor should try best near the power port. When a chip have several power ports, each power ports should have a decoupling capacitor.　

4. Independent component on the edge of PCB

Normally, PCB is delivered by panel. So components on the edge of PCB should comply with two rules. The first one is to parallel V-CUT direction. The second is should keep specified gap from the edge, so that to avoid damage on components when making V-CUT.

5. If connect two adjacent PADs, we should make sure they are connected outside of PADs and to avoid connecting as bridge. Moreover, in the meantime, we should notice the width of trace.

6. Traces along with the PAD should keep the same width. If not accordant with electrode size, we should check if short circuit happen or not. 

7. Pay attention that PADs should not have VIAs.

8. Leading wire could not be near the edge of PCB. Further, it’s not allowed to add copper at the edge of PCB or tooling holes.

9. If value of capacitor is big, we should firstly consider if the temperature of capacitor meet the requirement or not. And second assure the capacitor far from the heating area.

10. In the end, we should payment more attention on the technology of SMD assembly of capacitor. When do SMD near heating area, capacitors will be easily deciduous from PCB because of shaking during production.

The basic knowledge of printed circuit board (PCB)

Printed circuit board (PCB) almost appear in every electronic device. If there is electronic components in some kind of device, they also be mounted on various sizes of PCB. Except fixing these varieties of small sparts, the main function of PCB is to provide electrical connection for sorts of PCB parts to each other. As the electronic equipments become more complicate and require more spares, the circuits and spares on PCB also become more and more intensive. Standard PCB look like this. Bare board (without any top spares) is also often to be called Printed Wiring Board (PWB). 

The baseboard itself is made of insulate and inflexible materials. The tiny circuit material on the surface which can be seen called the copper foil. Oringinally copper foil is covering the entire board, but some parts of them were etched during manufacturing process, the left parts become tiny circuits like mash lines. These circuits are called conductor pattern or PCB layout, and used to provide electrical connection for PCB components.

For fixing the parts on the PCB, we weld their pins on the wiring directly. For a basic PCB (single-panel), all components were concentrated on the one side, and wirings were concentrated on the other side. As such, we need punch holes on the board, for pins to get through to the other side of the board, so pins of components were welded on the other side of the board. Because of it, the front side and back side of PCB are called Component Side and Solder Side.

If there is a certain part on PCB need to be removed or put back after the production is completed, socket will be used when the component mounting. Because the socket is soldered directly on the board, the parts can be any disassembly. See below is ZIF (Zero Insertion Force, zero-pluggable power type) socket, which allows parts (here refers to the CPU) can be easily inserted into the socket, also can be removed. Fixed pole near socket can be fixed after you inserted into the socket.

If you interconcet two PCBs, generally we will use the edge conncetor of known as "Goldfinger". Goldfinger contains many bare copper pads, in fact these copper pads are also one part of PCB routing. Normally, when connection we will put the gold finger from one PCB inserted into the appropriate slot from another piece of PCB (commonly called expansion slots). In the computer, such as graphics cards, sound cards, or other similar interface cards, are connected to the motherboard by the gold finger. 

Green or brown on the PCB is solder mask color. This layer is an insulating protective layer can protect the copper, the parts can be prevented from being welded to the incorrect place. Besides, a silk screen layer will be printed on the solder resist layer. Usually there will be printed some text and symbols (mostly white) to mark out the position of the parts on the board. The silk screen is also called legend.