Introduction to PCB Panelization

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Printed circuit board panelization is a technique where manufacturers of smaller boards manufacture them and connect them as a single array making it easier to move through an assembly line. The individual boards can easily be removed from the array for installation into a product.

An array which is also called a printed circuit board panel is a term used in printed circuit board manufacturing where a single PCB is combined multiple times to make a larger array of connected boards. The process is referred to as stepping out of the individual boards.

Many manufacturers have good ideas for coming up with different kinds of printed circuit boards. As they move to the warehouses to start producing them, it becomes difficult due to some misconceptions to come up with a standard printed circuit board. For this reason, it is important to have the following design considerations to meet the required standards in the industry.

Printed Circuit Board panel strength

An increased board count per panel increases the strength and reduces vibration. This then shows that for a manufacturer to produce a strong and long-lasting array board, he should consider using several arrays on the board.

The component layout

This includes the placement of all the components and connectors on the board. Those that hung off the edge are the ones that especially limit the penalization process. During the manufacturing process, the producer should be keen on the allocation of the components on the board to meet the standard.

Printed Circuit Board shape

Manufacturers produce different types of shapes of the Printed Circuit Board. The shape of the board can sometimes complicate parallelization. Some of the board shapes are complex. One can use Computer-Aided Design (CAD) software’s to fit unusually shaped boards into an array.

Tooling holes

All tooling holes should best be placed in the panel rather than in the circuit board when the boards are being placed in an array. The fabricators do not produce individual boards but produce panels, therefore, the holes should be placed in the panel.

ARRAY DESIGN TIPS

Boards that are brought in the array are the primary reason for making an automated assembly less expensive and faster. Arrays can also be useful because they can allow the increase of tooling rails, and holes which help in assembling.

Tooling rails/ frames of the array. They make simplify how to hold the arrays during the assembling process as it provides stability.

The tooling holes should be drilled from the top to the rails such that the array can be pinned down to avoid unwanted motion during the process of assembly. They are drilled to a required specification.

Fiducials are made out of copper on the rails which help the automated pick-and-place equipment by giving an equal reference point.

There are majorly three types of array that the manufacturers use and the manufacturer has to determine which one to use.

They include;

• Scored
• Tab routed
• The mixture of scored and tab routed

DESIGNING FOR SCORED PCB ARRAY PANELIZATION

The proper printed circuit board array panelization and arrangement ensures there is a low rate of damaging the individual boards when handling and during assembly. Scored array offers a few important benefits for separating boards from the array.

Advantages of using a scored printed circuit board

• It allows the designer to minimize the space between the individual boards.
• Minimal cost of assembly
• Less material per board is used.
• Has better mechanical stability.

TAB ROUTED ARRAYS

Tab routing is required when one has designed an irregular shape. Because the tab routed arrays are less sturdy than the scored arrays, the tooling rails should be added to all four sides of the array. This will give the array of printed circuit boards more support while handling the assembly process.

In tab-routed arrays, the printed circuit board is the one that is routed and held together using the small tabs.

In tab-routing panelization, the printed circuit board array that can conveniently use a V-groove method will instead use a tab routing method. With this type of method, the printed circuit boards are pre-cut from the array and held on the board with tabs.

Tab routing and scouring are used when board sides have given are straight and can be shaped while irregular sides should be tab-routed.

A diagram showing tab routing activity

In printed circuit board manufacturing, various components are chosen and used by the manufacturer to come up with the standard PCB required by the consumers. As a result, we have various methods of how to arrive at the required components to fit the need and meet panelization standards.

The following are various tips for choosing the components

1. Component footprint Decisions

As a designer, you must select printed circuit board component footprints and land patterns that will provide strong roots for the printed circuit board components. It is always good when you use the numeric keys to make a plan. A designer who cannot follow and comply with the datasheet has a high tendency to get an incorrect component footprint that leads to more errors.

2. Use of good grounding practices

The grounding planes are important features of the printed circuit board with all components that should possess the majority of the bypass capacitors. Capacitor size and frequencies should be keenly observed. You should ensure that you observe good grounding practices during the printed circuit design process.

3. None-lead free components to be separated from lead-free components

It is very key to separate all defined lead-free parts from the undefined to make sure a lead-free arrangement when choosing a printed circuit board component. It is advisable to label all the ingredients as lead-free to avoid confusion. It is always important for the designer to make his or her customer aware of the modifications because there is a variation that exists between lead-free and non-lead-free.

4. You should assign the virtual parts footprints

The virtual parts consist of power signals and ground. During the printed circuit board component schematic construction, all the virtual parts should be put into consideration and not ignore their importance in the process of designing printed circuit board components.

You should therefore get a better understanding of your printed circuit board assembly parts when you keep in touch with the bill of materials created.

5. Make sure you have the complete bill of material (BOM) data

Bill of Materials data is another thing to give maximum attention and it should be complete. One can follow the bill of the material report to get the information after that to review and fill in the manufactures data on every single part before advancing to the printed circuit board design stage.

Suppliers can work faster and solve some problems earlier when they have a complete bill of material.

6. Check the spare gates

To ensure that the whole printed circuit board works efficiently you have to check out for every additional obstacle. To ensure you promote the printed circuit board’s independent functions every spare gate in the drawing helps in understanding and running the board for other members. All component symbols made for printed circuit board layout and printed over the PCB board are helpful during the assembly and must be positioned correctly when connecting to unwired input.

7. Every connection with one pad

The composition of the printed circuit board components must follow one rule which is one pad for one connection for proper alignment during the assembly process. If there are other components on the pad like the capacitors and resistors another pad must be recreated.

8. Component package choice.

You should choose a component package that adds a touch of perfection to your design to speak for your work as a printed circuit board designer. Some choose components that work against them which leads to mistrust among their customers

The manufacturer also needs to choose what kind of board he will use to produce his printed circuit design. Before the development of the printed circuit boards, the board materials were being mostly covered by nests of entanglement that could easily fail. This could also result in a short circuit once the wires started to crack.

9. Speak to your component delivery

This is another technique a printed circuit board with perfectly formed components. According to the bill of material, the printed circuit board components should be delivered in all parts to make sure the appropriate arrangement of all the kits.

It is important to have an agreement with the manufacturer on the best means to get the components to prevent problems encountered during the delivery process.

A printed circuit board consists of four layers that are heat laminated together into a single layer. The types of materials used in printed circuit boards from top to bottom are;

• Silkscreen
• Solder mask
• Copper
• Substrate

Silkscreen

The silkscreen is the topmost layer of a printed circuit board that is used as a reference for placing components on the printed circuit board. It requires a special ink whose standards color is white, red, yellow, etc.

This layer applies ink traces to detect printed circuit board components, the test points, warning symbols, logos, and other marks. It can be found in the solder section. This kind of method is expensive.

DESIGN GUIDELINES FOR PCB SILKSCREEN DESIGN

Silkscreen designs vary from simple designs to complex ones that fail which if you do not apply is like having limited knowledge.

The guidelines below will guide you in making a workable silkscreen

• The method your printed circuit board manufacturer uses to make silkscreens

Most manufacturers cannot make silkscreens using the three-screen printing methods. The printed circuit board method affects your primary design elements like the size location of markings and others.

• Account for silkscreen items during printed circuit board layout

For someone to be able to read your screen well, marks such as polarity and reference indicators should be adjacent to their related components. As you make your design, you should be able to consider the additional spacing requirements to avoid covering the indicators.

• Choose your fonts according to your manufacturer’s printing method

Some of the printed circuit board design packages will allow you to make any silkscreen font. However, your manufacturer may only be able to support a few fonts. You should therefore contact your chosen printed circuit board service provider and guide you in choosing the right font.

• Do not use excess silkscreen markings

Do not be tempted to apply signs of every component and its information that is not useful to the assembly.

For you to make maximum use of printed circuit board identification and labeling even on small boards, you should observe the following.

• Start with regulatory requirements.
• Manufacturer markings and identification.
• Prioritize aids like polarity.
• Consider tasting aids like jumper indicators.

How to choose a printed circuit board silkscreen manufacturer

It is good and wise to seek services from reliable silkscreen manufacturers for you to produce high-quality products and have good services.

Almost all service providers have come up with a robust curve that suits the PCB printing process.

Ensure you maintain a good friendship with your manufacturer to perfect on Computer-Aided Design or the manual one before embarking on the actual production. This is where you will determine the font size, spacing, color, and other silkscreen design considerations.

After you are done, go through your design and check the errors and readability issues. Collaborate with your manufacturer to make good and valid decisions.

The Solder mask

The solder mask is also called solder resist. It is a thin polymer layer that is applied to the printed circuit board copper tracks to prevent oxygen reactions from taking place and also protect them against environmental damages.

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Purpose of solder mask

A solder mask is the printed circuit board’s primary protector from any form of corrosion and oxidation.

The solder mask also creates a cover between the soldered joints and other conductive parts during the assembly of the printed circuit board, therefore, protecting against the formation of the solder bridges.

Printed circuit board types of solder masks include

• Liquid epoxy

It is a low-cost form. You simply have to use the woven mesh to support the ink-blocking pattern. The epoxy liquid acts as a thermoset polymer for hardening during curing. The solder mask dye is combined with this liquid epoxy.

• Liquid photo imageable solder mask

This applies the photolithography technique that has a dry film. You can spray a liquid photo imageable solder mask over the board.

You are supposed to create the photography mask from the given Gerber files according to the required solder mask.

• Dry film

Dry film is placed on sheets of solder mask with the aid of a vacuum laminated process. This process makes the unexposed solder mask stick to the printed circuit board and removes bubbles that may occur in the film. After the exposure, the unexposed mask should be removed using a solvent and thermally cured for the remaining ones.

• Top and bottom side

On the two sides of the printed circuit boards, there are always two solder masks.

Copper in printed circuit boards

All printed circuit board manufacturers use copper because it is a good conductor of electricity. As the electric current moves along with the printed circuit board, copper keeps on heating which avoids damaging and stressing the entire printed circuit board. With other alloys, the printed circuit board could heat unevenly and the system may not function well.

Basics of copper base printed circuit board

It has multiple layers which include a copper base, an insulating layer, and the copper circuit layer. Copper-based PCB is divided into 2 categories.

• Embedded copper coin printed circuit board
• Buried copper coin printed circuit board

Advantages of copper printed circuit boards

1. The copper track is used between various components which makes the entire unit small to fit in any tiny device.
2. If any part of the printed circuit board is damaged and the labeling is transparent, the damaged part can easily be replaced.
3. The copper PCB takes less time to assemble.
4. Chances of the short circuit are eliminated due to its tight arrangement.
5. Correctly laid copper PCB reduces noise which enhances good performance.
6. Copper printed circuit boards are highly reliable and cost-effective

The disadvantage of copper printed circuit board

• Copper printed circuit boards can carry less current due to their small size.
• Its use is limited to small components only.
• Its soldering needs maximum attention since it’s tiny in size.
• It overheats and hence can damage the entire component.

Applications of copper printed circuit boards

Copper printed circuit board is applied in various fields of technology in different industries.

• It is used in solar power converters to increase its efficiency.
• Used in renewable energy.
• Use in power rectification.
• Used in communication devices.
• Applied in overload relays.

Substrate

Printed circuit board substrate is the substrate material used. The right choice in a printed circuit board design is the substrate used which is important for high-speed printed circuit board design. The substrate has a great influence on the finished printed circuit board design to withstand voltage, dielectric constant, and other electrical properties.

Types of substrates

Substrates can be grouped into five types each one of them having a unique set of characters and characteristics and specific applications.

• Flame Resistant two

This is a lower grade of the substrate which is made of impregnated paper that is easy to machine over a fiberglass substrate material. It is also called phenolic.

• Flame Resistant four

Fiberglass substrates are made up of fiberglass material.

• RF

This substrate comprises low dielectric plates and is used in circuit boards for applications in high-power radio frequencies. This material is rigid and can also be drilled, cut, or machined

• Flex

Not all circuit boards use rigid core materials. Some of them are designed to be slightly flexible or very flexible and are called flex circuits.

PANELIZATION GUIDELINES ON PRINTED CIRCUIT BOARD DESIGNS

1. Size of the panel

The maximum and minimum dimensions of the panel are determined by the machines used for each process of the printed circuit board manufacturing line. To enable proper handling of the panels the dimensions should be at least 50 mm in length.

2. Form of the panel

Some of the PCBs have irregular contours to meet the standard of limited installation spaces hence lacking the two parallel edges. For proper handling, machines material should be added around the irregular-shaped printed circuit board.

3. Handling margin

To ensure proper handling of the panels a narrow strip must be left free all around at the edge of the panel.

4. Preparation of singulation

There are two different ways of preparing the panel for the final singulation. The preventive measures protect the panel and printed circuit board from damage and increase the cutting speed.

5. Geometries of printed circuit boards

PCBs can have different and complex geometries due to individual requirements of the assembly. Mechanical separation like sawing is limited regarding their possible contour.

6. Technical cleanliness

Many industries like medical technology need to ensure the technical cleanliness of surfaces and the cutting edges. Various panel separation processes are different in their possibilities in terms of the degree of purity they can achieve. Some of the methods produce large particles that cannot be removed easily.

7. Space between printed circuit boards

For you to be able to cleanly cut out the printed circuit boards with the respective tool certain distances must be put into consideration during the design phase.

ADVANTAGES OF PRINTED CIRCUIT BOARD PANELIZATION

• It saves on money and time
• It improves work efficiency
• It improves product quality
• Prototype printed circuit design can add different design
• It protects printed circuit board from vibration and shock

All manufacturers are therefore advised to choose the right components when coming up with their designs to fit the customers’ needs and work efficiently.

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