Do you need help sourcing components for your PCBs? Want a guide to make your sourcing process more efficient? Read this in-depth guide about PCB component sourcing.
Introduction
PCB component sourcing is a vital process to complete your PCB design projects. Without component sourcing, you might end up with an incomplete project. Imagine all the hard work your team did, only to know that you cannot source all the components for your project.
Your company may face different challenges in sourcing components. You must consider several factors. These factors include component reliability, specifications, continuous supply, and suppliers. They determine which component and supplier is suitable for your company’s project.
Understanding PCB Components
There are thousands of different kinds of PCB components. Knowing the various kinds may help a project manager find different strategies during component sourcing. Below is a general list of the different types of PCB components.
Passive components
Passive components do not need external power to make them work. These components also do not do such tasks as amplifying or generating electronic signals. In short, passive components are more straightforward. They are generally less complicated to set up. Below are examples of passive components.
1. Resistors
These components define the resistance required for a circuit. They come in various sizes and power ratings. Usually, for the fixed-value ones, they are easy to set up during assembly. Examples of fixed-value resistors are carbon film resistors, thick film resistors, wire wound resistors, and the like. They may come in through-hole or SMD packages. Resistors can also be variable resistors, which may require special handling.
2. Capacitors store electrical charge.
Later, they discharge the charge to generate electricity. Examples of these functions include filtering and coupling electrical signals. Capacitors can also be used for timing applications. They can store electrical charge for a specific duration. Like resistors, plain capacitors are generally easy to set up during assembly.
3. Inductors are insulated wound components that serve a particular purpose.
They store electrical energy in current form. Capacitors store energy as voltage. They are widely used in switching regulators. They can boost (amplify voltage) or buck (reduce voltage) a power supply source. You’re sure to see inductors in a switching power supply. Inductors usually need a special process to make them. This is because they are wound.
4. Diodes are semiconductors.
They have a P-N junction made of P and N-type material. Diodes conduct electricity in only one direction. This characteristic allows diodes to act as switches, rectifiers, and signaling devices. A diode can alter an electrical signal. But, it does not need an external power source to work. This characteristic is the reason why a diode is not an active component. Plain diodes are usually easy to set up during assembly.
Active components
As their name implies, active components may require powering them up to make them work. They may also generate or amplify electronic signals. They generally have a more complex internal structure than passive components. A circuit designer usually prepares the required power sources and circuits for the active components on the PCB. This is because of these characteristics.
1. Transistors are three-terminal devices that amplify or boost a signal.
They have several applications because of their current or voltage-boosting capabilities. Example applications include load switches and simple amplifiers. Different kinds of transistors are available, such as the Bipolar Junction Transistor (BJTs) and Field Effect transistors (FETs), to name a few. They come in different power ratings and packages.
2. Operational Amplifiers
OP Amps are special ICs (integrated circuits) that aim to amplify voltage or current signals. Unlike transistors, OP-amps have built-in compensation circuits. These circuits help them amplify signals more efficiently. They usually come in an IC package, unlike transistors. Transistors are traditionally three-terminal devices. However, IC transistors are also available.
3. Integrated Circuits (ICs)
Inside ICs, you can see thousands or millions of transistors crammed inside an IC package. These ICs usually perform a specific function or can be used in simple to complex applications. Examples of simple applications include logic, charge control, sensor data processing, serial converters, etc. Complex applications require microcontroller (MCU) or application-specific ICs (ASIC). Advanced applications include microprocessors (or CPUs) or graphic processing units (GPUs) ICs. ICs usually have varying numbers of pins to interface with circuits. Usually, more complex applications require tighter pin pitch. This may be more difficult to handle.
Factors to Consider When Sourcing Components
There are different kinds of components that can come from various sources. With this, you must consider several factors. For example, consider how and where to source them. Verify key component parameters.
1. Component Data/Parameters
A component’s datasheet is one of the most essential documents. It provides your component’s data. You can find datasheets on every manufacturer/supplier’s website. The datasheet should be complete and easy to understand. Always check that the elements in your design do not exceed the most allowable specifications of the datasheet.
2. Component Cost
Cost is a defining factor for any electronic project. It can define how and to whom you’ll be able to sell your product. However, you must also check your component’s quality, reliability, and cost. Usually, you’ll have to weigh in on both of these parameters.
The cost usually comes with the quantity of the components you intend to purchase. It’s usual to see a component’s price decrease as you buy more batches. A manufacturer’s profit margin often depends on your purchase quantity. Ensure you get enough for your project’s lifetime.
3. Component Qualification/Reliability
Your component’s qualification and reliability data can be found on the manufacturer’s website. There are different component qualification standards, such as the ones listed below.
a. JEDEC
JEDEC stands for Joint Electron Devices Engineering Council. This council is a governing body. It is usually made for non-automotive semiconductor components or products. It applies to other applications as well.
b. AEC-Q100
AEC-Q100 is a qualification standard for ICs for automotive products. Testers rigorously test components qualified for AEC-Q100. They use extreme temperatures and stresses to survive the harsh nature of an automotive environment.
c. AEC-Q200 is like AEC-Q100.
It is a component reliability standard for passive components, not ICs.
d. ROHS
ROHS stands for Restriction of Hazardous Substances Directive. This standard restricts the use of hazardous materials on any of your components. If you’ve heard the term “Lead-Free,” it is synonymous with ROHS. You should follow ROHS, especially if your region strictly enforces this standard.
In addition to the standards, your components should have gone through several standard tests such as:
a. ESD-HBM and ESD-CDM tests
These tests evaluate the limits of semiconductor devices when it comes to electrostatic discharge. HBM stands for Human Body Model, while CDM stands for Charged Device Model. Ensure you find this data if you are worried about ESD destroying your device.
b. Environment testing
Environmental testing ensures your components don’t fail in various environments. These tests should include thermal cycling. They should also include stress tests, such as shock or vibration. Products/components meant for military/aerospace undergo more rigorous environment tests.
c. EMC test checks if your product emits or receives electromagnetic radiation. It must not affect your product’s function. Usually, this test is essential for components that have wireless capabilities.
4. Component Availability
Researching several component suppliers will help with your problems in component availability. Usually, you will find only some of the components you need from a single supplier. A hard-to-find component should show up being carried by a supplier through persistent research.
Researching Component Suppliers
There are different component suppliers across the globe. Ensure you’re dealing with reliable companies that practice professionalism. To do this, ensure they have a good track record and specific certifications. Below, we list such specifications.
1. ISO 9001 is a quality management (QMS) system certification.
2. ANSI ensures control programs that prevent your components from ESD exposure.
3. AS9120 – AS9120 is a QMS like ISO 9001, except that it caters to the aerospace industry.
Managing Component Obscolecense
You may successfully source your hard-to-find components; however, can you ensure you can source them again after some time? This situation is where component obsolescence takes place.
If you plan to use them indefinitely, your component should have a long End-of-Life program (EOL). A good-standing company usually posts an EOL program for some of its components. You may see a long-term parts availability document for this.
If your component has been EOL’d, you must replace them from your BOM with another element. You may have to do a review of your board. Review your product’s functional and environmental testing to test the new components.