What is PCBA?
Before diving into the details of free component offers, let’s briefly review what PCBA entails. PCBA refers to the process of soldering or mounting electronic components onto a printed circuit board (PCB). The key steps involved in PCBA are:
- Solder paste application
- Component placement
- Reflow soldering
- Inspection and testing
PCBA can be done manually for low-volume prototypes and hobbyist projects. However, for higher volumes and tighter deadlines, automated PCBA using pick-and-place machines and reflow ovens is much more efficient. This is where PCBA services come in – they have the specialized equipment and expertise to quickly assemble your PCBs.
The Cost of Components in PCBA
While the upfront cost of the bare PCB is easy to determine based on the size, layer count, and quantity, the cost of the components that go on the board can be harder to predict. The bill of materials (BOM) for even a relatively simple PCB can easily include hundreds of individual components of varying types and values.
Two of the most common types of components used in almost every PCB design are resistors and capacitors. These passive components perform critical functions like:
- Current limiting
- Voltage division
- Filtering
- Decoupling
- Timing and oscillation
Despite their low unit cost, the sheer quantity of resistors and capacitors used can make them add up to a significant portion of the total BOM cost. Here is an example breakdown for a hypothetical PCB design:
| Component Type | Qty | Unit Cost | Total Cost |
|---|---|---|---|
| Microcontroller | 1 | $2.50 | $2.50 |
| Transistors | 5 | $0.20 | $1.00 |
| Diodes | 10 | $0.10 | $1.00 |
| Resistors | 50 | $0.02 | $1.00 |
| Capacitors | 30 | $0.05 | $1.50 |
| Misc (connectors, hardware, etc) | N/A | N/A | $3.00 |
| Total | $10.00 |
As you can see, even though resistors and capacitors individually cost just a few cents, together they make up about 25% of the total BOM cost in this example. This percentage can vary depending on the complexity of the design and the other components used.
PCBA Service Freebies
To help customers save on BOM costs and make their PCBA services more attractive, many providers have started offering free placement of resistors and capacitors. The specifics of these offers can vary, but they generally follow a format like:
- Free placement of chip resistors and capacitors from 0201 to 1206 size
- Maximum of X number of free placements per board (e.g. 50, 100)
- SMT (surface mount) components only, through-hole is excluded
- Eligible components must be sourced through the PCBA vendor’s suppliers at their listed prices
Let’s consider a couple of real-world examples of PCBA Freebie offers:
JLCPCB
JLCPCB, one of the largest global PCBA providers, has an offer of:
- Free placement of chip resistors and capacitors sized 0201, 0402, 0603, and 0805
- Up to 20 free placements for 5 pieces, 50 for 10 pieces, 100 for 20 pieces, 150 for 50 pieces, 200 for 100 pieces
- Components must be from JLCPCB’s parts library with “BASICDATA” in stock
So if you were ordering 100 pieces of a design that used 100 basic chip resistors and capacitors, you could save $10 or more compared to buying the components yourself or having them placed at the standard rate of $0.002-$0.004 per placement.
PCBWay
PCBWay, another major player in the PCBA space, has a similar offer:
- Free setup and placement of 0201, 0402, 0603, 0805, and 1206 chip resistors and capacitors
- Up to 50 free placements for orders of 5-10 pieces, 100 for 11-50 pieces, 150 for 51-100 pieces, 200 for 101-500 pieces
- Parts must be from PCBWay’s component library and in-stock
The potential savings here are comparable to JLCPCB’s offer, just with some slight differences in the quantity tiers and eligible component sizes.
Maximizing Your Savings
To get the most out of these PCBA freebie offers, there are a few best practices to consider:
1. Design with the offer in mind
If you know you will be taking advantage of free resistor and capacitor placement, try to use as many eligible components as possible in your design. Stick to the common SMT sizes like 0603 and 0805 unless your design requires otherwise.
2. Check stock before finalizing your BOM
Since the components need to be sourced from the PCBA vendor to qualify for free placement, always check their component stock before committing to your BOM. They may not carry more exotic parts or less common values.
3. Compare total cost, not just placement fees
While the free placement is attractive, make sure to compare the total cost of your order (components + PCB fab + assembly) across different vendors. One may offer cheaper resistors and capacitors that offset the lack of free placement, for example.
4. Consider value-added services
Some PCBA vendors offer additional value-added services like functional testing, programming, and conformal coating which can save you time and effort. Weigh the cost and convenience of these services in addition to component prices and placement fees.
Summary
PCBA freebie offers that waive placement fees for common components like resistors and capacitors can be a great way to reduce your BOM and assembly costs. By designing with these offers in mind and sourcing your components strategically, it’s possible to save hundreds of dollars on larger orders.
However, always consider the bigger picture and compare the total cost and value across multiple PCBA vendors before making a decision. The lowest placement fees don’t always result in the lowest overall project cost once you factor in component prices, additional services, turnaround time, and quality.
FAQ
What is a resistor?
A resistor is a passive electronic component that resists the flow of electric current. It is used to control the current in a circuit, divide voltages, and provide electrical resistance for many other purposes.
What is a capacitor?
A capacitor is a passive electronic component that stores electric charge. It is used to filter signals, smooth power supply voltages, couple AC signals, and many other applications.
What does “PCBA” stand for?
“PCBA” is an acronym for “printed circuit board assembly”. It refers to the process of soldering or mounting components onto a bare PCB to create a functional electronic assembly.
What is reflow soldering?
Reflow soldering is a process used in automated PCBA where components are first attached to the PCB with solder paste, then heated in an oven to permanently melt and bond the solder. This allows many components to be soldered simultaneously.
What is a bill of materials (BOM)?
A bill of materials or BOM is a comprehensive list of all the components and materials needed to build a product. For PCBAs, the BOM typically includes a list of all the electronic components with their part numbers, values, quantities, and other specifications needed for procurement and assembly.
