What is the difference between SMT assembly with and without IP protection?

When you order a printed circuit board assembly, one of the first questions your manufacturer should ask is where the finished product will live. Will it sit on a dry indoor bench, or will it face rain, humidity, dust, and vibration in the field? The answer decides whether your boards are assembled with or without IP protection — and the difference between the two is far more than a layer of coating on the surface.

What does IP protection mean for an assembled board?

IP stands for Ingress Protection. The IP code, defined by the international standard IEC 60529, describes how well a product keeps out solid objects such as dust and liquids such as water. The first digit rates protection against solids, and the second digit rates protection against liquids. An IP67 product, for example, is dust-tight and can survive immersion in water up to one metre for 30 minutes.

For a bare assembled board there is no enclosure to do this job, so IP protection has to be built into the assembly itself. By adding a protective layer — typically conformal coating or low-pressure injection moulding — a manufacturer can make the PCBA itself resistant to moisture, dust, and corrosion, so the final product can reach the IP rating its application demands.

SMT assembly without IP protection

Standard SMT assembly produces a clean, functional board: solder paste is printed, components are placed, and the board passes through reflow soldering before inspection and testing. The result is an excellent electrical product, but also a bare one. Copper traces, solder joints, and component leads remain exposed to the surrounding environment.

Without protection, an assembled board is vulnerable to:

• Moisture and condensation, which can create leakage paths between conductors and cause short circuits
• Corrosion of copper traces and solder joints, especially in humid or salty air
• Dust and conductive debris settling between closely spaced pins
• Electrochemical migration, where moisture and voltage slowly grow metal across the board surface
• Falling insulation resistance, which can produce intermittent faults that are hard to find in the field

For many indoor, low-risk applications — consumer electronics in a dry housing, office equipment, or prototypes — unprotected assembly is perfectly adequate and keeps cost down. The enclosure provides whatever protection is needed.

SMT assembly with IP protection

When a product must survive outdoor conditions, washdowns, high humidity, or mechanical stress, an extra protection step is added after soldering and before final testing. Two of the most common methods are conformal coating and low-pressure injection moulding.

Conformal coating applies a thin, non-conductive polymer film that follows the contours of the board, covering traces, solder joints, and component bodies. It blocks moisture, dust, and mild chemicals while adding almost no weight. The material can be selected for the job — acrylic for fast, low-cost application, silicone for temperature extremes and vibration, polyurethane for chemical and abrasion resistance. Coated boards can usually be repaired by removing the film from the affected area, which makes conformal coating the more serviceable option.

PCBA low pressure injection coating goes a step further. A thermoplastic material is injected around sensitive components at low pressure, fully encapsulating them in a protective shell. It is a popular choice for sensors, connectors, battery packs, LED modules, and other components that need strong mechanical protection as well as waterproofing. Because the material is applied at low pressure, delicate parts are not damaged during moulding.

Both approaches share the same goal: to give the assembled board the environmental resistance it needs to reach the required IP rating and keep working reliably for years in the field.

The key differences at a glance

How to decide

There is no single right answer; the choice depends on where and how the product will be used. If the device will live in a controlled indoor environment with a protective housing, unprotected assembly is usually the economical choice. If it will be exposed to rain, humidity, dust, washdowns, or vibration — think automotive modules, outdoor lighting, industrial sensors, medical equipment, or marine electronics — IP-protected assembly is worth the investment. The cost of a coating or encapsulation step is almost always far lower than the cost of field failures, warranty returns, and damage to your brand.

Working with an experienced EMS partner

The quality of the protection depends as much on the assembly process as on the coating itself. A board with weak solder joints will still fail after it is coated, and connectors, test points, and other areas that must stay exposed need careful masking or selective application. This is why it pays to work with a manufacturer that controls the whole chain.

Farway Electronic is an electronics manufacturing services provider in Shenzhen, China, offering one-stop PCB, PCBA, OEM, and EMS services. Its SMT assembly service covers everything from prototype to mass production, supported by SPI, AOI, X-ray, ICT, and functional testing. When your product needs environmental protection, Farway provides automated conformal coating for boards up to 550 mm × 470 mm, as well as PCBA low pressure injection coating for components that need full encapsulation. Every protected board is verified through the company's PCBA testing process before it ships.

Whether your next project needs a simple unprotected assembly or a fully encapsulated, IP-rated board, the right partner will help you weigh the trade-offs and choose the solution that fits your product, your environment, and your budget.