IPC and ESD standards for PCB handling, storage and depaneling

Which standards govern how a board is stored, moved and separated

Most standards conversations in electronics assembly are about soldering. J-STD-001 covers how the joint is made, IPC-A-610 covers whether the finished assembly is acceptable, and between them they absorb most of the training budget.

The standards that govern what happens to a board before and after it is soldered get far less attention, and they are where a surprising amount of scrap comes from. A board that was handled correctly through every solder operation can still fail because it sat in the wrong container, absorbed moisture nobody measured, took an ESD hit nobody logged, or was snapped out of its panel in a way that cracked a joint two centimetres from the break line.

This page covers the standards that apply to handling, storage and depaneling, what each one actually asks for, and what it means when you specify equipment.

What do IPC Class 1, Class 2 and Class 3 mean?

Nearly every IPC acceptance standard is written in three classes. The class is not a quality grade you pick because you feel like it. It is set by what the assembly does and what happens if it stops working.

• Class 1, General Electronic Products. The requirement is that it functions. Cosmetic imperfection is not a rejection. Consumer goods, LED lighting, novelty electronics.
• Class 2, Dedicated Service Electronic Products. Continued performance and extended life are required, and uninterrupted service is desired but not critical. Computers, telecom, most industrial controls.
• Class 3, High Performance Electronic Products. Continued performance or performance on demand is critical, downtime is not tolerable, and the end-use environment is often harsh. Aerospace, implantable and life-support medical, military, automotive safety systems.

IPC-1601: the standard that actually covers storage racks

IPC-1601, Printed Board Handling and Storage Guidelines, is the document that directly addresses what you keep bare and assembled boards in. It is the least-cited standard on most shop floors and the most relevant one to a rack purchase. It addresses four risks:

• Contamination. Boards pick up residues from surfaces, gloves and the containers themselves. Materials that outgas or shed are a problem, especially before conformal coating, where contamination shows up later as adhesion failure.
• Physical damage. Scratches, dents, pad damage and edge damage from boards contacting each other or the container. The guidance is to support boards so they do not touch, which is what a slotted magazine rack does and what a stacking tray does not.
• Moisture absorption. Bare laminate and assembled boards absorb ambient moisture, which connects directly to J-STD-020 and J-STD-033 below.
• Electrostatic discharge. Handling and storage inside an EPA has to keep boards from accumulating and dumping charge.

The practical read for a rack: boards held on a fixed pitch, not touching each other, in a material that does not shed or outgas, that controls charge, and that can be tracked as one container through the process.

ANSI/ESD S20.20 versus ANSI/ESD S541: program versus material

These two get quoted interchangeably by vendors, and they are not the same thing.

ANSI/ESD S20.20 is a program standard. It defines the requirements for an ESD control program at a facility: the EPA, grounding, personnel training, verification and audit. Its international equivalent is IEC 61340-5-1. A facility gets certified to S20.20. A rack cannot be certified to S20.20, and any vendor who tells you their product is "S20.20 certified" is either confused or hoping you are.

ANSI/ESD S541 is the packaging materials standard. It classifies packaging and handling materials used inside an EPA by surface resistance:

A rack is a material inside your EPA, so S541 is the standard that applies to it. Your program is certified to S20.20; the rack has to be a material your S20.20 program can defend during an audit.

More conductive is not automatically better. A very conductive material discharges a charged board fast, and a fast discharge through a sensitive device is the event you are trying to prevent. For board handling the useful zone is roughly 10⁴ to 10⁶ Ω: charge leaves, but gradually.

What to require from a vendor

The measured number, not the phrase "ESD safe". Point-to-point resistance, resistance to ground, static decay time, and the temperature and humidity the test was run at. A test without conditions is not comparable to anything.

J-STD-020 and J-STD-033: moisture, and why a rack's temperature rating is a process decision

IPC/JEDEC J-STD-020 classifies moisture sensitivity level, MSL 1 through 6, for surface mount devices. The MSL sets the floor life: how long a part can be out of a moisture barrier bag before it has to be used or baked.

IPC/JEDEC J-STD-033 is the handling, packing, shipping and use standard for those parts, and its bake tables are what a shop actually works from. For most populated assemblies the practical window is 90 °C to 125 °C for 24 to 72 hours, depending on package thickness, body size and MSL.

Here is the part that touches equipment. A standard ESD magazine rack is rated to 80 °C. An oven running a J-STD-033 bake at 125 °C is well past that, so the boards have to come out of the rack, go into a bake tray, and go back into a rack afterward.

That transfer costs two extra handling operations per lot, two extra ESD exposure events, a physical damage risk at every touch, and a traceability gap where the lot is in a container it was not logged into. None of it appears on a purchase order and all of it appears in yield.

A rack rated to 200 °C removes the transfer: boards enter the rack at incoming and leave it at the loader, and the bake happens with the boards in place. Rated to 200 °C while running at 125 °C also means the rack is operating with margin rather than at its limit for 72 hours at a time.

Above that, 300 °C all-aluminum construction is for lead-free reflow direct loading, aerospace cure and high-heat stress testing, not for MSD bake. If your only high-temperature process is a J-STD-033 bake, 200 °C is the correct specification and 300 °C is capability you will not use.

IPC-A-610 and IPC-6012: what counts as depaneling damage

IPC-A-610, Acceptability of Electronic Assemblies, is the acceptance standard, and it contains the criteria that decide whether a separated board passes. The categories depaneling drives are edge condition, including burrs, nicks and roughness at the break; laminate condition, including delamination, measling and cracking near the separation; and damage to components and solder joints near the break line.

IPC-6012, Qualification and Performance Specification for Rigid Printed Boards, governs the board itself, including edge and laminate integrity.

All of these tighten by class. Edge damage that passes at Class 1 fails at Class 3, and Class 3 assemblies are exactly the ones where a hairline crack under a BGA becomes a field failure years later.

IPC/JEDEC-9704: board strain, the number that decides your depaneling method

IPC/JEDEC-9704, Printed Circuit Assembly Strain Gage Test Guideline, is the standard that turns "handle it carefully" into a measurement. It defines how to instrument an assembly with strain gauges and measure the strain, in microstrain, that a process imposes on the board.

It exists because the failures that matter are invisible. Excess strain cracks ceramic capacitors, fractures BGA solder joints and starts pad-lift that no visual inspection catches. The board leaves your floor testing fine and fails in the field.

Depaneling is one of the highest-strain operations most assemblies see, and the method determines how much:

• Manual V-break. The panel is bent and snapped along the score. The bending moment radiates several centimetres from the break, which is where MLCC micro-cracking and BGA joint fracture happen. Highest strain, least repeatable, entirely operator dependent.
• Router. Low strain and good edge quality, at the cost of dust, longer cycle time, tooling and programming per panel.
• Pizza-wheel or single circular cutter. A round blade rolls along the score with lateral force and no opposing blade, so pressure transmits into the copper.
• V-cut shear with opposing blades. A circular blade rides over a stationary linear blade, so the cut is a scissor action delivered inside the V-groove rather than around it. Force is isolated to the groove instead of radiating into the board.

How PCBRacks equipment maps to each standard

Five steps to specify handling and depaneling equipment that survives an audit

1. Fix your class first. Class 1, 2 or 3 determines every acceptance limit downstream. Specifying equipment before the class is settled means re-specifying it later.
2. Map your temperature path. Write down every process the board passes through with a temperature: bake, cure, reflow, stress test. The highest one sets the rack rating you need, with margin, not at the limit.
3. Demand measured ESD data, not adjectives. Surface resistance with the number, inherent versus topical, decay time, and test conditions. Five questions, one email, and it sorts the market immediately.
4. Measure strain before you choose a separation method. IPC/JEDEC-9704 gives you the procedure. If instrumenting is not practical, at minimum choose a method whose physics keeps force in the groove instead of bending the panel.
5. Keep the container count to one. Every transfer is a handling operation, an ESD exposure and a traceability gap. Equipment that lets a board enter one container at incoming and leave it at the loader is the cheapest process improvement available.

Where this shows up by industry

• Aerospace and defense work to Class 3 with full traceability, and typically drive the high-temperature and all-aluminum rack requirements through cure and stress-test schedules.
• Medical devices work to Class 3 with documentation demands that make the one-container, one-identifier point decisive during an audit.
• Automotive, particularly ADAS and safety systems, works to Class 3 or a tightened Class 2 and is generally the most sensitive to depaneling strain because of high ceramic component counts.
• Telecom and industrial work to Class 2, where the gains are throughput and handling damage rather than acceptance limits.
• Contract manufacturers carry every class at once, which is the case for standardizing on equipment specified to the tightest one.