PCB Handling and Logistics Between Shops

A finished board travels from a fabrication shop to an assembly line, and the condition it arrives in decides whether the first process step works. The handling between those two points is part of the product specification, and a change to it is a change to the process the customer receives.

What Leaves the Shop

The board leaves with a surface finish that has a defined shelf life, a solder mask that has a defined cure, and a cleanliness level that was measured. Each of those continues to change after the board is packed.

The finish oxidises, the mask absorbs moisture and the surface collects whatever the packaging carries. Our board quality notes describe the state that the board is in when it is packed.

Packaging as a Source

Paper that sheds fibre, foam that crumbles and bags that carry dust all deposit material on the product. The packaging is therefore qualified as a source rather than assumed to be neutral, and a change of packaging supplier is treated as a process change.

The requirement is a clean, non-shedding material that does not outgas, and the practical check is a wipe test on a sample of the packed board. Our cleanliness measurement notes describe how that is done.

Moisture and the Transit Environment

The board absorbs moisture in transit, and the amount depends on the humidity and the time rather than on the distance. A board shipped by sea in a sealed container reaches a different moisture content from one shipped by air in the same period.

Where the moisture matters, the packaging includes a barrier and a desiccant, and the receiving end checks the indicator before opening. Our fabrication notes describe how that requirement is stated.

The board is thin, and a stack of thin boards in a box bends under its own weight. The support has to be distributed rather than at the edges, and panels are normally shipped vertically in a rack rather than flat in a stack.

The edges are the second risk, because the plating on an edge or on a castellation is exposed and is easily damaged by a band or a clip. Protective material at the contact points is part of the packaging rather than an extra.

Static and the Unpacked Board

The board itself is not particularly static sensitive, and the components that will be placed on it are. That means the handling precautions at the assembly line are about the components, and the board packaging is about physical and chemical protection.

Where the board is delivered with parts already assembled, the packaging is an ESD packaging requirement as well. The two cases are separate and the specification should name which one applies.

Receiving Inspection

The receiving check covers the count, the physical damage, the moisture indicator where one is present and the packaging condition. It is a short check and it is the only point at which a transit problem can be attributed to transit.

Recording the condition at receipt is what makes a later claim possible. Without the record, damage found in the store is attributed to the supplier by default.

Storage Before Assembly

The board is stored in a controlled area, and the storage time counts against the shelf life of the finish. A finish with a six month shelf life that spends five months in a store has one month of assembly window.

The shelf life therefore has to be tracked from the fabrication date rather than from the receipt date, which is the reason the date code is marked on the board and on the bag. Our coating notes describe what happens to a board that is used beyond its window.

Process Control and Verification

The measurements that matter are the repeatable ones: conductor width and spacing, annular ring, finished hole size, plating thickness and surface finish are all verifiable on a coupon that travels with the panel. Running a first article through the same checks as the production panel confirms that the two agree, and that comparison is the cheapest form of process control available at prototype stage.

Keeping a sample from the panel turns a dispute into a measurement, because the same coupon can be re-examined by both parties without rebuilding the batch. Reviewing the design before the data is released is cheaper than correcting it after the panel is in the tank, because every step downstream inherits the decision made at the front end.

Documenting the assumption is part of the design work, and a short note on the drawing prevents a question that would otherwise arrive a day later and cost a day of schedule.

Does a sealed bag replace a clean board? No. It keeps the board in the condition it was packed in and it does not improve it.

Is transit damage a supplier issue? It depends on the record. The condition at receipt is what decides whether it is attributed to transit or to storage.

What does gopcb provide for board handling? We provide packaging qualified against shedding and outgassing, barrier and desiccant where moisture matters, rack shipping that supports thin boards, edge protection at plated features, receipts recorded with condition, and shelf life tracked from the fabrication date.

Checks Before Release

The checks that matter are the ones performed on the product rather than on a sample kept for the purpose, because a coupon that travels with the panel is the only evidence about that panel. Where a requirement can be measured, it should be measured at the point of manufacture and recorded against the board or the lot it applies to.

A parameter that is set once and never re verified drifts, and the drift is usually discovered by a defect rather than by the record. The tooling, the material and the profile form one system, and a change to any of them should be assessed against the other two before it is released.

Where the process window is narrow, the measurement resolution has to be better than the window, or the data cannot distinguish a good part from a marginal one.