X-Out Panels: How to Mark, Count and Ship Them
An x-out panel is a fabrication panel that still contains one or more good boards plus at least one board that failed test or inspection. The bad position is marked so that nobody mistakes it for good material, and the panel is delivered with the marking intact. What happens next is decided by a contract clause that many buyers never read until a shipment is rejected.
Handling x-outs badly costs money at both ends. A fabricator that ships them silently damages the account when the customer finds them; a customer that refuses every x-out panel pays for the material that was scrapped. Most supply agreements settle somewhere between those two positions, and the settlement should be written before the first lot.
What an X-Out Panel Is
The term describes both the panel and the individual bad position, which is why conversations about them go wrong. A supplier may report a 96 percent panel yield while every panel contains an x-out board, because the count refers to positions rather than panels. The two numbers should always be stated separately.
An x-out is created when a position fails electrical test, or when a visual or dimensional check rejects it after test. The position may have been good and been damaged later in the process, which is common on the outer layers and at the panel edge. Once marked, the x-out panel is a mixed lot by definition.
Why Fabricators Ship X-Outs at All
Multilayer fabrication is a batch process, and a defect on one inner layer can reject one position out of dozens on the same panel. Discarding the whole panel would multiply the loss across positions that were never at fault, and the cost of that would be carried by every customer who ever places an order.
Panel utilization is therefore the reason x-outs exist. Where a defect affects one position out of twelve, the panel is 92 percent usable, and most buyers would rather have eleven boards than none. The alternative, a no x-out policy, is available and it is priced accordingly, which is the part that is often missed at negotiation.
Marking Methods: Ink, Label, Drill and Laser
The marking has to survive every process the panel will see and still be impossible to misread. Permanent ink is the cheapest and the least reliable, because plating and coating steps can obscure it or bleed it across the surface. A sticker works until it falls off in an oven or a wash.
A drilled or punched hole through the position is unambiguous and cannot be removed, and it is the reason many x-outs arrive with a hole where the board should be solid. Laser marking is the modern alternative: it is durable, machine readable and it can carry a serial reference that links the position to the test record. Whichever method is used, it should be named in the purchase order rather than left to the shop.
The Panel Map and How to Read It
A panel map shows the position of every board on the panel with the x-outs identified by index. It is usually supplied as a data file or a printed sheet with the lot, and it is the only reliable way to know which positions were rejected without physically examining each one.
The map should also state the reason code for each x-out, because a position rejected for a cosmetic defect and one rejected for an open circuit are not equivalent. Assemblers that receive reason codes can decide per position whether to build or skip; assemblers that receive only an X have to treat every x-out the same way. Traceability starts at this document, not at the finished serial number.
Fabrication Yield, Assembly Yield and Panel Utilization
Three numbers are routinely mixed together. Fabrication yield counts good positions per panel; assembly yield counts good assembled boards per built position; and panel utilization describes how much of the panel area produced sellable product. Reporting only one of them hides where the loss occurred.
The relationship matters commercially. If a panel arrives with a 5 percent x-out rate and the assembly line loses a further 2 percent, the delivered yield is not 98 percent. It is the product of the two, and the quotation should be built from that figure rather than from either one on its own.
When Assembly Should Refuse an X-Out Panel
An x-out panel should be refused when its marking cannot be verified, when the panel map is missing, or when the x-out count exceeds the agreed limit. It should also be refused when the bad position carries the only copy of a critical feature, such as a coupon, a fiducial pair or a panel edge datum that the machine needs to align to.
Refusal is not a negotiating position; it is a control. A mixed panel that cannot be segmented reliably will produce a bad board that passes through reflow and inspection, and the cost of catching it at functional test is far higher than the cost of rejecting the panel at goods-in. The acceptance class of the product should drive the decision, as described in our notes on acceptance class.
Programming Assembly Equipment Around X-Outs
Most placement machines can be told to skip a position, and many can detect a bad mark automatically. The bad mark is a fiducial-like feature placed at each board position; the machine looks for it, compares the result against the program, and skips the position if the mark is present or absent as configured.
Setting that up correctly is a programming task, not a switch. The mark type, its size, the lighting and the threshold all have to be taught, and the configuration should be verified with the panel deliberately reversed so that a failure to detect does not pass as a good board. Printing is another decision point: paste on a skipped position is wasted and must be cleaned before the next process step.
Counting, Invoicing and Traceability
Delivery should be counted in good boards, with the x-outs listed separately as non-chargeable or chargeable according to the agreement. Where the contract prices per assembled board, the count of x-outs determines whether the shop is paid for work it did on a position that was later scrapped, so the counting rule belongs in the traveller instructions.
Traceability means being able to say which panel a delivered board came from, and that requires the panel index to follow the board through depaneling. Where panels are routed into individual boards with no reference, the link is lost and an x-out can no longer be distinguished from good material. Keeping a position reference, even a simple index, preserves the link at almost no cost.
Contract Language That Prevents Disputes
Four clauses remove almost every argument. State the maximum x-out count per panel or per lot; name the marking method; require a panel map with reason codes; and define how the delivered quantity is counted. Add the rule for panels that exceed the limit, whether they are credited or replaced, and the process is closed.
The panel design itself should also support the policy. Rail width, tab placement and fiducial layout all affect how easily a panel can be segmented and skipped, and they are settled at the layout stage rather than at delivery. The rail width and tab routing rules cover the geometry that makes an x-out panel workable rather than awkward.
FAQ
Are x-out panels allowed by default? No. The default in most purchase agreements is a clean panel, and x-outs are allowed only where the order says so. A supplier who ships them without a written allowance is taking a decision that belongs to the buyer, and the shipment can be rejected on that basis alone.
Can a marked board be repaired and sold as good? Only under a documented rework and retest procedure accepted by the customer. Removing a mark and shipping the position is not repair, and it breaks the traceability that made the marking meaningful in the first place. Most agreements forbid it outright.
How much should a buyer pay for an x-out position? Nothing, if the count is reconciled against the purchase order quantity and the shop is credited for the shortfall. The practical answer is a price adjustment agreed in advance, because arguing about yield after delivery costs more than the boards are worth.
