Introduction

Front-end Engineering

The first step is to make sure that the data that we will use to make your PCBs is correct. To find out how we do this, go to our blog “Front-end Data Preparation“.

Fabrication Tests

We run 3 types of test during fabrication, visual, non-destructive measurements and destructive tests. The destructive tests are used to check our processes. They are made on actual PCBs or on the test coupons which we put onto every production panel. After more than 30 years of PCB manufacturing experience, we have developed test coupons on the production panels which provide simple, non-destructive tests for more complex parameters.

Each fabrication step can be seen in our video “How to Make a PCB”. The sequence below is based on a multilayer PCB. Single- and double-sided boards do not use all these steps, but are tested in the same way.

Passport

The results of these checks are summarised for each job in its Passport which contains information on the materials used, measurements made and tests passed. You can access the Passport via the blue book icon with each job under View Running Orders once it has been inspected or under Order repeats/View history.

Traceability

If you need more information on a job, we have full traceability back to material batches etc. Contact euro@eurocircuits.com or your local sales channel for this service.

Standards

We inspect all boards to IPC-A-600 Class 2 This is the standard used for most PCBs, and is the standard most often specified by our customers. The IPC, or Institute for Printed Circuit Boards, is “a global trade association representing all facets of the industry including design, printed circuit board manufacturing and electronics assembly.”

The IPC-A-600 standard “describes the preferred, acceptable and non-conforming conditions that are either externally or internally observable on printed boards”. It divides PCBs into 3 product classes.

Class 2 includes “products where continued performance and extended life is required, and for which uninterrupted service is desired but not critical.” Class 3 (where uninterrupted service is critical) is used for aerospace, defence and medical applications. For more information visit the IPC website.

Customers, especially those supplying the US market, may also specify UL marking. In this case, we further inspect to UL796. The Underwriters’ Laboratory (UL) is “an independent global safety science company …. dedicated to promoting safe living and working environments, UL helps safeguard people, products and places in important ways, facilitating trade and providing peace of mind.”

For PCBs, the most important criterion highlighted by UL marking is flammability. All our FR4 material meets UL 94 V0 plastics flammability test. For more information please see our page What about UL.

Inspection Steps During Production

Base Material

This is automatically checked against the order details using a data-matrix. The material data (type, manufacturer, laminate and copper foil thickness) is entered into the job history and will appear in the final Passport.

Production flow of inner layer image

Data matrix drilled into the production panel image

Print and Etch Inner Layers

Visual checks.

This step includes 3 visual checks:

  • After printing and stripping to make sure that the unwanted etch resist has been stripped away cleanly
  • After etching to make sure that all the unwanted copper has been etched away.
  • At the end of the process to make sure that all the etch resist has been stripped from the board.


Sample check.

Each production panel has a specially developed test coupon which indicates that the board has been correctly etched and that the track widths and isolation distances are correct. The type of etch resist used and the values for track width, isolation distances and annular ring are entered into the Passport file.

Inner layer imaging image

For more information please see our page “PCB Manufacture Step-by-Step“.

Inspect Inner Layer Copper Patterns

We use Automatic Optical Inspection equipment to scan the inner layer copper and compare it to the design data. The machine checks that all track widths and isolation distances correspond to the design values and that there are no short or open circuits which will cause the finished board to malfunction.

A Pass is entered into the Passport.

Innerlayer optical test image

inspect inner layer copper patterns image

For more information please see our page “Registration and Inspection of Inner Layers in PCB Production“.

Multilayer Bonding

Material.

This is automatically checked against the order details using a data-matrix. The material data (type, manufacturer, pre-preg and copper foil) is entered into the job history and will appear in the final Passport.

Thickness after bonding.

This is measured on each production panel and the result entered into the Passport.

Production flow of outer layers image

For more information please see our page “PCB Multi-layer Fabrication“.

Drilling

The drilling machines automatically check drill diameters to ensure that the size of the holes will be correct. A special test coupon on multilayer boards confirms the position of the drilled holes relative to the (already printed) inner layers.

The smallest finished hole size is entered into the Passport.

drilling image

For more information please see our page “Drilling Printed Circuit Boards“.

Hole-Wall Preparation

We deposit a layer of carbon on the walls of the holes to make them conductive for electroplating. We enter the process into the Passport.

Hole-wall preparation image

Apply Plating Resist

Visual checks.

After printing and stripping to make sure that the unwanted plating resist has been stripped away cleanly

Type of resist is entered into the Passport.

Outer layer imaging image

Production panel with resist image

For more information please see our page “Image the Outer Layers“.

Copper and Tin Plating

Non-destructive sample check.

The operator measures the copper thickness in the holes at 5 or more locations on one panel from every flight bar. The result is entered into the Passport.

Outer layer galvano image

Plating measurement image

For more information please see our page “Plating“.

Outer Layer Etching

Visual checks.

After etching to make sure that all the unwanted copper has been etched away.

Sample check.

Each production panel has a specially developed test coupon which indicates that the board has been correctly etched and that the track widths and isolation distances are correct. The type of etch resist used and the values for track width, isolation distances and annular ring are entered into the Passport file.

Outer layer etching image

Production panel after etching image

For more information please see our page “Etch Outer Layers“.

Soldermask

During process.

Visual checks:

  • Each panel is evenly coated with soldermask ink (laquer)
  • Alignment of soldermask phototool to the PCB


Sample checks:

The operator uses a projection microscope to check every panel to ensure that the soldermask is correctly aligned and that there are no solder-mask traces on pads.

Soldermask registration check image

The adhesion of the soldermask to the surface of the PCB is checked by the tape test used after legend printing.

The type of soldermask ink used is entered into the Passport data.

Solderresist coating

For more information please see our page “Applying Soldermask“.

Surface Finish

Sample checks on all surface finishes:

The thickness is measured using an X-ray scope.
We check the adhesion of the surface finish to the surface of the PCB using the tape-test after legend-printing.
100% visual inspection.

Lead-Free Hot-Air Levelling

The surface must be flat and even across the PCB without any non wetting. Component holes must not be narrowed or blocked. A few via holes may be blocked if they are not covered by soldermask.

Electroless Gold over Nickel

The finish must cover all exposed copper and have the same colour across the PCB. There must be no discolouration even in the holes

Chemical Silver

There must be no tarnishing or blackening.

The surface finish used is entered into the Passport, even where the order is for “Any leadfree”.

Plating flow 11 image

For gold and silver finishes we also enter the actual values measured.

Plating flow 11a image

For more information please see our page “RoHS Compliant Surface Finishes“.

Component Legend

Sample checks after curing:

The operator makes a tape test to check the adhesion of the surface finish, soldermask and legend to the surface of the PCB. We press a strip of pressure-sensitive tape across the test area and then pull it off sharply. There should be no bits of copper, surface coating, soldermask or legend ink adhering to the tape.

Visual check.

The operator checks that the legend on every board is clean and legible without blurring or smudging.

For more information please see our page “Silk-Screen and Cure“.

Electrical Test

All boards are electrically tested except single-sided boards where electrical testing is an option.

  • Shorts and open circuits.


We build a netlist from the Gerber and drill data. We use this as a reference netlist to test all nets are tested for shorts and open circuits. A pass is recorded in the Passport. As an extra precaution, if your design system outputs IPC-D-356A netlist format include the file in your data-set. We can then use this to check the Gerber netlist against your design netlist.

  • Inner layer registration.


A special test coupon allows us to confirm that the inner layer registration is correct.

Electrical test image

For more information please see our page “Electrical Test“.

Profiling and milling

We check the size and position of the board profile and internal milling using special test coupons.

Mechanical finishing image

Production panel completed image