It
is pretty much impossible to think of electronic devices available nowadays
without thinking of PCBs (
Printed Circuit Boards). After all, it is PCBs that
ultimately decide the measure of functionality of your electronic devices. The
better your PCB is, the more proficiently your device is bound to run.
To ensure that you
get PCBs to fit into your device, the newly fabricated PCBs have to go through
a series of internal and external tests to measure their overall quality.
The internal
quality of the PCBs is inspected and verified using IPC inspection guideline with a process called
Cross Section Analysis (also known as Micro Section).
What Does the Process Entail?
To
begin the analysis a small part of the PCB is cut out called ‘Puck’ named such
because it is immediately placed in a very soft acrylic that hardens around it
and begins to resemble an ice hockey puck. This makes it possible for the board
to be viewed from the side under a microscope.
Cross section
analysis can also be called a threefold inspection tool of the internal makeup
of a PCB as it is effective for in process verification as well as a failure
analysis. The sections are usually taken from coupon sets procured with the
production boards. The criteria for the inspection are set by the product
specification referred by the customer IPC 6012 class, MIL-PRF-55110/31032 or
by the customer’s very own requirements.
The coupons are
positioned on the production panels with the boards and are processed along
with the production panel where they reflect the process effects that are made
to the entire panel. This eliminates the need to remove a production part to
verify that the board meets the criteria.
Through hole
coupons are usually used to determine:
- Surface and Hole Wall Plating Thickness
- Separation of the Inner Layers
- Registration of the Drill to the Outer and Inner Layer Images
- Inner Layer Connectivity
- The Condition of the Laminated Materials Surrounding the Holes
- Other methods are also used to evaluate:
- Solderability
- Peel Strength of the Copper
- Electrical Characteristics of Inner Layer Traces
- Solder Mask
- Legend Inks
With this, the
manufacturers can inspect the prepared sections at various stages of production.
Through this, they can get clues to possible process issues and the viability
of the boards on a specific panel.
The corrupted/poor
product is separated from the batch which is identified by the markings on the
coupons and boards on which the panel was fabricated. The markings also help to
identify the processing specifics for boards that may be involved in future failures
thus becoming a very important part of the entire process.
The second role of
the cross section analysis is to act as an effective failure analysis tool. If
there is any indication of internal failure then individual boards may be
subjected to sectioning. A visual inspection of the section helps to identify
the reasons for internal process failures but other defects such as extraneous
copper, over etch, poor solder mask developing, and etc. can be identified with
cross sectional views of the surface trace work, pads and solder mask.
Data that is collected
during the sectioning of a single or various lots of boards can be used for
process improvement as well validation of the various processing steps used to
fabricate the PCBs.
When you reach out
to a company to have your PCBs manufactured, make sure to ask them about their
process of quality inspections.
Super PCB is a
company that provides the best boards each and every time, while ensuring that their
boards pass all standard quality tests. To get custom printed circuit
boards,
PCB prototype
and so much more, visit
http://www.superpcb.com
right now!
