Quality Control

 

Quality Control for PCB


a) DRC Check

The Design Rules Check (DRC) is a very important step in PCB quality control. When we receive a new order from a customer, we will use an automated tool to verify that the layout does not have any specific placement, routing or other addressable layout errors.?

This DRC check will check the netlist and layout against the PCB design constraints and rules. It checks the board’s component placement and trace routing integrity for overlapping components, untraced pins, incorrect layer placement and constraints that are WHERE set for trace width routing and clearances.?We also do the manufacturing rule check to make sure the PCB design is manufacturable. If we find any errors we will get in contact with the customer.

b) Electrical Testing

Prototype Orders: We offer Flying-Probe E-Test for small volume and prototype orders. Your circuit board (PCB) is checked through a device called a Flying-Probe E-Tester. The Flying probe testers we use have few restrictions on access, require no test fixtures, and can test boards with virtually unlimited number of nets. The Tester will check for short circuits, open circuits and make sure the nets of the PCB we made is the same as the nets in your design. After testing is complete, the fail rate of your boards will be less than 1%.?

Production Orders: We use Testing fixtures to test production orders. A bed of nails tester is a traditional electronic test fixture which has numerous pins inserted into holes in an Epoxy phenolic glass cloth laminated sheet (G-10) which are aligned using tooling pins to make contact with test points on a printed circuit board.

The fixture contains an array of small, spring-loaded pogo pins; each pogo pin makes contact with one node in the circuitry of the DUT (device under test). By pressing the DUT down against the bed of nails, reliable contact can be quickly and simultaneously made with hundreds or even thousands of individual test points within the circuitry of the DUT.

The Tester will check for short circuits, open circuits, and make sure the nets of the PCB we made is the same as the nets in your design. After testing is complete, the fail rate of your boards will be less than 0.1%.

c) AOI(Automated optical inspection)

We use an AOI to check the inner layers of multi-layers PCB. AOI visually scans the surface of the PCB. The board is lit by several light sources and observed by a scanner or by a number of high definition cameras. This enables the monitoring of all areas of the board.

AOI for a bare PCB board inspection will detect these features:

* Line width violations

* Spacing violations

* Excess copper

* Missing pads. ?I.e. a feature that should be on the board is missing

* Shorts circuits

* Cut traces or pads

* Hole breakage.( Breakout ) ?I.e. a drilled hole (via) is outside of its landing pad?

This inspection is much more reliable and repeatable than manual visual inspection.


Quality Control for PCB Assembly

Components Quality control

To make sure the components to be used are good quality, there are several processes that we follow:

1. An overview of the visual electronic components inspection process includes:

* Packaging examined:

-Weighed and checked for damage

-Taping condition inspected-dented package etc.

-Original factory sealed vs. non-factory sealed

* Shipping documents verified

-Country of origin

-Purchase order and sales order numbers match

* Manufacturer P/N, quantity, date code verification, RoHS

* Moisture barrier protection verified (MSL)-vacuum sealed and humidity indicator with specification (HIC)

* Products and packaging (photographed and cataloged)

* Body marking inspection (faded markings, broken text, double print, ink stamps, etc.)

* Physical conditions inspection (lead bands, scratches, chipped edges, etc.)

* Any other visual irregularities found

Once our visual distribution inspection is completed, products are escalated to the next level-electronic components engineering distribution inspection for review.

2. Engineering Components Inspection

Our highly skilled and trained engineers receive the components for evaluation at a microscopic level to ensure consistency and quality. Any suspect parts or discrepancies that are discovered in the visual inspection process will either be verified or discounted by taking a product sampling of the material/parts.

The engineering electronic components distribution inspection process includes:

* Review visual inspection findings and notes

* Purchase and sales orders numbers verified

* Verification of labels (bar codes)

* Manufacturer’s logo and date log verification

* Moisture sensitivity level (MSL) and RoHS status

* Extensive marking permanency tests

* Review and comparison to manufacturer datasheet

* Additional photos taken and cataloged

* Solderibility Testing, the samples undergo an accelerated ‘aging ‘ process before being tested for solderibility, to take into consideration the natural aging effects of storage prior to board- mounting; In addition to the Engineering Components Inspection we have a higher level of inspection under the customer request.


X-Ray Inspection for BGA Assembly

Our automated X-ray inspection systems are able to monitor a variety of aspects of a printed circuit board in assembly production. The inspection is done after the soldering process to monitor defects in soldering quality. Our equipment is able to”see” solder joints that are under packages such as BGAs, CSPs and FLIP chips WHERE the solder joints are hidden. This allows us to verify that the assembly is done right. The defects and other information detected by the inspection system can be quickly analyzed and the process altered to reduce the defects and improve the quality of the final products. In this way not only are actual faults detected, but the process can be altered to reduce the fault levels on the boards coming through. Use of this equipment allows us to ensure that the highest standards are maintained in our assembly.


AOI inspection for SMT

As a primary testing technique in PCB assembly, AOI applies to fast and accurate inspection of errors or defects occurring in PCB assembly process so that high quality of PCB assemblies can be ensured with no defect after their leaving assembly line. AOI can be applied both to bare PCBs and PCB assembly. Here at HR Circuits, we mainly apply AOI to inspect SMT (Surface Mount Technology) assembly line and for testing of bare circuit boards,flying probe is used instead.

In HR Circuits, AOI equipment is depending on a high-definition camera, this equipment can capture images of PCB surface with the help of numerous light sources. Then, comparison will be made between the captured image and board parameters that have been input into computer in advance so that differences, abnormalities or even errors can be clearly indicated by its built-in processing software. The whole process can be monitored at any second.

AOI is contributive to efficiency improvement because it is placed on SMT assembly line, just after reflow. As soon as some problems are inspected and reported by AOI equipment, engineers can instantly change corresponding parameters in the previous stages of the assembly line so that remaining products will be correctly assembled.

Defects AOI can cover primarily come in soldering and components categories. In terms of soldering, defects can range from open circuits, solder bridges, solder shorts, insufficient solder to excess solder. Component defects include lifted lead, missing component, misaligned or misplaced components.