Rush PCB Inc., one of the most popular and prominent contract manufacturers ensure the quality of their products for their customers, taking no chances and double-checking before the products leave our premises.
Activities like PCB assembly require several complicated steps and processes, and as a contract manufacturer, we make sure before starting that our customers’ boards will not have any design issues hampering manufacturing processes. Therefore, we perform several PCB Design for Manufacturing or DFM checks to ensure we move ahead with your PCB assembly smoothly.
Design for Manufacturing Checks
As a contract manufacturer, when we receive your design data for the first time, we process it through a design review. Our design review of your data depends on the format you have chosen to send.
If the customer’s PCB design data is in CAD database format, we send it to our engineering section for review. Design data that we receive in any other format, we must import or translate it into other formats that we regularly use. Translating or importing data is a lengthy process and prone to errors, making it much less reliable. Therefore, we prefer and advise our customers to send us the original CAD database format. Moreover, if we need to make any design changes, we can do it more easily in the original data format.
We review the customer’s data in several simultaneous steps. For instance, some of our engineers will start with a review of the customer’s Bill of Materials or BOM. They will look for the following:
- Parts that manufacturers are no longer recommending for use
- Parts with long lead times
- Parts that are nearing their end of life (EOL)
As a parallel exercise, a second team of engineers will be reviewing the customer’s design data for manufacturing issues like:
- DFM problems
- PCB manufacturability
- Signal Integrity issues
Resolving DFM Problems
This involves component review, and we will review the parts in your BOM, matching them to the master inventory database that we maintain for components. We update our database consistently in real-time, so that our engineers always have up-to-date information on component availability.
Based on the conclusion our engineers reach, we recommend that our customers go for necessary replacement of parts. Some parts may be nearing their end of life, and there may not be an exact replacement available. In such cases, we recommend parts that are functionally similar.
At the same time, another group of our design engineers is in the process of design review of the customer’s data, checking for functional performance. They recommend suitable base material for the board. They will also recommend changes in stackup, if they are able to improve on impedance controlled routing. They also review component placement, suggesting ways of improving signal integrity.
All this time, another group of our manufacturing engineers has been busy reviewing the customer’s design layout data for assembly and testing problems that can hamper manufacturing. They look for issues like:
Pad Dimensions: Pad sizes not meeting the component manufacturer’s recommendation can lead to inadequate soldering or solder bridging. Unequal pad sizes for the same component can lead to tombstoning, where the SMT component stands up on one of its ends.
Component Location: Placement of parts can affect their soldering quality. Larger parts can absorb more heat during reflow, depriving smaller neighboring parts of adequate heat, resulting in their soldering quality being poorer. An untented via placed too close or on the pad of an SMT component can wick solder away, resulting in a dry joint.
Component Spacing: Pick-and-place machines may disturb placement of neighboring SMT components, unless they have adequate spacing. Assemblers may face cabling problems with connectors surrounded by tall components. Without adequate spacing between components, it may be difficult to rework or repair the board.
Drill Optimization: Using too many drill sizes can increase the cost of board fabrication and the lead time. We recommend consolidating drill sizes to optimize the drilling operation.
Masking: Missing solder mask between close pitched IC solder pads can lead to solder bridging, shorting two pads that should not connect.
Acid Traps: Acute angles in trace routing can trap etching and cleaning chemicals, causing a reduction of track width and possible signal integrity problems.
Testability: We look for several design related issues such as spacing between components and board edges, overhanding components, position of interconnecting connectors, and presence of test pads for in-circuit testing. We also look for the possibility and viability of building a text fixture for the board.
After we have completed the design review, we prepare a report of the changes necessary to comply with the DFM check, and we send it to the customer. The customer can make the changes themselves, or our experienced designers can do it for them.
Partnering with the Contract Manufacturer
As there are several areas where the customer can improve on the design of their PCB for potential DFM issues, we recommend a three-step formula for eliminating them before sending the design for manufacturing:
- Start consulting your CM from the start of the design cycle. Any good contract manufacturer will want to work with their customer to help them get their design ready for manufacturing from the beginning of the design phase.
- Always clarify from the CM regarding issues that are unknown or not clear.
- Trust your contact manufacturer with their recommendations. An experienced contract manufacturer will offer valuable guidelines because they understand the board materials better, including DFM requirements for layer stackups.
At Rush PCB Inc., we understand that a successful customer is a guarantee for our own success. When our customers partner with us, we make sure that they get their board built the way they intended, including the critical step of total compliance with the DFM check—we ensure the project is successful.