BESTProto Guidelines

For RFQ Submissions, Parts Kits, and Box Builds

Table of Contents

RFQ Guidelines

Guidelines for RFQs, Kits, and Box Builds

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Quotations

To provide you with an accurate quote, please let us know your project requirements and provide the following information:

  • Gerber files (electronic)
  • Bill of materials (BOM) in Excel format
  • Quantity
  • Lead time
  • Who is supplying the PC boards and components
  • Supporting documentation containing special requirements for assembly processes and build sequences, e.g., conformal coating, part programming, and flying probe testing.

If the above information isn’t available, we will provide a budgetary quote based on the information we have. BESTProto reserves the right to revise our quoted price and lead time once the final documentation is available.

Customer Requirements

Since we cannot possibly know and understand all the intricate details of every board we produce, we rely on you, our valued customers, to let us know about the particulars of a given board design.  Our experience and proven industry practices will guide us through some of the unknowns, and having more information than less will help ensure our mutual success.

Below are some examples of the types of information we need from you for BESTProto to do our best work on your behalf: 

Lead-Free Components or Solder: Please inform BESTProto of the existence of any lead-free components, e.g., BGAs, or any related RoHS compliance requirements or the need for us to use lead-free solder.  In many cases, lead-free solder isn’t an absolute necessity on prototypes, even though it will be used in production.

Parts Kits: To cover shrink and scrap, we require an additional 5% or 30 extra parts (whichever is greater) for SMT passive components. For active and larger components (I.C.s, connectors, etc.), we ask that you provide 2% or 5 extra pieces in case we need them.  Large, expensive parts (BGAs, etc.) may be exact quantities, but extras are helpful.  Any parts shipped to us are assumed to be in good order, acceptable, and “machine-ready” to use for the build at hand.

Labels with corresponding BOM line-item numbers on bags, reels, tubes, and trays help check in the kit and also set up the machines.

Unused components will automatically be shipped back to you with your assembled boards.  As always, feel free to contact us if you have questions.

PCB Design Files: We can accept the following files for use in programming our machines:

  • IPC 356
  • ODB++
  • GENCAD
  • ASCII CAD

PC Board Polarity Designators: We expect that Printed Circuit Boards have reference and polarity designators clearly marked. The boards are expected to have been electrically tested by the board fabricator; otherwise, this may affect the quality of assembly and the quoted price and lead time.

Component Polarity: All polarized parts must include clearly visible marks for “pin 1” identification. If a part is not clearly marked with polarity indicators from the component manufacturer, you will need to provide that information to us; otherwise, we’ll assume polarity isn’t a consideration on that part.

Moisture Sensitive Devices (MSDs): It is critical for you to alert BESTProto about ANY MSD parts that require a “bake-out” before the assembly process.  If you are uncertain about possible exposure to moisture, we HIGHLY RECOMMEND that you let us know which parts are suspect, so we can perform a bake-out operation. Typically, components received in factory-sealed and labeled moisture-barrier bags may be processed without prior baking; however, we have no way to verify their condition. BESTProto accepts no responsibility for any damage to the assembly or component devices due to the failure to perform bake-out. Components that are received dry-packed in moisture barrier bags will be returned to you in the same condition.

Heat-Sensitive Parts: Many assemblies contain components that may be heat-sensitive (batteries, connectors, etc).  It is the customer’s responsibility to inform BESTProto of the presence of any heat-sensitive devices that can be damaged by temperatures up to 260ºC.

Non-Washable/Non-Cleanable Parts: If your chosen board assembly process includes cleaning or washing and has component devices that aren’t suitable for that operation, you need to let us know so we can make appropriate process changes to avoid damaging those parts.

Lead-Times: Work may commence after we’ve received a purchase order, ALL the necessary data, and ALL parts required for the build. In cases where an expedited delivery has been quoted and specified in the customer’s PO, any parts, files, fixtures, etc., received after 11:00 am CST shall be considered to have been received the following day.

Programmable Parts: Are there any parts that need to be downloaded and/or configured before being placed on the board? These are devices that contain memory or programmable logic arrays.

Solder Paste Deposition: PCBs are paste-printed using a state-of-the-art solder paste jet-printing machine (Jetter), which allows for a stencil-less process. We no longer reference standard paste layer designs, as used with typical screen printing, that utilize stencils. The “Jetter” utilizes the provided PCB design files to determine pad locations and automatically creates solder deposits on all SMT pads. BESTProto typically alters programs to ensure all solder joints meet IPC guidelines. If you prefer not to have solder on certain pads/locations or have special soldering requirements, please note that fact in the assembly instructions (e.g., assembly drawing notes) and on the BOM.

Special Mounting instructions: If there are unique component mounting requirements, they must be identified overtly in the instructions. Examples of some special mounting requirements are:

  • Shield fence needs to be soldered to the PCBA 100%
  • Leads on resistor R123 must be preformed to hold the part more than 0.25 +/- 0.05 inches above the plane of the board
  • Inductor I42 needs to be secured to the board with RTV (Include RTV spec)
  • Connector 5 (J5) needs solder build-up from the PCB to connect the pad to the connector pin 1, etc.

Testing and Inspection

When you’re working with Prototypes and small-batch production, it is quite common for test procedures to be undefined or make economic sense; therefore, we rely on visual manual or, in some cases, AOI (Automatic Optical Inspection).  We welcome the opportunity to discuss with you the various available test methods to help you decide what makes the most sense for your particular application.

Visual Inspection: We inspect part polarity, orientation, and overall quality of solder joints. When BGA and QFN devices are present, we may use X-ray equipment to verify that there are no solder shorts underneath the device.  Endoscopic inspection may also be used to inspect the sides of the device to verify whether the solder joints look to have collapsed uniformly.  Visual inspection is a manual process performed by highly trained and skilled inspectors, and can be effective in screening out manufacturing defects; however, it’s not intended as a replacement for a thorough electrical test.

Functional Board Testing: Is there a high-level functional test you would like to have executed on the prototypes? Typically, this is a Test Set developed by the customer to provide a PCBA electrical start-up and initialization test that ensures at least a minimal configuration and/or functionality is present.  Depending on the level of troubleshooting capability support provided by the customer, this is a good way to know if a board can initialize.  BESTProto will remove any workmanship-type defect it can detect, but component failures and design margin failures will not be diagnosed during this testing.  This testing capability is offered by BESTProto as a test execution service based on the time it takes to execute a test.  Additional troubleshooting and diagnosis will need to be discussed if requested.

Additional Test Methods: Examples of other types of PCB assembly testing methods available through a third-party contractor include Flying Probe Testing (FPT) and In-Circuit Testing (ICT).