Printed circuit board (PCB) fabricators receive dozens of requests for quotations (RFQs) every day. While many requests have moved to more convenient online quoting formats such as our in-house application InstantPCBQuote, many customers still send requests the old way via either files or alternate forms of describing their manufacturing requirements.
The quality and completeness of the information received varies widely from complete data packages that include fabrication drawings down through PDF partial drawings or even simply verbal descriptions with little or no form of formal documentation.
It’s not an exaggeration to say that the limits of custom PCB specifications will be tested for PCB manufacturers. We once received a photograph of a cigarette package, with the notation: “for scale -- build regular”, which is not advised, to say the least. Any of these forms will eventually result in at least a budgetary quote, but the better and more comprehensive your information is, the more easily, quickly, and accurately you will receive your quotation.
PCB Fabrication Drawing to Scale
Below we explain the reasons why certain items are important and how their absence can undermine your efforts to find out how much your PCB will cost.
Complete PCB Information
The first thing to remember is how you communicate your information directly impacts the person processing that information on the other end of the request. When you fill out forms for online orders, information is required for a reason. If you left the quantity field blank, or didn’t specify your clothing size, you might end up with a dozen extra baggy sweaters instead of the one you wanted that fits just right.
As an example, maybe you are about to go to lunch, so you quickly fire off an RFQ with a fabrication drawing that shows the basic dimensions and hole quantities for your PCB but little else. You do so assuming you’ll return from lunch with a shiny new quote waiting in your inbox. However, at the other end, the customer service representative (CSR) has found it impossible to create a meaningful quote from that one document.
- Where is the material information?
- Where is the layer count?
- How heavy is the copper?
- What design rules are used for the circuitry?
- Does the PCB need to be panelized for assembly?
Perplexed, the CSR picks up the phone and calls you to fill in the blanks but you’re at lunch, so they leave a message. When you return to see your phone blinking, you listen to the voicemail. Then to get the missing information, you must chase down either somebody in your organization or your own customer.
When you finally have the information, you call the CSR back, but the process has already been delayed. This is clearly a stress-inducing situation all around with real consequences that could have been avoided, had all the information been available from the start.
Printed Circuit Board Quotes
Some companies may give you a quote based on their very loose interpretation of your incomplete information. Such companies may even be your favorite suppliers to deal with since they don’t take up time nitpicking for seemingly unimportant details and their pricing always seems to be attractively low.
But how accurate is the quote they are giving you really going to be? When you place the purchase order (PO) and give them the rest of the information, do you still get that same low price? Probably not.
That’s because they based their quote on “least expensive” materials and practices. For surface finish they quoted tin-lead, for material they quoted low-temp FR4, for material utilization they assumed they could panelize the order using v-scoring with no space between.
When the full drawings are received and the boards actually require a gold finish on high-temp laminate and can’t be v-scored because the copper features are too close to the outline, they must inform you that the price is significantly higher than their original estimate. Suddenly their previously enticing prices are now higher than the company that stopped the process to ask for more detailed specs.
Whether you stick with your first supplier or not, you’re still stopping in your tracks to cut a revised PO. Again, the stress level rises, but now there is even more pressure because the schedule may slip.
The good news is, it’s not too difficult to make sure you are providing suppliers with adequate information so that you receive your quotes on-schedule and accurately.
So, what are the items any fabricator will need to gain a complete picture of what you are asking them to build?
- Gerber files for ALL layers, including circuitry, solder mask, silkscreen legend, solder paste, and an accurate outline showing all mechanical features such as slots, etc. on a single layer.
- Fabrication drawing, including (at least) laminate information, hole sizes and locations, surface finish / metalization, solder mask color, silkscreen color, IPC inspection class. If required express impedance requirements, the material stack-up, and any special testing or qualification requirements that are unusual. Don’t panic if you don’t have a fabrication drawing, a README or similar document listing the requirements is fine.
- If the PCB will be panelized, supply either a panel drawing or at least a description of how many PCBs on the panel, how wide the scrap rails must be, and removal method (routed, scored, or both.)
- If the PCB is subject to ITAR, aerospace, automotive, medical, or military rules, it is very important to state this. Many PCBs are built outside of the USA. If you need your PCBs to be built in the USA, then that may have a noticeable effect on pricing. In addition, special rules apply for transmitting data files. Emailing files for ITAR-restricted work is illegal.
Summary
Attention to all the necessary details just to get a PCB quote may appear very time-consuming, but the more information you can provide, the more accurate the resulting quote will be. A little more time spent up front, gathering more complete information, will enable you to receive quotes quickly from all suppliers with little or no variation caused by differing assumptions about missing requirements. Receiving the most accurate quotes up-front also allows you to make apples-to-apples comparisons of the competing quotes, thus making informed decisions about awarding your purchase order to the ideal supplier.
