10 Tips for PCB Manufacturing and Assembly

These 10 tips will help new PCB designer to improve their PCB board design. It will make their board more easy to produce and improve the pass rate. This entry will discuss how to apply the concepts of design for manufacture and design for assembly to PCB designs and how using these concepts will benefit you when undertaking the design of your next PCB based product.

1. Reduce the number of parts in a PCB design.

Reducing the number of components in a PCB design is a straight forward goal with obvious benefits. It will reduce that design's cost and the complexity of assembling it, though not as apparent, it is of great benefit. For example, when pick and place machines are used to populate PCB assemblies, they are limited to the number of components they can support in a single pass. Being mindful of the number of components the pick and place machine used in assembling your circuit board can lead to non obvious cost reductions. If for instance, your design requires a 20K resistor and you are already using 10K resistors in that design, it may actually be cheaper to use two 10K resistors in series if that can reduce the number of times the pick and place machine being used for manufacture needs to be set up. Along the same lines, looking for standard integrated circuits that can consolidate a portion of your design into a single IC can speed up assembly time and shift portions of testing requirements onto the IC manufacturer. As such, being mindful of PCB component counts and component types is probably the most important step to reducing overall PCB design cost.

2. Develop a Modular PCB Design

Consider breaking apart PCB designs into functional blocks if you can use those blocks across a number of different products. Increasing the quantity of a particular module that is ordered from a manufacturer can greatly reduce that module's per unit cost. Also of note, using modules can reduce the cost and complexity of testing a completed assembly by simplifying the test process. Smaller systems are inherently easier to test and repair than larger ones. Obviously the cost benefit that you can obtain from using a modular design must be weighed against the increased interconnection costs associated with using several modules.

3. Use of Standard Components

Using standard components greatly reduces design development time and cost. It goes without saying that specifying a complex custom solution will greatly increase the upfront cost of any product and may make a design infeasible. Using more common components can also simplify a product's supply chain and alleviate component supply concerns. Another benefit to the use of standard components is that their foot prints are more easily verified before being used in a PCB design.

4. Use multifunctional components

Whenever an electrical component can serve multiple purposes in a design it behooves the PCB designer to take advantage. The example discussed in the previous section also applies to PCB based designs: using an enclosure that can also serve as a heat sink in a design can offer significant savings to a design's cost. Another example of a dual use device is using a standoff as a connection to earth ground from the PCB to the PCB's enclosure through a connected mounting hole on the PCB.

5. Design modules for use in multiple products

Using standard PCB modules across a number of products can yield lower product production costs and allow for simpler verification schemes. It is often much easier to find error in a module than it is to test a complete product. Using modules also allows for a good deal of design effort to be reused across several projects.

6. Design for ease of fabrication

It is fairly apparent that when designing a PCB, if the level of complexity of design is higher than normal, you can expect lower yields and higher assembly costs. Complex machining operations and using tighter tolerances can commonly be accommodated by higher trims of PCB production, but will be reflected in the PCB's production cost and assembly costs.

7. Reduce and if possible avoid the use of fasteners

When a PCB is to be assembled, as with all products, it costs more to use fasteners to mount components than to use press fit type mounting techniques. To take advantage of this, try to reduce the use of fasteners in your assembly. One way to do this is to use surface mount versions of power ICs and integrate heat sinking into the design of your board. For example: switching from a TO-220 version of an IC that uses an external heat sink to a D2PAK version using the PCB as an integrated heat sink, can save a substantial amount in your final design.

8. Minimize assembly directions

Simply put, producing a PCB with components placed on only one side of the board will ultimately lead to a less expensive product. As with all design decisions, the PCB designer will have to weigh whether it is better to produce a smaller PCB with components placed of both sides of the board verse designing a larger PCB with components placed on only one side of the board.

9. Maximize component placement acceptance

Design your PCB in such a way that component mounting errors will be reduced. This can be achieved by using components that have higher dimensional tolerances (higher pin spacing) or avoiding issues such as tomb-stoning, which will be discussed in detail in the next section.

10. Minimize repositioning and handling during PCB population

Any time that a PCB must be repositioned during the assembly process will increase the amount of time required to populate that PCB. As discussed above, repositioning is incurred whenever a PCB is two sided and components are installed on the front and back face of the PCB. When possible use all surface mount components one a single side of a board. Using only surface mount components will limit the soldering portion of the assembly process to a single re-flow step, while the inclusion of through hole components may require an additional wave soldering step or manual soldering. Essentially, the more handling required in the PCB assembly process the higher the assembly cost will be.


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