Tips from electronics manufacturing: Design for manufacturing
With our 10 practical tips, you can put your project on the right track for series production right from the development stage. This will save you costs and effort while ensuring a smooth start to production.
In electronics production, we always carry out a technical feasibility check for new inquiries. Today, there are hardly any projects that cannot be implemented. Rather, in most cases it is a question of effort and therefore also cost. The cost factor is a major aspect, particularly in the area of series production. Under the keyword Design for Manufacturing, a number of factors should be taken into account as early as the development phase of an electronic product in order to subsequently ensure cost-optimized series production.
Design for manufacturing starts with the selection of components
It is fundamentally important to select the electronic components for the project as early as the development stage. In addition to the cost factor, the type of components is decisive for the availability and delivery time of the end device and also for the product life cycle.
Tip 1: Passive components without manufacturer loyalty
Passive / discrete components - resistors, capacitors, diodes, transistors - should be considered without manufacturer loyalty if possible. Instead, information on the electrical and relevant characteristic values should be provided for the item in the parts list. In this way, the electronics manufacturer can access its stock or procure the best item currently available in terms of price and availability. This also provides greater flexibility when using alternatives in the event of discontinuations.
Tip 2: Combine the same components
The more different components are used in a project, the more work this causes for the electronics manufacturer. If, for example, a parts list contains a capacitor with the same electrical characteristics but in three different designs (e.g. 0402, 0603 and 0805), we as an EMS service provider have three times the workload with article creation, ordering, incoming goods inspection, removal from storage, set-up, return to storage, etc.
Tip 3: Check alternatives for active components at an early stage
By taking alternatives into account, it is possible to change different assembly variants at short notice without having to adjust the layout. In addition to the alternatives, the approved temperature range should also be taken into account. If several available temperature ranges of a component are sufficient for the application, this information should also be included in the parts list. Depending on the market situation, the availability of a component type in the different temperature ranges can vary greatly.
Tip 4: Always keep an eye on the life cycle of components
It is currently quite time-consuming to consider the life cycle of components. This does not mean the useful life until a possible component defect, but the time between market launch and discontinuation of the component. The manufacturer does not disclose this information at the time of market launch. However, previous discontinuation periods can be used to derive empirical values for the life cycles of the various manufacturers. However, it is very time-consuming for developers or purchasers to keep track of this information for an entire assembly.
Practical example of dielectric strength
Pay attention not only to the design, but also try to combine different dielectric strengths into one type. Example: Instead of using an equivalent capacitor with 16V and 25V dielectric strength, it is better to use the same capacitor with 25V twice. Based on the current market situation, we recommend the use of types 0402 or 0603 in terms of both cost and availability. The smallest type that we currently fit is 0201, but our machines are also able to fit the smallest type, 01005.
The correct placement of electronic components
Not only the selection, but also the placement of components on the PCB has a major influence on production. In the area of SMD components, for example, so-called shadowing can occur if very small components are placed next to tall components. Particularly when checking SMD solder joints using a 3D AOI (automatic optical inspection), shadows can lead to not all areas being sufficiently exposed and assessed. This results in many pseudo defects or, in the worst case, real defects may even be overlooked. In addition, double-sided SMD assemblies can cause difficulties with possible wave soldering.
Tip 5: Position components with different paste requirements correctly
Components often require different amounts of solder paste, which must be taken into account when placing them. For example, power components should not be placed directly next to fine-pitch components. The different paste quantities can be realized with the help of step stencils. A certain distance between the components is necessary in order to work the steps into the templates. Another option is to use a jet printer.
The jet printer has a fine dispensing head with which it can apply additional paste to individual pads. In addition to the possibility of applying different amounts of paste, the jet printer can also be used for the production of prototypes without the need to purchase a stencil. A print program is created based on the circuit board data. Using the same procedure, the jet printer can also apply specific adhesive dots.
Tip 6: Even distribution of the number of components
Placement machines are designed to place several thousand components per hour. If, in extreme cases, only a single SMD component is to be placed on the underside of an assembly, the machine has to wait for a significantly longer reflow process and is idle during this time. For cost reasons, it is therefore important to ensure that the number of components is distributed as evenly as possible on both sides of double-sided assemblies. However, heavy components should be placed on one side. This prevents them from falling off during the second heating process in the reflow oven.
Tip 7: Maintain a minimum distance between components and the edge of the PCB
A familiar problem for us is the placement of components too close to the edge. In automated production, the assemblies run on conveyor belts between and through the machines. For clamping on these conveyor belts, a minimum distance to the edge of the PCB of ≥ 3 mm is required for SMD components and ≥ 5 mm for THT components.
The selection of a suitable PCB
In addition to the components, attention should also be paid to the selection of a suitable PCB during the development phase. For the best possible machine utilization, we manufacture most assemblies in panels. The size of the panel is determined in cooperation with the PCB supplier.
Tip 8: Observe the minimum distances between the conductor tracks and copper surfaces
There are two different techniques for processing PCB edges. Not only must the components have certain distances to the outer edge, but the conductor tracks and copper surfaces also require a minimum distance. The rule here is that all traces and copper surfaces should have a distance of ≥ 0.5mm from a scribed edge and a distance of ≥ 0.2mm from a milled edge.
Tip 9: Pay attention to the selection of the PCB surface
The selection of the PCB surface should also be taken into account in the development status of the project. This contributes significantly to the quality of the assembly and also to the durability and shelf life of the raw PCB. For assemblies with fine-pitch components and components with connections below the component, we recommend using a gold surface.
Tip 10: Specify test points directly for later testing
The correct selection of PCBs is particularly important if the assemblies are to be electrically tested after production. This is because necessary test points must already be taken into account by the developer in the PCB design and included in the PCB data. Based on these test points, the electronics manufacturer can build a needle bed adapter in test equipment construction with which these are contacted.
Are you currently working on a project in the development phase? Then contact us and we will go through the requirements in electronics production with you. This will ensure that your project is optimized for series production even beyond the development phase.
