Fra prototypekredsløb på brødbrætter til design af vores egne printkort (PCBS), it was like getting off the training wheels. There’s a lot to learn about this process, so let’s get started. PCB -design udføres i en elektroteknisk (EE) proces. EE skaber “hjernen” for, hvordan enheder fungerer. Without electronics, you’re left with little more than a pile of metal and plastic.

Things to know before starting PCB design: 1. PCB size – this depends on your product size (or case size). Produktdimensioner er defineret under den elektroniske konstruktionsproces. You can watch a video about it here. 2. PCB -lag – Jo flere lag, jo mere kompleks er fremstilling af PCB. (Bemærk: Selv et enkeltlags PCB kan være et komplekst PCB, men her taler vi om kompleksiteten ved at lave et PCB. Jo flere lag et printkort har, desto dyrere er det at fremstille.)

Layer 2 is usually used for simple toy products

Iot -relaterede produkter har normalt 4 lag

Typically used for floors 6 to 8 of a smartphone or smartwatch.

3. Your PCB manufacturer’s requirements. Be sure to read the guidelines for rhythm, trace size, power isolation, and file naming before you start designing.

Oplysninger, du skal give til PCB -producenter:

Number of layers (e.g. 2, 4, 6, etc.)

Materialer (FR-2 (fenolbomuldspapir), FR-3 (bomuldspapir og epoxy), FR-4 (glasfiber og epoxy … etc.)

Tykkelse (0.5 mm, 1.0 mm … etc.)

Color (red, black, green… etc.)

Overfladebehandling (ENIG (kemisk nedsænkning af nikkel/guld), DIG (direkte neddybning af guld), OSP (organiske loddbare konserveringsmidler osv.)

Copper weight (1 oz (35 microns), 2 oz (70 microns), 0.5 oz (18 microns)… etc.)

Gerber-fil

PCB design process:

Kredsløb design

For this step, you need to create the schematic. This is a document, like a blueprint, that describes how components relate to each other and work together. To create the schematic file, you will need a software tool. Vi kan godt lide Quadcept, fordi det er optimeret til at designe PCBS til fremstilling (f.eks. Kan du eksportere en stykliste (BoM) direkte fra værktøjet) og er skybaseret, så det let kan bruges overalt. (They also offer a free community version of the tool for manufacturers and students.)

There are many other options you can choose from:

Altium

ExpressPCB

Frekvensapparat

KiCad

Cadence allegro

Mad

Computer hjulpet design

DipTrace

After you install the selected tools, you need to obtain the component specifications for each selected component. They can often be found on the supplier’s website. Modelfilen hjælper dig med at tegne skematisk. This component becomes available in the database when you upload the model to the software tool. Then, all you have to do is follow the data manual and connect the wire to each pin in the component. (Bemærk: detaljerne i designprocessen afhænger af det valgte softwareværktøj).

Each schematic symbol needs to have an associated PCB space area to define the physical dimensions of the component and the location of the through holes on the brazing pad or PCB. You should have selected the components (or are now selecting them), and we describe this process in the EE Design Process video (see video).

Example diagram

A good schematic is really important, as it will be used as a reference document during debugging and is a good communication tool with other engineers. Desuden kan producenten teste enheden gennem testpunkterne i dette dokument.

PCB layout + Gerber file

To design the PCB layout and create Gerber files, you can use the same software tools we mentioned in circuit design. I modsætning til en skematisk tildeler et PCB -layout de faktiske komponenter til nøjagtige placeringer på printkortet og viser de spor, der forbinder hver komponent mellem PCB -lagene. As mentioned at the beginning of this article, the more layers, the more complex the manufacturing required, and the higher the cost.

Divide the PCB into logical parts based on functions (e.g. power supply, audio output, etc.). Then, be sure to group the components of each section into the same area. På denne måde kan du holde det ledende spor kort og reducere støj og interferens.

Brugergrænsefladen (UI) skal også tages i betragtning, når du designer et PCB. Komponenter som lydstik, stik, lysdioder osv. Skal justeres for at opnå den bedste brugeroplevelse.

Once the layout is designed, a Gerber file is generated. Din PCBA -producent vil bruge denne fil. There are many companies that offer these services, and from HWTrek’s expert library we recommend Kingbrother, NexPCB, and HQPCB.

Sample Gerber files

Placering af komponenter på printkortet er meget vigtig. Some components can interfere with each other and cause unexpected behavior. For eksempel, hvis du har både Bluetooth- og Wi-Fi-moduler, har de samme båndbredde på 2.4 GHz og kan forstyrre hinanden, hvis de placeres forkert.

PCB production

When you send the Gerber file to the PCB manufacturer, they can print the board. Dette vil være grundlaget for yderligere at bygge fundamentet for tilføjelse af komponenter til printkortet og fremstilling af PCBA (printkortmontering).

Unassembled PCBS

PCBA (Assembly)

Materialeforberedelse

På dette tidspunkt i dit EE -design skulle du have valgt komponenterne. You can ask the PCBA manufacturer to order the required components for you, or do it yourself if you choose a supplier. Sager, der har brug for opmærksomhed:

Lead time: As these components come from different suppliers, keep the lead time in mind. For some components, it can take up to 8-16 weeks.

Packaging: Order components from reels that are automatically picked up by SMT machines instead of packaging them individually.

Minimum ordremængde: Kontroller komponentens mindste ordremængde. Hvis du køber mindre end minimumet, skal du sørge for, at de valgte komponenter er på lager. For small batches (up to 50), you can order online from DigiKey or Mouser. Spørg råd fra din producent for flere mængder.

Loss: Order 10% more to cover loss (not for expensive components)

Install components on the PCB

There are two main ways to place components on a PCB surface:

Through-holes (through-holes) are manual methods of assembling assemblies with wires into holes on the surface of a PCB. It is also commonly known as DIP or dual in-line packaging process. (See SMT in progress in this video)

SMT (overflademonteringsteknologi) er den mest anvendte metode til masseproduktion. It is done by fast, accurate SMT machines that save you time, money and avoid human error.

Ting at huske:

Your component type number must not exceed the number of reels that the manufacturer’s SMT machine can support.

Optimize and consolidate your components so that only one SMT runs.

Check manufacturer supported footprint pad sizes. Otherwise, the SMT machine will not install components correctly.

Some larger components cannot be installed by machine and still require manual through-hole work. Therefore, both technologies can be used on the same board.

Any components you need to manually add via the through-hole method add to the manufacturing cost.

Loddefyldning igen

Reflow soldering is the process of making components “stick” to the PCB. The PCBA heats the circuit board through a reflow furnace or an infrared lamp until the solder melts, thereby permanently attaching the component to the circuit board.

Den vanskeligste del her er ikke at overophedes eller beskadige komponenterne, fordi de termiske egenskaber for hver pakke er forskellige. En pålidelig PCBA -producent vil være ansvarlig for denne proces, og alt du skal gøre er at give dem komponentspecifikationer.

Reflux proces.

Other welding methods:

Wave soldering is mainly used for manually added components by the through-hole method. I dette tilfælde vil din PCBA først gå gennem reflow -svejseovnen og derefter tilføje andre komponenter manuelt, efter at den vil gå gennem bølgelodningsmaskinen.

Jern svejsning kan bruges til specifikke situationer, men ikke til masseproduktion.

Test og kvalitetskontrol

I dette trin testes PCBA -prøver for at sikre kvaliteten. Almindelige fejl er: kortslutninger i frakoblede komponenter, fejljusterede komponenter og dele af kredsløbet, der ikke bør tilsluttes. De mest almindelige tests:

IKT (Online test). When designing a PCB, some test points are usually reserved for debugging, programming, and other purposes. IKT -maskinen vil bruge disse testpunkter til åben/kortslutningstest og kontrollere, at værdierne for de passive komponenter (modstande, induktorer, kondensatorer) ligger inden for specifikationsområdet.

AOI (Automatisk optisk inspektion). Manufacturers use a “gold sample” (reference PCBA) to compare with other samples. Til denne test skal hardwareopretteren levere specifikationer og tolerancer til producenten for at indstille parametrene.

Røntgen. The PCBA manufacturer will use X-rays to check the welding conditions of the BGA (ball Grid Array) components. Se røntgenundersøgelsen i denne video.