Blog de PCB - Elementos que deben inspeccionarse una vez finalizado el cableado de PCB

1.. PCB Board design inspection
The following checklist covers all aspects of the design cycle, Elementos adicionales para aplicaciones especiales. Todos PCB Board design drawing inspection items:
1) The circuit is analyzed or not, and the circuit is divided into basic units in order to smooth the signal;
2.) Whether the circuit allows the use of short or isolated key leads;
3) Where must be shielded, whether it is effectively shielded;
4) Make full use of the basic grid graphics without;
5.) Whether the size of the printed board is the size;
6.) Whether to use the selected wire width and spacing as much as possible;
7.) Whether the preferred pad size and hole size are used;
8.) Whether the photographic plate and sketch are suitable;
9.) Whether there are few jumper wires used; whether the jumper wires should pass through components and accessories;
10) Whether the letters are visible after assembly; whether their size and model are correct;
11) In order to prevent blistering, Apertura de láminas de cobre de gran superficie?
12) Whether there is a tool positioning hole;

2. PCB Board electrical characteristics inspection items
1) Whether the influence of wire resistance, inductance and capacitance has been analyzed; especially the influence of the key voltage drop to grounding;
2) Whether the spacing and shape of the wire accessories meet the insulation requirements;
3) Whether the insulation resistance value is controlled and specified at key points;
4) Whether the polarity is adequately identified;
5) The influence of wire spacing on leakage resistance and voltage was measured from the geometrical point of view;
6) Whether the medium that changes the surface coating has been identified;

3. PCB Board physical characteristics inspection items
1) Whether all pads and their positions are suitable for final assembly;
2) Whether the assembled printed board can meet the Conmoción and Vibración power conditions;
3) What is the spacing of the specified standard components;
4) Whether the components that are not firmly installed or the heavier parts are fixed well;
5) Whether the heat dissipation and cooling of the heating element are correct; or whether it is isolated from the printed board and other thermal elements;
6) Whether the voltage divider and other multi-lead components are positioned correctly;
7) Component arrangement and orientation for easy inspection;
8) Whether all possible interference on the printed board and the entire printed board assembly has been eliminated;
9) Whether the size of the positioning hole is correct;
10) Whether the tolerance is complete and reasonable;
11) Control and sign off the physical properties of all coatings;
12) Whether the ratio of the diameter of the hole to the lead wire is within the acceptable range;

4. PCB Board mechanical design factors
Although the printed board supports components mechanically, No se puede utilizar como parte estructural de todo el dispositivo. Borde de la placa, Al menos una vez cada 5 pulgadas para obtener un cierto apoyo. The factors that must be considered in the selection and design of printed boards are as follows;
1) The structure of the printed board - size and shape.
2) The type of mechanical accessories and plugs (seats) required.
3) The adaptability of the circuit to other circuits and environmental conditions.
4) Consider mounting the printed board vertically or horizontally depending on factors such as heat and dust.
5) Some environmental factors that need special attention, Como la disipación de calor, ventilación natural, shock, vibration, Humedad. Polvo, Niebla salina y radiación.
6) Degree of support.
7) Hold and fix.
8) Easy to take off.

5. Installation requirements for printed circuit boards
It should be supported at least within 1 inch of the three edge edges of the printed board. Sobre la base de la experiencia práctica, Espaciamiento de los puntos de apoyo de la placa de circuito impreso con espesor 0.031 - 0.062 pulgadas debe ser de al menos 4 pulgadas; Para placas impresas de espesor superior a 0.093 in, La distancia entre los puntos de apoyo debe ser de al menos 4 pulgadas. 5 pulgadas. Esta medida aumentará la rigidez de la placa de circuito impreso y destruirá la posible resonancia de la placa de circuito impreso.. Antes de decidir sobre su tecnología de instalación, la placa de circuito impreso debe tener en cuenta los siguientes factores.
1) The size and shape of the printed board.
2) Number of input and output terminals.
3) The available equipment space.
4) Desired ease of loading and unloading.
5) The type of installation accessories.
6) The required heat dissipation.
7) Required shieldability.
8) The type of circuit and its relationship with other circuits.

6. Dial-out requirements for printed boards
1) No printed board area for mounting components.
2) The influence of plugging tools on the installation distance between two printed boards.
3) The mounting holes and slots should be specially prepared in the design of the printed board.
4) When the plug-in tool is to be used in the equipment, En particular, su tamaño debe tenerse en cuenta.
5) A plug-in device is required, Normalmente se fija a un conjunto de placas de impresión con remaches.
6) In the mounting frame of the printed board, Requiere un diseño especial, como bridas de carga.
7) The adaptability of the plugging tools used to the size, Forma y espesor de la placa de circuito impreso.
8) The cost involved in using plugging and unplugging tools includes both the price of the tool and the increased expenditure.
9) In order to tighten and use plug-in tools, Requiere un cierto grado de acceso al interior del dispositivo.

7. PCB Board mechanical considerations
Substrate properties that have a significant impact on printed circuit assemblies are: water absorption, Coeficiente de expansión térmica, Propiedades térmicas, Resistencia a la flexión, Resistencia al impacto, Resistencia a la tracción, Resistencia a la cizalla y dureza. Todas estas características afectan la función de la estructura de la placa de circuito impreso y la productividad de la estructura de la placa de circuito impreso. Para la mayoría de las aplicaciones, the printed circuit board's dielectric backing is one of the following:
1) Phenolic impregnated paper.
2) Acrylic-polyester impregnated glass mats with random arrangement.
3) Epoxy impregnated paper.
4) Epoxy impregnated glass cloth.
Cada sustrato puede ser ignífugo o inflamable. Arriba 1, 2, 3 perforable. La tela de vidrio epoxi se utiliza comúnmente en la placa de impresión de agujeros metalizados. Su estabilidad dimensional es adecuada para circuitos de alta densidad, Y puede reducir la ocurrencia de grietas en los agujeros metalizados.. Una desventaja de los laminados de tela de vidrio epoxi es la dificultad de estampar dentro del espesor normal de la placa de impresión, Por lo tanto, es común perforar todos los agujeros y utilizar la operación de fresado de copia para formar la forma de la placa de circuito impreso.

8. PCB wire spacing
The conductors must be spaced to eliminate voltage breakdown or arcing between adjacent conductors. Spacing is variable and depends primarily on the following factors:
1) Peak voltage between adjacent wires.
2) Atmospheric pressure (working height).
3) Coating layer used.
4) Capacitive coupling parameters.
Los componentes críticos de impedancia o los componentes de alta frecuencia se colocan generalmente estrechamente juntos para reducir el retraso de la fase crítica. Los transformadores y los conjuntos de inducción se aislarán para evitar el acoplamiento; Las líneas de señal de inducción se colocarán ortogonalmente en ángulo recto; Los componentes que generen ruido eléctrico debido al movimiento del campo magnético se aislarán o instalarán firmemente para evitar vibraciones excesivas..

9. PCB Board Modo conductor inspection
1) Whether the wire is short and straight without sacrificing function;
2) Whether the limitation of wire width is complied with;
3) Check whether the distance between wires, Entre el cable y el agujero de montaje, and between wires and pads must be guaranteed;
4) Whether the parallel arrangement of all wires (including component leads) is relatively close is avoided;
5) Whether acute angles (90°C or less) are avoided in the PCB Board wire pattern.