What are the specific PCB/PCBA process reviews?

What are the specific PCB/PCBA process reviews?

Publish Date:2019-09-05 09:50:33 Clicks: 315

PCBA-process-reviews.jpg

Printed circuit board manufacturability design review criteria and basis:

  • The manufacturer's printed circuit board manufacturing design standards.

  • Domestic GJB, QJ, SJ and other standards, IPC international standards.

  • Component size and recommended pad design drawings or component specifications provided by component manufacturers.

  • Printed circuit board design sulfuric acid paper.

  • Design documents.

 

General content:

1. The selection of components.

  • Solderability.

  • heat resistance.

  • Coplanarity.

  • In the PCBA design, the chip components can be selected as much as possible, and the duty ratio of the chip components on the PCBA is 95% or more.


2. Selection of PCB substrate.

  • Solderability.

  • heat resistance.

  • Flatness.


3. PCB design rules.

  • Conductive graphic layout and wiring.

  • Pad design and component spacing design requirements.

  • The size of the printed conductor and the pad and the metallized hole (the insertion hole, the relay hole) and the safety distance between them.

  • Electromagnetic compatibility.

  • Heat conduction and heat dissipation.

  • PCB surface coating.

  • Solder mask graphics.

  • Machinability.

  • Detectability.


4. Design and process requirements for prohibition.

5, Component installation.

6, The requirements of special components.

7, Component reinforcement and conformal coating requirements.

 

Review of PCB and its PCBA pattern design process

1, PCB.

  • Do not share the same pad between surface mount components, surface mount components and through-hole components, surface mount components and leads, in accordance with GJB 3243-1998, SJ/T 10670 -1995 and IPC-SM-7351B-2010 requirements.

  • Printed circuit board design documents and product objects are exactly the same in name, figure number, bit number, model, specification, etc.: the diameter of the metallized hole should be larger than the outer diameter of the component lead or the outer diameter (0.2~0.3mm) of a wire core.

  • In addition to the need to install components and chip components directly on the copper foil or tin plating layer for grounding and heat dissipation, the non-mounting soldering area on the printed circuit board surface must have a solder mask layer, and there must be no fusible under the solder mask layer. metal.

  • Solder mask coating requirements.

  • Printed wire and pad surface plating requirements.

  • When the printed circuit board needs to pass a large current, the width of the printed circuit can be widened by using an external wire or a thick copper-plated substrate.


2, PCBA.

  • The dimensions and mounting and fixing methods of the printed circuit board should match the reserved position and fixing method of the structural parts.

  • Components, especially high-density integrated circuit layout (density, installation space and adjacent spacing) and reinforcement measures.

  • Heat and heat dissipation measures and reinforcement measures and installation space.

  • Rationality, stability and safety distance of component installation.

  • PCBA anti-warping and anti-mechanical environment reinforcement and protection against environmental erosion.

  • Installation requirements for terminals and wires.

  • Maintainability and implementability.


3. Technical requirements for printed circuit board assembly drawings.

  • Assembly welding is carried out according to QJ165B.

  • Component mounting height (refers to the distance between the top of the component and the surface of the PCB) and the special forming requirements of the component.

  • Do not install shorted or unconnected components.

  • Requirements for components to be equipped with sockets.

  • Indicate the code, name and model number of the anti-static component.

  • Components with a mass greater than 14g shall be marked with reinforcement bonding requirements.

  • Ning the fixed point and method of the jumper.

  • High-temperature components that are prone to short-circuit (such as metal film resistors and wirewound resistors above 1W) must not be mounted on the board.

  • Pins of triode are not allowed to be cross mounted.

  • Printed circuit board conformal coating requirements.


4. Except for the high-frequency microwave circuit, there is no lapped wire on the printed circuit board. It is not allowed to use the lap-mounting method for the plug-in components, that is, discrete R, C, L, IC, Components such as G are lapped on printed circuit board pads, printed conductors, and component leads.


5. Jumper on the printed circuit board.

  • Generally, there is no jumper on the printed circuit board. If it is necessary to use, the number of permitted jumpers shall not exceed two in principle: when the number of jumpers exceeds two due to discrete components, etc., it shall be approved by the engineer.

  • The jumper should be as short as possible.

  • Traces must not interfere with the replacement of components or other jumpers.

  • The maximum length of the jumper should be one fixed point every 25mm.

  • Jumper wires should be considered as axial lead components and should meet the detailed requirements for axial lead component installation.

  • Jumpers should not traverse the upper or lower parts of other components, including jumpers.

  • When the length of the jumper is less than 12. 5mm, and the route of the trace does not pass through the conductive area and meet the electrical spacing requirements, the bare silver-plated copper wire can be used.

  • Jumper in “Repair and Modification of Printed Circuit Board Assembly”.

  • Allow up to two jumpers to be connected to the pads of any empty component.

  • The jumper should be routed along the X-Y axis, and there should be no distortion or crack on the wire.

  • The jumper should be as short as possible, and should not be routed above and below the components.

  • The length of the jumper contact shall not be less than 1/2 of the length or height of the metallized terminal of the component (see Appendix A of SJ 20632-1997).

  • If multiple jumpers are soldered to one end, the uninsulated parts of the wires can be twisted together and soldered.

  • The jumper is firmly fixed to the place where the positioning is required, and the adhesive is melted with the conformal coating.

  • Each metallized hole is only allowed to solder one component lead or one wire.

  • Surface mount components must match the pads on the printed circuit board to meet the requirements of GJB 3243-1998, SJ/T 10670-1995 and IPC-SM-7351B-2010.

  • Printed circuit boards should be nickel plated gold or hot air leveling (SMOBC) and noted on the assembly drawing.

  • The connection line is not allowed to be spliced or serially connected.



Copyright 2009-2020 All Rights Reserved by NOD Electronics
Building E, Qixing Industrial Area, Xintang Town, Zengcheng District, Guangzhou 511340, China
Powered by MetInfo 7.2.0 ©2008-2024  mituo.cn