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How Long Is PCB Storage Time?

Le 24 mai 2017, 17:21 dans pcb 0

There is a storage time after PCB complete need be baked if more than storage time,otherwise there easy occur burst board problems when make SMT.The storage time of PCB and the temperature and time of baking PCB are standard in industry.

I. Regulation of PCB control

 (1.) PCB unpacking and storage

    (a.) PCBs can be directly use online if unopened within 2 months manufacturing date.
    (b.) PCBs must be labeled unpacking date within 2 months manufacturing date.
    (c.) PCBs must be finished use online within 5 days after unpacking within 2 months manufacturing date.

(2.) PCB Baking

    (a.)PCBs in the manufacturing date within 2 months of sealing opened more than 5 days, please take 120 +/- 5 ℃ baking for 1 hour.
    (b.)If PCBs exceeds 2 months of manufacture date, please bake for 1 hours at 120 + /5 ℃ before online.
    (c.)PCBs are over 2 months to 6 months before the manufacture date, please bake for 2 hours at 120 +/- 5 ℃ before the online.
    (d.)PCBs are over 6 months to 1 year after the date of manufacture, please bake for 4 hours at 120 + /-5 ℃ before on-line.
    (e.)PCBs be baked should be used within 5 days (put into IR REFLOW), it need to bake one more hour before reuse.
    (f.)If PCBs are more than 1 year before the date of manufacture, please refer to the 120 +/- 5 ℃  baking 4 hours, sending back to PCB factory to remake HASL.

(3.)The method of PCB baking

    (a.)Large PCBs place with flat,a stack up to 30pcs,open the oven and take out PCBs flat to natural cooling( need press fixture to anti warp and twist) after baking completed.
    (b.)Medium and small PCBs place with flat,a stack up to 40pcs,upright type is not limited,open the oven and take out PCBs flat to natural cooling( need press fixture to anti warp and twist) after baking completed.

II. Preservation and baking of PCB in different regions.

The specific storage time and baking temperature of PCB are not only related to the manufacture ability and manufacturing process of PCB manufacturers, but also to the region.

OSP and pure gold PCB, the storage time is usually 6 months, for the OSP process is generally not recommended to bake. The region is a great related to PCBs preservation,in general moisture is heavy in southern region,it’s very damp in Spring.PCBs must be used up within 24 hours,otherwise easy to oxidation,it’s the best used up within 8 hours after unpacking.The weather is generally dry in the Northern region,PCB has a longer storage time and a shorter baking time.the baking temperature is generally 120+/5℃,baking time according to the specific circumstances to decide.

What Kind Of PCB Is Good Quality?

Le 21 mai 2017, 15:42 dans pcb 0

With the rapid development of mobile phone,electronics,telecommunications and other industries continue to grow and also prompted the PCB circuit board industry quantity at the same time ,people requirements are more and more high in components of number,weight,color,material,precison and reliability.

However,due to the fierce competition in the market price,the cost of PCB circuit board material is also in the rising trend,more and more manufacturers at a low price to monopolize the market in order to enhance the core competitiveness.However ,these ultra low cost behind is reduction of material cost and production cost, lead to the devices are usually easy to crack,scratch, comprehensive factors included the precision,performance were not certificated,the serious influence the solderability and liability of products use.

In the face of the market all kinds of PCB circuit board, a good circuit board can distinguish from two aspects; the first method is to judge from the appearance, the other is from the PCB board specification quality.

Method for judging the quality of PCB circuit board:

First: from the appearance of the circuit board to distinguish between good and bad.

Generally, the appearance of the PCB circuit board can be analyzed and judged in three aspects;

1.Standard rules for size and thickness

Circuit board to standard circuit board thickness is different size, customers can measure and check according to their product thickness and specifications

2.Light and color.

The external circuit board is covered with ink, and the circuit board can play an insulating role. If the board color is not bright and the ink is less, the insulation board itself is not good.

3. Weld appearance.

Because of the more parts of the circuit board, if the welding is not good, the parts will easily fall off the circuit board, seriously affecting the welding quality of the circuit board, the appearance is good, carefully identified, the interface stronger is very important.

Second: high-quality PCB circuit boards need to meet the following requirements

    1.  Copper surface is not easy to oxidize, affect the installation speed, oxidation soon after the bad;
    2. After the components are installed, the telephone is easy to use. That is to say, the electrical connection should meet the requirements;
    3. By the high temperature copper skin is not easy to fall off;
    4. The line width, line thickness, line spacing meet the requirements, so as to avoid line heating, break, and short-circuit;
    5. No additional electromagnetic radiation;
    6. And high temperature, high humidity and resistance to special environment should also be considered within the scope;
    7. The shape is not deformed, so as not to install after the deformation of the shell, screw hole dislocation. Now all mechanical installation, the circuit board hole position and line and design deformation error should be within the allowable range;
    8. The surface mechanical properties should meet the installation requirements;

The above is the PCB circuit board to judge the good and bad methods, in the purchase of PCB circuit board, be sure to polish your eyes.

PCB Assembly Files- PCB Enginner Need To Know

Le 16 mai 2017, 12:23 dans pcb assembly 0

Some complex PCBs design be finished,you must take PCB to assembly plant when PCBs get back from PCB manufacturer.That assembly plant need you provide some necessary documents for production.Where the captain guy gave you talk about the PCB assembly when production of documents required,and what the representative of the file is useful.

PCB assembly processing required documents are the following:

1.Stencil file

Stencil file is solder paste file, it used in brush paste when PCB assembly, it can be automatically welded when PCB through high temperature furnace. But stencil file didn’t be included plug-in components information,it’s surface mount components information.What kind of stencil is? The following is a kind of stencil.

Above aperture is exposed for each surface mount components,no components area are covered. And the stencil is a certain thickness,the exposed holes are filled with solder paste when brush paste, then pcb pad coated with solder paste. The solder paste melting to stabilize assembly when soldering in high temperature.

2.Pick Place file

When assembly is processed with a have to tell the machine how to paste the components,which requires the coordinates of the document.Coordinate file also call pick place file,it has the coordinates of each components, layer, rotation angle and other information,the machine will be able to read this information,according to the requirements to paste components.

There are components labels.X,Y coordinates,rotation angle,where level.

3.Component bitmap file

The component bit map file,in fact is the component silkscreen. It’s provided to operate workers to comparison in the production processing.Inspect if there’s any wrong of assembly.The component bitmap is shown below:

4.PCB assembly fixture file:

PCB assembly fixture file, it’s used in covering surface mount components and expose plug pin when PCB through reflow welding machine.Because in the production of the first process is surface mount welded,and then the plug-in welding.the plug-in soldering is done with wave soldering, it must be through wave furnace. The fixture is avoid surface mount components be assembled don’t fall when through wave furnace.

5.Panel drawing file

If PCB is made from panel,it also need provides panel file.Because the assembly manufacturers need panel drawing to make coordinates files.

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