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This article mainly introduces "the method of Cadence package size". In the daily operation, I believe that many people have doubts about the method of Cadence package size. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubts about "Cadence package size method"! Next, please follow the editor to study!

1. Watch sticker IC

A) Pad

The pad of the table-mounted IC depends on four parameters: toe length W, toe width Z, distance between toe fingertip and chip center D, pin spacing P, as shown in the following figure:

Calculation of pad size and position:

X=W+48

S=D+24

Y=P/2+1, when P26mil

B) silkscreen

The distance between the screen printing frame and the inner edge of the pin > = 10mil, linewidth 6mil, rectangle. For the package of two-side pins such as sop, the length boundary can be taken as the non-pin boundary of IC. Dot mark near the first foot in the screen printing frame, outside the screen printing frame, near the first foot, the dot line width depends on the size of the element, it is appropriate. For QFP and BGA packages (packages with pins at the bottom of the chip), it is common to chamfer on the screen frame to indicate the position of the first foot.

C) place bound

This area is set to prevent components from overlapping, the outer edge of the welding pad and the outside of the component body + 20mil can be selected, and the linewidth does not need to be set, just a rectangle. That is, a rectangle is drawn along the component body and the outside of the element pad, and then the length and width of the rectangle are + 20mil respectively.

D) assembly

This area can be smaller than silkscreen 10mil, line width does not need to be set, rectangle can. For irregular devices, assembly refers to the area of the device body (usually a rectangle), which must not be roughly replaced by a rectangle that covers almost the entire package area.

PS: for a relatively certain package type, LP Wizard can be used to calculate the detailed pad size and position, and then get the pad size and position, but also get the relevant data of silkscreen and place bound, for the latter two data, can be adopted or not.

2. Through-hole IC

A) Pad

For through-hole components, you need to set up conventional pads, hot pads, resistance pads, it is best to set the begin layer, internal layer, bottom layer all set up the above three pads. Because the top and bottom layers may also be negative, or they may be used as the inner layer.

Through hole diameter: 8-20mil larger than pin diameter, usually 10mil.

Conventional pad diameter: it is generally required that the conventional pad width is not less than 10mil, and the 20mil is usually larger than the through hole diameter (at this time, the size of the conventional pad is exactly the same as the inner diameter of the flower pad). This value is variable, the through hole is larger, such as + 20mil, and the through hole is smaller, such as + 12mil.

Flower pad diameter: the inner diameter of the pad is generally larger than the through hole diameter 20mil. The outer diameter of the flower pad is generally larger 20mil than that of the conventional pad (if the conventional pad is larger than the through hole 20mil, the outer diameter of the pad is larger than the inner diameter of the pad 20mil). These two values can also be changed, and can be flexibly selected according to the size of the through hole, and the through hole hour can be + 10-12mil.

The diameter of the resistance pad: generally larger than the conventional pad 20mil, that is, it should be consistent with the outer diameter of the pad. This value can also be adjusted to + 10-12mil according to the size of the through hole. Note that it needs to be consistent with the outer diameter of the disk.

For plug-in IC, the TOP (begin) pad of the first pin needs to be set to square.

B) Silkscreen

It is drawn in the same way as the watch sticker IC.

C) Place bound

It is drawn in the same way as the watch sticker IC.

D) Assembly

It is drawn in the same way as the watch sticker IC.

3. Discrete components for watch sticking

Discrete components generally include resistor, capacitor, inductor, diode, transistor and so on.

For patch discrete components, the packaging rules are as follows:

A) Pad

Watch sticking discrete components, mainly for resistors and capacitors

X=W+2/3*Hmax+8

Generally speaking, this number should be slightly larger than L, such as + 6-8mil.

R=P-8, which is used to determine the position of the pad.

Generally speaking, the pad data in accordance with the IPC standard can also be obtained through LPWizard.

B) Place bound

Same as watch sticker IC. That is, the component body and the outer edge of the pad rectangle + 20mil, line width does not need to be set, rectangle can.

C) silkscreen

Generally choose a rectangular box that is slightly smaller than place bound, such as-4mil, linewidth 6mil. For discrete components with polarity, they need to be displayed on the screen printing frame. For example, the screen printing frame of the positive pole is slightly thicker, such as 8mil, or double lines can be drawn at the positive pole. For the surface-mounted Triode screen printing layer, as shown below:

D) assembly

Slightly smaller than the screen printing frame, such as-4mil, the line width does not need to be set, the rectangle is fine. However, for irregular packaging, for example, the TO or SOT,assembly region refers to the area of the component body (usually a rectangle), it can not be replaced by a rectangle that covers almost the whole area, otherwise there will be a big problem of inaccurate placement of the patch.

PS: because the sizes of discrete components are relatively small, the choice of linewidth can be slightly smaller.

4. Plug-in discrete components

Such as pins, buttons, etc.

For these components, the parameters of the pad are the same as those of the upper through-hole IC.

The corresponding parameters of Place bound,assembly,silkscreen and surface mount discrete components are basically the same.

Summary: for the packaging of components, the requirements for the pad are relatively strict, if you can use LP Wizard calculation, it is best to use the pad parameters obtained by LP Wizard. Assembly is also relatively strict, at the very least, the center of the component body should coincide with the center of the painted assembly, so that the position of the watch sticker can be guaranteed.

Pad category explanation:

Conventional pad: that is, the pad used for positive film, connected to other resources through wiring, mainly used in the signal layer.

Hot air pad: also known as flower pad, mainly used for negative film, the function is to prevent heat loss and virtual welding, etc., mainly used in the power layer and stratum, that is, in the stratum or power layer, through the flower pad to connect with the stratum or power layer.

Anti-solder pad: mainly used for negative film, that is, disconnecting the through hole from the corresponding inner layer (such as power supply or stratum).

At this point, the study of "the method of Cadence package size" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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