BGA will become the main form of assembly in the future

Market demand for electronic products is small in volume, light in weight, easy to carry. This trend is driving semiconductor industry in high density assembly will continue to seek a new method of solving the problem. Many industry experts believe that, ball grid array BGA (ball grid array) components will become high density and high I / o applications of semiconductor component design breakthrough. Their reliability is rapidly increasing, a lot of companies that BGA will become the mainstream of the future assembly form.

The BGA concept increasingly popular. The so-called BGA is refers to the components of the contact neither lead nor pin, but the connection at the bottom of the device into an array like very small (diameter of 0.8mm) tin / lead alloy ball, pitch 1.5mm (0.060 inches), accordingly to provide reliable connection. This style of components not only for the single chip connection is ideal, and the high performance multi chip module (MCM) connection is also very reliable.

Very small diameter of tin / lead alloy ball instead of lead means can be removed by the lead coplanarity and skew caused most of the problems. With the increase of the number of I / O, BGA is not simply towards more and more fine pitch, but the use of contact spacing book of slightly larger than the fine pitch device spacing.Jedec note 1.0,1.27,1.5mm. currently being launched 1.27 and 1.5mm pitch instead of 0.5 ~ 0.4 mm fine pitch devices.

These components single chip and multi chip structure. This technique can be the I / O expansion to more than 1000. Estimated that at the end of this century, the future all ASIC applications will have 50% for 200 or more than 200 i/o. use of fine pitch devices, its fine wire is easy to damage and is extremely fine accurate placement and strict lead coplanarity.

There are three types of BGA. Another advantage of BGA assembly is adapted to existing SMT assembly process and equipment, that can use existing solder paste screen printing equipment, pick and place equipment and reflow soldering equipment. Due to the BGA average wirelength than equivalent I / O assembly line length, so it has better electrical characteristics.

FR4 PCB Board Manufacturing

Epoxy glass Burkina board, based on epoxy resin as the binder, the electronic-grade glass fiber cloth as a reinforcing material based substrate. It’s bonding sheet and the inner core thin CCL is an important base of manufacturing a multilayer printed circuit board. Mechanical properties of epoxy fiberglass cloth plate, dimensional stability, impact resistance, moisture resistance than paper substrates. It's electric excellent performance, high temperature, low environmental impact by the performance itself. In the process, other than the resin fiberglass cloth panels have great advantages. Epoxy fiberglass cloth panels, the most widely used product model for FR-4.

FR-4 material is a fire code rating, represents a material specification is meant a resin material through the combustion state must be self-extinguishing, it is not a material name, but a material grade. So now FR-4 grade material is typically used in circuit boards, there are many species, but most are based on the so-called four-function (Tera-Function) plus epoxy filler (Filler) and glass fiber made composite materials. These products are mainly used for double-sided PCB, a great amount. In recent years, due to the installation techniques and electronic products PCB technology development needs, it appeared high Tg FR-4 product.

FR4 PCB medium relative dielectric constant of air is 4.2-4.7. The dielectric constant with temperature changes within the temperature range of 0-70 degrees, the maximum variation range of up to 20%. Changes in the dielectric constant of the delay will result in a 10% change in the line, the higher the temperature, the greater the delay. Dielectric constant also changes with the signal frequency, the higher the frequency the smaller the dielectric constant. 100M the following can be used to calculate plate capacitance between 4.5 and delays.

General FR4 material PCB board signal transmission speed is 180ps / inch (1inch = 1000mil = 2.54cm). Surface generally, as the case may be, generally between 140 and 170.

Dielectric constant (Dk, ε, Er) determines the electrical signal propagation velocity in the medium. It is verse between Electrical signal propagation speed and proportional to the square root of the dielectric constant. The lower the dielectric constant is, the faster the signal transmission is.

The dielectric constant is not very easy to measure or definition, it is not only the characteristics of the medium itself, but also with the test methods, test frequency, material condition before testing and test related. Dielectric constant also with temperature changes, some special materials in development will take into account the temperature factor. Humidity is also an important factor in the impact of the dielectric constant, because the dielectric constant of water is 70, very little water It will cause significant changes.


In addition to the direct impact on the dielectric constant of signal transmission speed, it is still largely determines the characteristic impedance, in different parts so characteristic impedance matching is particularly important in microwave communication.