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PCB Circuit Board Testing, Inspection and Specification (3)

Posted:04:09 PM June 17, 2019 writer: G

51.Optical Instrument

Inspection of the board in the process and on the finished product often requires some instruments related to "optics", such as monitoring instruments that detect the concentration of the bath in a "photocell" manner, as well as high-power tomography microscopes that look at micro-sections. , or low-power stereo microscopes, as well as more precise "optical contrast", SEM, TEM and other electron microscopes combined with electronic technology, even a very simple magnifying glass, are optical instruments. At present, its functions have been gradually enhanced and the effects have been greatly improved. However, these modern equipment are very expensive, making the high-end PCBs soar.


In the broad sense, the through holes that can be seen on the various surface layers are called pinholes, and the circuit boards refer to the appearance defects on the lines or the walls of the holes. The figure shows four different disadvantages, which are called Dents, Pits, Pinholes and Voids.


Refers to the depression of a small area on the surface of the metal. When the plating process of the gloss nickel is poorly managed (organic pollution), dense pits often appear in the high current area. The reason is that many hydrogen accumulations are caused by the common shortage. Mix this word with the "Pin Hole Pin Hole". In fact, the Pits is a bottom hole that is not the same as the pinhole that is seen at the bottom.

54.Pogo Pin

The electric measuring machine is used for the bead of Nail Testing. The front part of the probe is divided into two parts: the outer casing and the inner needle. The inside is equipped with a spring, which can make thousands of needle tips maintain the elastic force required for conduction when the dial of the set pressure is in contact with the measuring surface of the board to be tested. The telescopic probe is called Pogo Pin. This kind of probe is also called Spring Probe. When the QFP is above 256 feet and the pitch is dense to 15mil, it must be touched on the pad in an interlaced manner to avoid the probe itself being too close and shorted.


It is a kind of elastic which can maintain a certain pressure, and each measuring point of the board surface to be tested is subjected to urgent contact, so that the testing machine can perform the electrical test. The gold-plated or rhodium-plated stylus is called Probe.

56.Qualification Agency

US military products are supplied by private companies, but before dealing with the US == or the military, the supplier must first qualify as a "qualified supplier." Taking the PCB as an example, not only the supplied circuit boards must pass the inspection of the military regulations, but also the supplier itself must pass the qualification examination of the military regulations. This "qualification certification body" is the examination and quality inspection of the supplier documents. , and the special unit of the test supervision.

57.Qualification Inspection

It means that the supplier should test the sample specified by the customer before the production of any product, to demonstrate its engineering and quality control capabilities, and be listed as a qualified supplier with the approval of the customer. After that, you can continue to produce actual products with various item numbers. This formal "qualification" inspection process is called Qualification Inspection.

58.Qualified Products List

It is the language of the US military. Take the circuit board as an example. If a supplier has passed the military qualification test, it can produce a certain board, so the military will name the company's name and address, etc., and publish it on a list that is reissued every year. Medium, for the United States == reference for each purchasing unit. This QPL was originally only available to the domestic industry in the United States and is now open to foreign suppliers. It should be noted that this QPL is only listed for the product category and is not recognized by the supplier. For example, a circuit board factory can produce single-sided and multi-layer and soft board, but only double-panel is passed during the qualification examination. Therefore, QPL only enters its name under the double-panel project, and other items are not included. Therefore, QPL only recognizes products rather than recognizes manufacturers. At present, this QPL system is valid for three years and will be re-applied after the expiration.

59.Quality Conformance Test Circuitry(Coupon)

It is placed on the outer edge of the "Process Panel" of the circuit board. It is a sample of seven special circuit patterns for each group. It can be used to judge whether the board can pass the inspection basis. However, such "board edge sample" combinations are mostly found in military boards or high reliability boards. Generally, commercial boards use less troublesome samples.


When the manufactured product does not meet the specifications and data in some quality inspection items, it cannot be normally accepted, that is, Rejection or Reject.


Refers to the work of improving the defective board. However, the degree and scope of this Repair is relatively large. For example, the eyelet (Eyelet) installed after the plated through hole breaks, or the repair of the open circuit, etc., must be approved by the customer before construction, and the small action "rework "Rework is not the same.


When a small flaw is found on a product that has been completed or is still being manufactured, various measures are taken to remedy it, called "Rework". Usually, such "heavy work" is a small-scale action, such as the flattening of the slab, the trimming of the burrs or the elimination of the short circuit, to a lesser extent than the Repair.


Various groove-shaped or V-groove-like scratches appearing on the surface of the object are called.


When there is a path between the two conductors where the current should not communicate, it is called a short circuit.

65.Sigma (Standard Deviation)

It is a statistical noun. When a lot of data is obtained by sampling the quality control, first, the arithmetic mean X of each data (that is, the sum divided by the number of samples) can be obtained, and then the difference between each individual sample value and the average value is obtained, which is called "deviation". "(Deviation such as X1-X, X2-X, ... Xn-X), and further obtain the "root mean" value (RMS, Root Mean Square Value) of each "deviation value", that is, the so-called "standard" Poor Standard Deviation". Generally, the Greek letter σ (sound Sigma) is used as a representative symbol, and the "standard deviation" can be used as a tool for statistical process control. σ=(√((X1-X)2+(X2-X)2+X3-X)2+...(Xn-X)2))/n is a normal bell-shaped curve of normal distribution (Bell Curve) If all the areas covered are integrated from negative to positive, and the obtained value is 100%, the area under the jurisdiction of ±3δ will reach 99.73%, which means that the defective product can become the fisher of the net. The probability is only 0.27%. Recently, many large electronics companies have emphasized the need to strengthen quality control. It is said that it is necessary to upgrade to ±6δ. Chen Yitai is not easy to do.


On both sides of the board surface, at the uppermost edge surface, as the thickness of the plating layer exceeds the thickness of the resist, lateral growth will occur on both sides. Such a slender suspension has no support under the front, and is often easily broken off and left on the board, which may cause a short circuit. Such broken or unbroken side edge silk is called Sliver.


Specifications refer to various materials, products, and processes, which are individually documented quality or workbooks. In general, these documents are characterized by rigorous text, detailed drawings, thoughtful considerations, and detailed references. As for the specific pass number for a particular request, similar to Criteria, it should be translated as "Specifications".


Refers to the sample unit (Sample Unit) obtained from the finished product or partial process, which is a partial or total actual representative sample, which is called Specimen.

69.Surface Resistivity; Volume Resistivity

The former refers to the resistance between two adjacent metal areas on the surface of the material; the latter refers to the volume resistance between the two metal surfaces on the sample.

70.Taper Pin Gauge

It is a tapered tapered long needle-like body that can be inserted into a through-hole to detect a variety of apertures, and has a surface reading to present the measured data, which is convenient.

71.Taber Abraser

Two unpowered soft wheels were used to attach them to the surface of the sample to be ground, and the plate was placed on a slow rotating circular platform. When the motor is started to rotate horizontally, the horizontal rotation of the template will drive the two weighted grinding wheels to rotate in mutually opposite directions, and then the surface to be tested is subjected to a grinding test under the weight of the weight.


Refers to the various dimensions of the product to be tested (Demension), the total amount of positive and negative changes allowed in the specification is the tolerance.

73.Touch Up

Refers to the small shortcomings of the board that do not affect the function, and can be carried out with a simple tool in a bare-handed operation, called Touch Up; similar to Rework.


The fingerboard surface is deformed and tilted from the corners on both sides of the diagonal line, which is called Twist. There are many reasons for this. For films with fiberglass cloth, most of them are stacked in the latitude direction (the warp direction must be warp, or the latitude to the latitude). The method of board warpage detection is to first make the three points in the four corners of the board close to the platform, and then measure the height of the raised corner. Or use a ruler to connect to the diagonal, and then use the "hole gauge" to measure the floating distance of the ruler across the board.

75.Universal Tester

Refers to the standard "grid" (Grid) with a large number of measuring points (often 10,000 points) to fix large dials, and can make the movable probe's dials according to different item numbers, and align the two with each other. In terms of the measured models carried out after the connection. As long as the active dial is changed during mass production, the mass production of different material numbers can be tested. This type of mainframe can still use high voltage (such as 250 V) to perform Open/Short electrical measurements on the finished board. These high-priced "Automatic Testing Machines" (ATE Automatic Testing Equipemtn) are general-purpose or widely used electric measuring machines. In contrast, there is a relatively simple "Dedicated Tester".

76.Vision Systems

A method of comparative inspection of the different reactions of the plate conductor line and the substrate on the "gray-scale" by means of optical inspection technology, so-called "automatic optical inspection" (Automatic Optical Inspection) ; AOI) technology to check the inner layer before pressing.

77.Visual Examination(Inspection)

Visual inspection of the appearance of the product with the naked eye without vision correction, or visual inspection with a magnifying glass (3X ~ 10X) at a specified magnification, both called "visual inspection".


When the product appears to be less important, the situation is called Waive because the situation needs to be temporarily passed, or subjectively recognized, and the test is temporarily abandoned.

79. Warp, Warpage

This is a term used in the early days of the PCB industry. It refers to the problem that the circuit has a flatness, that is, the bending deformation of the length of the board. The current term is called Bow.

80.Weave Eposure; Weave Texture:

These two terms are more correctly described in Section 2.5 of the IPC-A 600D. The so-called "texture revealing" means that the resin layer (Butter Coat) on the surface of the board has been damaged and lost, so that the glass cloth in the board is exposed. The latter's "texture looming" means that the resin on the board surface is too thin and translucent, so that the internal texture is also faintly visible.

81.White Spot:

Especially refers to the high-frequency use of glass fiber cloth and Teflon (Teflon or PTFE resin). On the board surface where the PCB process is completed, the woven dots appearing on the "secondary outer layer" can often be seen through. (Knuckles), the appearance of white or transparent discolored foreign matter appears, slightly different from the Measling or Crazing that often appears in FR-4 sheets. This term "white point" appears on IPC-T-50E (1992.7).

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