Circuit Board Test, Inspection, and Specification Glossary

Circuit Board Test, Inspection, and Specification Glossary

56. Qualification Agency

U.S. military products are all supplied by private companies, but before dealing with the U.S. government or military, the supplier must first obtain the qualification of "qualified supplier". Taking PCB as an example, not only the circuit boards supplied must pass the inspection of military regulations, but also the supplier itself must pass the qualification examination of military regulations. This "qualification certification body" is the review and quality inspection of the supplier's documents , and a dedicated unit for test supervision.

57. Qualification Inspection

It means that the supplier should make a trial sample of the sample designated by the customer before ordering any product to demonstrate its engineering and quality control capabilities, and be listed as a qualified supplier after being approved by the customer After that, we can continue to make actual products of various material numbers. This full formal "qualification accreditation" inspection process is called Qualification Inspection.

58. Qualified Products List Qualified Products (Suppliers) List

It's a term used by the U.S. military. Taking circuit boards as an example, if a certain supplier has passed the qualification inspection of the military and can produce a certain type of board, the military will post the name and address of the company on a list that is republished every year. , for reference by various procurement agencies of the US government. This QPL was originally only applicable to the domestic industry in the United States, but is now also open to foreign suppliers. It should be noted that this kind of QPL is only listed for product categories, not for the recognition of suppliers. For example, although a circuit board factory can produce single-sided, multi-layer and flexible boards, but only passed the double-sided board during the qualification examination, it is only listed under the double-sided board item in the QPL, and other items are not included. It is known that QPL only recognizes products rather than manufacturers. At present, this QPL system is valid for three years, after which a new application for accreditation is required.

59. Quality Conformance Test Circuitry (Coupon) quality conformity test circuit (model)

It is placed on the outer edge of the "Process Panel" of the circuit board. It is a sample of seven special circuit graphics in each group, which can be used to judge whether the board can pass various quality inspections. However, this kind of "board edge sample" combination mostly appears in military boards or high-reliability boards, and such troublesome samples are rarely used in general commercial boards.

60. Rejection

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

61. Repair

Refers to the work of improving the defective board. However, the degree and scope of this repair is relatively large. For example, the eyelet installed for rescue after the plated through hole is broken, or the repair of the broken circuit, etc., must obtain the consent of the customer before construction, which is different from the "heavy industry" of small actions. "Rework is different.

62. Rework(ing) heavy industry, reprocessing

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 immediately, which is called "Rework". Usually this kind of "heavy work" is a small-scale operation, such as flattening the board, trimming the burr, or eliminating the short circuit, etc., which is much lighter than Repair.

63. Scratch

All kinds of groove-like or V-groove-like scratches appearing on the surface of objects are called.

64. Short circuit

When there is a path between two conductors that should not be connected to each other under abnormal conditions, it is called a short circuit.

65. Sigma (Standard Deviation) standard deviation

is a statistical noun. When a lot of data is obtained from quality control sampling, the arithmetic mean X of each data can be obtained first (that is, the sum is divided by the number of samples), and then the difference between each individual sample value and the average value can be obtained, which is called "deviation". "(Deviation such as X1-X, X2-X,... Xn-X), and further calculate the "root mean square" value (RMS, Root Mean Square Value) of each "deviation value", that is, the so-called "standard Poor standard deviation". Generally, the Greek letter σ (pronounced Sigma) is used as a representative symbol, and "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 according to the normal distribution (Normal Distribution) of the standard bell curve (Bell Curve) , if we integrate all the covered area from negative to positive, and take the obtained value as 100%, then the area governed by ±3δ will reach 99.73%, that is to say, at this time, the defective product can become a fish that slipped through the net. The probability is only 0.27%. Recently, many large electronics companies have emphasized the need to strengthen quality control, saying that it is necessary to improve the quality control to ±6δ, which is not easy for Chen Yitai in his high school days.

66. Sliver edge wire, edge strip

On both sides of the board circuit, at the uppermost surface, once the thickness of the plating layer exceeds the thickness of the resist, lateral growth on both sides will occur. This kind of slender hanging edge is easy to break off and stay on the board because there is no support directly below it, and a short circuit may occur. This kind of broken or unbroken edge wire is called Sliver.

67. Specification (Spec.)

Specifications refer to various materials, products, and processes, and their separate formally written quality or operation manuals. Generally speaking, such documents have the characteristics of rigorous text, detailed illustrations, thoughtful consideration, and detailed references. As for the specific passing number for a special requirement, when it is similar to Criteria, it should be translated as "specification".

68. Specimen sample, sample

Refers to the sample unit (Sample Unit) obtained from the finished product or partial manufacturing process, and its partial or entire actual representative sample is called Specimen.

69. Surface Resistivity surface resistivity; Volume Resistivity volume resistivity

The former refers to the resistance value between two adjacent metal areas on the material surface; the latter refers to the volume resistance value between the upper and lower metal surfaces of the template. These values are very related to the test environment conditions, and the test is carried out according to the graphics and regulations in 2.5.17.1. of IPC-TM-650. There are three copper surface electrode points, namely: 1. The back ground layer (that is, the disc with a diameter of D3) that withstands the stray current and maintains the correct measurement value; 2. The disc in the center of the front (D1); 3. The ring on the front periphery (that is, the copper ring formed between D5 and D4). According to the method of 2.5.17.1. in IPC-TM-650, the error value of the Megaohm meter used for measurement and reading must still be within ±5% when it reaches 1012 Ω. Apply a DC voltage of 500 V to the "high/low" points to be measured in the figure for a total of 60+5-6 seconds to measure the "Surface Resistance" and "Volume Resistance" respectively, and then substitute them into The following formulas can obtain two kinds of "resistivity" respectively: 1. surface resistivity r'=R'P/D4; R' is the measured surface resistance value; P is the circumference (cm) of the grounding copper plate; D4 is the width of the space between the ring and the disc. 2. Volume resistivity r=RA/T; R is the measured volume resistance value; T is the average thickness of the plate (cm); A is the area of the copper ring. According to the regulations of MIL-S-13949H/4D (1993.10) of the U.S. military plate specification, the lower limit of surface resistivity of commonly used plate FR-4 is 104MΩ, and the lower limit of volume resistivity is 106MΩ.

70. Taper Pin Gauge

It is a tapered elongated needle that gradually becomes thinner. It can be inserted into the through hole to detect various apertures, and the measured data can be displayed on the surface, which is very convenient.

71. Taber Abraser

It uses two non-powered soft grinding wheels to press and attach it to the surface of the sample to be ground, and the sample is placed on a slow-rotating circular platform. When the motor is turned on to rotate horizontally, the horizontal rotation of the template will drive the grinding wheels of the two counterweights to rotate counter-rotatingly, and then the surface to be tested will be ground under the pressure of the counterweight. For example, on the IPC-B-25 small test board that has been printed with green paint, after drilling a set of holes in the center of the board, it can be installed on the platform. In addition, add a counterweight of 1 kg to each of the two vertical grinding wheels, and then start the platform to rotate several times, so that the green paint can be directly subjected to slow continuous grinding. After the specified number of laps has been ground, the test board is removed, and the green paint layer with ring-shaped abrasion marks is inspected to see if the copper circuit has been worn through. According to Section 3.5.1.1 of IPC-S-840B, the Abrasion Resistance (Abrasion Resistance) test stipulates that the green paint of Class 3 must pass 50 laps of grinding without being worn through. In addition, the hard anodized layer of aluminum in the metal surface treatment industry, or other electroplating layers often require wear resistance tests.

72. Tolerance

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

73. Touch Up touch repair, brief repair

It refers to some small defects on the board surface that do not affect the function, and can be carried out with simple tools and small-scale maintenance under bare-handed operation. It is called Touch Up; it is somewhat similar to Rework.

74. Twist

The fingerboard surface deforms and warps from the corners on both sides of the diagonal, which is called Twist. There are many reasons for this, most of the films with fiberglass cloth are stacked wrongly in the weft and warp directions (warp to warp, or weft to weft). The method of board warping detection is first to let three points in the four corners of the board touch the platform, and then measure the height of the warped corner. Or use another ruler to follow it on the opposite corner, and then use the "hole gauge" to measure the floating distance of the ruler across the board surface.

75. Universal Tester

Refers to the standard "Grid" (Grid) fixed large dial with a large number of measuring points (often more than 10,000 points), and the dial of movable probes can be made according to different material numbers, and the two are aligned. In terms of the actual measured models carried out later. During mass production, as long as the movable dial is replaced, mass production testing of different material numbers can be performed. And this kind of mainframe can still use high voltage (such as 250 V) to conduct Open/Short electrical test on the completed circuit board. These high-priced "ATE Automatic Testing Equipment" (ATE Automatic Testing Equipemtn) are called universal or wide-ranging electrical testing machines. In contrast, there is a simpler "dedicated" tester (Dedicated Tester).

76. Vision Systems

Using optical inspection technology, a method for comparative inspection of the different reactions of the conductor circuit on the board surface and the substrate on the "Gray-Scale", that is, the so-called "Automatic Optical Inspection" (Automatic Optical Inspection) ; AOI) technology, the inner board can be inspected before lamination.

77. Visual Examination (Inspection)

Visual inspection of the appearance of the product with uncorrected eyes, or with a magnifying glass of specified magnification (3X ~ 10X), both are called "visual inspection".

78. Waive is temporarily allowed to pass the customs, but will not be inspected for the time being

When there are relatively minor defects in the product, due to the needs of the situation, it has to be accepted temporarily, or the quality is subjectively recognized, and the inspection is temporarily abandoned. The American jargon is called Waive.

79. Weave Eposure texture reveals; Weave Texture texture looms

This term has a more correct description in Section 2.5 of IPC-A 600D. The so-called "texture exposure" means that the resin layer (Butter Coat) on the surface of the board has been damaged and lost, resulting in the exposure of the glass fabric inside the board. The latter's "looming texture" means that the resin on the surface of the board is too thin, showing a translucent state, so that the internal texture is also faintly visible.