Circuit Board Test, Inspection, and Specification Glossary

Circuit Board Test, Inspection, and Specification Glossary

1. Acceptability, acceptance

The former refers to various operating conditions and written guidelines that should be observed when inspecting semi-finished or finished products. The latter refers to the process of performing acceptance tests, such as Acceptance Test.

2. Acceptable Quality Level (AQL) Acceptable quality level

It refers to the "upper limit of defective rate" that is considered to be able to meet the requirements of the project at the time of random inspection, or the upper limit of the percentage of defects. AQL is not designed to protect a particular batch, but a guarantee for the quality of continuous batches.

3. Air Inclusion

When the board is coated with liquid materials, there are often air bubbles remaining in the coating, such as air bubbles in the film resin, or air bubbles in the green paint printing film, etc. The mixed air bubbles are very bad for the electrical or physical properties of the board. .

4. AOI automatic optical inspection

Automatic Optical Inspection is an optical device that uses ordinary light or laser light with computer programs to visually inspect the appearance of circuit boards to replace manual visual inspection.

5. AQL quality acceptance level

Acceptable Quality Level is a quality control technology that selects a small number of items from the quality inspection items of a large number of products for inspection, and then determines the movement of the entire batch.

6. ATE automatic electrical testing equipment

In order to ensure the smoothness of the circuit system of the completed circuit board, it is necessary to use a needle plate with a specific contact point to conduct electrical measurement on the board on a high-voltage (such as 250 V) multi-measurement point general-purpose electric tester. The type of testing machine is called Automatic Testing Equipment.

7. Blister localized delamination or blistering

In the circuit manufacturing process, delamination between local boards or local boards, or local copper foil floating, often occurs, which are called Blister. In addition, in the general electroplating process, due to unclean substrate treatment, blisters often occur in the coating, especially silver-plated objects are most prone to blisters during post-baking.

8. Bow, Bowing plate bending

When the board loses its due flatness (Flatness), it is placed on a flat table with its concave side facing down. If the four points of the board corners cannot be kept on a plane, it is called board bending or board warping (Warp or Warpage), if only three points fall on the plane, it is called Twist. However, usually when this kind of twisting is very slight and not obvious, it is commonly called warpage.

9. Break-Out

It means that the drilled hole has broken out of the circle (Pad) to form a broken ring; that is, the hole position and the circle (Pad) to be drilled are not aligned, so that the two circle centers are not aligned. fall on one point. Of course, both drilling and image transfer may be the cause of misalignment or breakout. However, there are thousands of holes on the board, and it is impossible to align all of them. As long as there is no "breaking out" and the narrowest part of the formed hole ring is not lower than the specification (generally 2 mil or more), it is possible. Acceptance.

10, Bridging bridge, bridge

It refers to the improper short circuit that occurs between two lines that should be isolated from each other.

11. Certificate certificate

When a specific "personnel training" or "quality test" is completed and meets a certain professional standard, the document that is recorded in writing to prove it is called a Certificate.

12. Check List check list

In a broad sense, it refers to the items that should be checked one by one for safety considerations before various operations. In a narrow sense, it refers to various items that are inspected one by one in the PBC industry when customers go to the site to understand the quality.

13. Continuity Connectivity

Refers to whether the current flow in the circuit is smooth or not. In addition, Continuity Testing refers to the test of the energization of each line, that is, two points are found at both ends of each line, and elastic probes are used to make urgent contact with them (the whole board is implemented with a needle bed), and then Apply the specified voltage (usually twice the practical voltage) to conduct a "connectivity test", which is commonly known as Open/Short Testing (open short circuit test).

14. Coupon, Test Coupon edge sample

To understand the detailed quality of circuit boards, especially the through-hole structure of multi-layer boards, it is not only possible to rely on visual inspection and electrical testing, but also to conduct further microsection (Microsectioning) microscopic inspection of the structure. Therefore, it is necessary to set an additional "through hole and circuit" pattern at one or more places on the edge of the board, as an anatomical slice matching sample (Conformal Coupon) for monitoring the structural integrity of the board. If the quality is particularly strict, when the cut sample fails, the board will not be shipped. Note: this kind of board edge slicing can not only be used as a quality inspection item for shipment, but also can be used as a countermeasure study for problems and a monitoring tool for quality improvement. In addition to micro-section samples, a special Coupon for checking "characteristic impedance" is sometimes added to the edge of the board to check whether the "impedance value" of each multilayer board is still controlled within the specified range.

15. Crazing white spots

Refers to the defects in the appearance of the substrate, which may be due to the partial split between the glass fiber cloth and the epoxy resin, or between the yarn bundles of the cloth itself. The white area that can be seen from the appearance is called Crazing. Smaller ones that appear only on weaving points are called "white spots" (Measling). In addition, when the Conformal Coating coated on the surface of the assembled board is cracked, it is also called Crazing. Generally, ordinary daily necessities porcelain or tiles, after a long period of use and aging, also have irregular cracks on the surface due to the release of force, also known as Crazing.

16. Crosshatch Testing

It is a destructive test for the adhesion of the board surface film. Based on the adhesive tape tearing method of ASTM D3359 with slight changes, it is an adhesion test for various dry and wet coatings on the board surface. Use a multi-edged cutting knife to cut vertically and horizontally on the surface of the film, cut it into many small squares, press it tightly with adhesive tape, and tear it off forcefully. The incisions of all the squares are smooth and not torn off are given 5 points, the incisions are broken and the squares are torn between 35% and 65% are only given 1 point, and the worse ones are 0 points. After several times of comparison, the total score is the score of film adhesion.

17. Dendritic Growth

It refers to the fact that the two conductors on the circuit board surface are in a humid environment and are affected by long-term voltage (bias), resulting in the growth of metal ionic dendrites, which will eventually form an overlap across the surface of the insulating board, resulting in leakage or The situation of short circuit is called "dendritic growth". And when it continuously penetrates into the insulating material, it is called Dendritic Migration or Dentrices.

18. Deviation

It means that the measured data is not good, and the gap between it and the normal acceptance specification is called Deviation.

19. Eddy Current eddy current

In the PCB industry, it is a working principle and method for measuring the thickness of various films. It can measure the thickness of non-conductive films on non-magnetic metal substrates (such as the thickness of resin layer or green paint on copper surface). (Probe) is wound with a coil, and high-frequency oscillating alternating current (100KHz~6MHz) is applied to generate a magnetic field. When the probe touches the surface to be measured, the bottom metal layer (such as copper) will be induced to generate "eddy current", and the signal of this eddy current will be detected by the probe. The thicker the non-conductive film on the surface, the greater the effect of blocking eddy current, and the weaker the signal received by the probe. Conversely, the thinner the film, the stronger the signal received by the probe. Therefore, this principle can be used to measure the thickness of non-conductive film. Generally, it can measure the thickness of anodized film on aluminum surface, the thickness of substrate on copper foil substrate, and any similar combination. Eddy currents are also generated in general circuit systems, but they are ineffective currents that can only generate heat and be wasted.

20. Dish Down

Refers to the local area on the copper conductor line on the circuit board, which is called "dish depression" because of the improper circular depression during pressing, and unfortunately still remains on the circuit after etching. In a high-speed transmission line, such a local sag will cause a sudden change in the impedance value, which is detrimental to the overall function, so it should be avoided as much as possible.

21. Edge-Dip Solderability Test

It is a simple test method for the solderability of circuit boards (or other component feet). After the sample of a specific circuit is dipped in flux, it is clamped by a testing machine or manually, and it is slowly pressed vertically into the molten tin. In the pool, stay for 1~2 seconds and then take it out at a constant speed. After cleaning, you can observe the tin staining of the conductor or through hole on the surface of the board.

22. Eyelet

It is a hollow rivet made of bronze or brass. When a through hole is found to be broken on the circuit board, this "Eyelet" can be added. It can not only maintain the conductive function, but also accept soldering parts. However, due to the industry's stricter requirements on the quality of circuit boards, there are fewer and fewer opportunities to add Eyelets.

23. Failure failure, damage

Refers to the situation where a product or component fails to perform its normal function.

24. Fault defect, defect

When some substandard quality defects appear on components or products, or normal operation cannot be performed due to bad factors, it is called Fault.

25. Fiber Exposure

It means that when the surface of the substrate is attacked by external mechanical friction, chemical reaction, etc., it may lose the resin layer (Butter Coat) covered by the surface and expose the glass fiber cloth of the substrate. It is called "Fiber Exposure", also known as "Fiber Exposure". "Weave Exposure texture reveals", and the uneven cutting of glass fiber bundles on the hole wall is called glass fiber protrusion (Protrusion).

26. First Article first product

Various parts or assembled products, in order to achieve the goal of smooth mass production, whether there are still flaws in the overall coordination of the mature processes, equipment, materials and test inspections, and whether the obtained products can meet various established requirements. Requirements, etc., should be fully understood in advance, so that there is still a chance to make corrections before mass production. The first article or the first batch of small-scale products that are trial-produced for this purpose are called First Articles.

27. First Pass-Yield initial inspection yield rate

After the finished products are pre-inspected according to the established specifications for each item to be inspected, the proportion of qualified products to all products is called the initial inspection yield (or First Accept Rate), which is a measure of whether the process management is good or not. A specific pointer for

28. Fixture

Refers to the tools that assist products in various operations during the manufacturing process, such as the dial for electrical testing of circuit boards, which is an important fixture. It is called "jig" in Japanese.

29. Flashover

It refers to the "disruptive discharge" (Disruptive discharge) on the surface of the insulator between the two conductors on the board (even if there is green paint), when there is voltage, which is called "flashover".

30. Flatness

It is a new expression of Bow and Twist. Early boards in the era of wave soldering and insertion did not pay much attention to the flatness of the board surface. The upper limit of the general board thickness required by the IPC specification is 1%. In the SMT era in recent years, the overall flatness of the board has a great impact on the solder paste solder joints, and it has been strictly required that the degree of uneven warpage must be less than 0.7%, or even 0.5%. Therefore, in various specifications, the "flatness" with a stronger concept has been changed to replace the early terms such as plate bending and plate warping.

31. Foreign Material

In a broad sense, it refers to the existence of some abnormal foreign objects in various raw materials of pure quality or modulation, such as ash, sand, and resist debris in the bath liquid; or refers to abnormal particles in the plate resin and coating, etc. The narrow meaning refers to the foreign matter that is fully sealed or half-covered in the molten tin layer or solder layer, forming a rough, shrinking tin, or lumpy uneven appearance.

32. Gage, Gauge gauge

These two words both refer to the gauge used for measurement, such as the "hole gauge" for measuring the diameter of the aperture.

33. Standard board for Golden Board test

It means that when the completed circuit board is tested for electrical continuity (Testing), there must be a board of the same material number that is known to be intact and correct for comparison. This standard board is called the Golden Board.

34. Hi-Rel high reliability

It is the abbreviation of High-Reliability. Generally, circuit boards can be divided into three grades according to their required functions and quality, among which the third grade (Class 3) is the highest grade, namely "high reliability grade".

35. Hole breakout

Abbreviated as "Breakout", it refers to the formed hole drilled, and part of the hole body has been located outside the copper plate area or the square copper pad area (Pad), so that the hole wall is not fully protected by the hole ring. Surrounding, that is, the annular ring is broken and incomplete, which naturally greatly reduces the reliability of the interconnection between layers. Generally, the reason why the board is "broken out" is that the image transfer deflection is more responsible than the inaccurate drilling.

36. Hole Counter

It is a machine that uses the optical principle to automatically check the number of holes. It can quickly check whether there are missing drills or plugged holes in the drilled board.

37. Hole void hole

Refers to the through-hole wall that has completed electroless copper and copper electroplating twice. If there is a hole on the hole wall that "sees the substrate" due to negligence in the processing process or poor bath condition, it is called Void. This kind of hole wall hole has a bad influence on the quality of the socket welding. It is often hidden in the hole due to the inhalation of water vapor, causing gas to be ejected from the broken part during high-temperature welding, making the hole in the through hole The tin filling is blown into a cavity before solidification, making this kind of through hole a notorious blow hole (Blow Hole), so it is known that the "broken hole" is actually the culprit of the blow hole. A and B in the left picture are both bottomed holes, the latter is a big hole, and C is a bottomed hole. The U.S. military standard MIL-P-55110D stipulates that any hole with a copper thickness below 0.8 mil is regarded as a "hole", which can be described as very strict.

38. Inclusion Foreign matter, inclusions

In the PCB, it refers to the resin of the insulating board. There may be foreign impurities mixed into it, such as the plating of metal conductors or tin slag, and various foreign objects of non-conductors, etc., which are called Inclusion. Foreign matter in this kind of substrate may cause leakage or short circuit between board lines or layers, which is one of the items of quality inspection.

39. Insulation Resistance

It refers to the insulation of the plate between two conductors, and its unit of expression is volts. Here, "between two conductors" can refer to two adjacent conductors on the board, or the conductor between two adjacent layers of a multilayer board. The test method is to deliberately place a special fine comb-shaped circuit sample in a degraded environment of high temperature and high humidity for tossing to test the quality of its insulation. The standard test method can be found in the "Moisture and Insulation Resistance" test method of IPC-TM-650, 2.6.3D (Nov.88). This word is also related by the term SIR.

40. Isolation isolation, isolation

The correct meaning of this word refers to the quality of the spacing (Spacing) between the conductor lines on the board surface. The quality of the spacing must be checked by the needle bed electrical measurement method. According to the most widely used international standard IPC-RB-276 in its section 3.12.2.2, at a DC test voltage of 200V, after 5 seconds, the passing standard of the resistance reading value obtained is Class 1 For low-level boards, it must be above 0.5MΩ; for Class 2 and 3 high-level boards, it must exceed 2MΩ. This kind of "isolation" is commonly known as "short circuit" (Short) or Measure leakage (Leakage). Most operators often mistakenly refer to this electrical test as the test of "insulation quality". Sexual quality, rather than expressing the production quality of the "spacing" of the line. As for the lack of copper slag, copper fragments, or incomplete washing of the conductive liquid, it will cause poor "spacing quality". The industry has been accumulating for a long time, and even the most basic definition has been blurred. There are two routine electrical tests before the finished circuit board is shipped. In addition to the above-mentioned Isolation, the other is to test the continuity of the circuit. According to 3.12.2.1. of IPC-RB-276, under the test voltage of 5V, the connection quality of Class 1 low-level boards must be lower than the resistance of 50Ω. The connection quality of Class 2 and 3 high-level board powder must be lower than 20Ω. This test is also commonly known as "open circuit". Therefore, the "Open Short Test" that everyone in the industry can catch up with is actually just a negative term for unprofessionalism. The professional correct term should be "Continuity/Ioslation Testing".

41. Lifted Land annular ring (or welding pad) floating

The through-holes of the circuit board are equipped with grommets at both ends, which are firmly attached to the upper like shoelace buckles. When the board is heated during assembly and welding, it will expand in X, Y, and Z directions. Especially in the Z direction, since the expansion of the "resin part" in the base material will be much larger than the "copper wall" of the through hole, the outer edge of the ring is also lifted up. Since the adhesion between the rough surface of the copper foil and the resin of the board has been damaged by the expansion and pulling, when the board cools and shrinks, the outer edge of the ring will no longer be able to retract with the resin, so separation and floating will occur. The phenomenon. This kind of shortcoming is in the IPC-ML-950C (see 3.11.3) or IPC-SD-320B (see 3.11.3) before 1992, which stipulates that the maximum float can only be 3 mil; and it is also required to be still attached without floating The open ring width must account for at least half of the full ring width. However, this provision has been completely abolished in the newly issued IPC-RB-276 (Mar.1992) (see P.79 Table 10 of Issue 58 of Circuit Board Information Magazine for details).

42. Major Defect serious shortcomings, main shortcomings

Refers to the shortcomings found during the inspection. When they reach the "identification standard" with serious impact, they are identified as serious defects, and those who fail to meet the identification are called "minor defects". The original meaning of Major is to express the main or important idea. For example, the main function, main cadres, etc. are positive expressions. If they are used to describe negative "shortcomings", they seem to be a little inconsistent, so it is appropriate to translate them as "serious shortcomings". The above-mentioned identification standards for PCB defects have various situations, and MIL-P-55110D is the most authoritative for those with express regulations.

43. Mealing bubble point

According to the interpretation of IPC-T-50E, it means that the assembled circuit board, the Conformal Coating coated on the board surface, has a spot or flake floating on the local board surface, or it may be from Localized lifts on the part are called bubble spots or blisters.

44. Measling white point

According to the explanation of IPC-T-50E, it refers to the local separation between the glass fiber cloth of the circuit board substrate and the resin at the interweaving point of the warp and weft yarns. The reason for this may be that the plate encounters high temperature and the stress is pulled. However, once the FR-4 sheet is infiltrated by free fluorine chemicals (such as fluoboric acid), the glass will be severely attacked, and regular white spots will appear on each interweave, which is called Measling.

45. Minimum Annular Ring

After the pads on the board are drilled, the width of the narrowest part of the "Annular Ring" around the hole will be used as the object of detection, and the specification allows this part The lower limit of the value is called the "lower limit of the annular ring". This is an objective standard of PCB quality and technology. Since the round pad is produced first (resist and etching), and the hole ring is formed after the drilling process, the cooperation between the two manufacturing processes must be precise, and a slight error will inevitably lead to deviation, resulting in the hole ring. The width varies. The width data that must be kept at the narrowest point has been stipulated in various written specifications, such as the various data in Table 6 of IPC-RB-276. As far as the motherboard of a PC computer is concerned, it should be classified as Class 2, and its "lower limit of the annular ring" must be 2 mil. According to the two figures (Fig. 5-15 and 5-16) in the following IPC-D-275, the definition of the inner annular ring will not include the hole wall, while the outer annular ring must include the hole wall counted.

46. Misregistration is inaccurate, inaccurate

In the circuit board industry, it refers to the front and back sides of the board, and certain members (such as gold fingers or rings, etc.) that should be aligned with each other. Once there is a deviation, it is called "misalignment". This word especially refers to the misalignment between the rings of the layers connected outside the through holes of the multi-layer board, which is called "interlayer misalignment". Accuracy" data come. The picture below is the explanation on "Alignment" in the US military specification MIL-P-5511D. This term is called "coincidence" or "non-coincidence" in the mainland industry

47. Nick Gap

A nick that appears on the edge of a trace on a circuit board is called a Nick. The other word Notch is often used in machinery and is less common on PCBs. And Dish-down refers to the local depression of the line in terms of thickness.

48. Open Circuits disconnection

After the thin-line inner layer of the multi-layer board is directly etched by the positive film method, broken lines often occur, which can be found out by automatic optical inspection. . Outer layer disconnection can be remedied by selecting "Brush Plating" copper (see attached picture). Under the strict quality requirements of modern times, such repair work must be approved by the customer in advance, and relevant documents must be kept on file to comply with the spirit of ISO-9002.

49. Optical Comparator (optical amplifier)

It is a kind of circuit board object or negative film, through the transmission and reflection of light, and then through the lens magnification system of the machine or electronic focusing method, a clear picture can be obtained from the display screen to assist visual inspection. As shown in the figure, the Optek 104 model produced by OTI Company in the United States can magnify the image by up to 300 times, and it has a movable X and Y table driven by a DC motor, which can flexibly select the fixed point to be observed. This kind of "optical contrast device" has many functions and can be used for inspection, measurement, communication and discussion, etc., which is very convenient. In addition, a relatively simple "learning comparator" is also installed on the program tape machine, so that it can zoom in and align the hole positions required for marking, so that the paper tapes with X and Y data can be printed out correctly.

50. Optical Inspection

This is an inspection technology that has only matured in the field of circuit boards in the past 10 years, also known as "automated optical inspection" (AOI). It is to use the computer to store the correct circuit pattern in the memory in digital form, and then quickly scan and compare the produced boards. This method can replace the visual inspection to find out the abnormal situation of short circuit or open circuit, and it is most effective for the inner layer board of multi-layer board. But this kind of "optical inspection" is not a panacea, and it is inevitable that it is not enough. It must also cooperate with "electrical testing" to strengthen the reliability of the shipping board.

51. Optical Instrument

The inspection of circuit boards in the process and on finished products often requires the use of certain "optics"-related instruments, such as monitoring instruments that use "photoelectric cells" to detect the concentration of the bath solution, and high-power tomographic microscopes for viewing microsections , or low-power stereo microscopes, and electronic microscopes such as "optical contrast instruments" that are more sophisticated in combination with electronic technology, SEM, TEM, and even simple magnifying glasses are all optical instruments. At present, its functions have been enhanced day by day, and the effect has also improved a lot. However, the price of such modern equipment is very expensive, which makes the advanced PCB also rise accordingly.

52. Pinhole

In a broad sense, the through-holes that can be seen on the substrate on various surfaces are called pinholes, and on the circuit board, it refers to the appearance defects on the circuit or hole wall. As shown in the figure, there are four kinds of defects with different degrees, which are called Dents (sags), Pits (bumps), pinholes (Pinholes) and holes (Voids).

53. Pits concave point

Refers to the small area of sunken pits on the metal surface. When the glossy nickel plating process is poorly managed (organic pollution), dense pits often appear in high-current areas. The reason is that many hydrogen gas accumulates and adheres. Confuse this word with "Pin Hole". In fact, Pits are bottomless holes, which are not the same as bottomless pinholes.

54. Pogo Pin telescopic probe

When the electric testing machine uses a bed of nails for electrical testing (Bed of Nail Testing), the front section of the probe is divided into two parts: the outer needle and the inner needle. There is a spring inside, and when the pressure setting dial is aligned with the measuring point on the board to be tested, it can keep thousands of needle tips at the same time maintaining the elasticity required for their conduction. This kind of stretchable probe is called Pogo Pin. This kind of probe is also called Spring Probe. When the QFP has more than 256 pins and the pin pitch is as dense as 15mil, it must be pressed on the test pad in a staggered manner to avoid the probe itself being too close to short circuit.

55. Probe probe, probe rod

It is a kind of flexible and capable of maintaining a certain contact pressure. It implements urgent contact with each measuring point on the circuit board surface to be tested, so that the testing machine can complete the due electrical test. This kind of gold-plated or rhodium-plated probe is called Probe.